Thanks for watching. Let me know what you think in the comments below. More videos like this here: kzfaq.info/sun/PLmgCmljtdCzUPlkO9kNjj0ARrfojWPFFU

As an engine builder i can say with 100% certainty it not only creates a cleaner engine it also improves the air fuel ratios which leads to better preformance. Re-breathing is not healthy for any engine.

I used to have to clean my throttle bodies on all of my cars and bikes almost annually. Since adding a "catch can" system to my cars and an external breather to my Harley's, not once in all of the years and miles since. I would rather have only fresh air in my intake systems. Have a great day!

Same bike, same rider. Added external breather at 30k . Performance improved ( dyno prior to change and again after 10k ) Gained 6 hp and 10 torque. Borascope showed noticeable improvement in build up. Good enough to put it on all my Harleys

Regardless of any potential performance gains, breathing the engine somewhere besides into the throttle body makes sense in many ways and should be done. From an internal cleanliness standpoint alone it is a smart idea 🤓. And everything we know makes this a theoretical/logical efficiency improvement🤘

Here in America, the debate isn't about carbonization or performance improvements. It's about the oily mess inside the air intake. For me, not having that mess has made me very happy. That said, your video was well thought it and enlightening for me. I learned a lot and that's always a good thing. Thanks and keep up the great work!

RevelatorAlf Thanks for adding logic to this conversation. I'm not going to lose sleep over this anymore. I don't like the looks of it either.

Good points. I have a 90’s EVO, S&S carb, drag pipes and minimal electronics. I’m doing it for the simple fact that I’m tired of all the oil in my air filter and wiping that occasional drip. They aren’t huge deals, but annoying and my bike is pretty raw so it’s a solution for me.

i keep hearing that external breathers allows more colder air to go to the engine to keep engine cooler but I think its just for ppl who want to race or looking for higher performance.

My bike started to fail on the front cylinder... I discovered that the spark plug was failing. Even new ones. It mostly happened after a short break on a trip. After doing an external oil breather, the engine started working perfectly and never had any problems again.

You are talking good science to me. I think alot of people pushing these kits are also selling them! If you are burning alot of oil you my have an issue definitely. My 107 never burned much oil or had much " blow by" in the air filter. The oil pump did quit at 43k however. I think they have addressed this problem with there new oil pump. A vented dipstick my be a good alternative.

Finally, someone else who still uses the term de-coking! :-D My project bike already has an aftermarket air filter, as it has the Mikuni HSR42 on it. I am thinking of routing it to an external catch can to separate most of the oil Harleys are known to spit out, then back into the air filter. I think your little talk has settled that for me - no downsides (I studied Physics, the percentage of gas from the breather is so small it is insignificant to the engine,) but an upside - the oil does tend to dirty the carb.

i have an external breather on my bike....not for the so called performance gains but because i have an aftermarket air cleaner...now their is no more oil dripping from the air filter and ending up on my side covers...it was never excessive it just bothered me

You may be right but venting save you air filter and keeps you throttle body alot cleaner. I do it mostly for that reason.

If you have a blow by problem this could help. But if your bike is running properly Little to no gain from this. I have 13k on my m8 and have never had any oil at all in on or around the air cleaner or throttle body. Not to say that at higher mileage this won’t change. Time will tell. Happy with my stock Harley for now. Great video.

I've had an external crankcase breather system on my carbureted 2005 Sporty for years with the stock breather bolts and stock air cleaner. The only visible difference is a black rubber hose coming out of the black backside of the breather box which runs a short distance to the swing arm. You have to actually step back to see it because it is not noticeable at all. There is no catch can or filter at the bottom of the tube. To see this part, you have to go to the left side of the bike and look underneath the bike and it is still not noticeable. The results are a clean and dry air filter, clean and dry air intake, and COOL, clean and dry air going into the engine. I do have to place a paper towel underneath the drain hose when I park the bike in the garage to catch the ONE teardrop size drop so the floor will stay clean. As long as I don't overfill the oil tank, there is never any more than this. As far as performance difference with leaner air/fuel mixture is concerned, there isn't any. I What's not to like? Clean and cool is better than hot and oily. 'm happy with this.

For me, it was personal preference to add an external breather / catch can setup. I have an aftermarket air filter which has a Lexan see-through outer cover allowing you to see right into the throttle body. Now the throttle body and butterfly remains clean instead of being covered with a film of "Blow-By" oil. If oil mixed in with fuel is what anyone wants, that's their choice. I do mods to my bike for me. Harley do this to the bikes to meet EPA standards and regulations. In some states its is illegal to vent straight to the atmosphere.

I haven't made the mod yet, but I'm seriously thinking about it. I have a 96ci twin cam (2011 dyna) with a stock air filter that keeps getting soaked with oil. I'm 90% sure that my problem is being caused by this issue.

Just got my first HD, a 05 Electra Glide. I appreciate the info and you cutting thru the hype and myths.

Just bought one and installed it on my bike. Wish I would have seen this video before I purchased it. I may have consider not purchasing it. I have a 2020 Tri Glide with 9058 miles. There was very little evidence of any oil in the area around the throttle body butterflies or anywhere else in the air cleaner apparatus caused from the OEM breather tube dispensing oil into the cylinder. It still looked pretty new in there. Now you got me concerned about upsetting the balance. Hope my engine light doesn't come on in the future. Well, I guess if it does then I now have an idea of what the issue would be, before reading any codes. Anyway, good video, and it's always good to hear the other side of an idea. Thanks.

When I got my 2007 Dyna it was bone stock with 6800 miles. When I pulled the plugs they looked good except for a little bit of deposits built up. I put on a high flow a/c, vented the heads to the atmosphere, some Screamin Eagle slip on mufflers and an FP3 tuner. It has 37700 miles. I check the plugs since the changes and never have any deposits on them. The bike has always run great.

I installed a external breather to a 2015,Ultra Limited, because my stage 1 air cleaner has a open small air filter, and I was getting small amount of oil settling on the air filter and leaking on my timing cover, after about 3K miles.

The scavenge side of the oil pump has two inlets- one for the crankcase and one for the cam chest, so when one inlet has cleared the oil and is then sucking air, the other side is not clearing oil. This causes no major problem if the total amount of oil in the engine and oil tank is correct. When the bike sits without running, any oil in the engine collects in the bottom of the crankcase and timing chest and can measure as much as one litre of oil. Oil expands when it is warm, and if the oil level is checked with the bike on the 'jiffy' stand then the reading is false as the bike ,when running , is upright and the level reads higher on the dipstick. When you start the engine, all the oil that is sat in the bottom of the cases (crank and timing chest) gets sent by the scavenge pump into the oil tank , so if you have over-filled the tank then it - the excess oil - will then go from the tank into the crankcases again via the oil tank/crankcase vent. When you have too much oil in the crankcases and the crank churns it up, the 'oil-mist' becomes over oiled and any air going through the separators in the rocker box breathers carries more oil into the airfilter/engine.... that is how you get the 'blowby' as it is so named. The way to avoid this is to only check the oil level when it (the bike and oil) is warm AND with the bike upright, making sure that the level is about halfway between the upper and lower marks on the dipstick. This way there will be enough room for the oil that has collected in the engine to be returned to the tank AND there will be less - if any - oil going from the oil tank vent back into the cases and causing the oil mist to be so heavy as to overcome the 'oil-seperators' or sponge in the rocker box breathers. S&S oil pumps have two scavenge pumps - one for the crank and one for the timing chest - and keep the level of oil in the crankcase lower thereby stopping the oil-mist becoming too oil rich AND slowing the crank from spinning. SIMPLE REALLY AIN"T IT ?

I actually went with the Trask crank case vent . My throttle body on my 2019 Street Glide did'nt have much blow by going into the throttle body. I will say I have the Stage one kit and A stage one tune. The crank case breather for me it to more ensure my oil in the crankcase doesn't get to oxygenated/bubbly. As I've stated my M8 didn't exhibit excessive oil residue in my throttle body. I'm at 4,500 miles on my bike and I ran a bore scope in my cylinders and they did'nt have any excessive carbon build up. I run 91 octane gas in my scooter and I'm at 5,100 ft elevation.

I did it for one simple reason. I was tired of my 2017 M8 engine spitting oil out the air cleaner and consequently on my leg and down the bike. I do long trips at highway speeds frequently.

I finished the video enjoyed it very much just to let you know DK customs has a video where they put a bike on the dyno same bike without the external breather and then leaving the bike on the Dino install the external breather and it got a 7 horsepower gane and a little more torque you should check that out

I have a Screamin Eagle Stage 1 air filter kit on my 2019 Fat Boy 107. I can connect to this video you mentioned. All I did is to open up the air filter sprayed some Liqui Moly throttle body cleaner over the throttle body as prescribed on the bottle which helped clear oil and other gunk from the intake valves and I could see that the engine was breathing a little bit better as the revs it needed to sustain while idling was reduced by 20 to 30 RPM and overall it also improved my pick up and acceleration although a wee bit but noticeable. Worth trying it Liqui Moly recommends the activity every service but should be fine every 3000 miles too

We used to call those things puke cans. It's more of a problem with engines with direct injection where the valves aren't cleaned by fuel. Some manufacturers actually have a decarbonizing service that needs to be done every 75-100k miles on cars. Techtron is one I use once in a while. The problem with fuel where I live is ethanol and 91 AKI is the highest octane one would find at the pumps. Back east I could get 93-94, but it still would have ethanol. You can use a scope through the spark plug hole to see the condition of the pistons etc.

My issue is the oil reside in the throttle body in particular the idle air port getting blocked and requiring cleaning. That’s why I’m considering an external breather kit

Interesting video, thanks. I personally won't be worrying about it and I'm sure it will have little or no detrimental impact on the motor. I certainly won't be pulling my heads off anytime soon and I always use Esso Supreme as it has much less ethanol if none at all.

My stock 1200 2009 sporty has given me zero problems with oil buildup so I guess my bike will be one of the few stock bikes left. I don't need to install a breather kit to feel like a biker/wrencher. I do all my work save tires and such. I do have the SE air filter and put my stock mufflers back on after my ears were bleeding from the rumble. No worries about cops and tickets anymore

Thanks from Australia mate. I dont think ill bother now. And i wonder how 2 strokes got on for so long with all that oil in the fuel "coking" up the top end. Ive got a 30 year old chainsaw, cut tons of wood still runs like new. Wonder theres any room left on top of the piston in that tiny combustion chamber with all that carbon cake on it from "all that bad oil"

Very interesting and informative. I like that you showed the pros and cons. But they use the same system in every car and bike made. So it really can't be that bad by not having one. And to gain a few HP and possible check engine issues later is it really worth it. Cleaning the throttle body every now and then I guess will help. But thank you for you open minded thoughts.

I've experienced increased blow-by after installing stage 2 upgrades on my 1200 efi sportster. Caused issues gumming up the sensitive iac valve. Been blowing that shit into the atmosphere for 20k miles now with zero issues.

my XB12R, when hot would miss and fart and surge around 1500rpm, making traffic crawling a chore. When I removed the cylinder breather from the air cleaner it became a different bike. smooth and civilized.

I have a 2013 FLHTK - tired of oil collecting in the air filter and spraying all over the side of my bike so I installed a catch can system- if HD had a setup to where the oil wouldn't leak out I would go with it. I've also tried a V&H intake and a K&N both still had oil collecting in the air filter.

After bumping my old Evo to a Stage 2, my head breathers got terribly pukey afterwards. My air filter's bottom side would become saturated and dripping only after 300 miles. My aluminum backing plate was stained with oil deposits. I made a breather system for it with a catch can (because I HATE oil on the floor, even with Harleys lol). Yep here's more anecdotal evidence, but I also know my bike. Since installing it, I haven't really gained any power but it's definitely more responsive on the throttle blips. I always dealt with a "coughing throttle", even after I rebuilt the carb, but this seems to have eliminated it. Cheers from 🇺🇸

A definite improvement with external breather at slow speed maneuvering with better throttle control.

I watched your video with great interest. You presented good well thought out reasoning. I have a 2007 fxstc and tried venting externally last summer. It has a Stage One setup with a high flow air filter. It seemed to work initially but then the engine ran strange and wouldn't idle right. I took it off and it's been fine since. I think the bike (computer) was telling me to stop messing around! Thx for sharing! R

Pretty good video and well thought out. I think if I felt pretty confident breaking the engine open to clean everything out, I'd skip a breather. I don't want an external breather for performance but having clean cool air to hopefully cool the engine down a few degrees and hopefully prevent build up over the long term is what I am searching for. I got a brand new bike and want to keep it for the long haul. Thanks for the vid.

All great points. I don't think it is a performance issue. It is a maintenance and cleaning issue. My main reason for a catch can is during my long rides in hot temperatures, I will have oil splatter all the way down the right hand saddle bag and on my leathers, due to the oil leaking from the breather. I ride annually to Sturgis from North Carolina for a total of 8500 to 10,000 miles per trip. The oil residue isn't an issue on short trips or riding around town. It is an when you are riding 600 to 900 mile days at a constant 3,000 rpm, for days on end in 80 to 90 degree temperatures. I know some will say it is a dirty air cleaner or a topend issue. It's not. During these long trips, I change and clean the air filter every few days. The bike also has good compression so it isn't a ring issue. The average weekend warrior won't see enough venting to warrant a catch can in my opinion. People doing a lot of long distance touring with high daily milage with prolonged periods at high rpm, will see a lot of venting. It has happened on every single long distance ride. I have lost anywhere from 1/4 to 1/2 a quart of oil on a 5,000 to 10,000 mile ride since day 1 with my M8. Running lower oil levels does seem to help with the amount of venting, but it is still an issue.

I made my own kit for my Evo Road King. Total cost about 20 bucks and about 1/2 an hour of work.

Nice video, but my 21 bob 114 is finally up for its 1k service, and its got some oil residue on the inside of the filter cover that i can wipe off with my finger. I do plan to do an external breathing set-up on my bob, but the only set-up im willing to go with, is the one that the Blockhead channel has. His $12 fix shows drilling and tapping holes on the outside of the cover where the breather bolts go through, with the ends plugged. Once drilled, zerk grease fittings with the little ball removed, are installed with rubber hose teed off, running back to the transmission cover, which has another zerk fitting installed on top the transmission cover. This set-up makes sense to me, since it routes the vented oil back into the transmission, then vented out the transmission.

on a side note, seen a dyno with aftermarket 2-1 fitted only= made no difference just louder over bone stock M8

I had to put one on my 2015 flstc. My problem was that oil was getting into the sensor in the throttle body causing it to stall when coming to a stop. Since then, no stalling out.

Milwaukee M8, long rides, oil goes everywhere pouring out of the air cleaner all over your motor. It’s disgusting. Great idea to reroute that blow by and put it through a filter or catch can. Less boil mist in the motor would equal less carbon buildup no matter how small. External breather is a must for any Harley I own.

Correction..... Not pressurized air being recirculated....... it is oil, oil vapor, moisture, nitric acid vapors, carbon dioxide, water, hydrochloric acid, to name a few items that are sent back into the engine..... Typically small amounts but that depends on the engine. The big damage is to seals and gaskets as they will leak sooner and greater.

This all reminds ,e of in the states in the late 70s when they added a PCV for emissions. I suspect that it’s most common with engines that have the stage 3 and 4 and they are really pushing it and it’s blow by. The only one I can see working is the Trask performance system vented top cover. They are using them on their race baggers and have some objective data form race bikes. Is it worth it for the average rider to spend the money on it ? I doubt it. I think keeping your air intake filter clean and a good map would probably do more.

I can tell a riders habits just looking in the carburetor. Someone who just cruises around doesn't have much transfer of oil through carburetor. Someone who likes to bounce off the Rev limiter will need a catch can . All these bikes are basically designed the same so the only real difference is the rider. This guy is being too technical. I have a buddy who could ride 20 different Harleys and the breathers wouldn't be an issue. Have me ride those Same bikes and you'd need a catch can and not one of those tiny ones but with a drain on the bottom. Every police bike in my area has a bypass with catch can. I learned that decades ago and it's just logical that getting rid of hot air going into carburetor is beneficial. Only helps on warmup.

On the same token, adding fuel additive to clean the engine would be the same lines..no proof it cleaned, but keep in mind that hard carbon deposits can break off and cause scoring of cylinders, so reducing carbon build up is important..another couple things you did talk or touch on is the effect over filling the crankcase oil level, or talk of changes in top end engine vacuum when removing the OEM set up..i errored on the side of caution and pulled the re- directed out of the intake chamber, and made a mini 1 ounce catch can, and set it inside the air box, but outside of the filter..now I will check it for oil and for vapor issues in a few hundred miles

My experience. With my early ones had a times rotary breather valve. Had breather kit. But did leak. But road 10 hours on freeway at 70+ mph. But did hear they sucked in dirt. Twin cams seem to have a rubber type valve from memory and go hard in time. So if not sealing well will suck grit back in if not filtered .. I get a bit of oil on my filter. But just wash it off at a service and re oil. Only time I know oil is a problem in a combination chamber is at super high compression and week gasoline to cause pinging .... mine runs 10.5/1 run it 10+ hours on a freeway at 70+ mph and have no problems. But maybe I’m lucky....jon from Australia

I ride a 2016 SGS I bought new, after 2300 miles I had HD install a Stage V Tire Shredder Kit. My main reason for installing an external breather is that every oil change, I have to clean my whole intake, throttle plate and spray off all the oily residue that has collected on the MAF sensor with MAF sensor spray cleaner, don’t see how the MAF sensor sends good singles when covered with oil, that alone is worth it to me!

That was extremely interesting having done 4 stage 1 upgrades on various Harleys myself I have witnessed only 1 occasion on 1upgrade where there was any appreciable build up of misting oil inside the entrance to the throttle chamber. On speaking to the head technician at my local Hd dealership where I had some work done outside my skill set,he stated to me that in 28 years of stripping the guts out of all build engines he could not honestly say how carbon build up in any engine may have had contributing factors. There are too many variables to state with more than 90% probability of fact that one factor contributed to an excessive carbon build up over another.The point I’m trying to make as well is ,can we all reasonably believe that HD would engineer a system that would given unaltered ( no upgrade of any sort) create an inherent failure built into the basic running of the engine.Thank you for an enlightening upload my mind is definitely made up now keep to the basics.

I have 2 of the same exact engines one with bypass and one without, rebuilt both at same time and I can guarantee you are highly mistaken. No big deal but there is evidence thats not anecdotal it's not that hard to find. No experiment is perfect but it doesnt have to be perfect to get reliable real world data. I enjoyed your video and your thoughts and if I didnt see the proof first hand many times I would probably agree with most of your points. I will say it's possible the the slight increase in compression may ad a horsey or two but I thinks it's better to just keep it clean. It's mostly water that comes out of the crank case, especially with ester based oils.

I welcome the cooler/cleaner air on my HD. The ol lady welcomes the fact that with the oil soaked mist is no longer flowing in the air cleaner, which eliminates the oil build up and keeps it off her jeans.

Interesting video. I have watches some reviews on those who have done ventilation and claim quicker acceleration and deceleration

If your main concern is really just the annoyance of the oil getting on your saddlebags and side cover all the time (White Road King), what is the easiest solution to that? Would the Feuling Vented Dipstick help with no real modifications required?

I would think keeping that hot, oily air, out of the combustion chamber would be a no brainer.

Great explanation. The biggest car and motorcycle manufacturers of the world are doing it the same way as that is not a real issue. If that was a real issue for all those engineers designing best engines of the world they could easily do it nicely adding breather right installed nicely from the factory properly just adding few dollars cost. If they didn’t, doesn’t mean few dollars cost cutting. is just because it’s not an issue as it is claimed by aftermarket parts makers. This issue is just been created by aftermarket parts producers who haven’t even been to college or university to make useless products to sell to people who believes in their lies to make money. In this video the author explained very honestly and professionally in an excellent scientific way the truth. Of course people are still free to believe the lies of aftermarket part producers and let them make money on their simplicity. Open your eyes.

Hello Alf, Like your Videos .you Do get a benefit from fitting a external breathing kit, you don't get an oiled up filter when you over fill your oil tank, and get oil blow back ,and your throttle body is clean. I have an EB kit on my 2017 dyna street Bob. had it for 2 years.my plugs are always spot on, And the Bike feels like its running better, to me it makes sense clean cool air going into the engine. We know Harley do things like they do to Pass emission Laws. Then leave it To the Buyer to sort their shit out .DK customs have done some tests and Have EB kits, Its worth a look on you tube. If we wait for People to do tests on loads of bikes, we will learn nothing. And if it comes down to cost.my EB Kit cost £6. Keep the Videos coming Alf I really enjoy them. Regards Bob

After listening to your video, I will not add the catch-can setup I bought. Thank you!

Apart from the fact that it’s obviously not doing your engine any good however slight it may be. The main annoyance is having oil leaking out the filter housing and onto the engine after long rides.

You know Mr. Alf, you're smarter than you look. Just bought a new Low Rider S 117 and I have all sorts of questions and you answered a lot of them. It has a TBR pipe and tune and it's pulls hard. But, I'm a Z900 guy and all this mumbo jumbo relating to blowby, sumping and excessive crankcase pressure is starting to bug me. Dig this bike, but time will tell.

Makes a ton of sense. Thanks.

Firstly .I'm sorry its taken 2 years to make a comment on this vid, My sg has now done 15000 miles and for the first 5000 I did not have any external vent, when I scoped my pistons the carbon build up was excessive," i am saying this as a 40 yr experienced Mechanic" it looked like a very old oil burner, plus on summer tours the amount of oil I was putting in was wrong 1ltr per 2000 mls. I fitted an external breather .firstly a dip stick one then the trans cover one , I did a 5000 mile tour of Spain and didn't use any oil, Very different experience . My conclusion from this is due to Euro/us emissions rules the internal crankcase pressures are best to be vented to atmosphere to save my engine , selfish maybe but at least ill be riding my Harley in Hell whilst your all sitting having a coffee in Heaven Harley Davidson waiting for you bike to be fixed.😂

Ya for the cost it's not going to hurt

I could imagine the spark plugs fowling faster too.

Love that the advert at the start of this video was for the HD Livewire.

Keep your day jon

You cannot ignore that the Hot air from the crankcase (engine hot) is sucked in the airbox while on that moment the piston is going down and builds up pressure in the crankcase i don't want that I want clean air or not?

Great insight 👍 I was skeptical in the beginning of the video, because of videos I've seen on catch cans but you bring a lot of logic to the topic. I agree, how much oil are you collecting between oil changes? I'd love to see conclusive research. Thank you.

I don’t know if I missed it but did you get a Dyno tune on your bike after installing the breather? I know it’s recommended having your bike tuned when anything is changed in the combustion process.

I've not seen any issues with the $ light coming on due to external venting of the PCV system. Changing EGR settings quite likely will on modern FI engines. I'd suggest venting the PCV just because, is a waste of time. YMMV. Edit. This applies to mechanically sound engines. If there's excessive oil in the PVC system due to wear, or sumping etc, venting will not help.

This might sound silly and please anyone with more knowledge please correct me but what about the loss of crank case pressure? Can’t this add to possible sumping and a loss of oil at the top end even if minimal? I am only curious as I definitely understand twin cam big twins and most definitely believe although that may seem like a small amount of crank case pressure it definitely aids getting oil up top??? Any comments would be appreciated.

Can't see my catch can, there is room inside the Road King stock air box for one

The only mod a stock 107 M8 needs is a new seat..

To be sure I only use premium fuell 98 ron like excelum (aral) vpower ( Shell)

I wonder if the real culprit is ethanol fuel mixes.

I got a catch can on my Harley. Now I have no oil going back in the engine or air filter.

I am building a bike, and I have been looking for data on the before and after dyno performance of a hyper-charger. My last bike came with one , but I could not compare it with a stock engine. Is there any comparative tests done? At this point I am focusing on using conventual means of optimal breathing of the engine. I would appreciate any info that could be of help? Thanks

A1 sells one for 89 there's is in the dip stick 👌

Well just vented mytwincam this morning the throttle valve was covered in thick black grease like substance and cheçked my bores with a camera and the pistons a black! This is a recent rebore...venting is the only way sorry

Well...you talked me out of it. I have a 96 c.i. twin cam with 8,000 miles and was going to install a breather by-pass this weekend. After all the hype I read looks like it's not necessary.......Thank's

Put a external breather on mine 93 harley fatboy Pick up a lot of power by doing this

My question to you Revelator Alf is would you fit it to your breather?Y or N

I've recently put a DK external breather kit along with a K&N air filter and cover plate on on SG, bit to early to tell yet if there is any benefits. But must say, cosmetically the bike looks much better with the new air filter and new cover vs. the stock SG set-up. just the addd air flow alone though is a benefit already and noticeable. But whether the external breather kit was over kill or not, based on what I have looked into (sure its all anecdotal) its not going to harm the bike and more likely to help the engine then not. Have not seen anything yet to say it would harm the bike to have an external breather. Once I change the exhaust in the new year, then at that point i will also have to re-tune the bike and possibly put on an auto-tuner. As far as looks.... the external breather kit is hardly noticeable and it has been done very neat and tidy. You actually have to look hard to spot what we did when we installed it when changing the air filter set-up. Also, adding the 2" riser lugs for the handlebars from Dk instead of HD risers or pull back risers meant that I did not lose or have to change out the stock top clamp which I was very pleased about as I don't like a lot of the other HD or aftermarket options for even the 4" pullbacks which meant you lost the stock top clamp.

Is it a good idea to use Marvel Mystery Oil a small amount to add to fuel tank at times?

Great Insight and Exposition Alf..If Possible Pls Give us your Take on the 5 Micron HD Super Premium Oil Filter Flow Efficient which is what KEVIN BAXTER Touched on in Recent Live hang out QnA at 35-36 minute Section ..Saying they block at 3000 miles on average thus Run Via Bypass valve after..There may be Several Variables to Contribute to this.Thanks..

Back in the late 50's we would always joke about taking our old Chevy's out on the freeway and stomping on the gas to blow the carbon out once in a while. And we did just that. You could see the carbon smoke out the tailpipe. LOL

I'd say to the unnecessary statement. We ride Harleys. I didn't get on my Softail because it was necessary. And for 60 to 80 bucks on top of an air cleaner we are likely buying anyway, any improvement on a Harley for the price point is worth it. That being said, I go back to the we ride Harleys. The most beautiful thing about the bikes is that if you want to do something to it, there are likely options. Totally respect you're not sold on the external breather. As I'm still researching it for myself, if I believe it'll make the Slim last me longer I'll likely do it for the above stated reason. If there's a benefit to be had, the price point makes it incredibly compelling.

Carbon buildup on the pistons and valve's on my bike's are from oil from the breathers,the carbon is oily not from fuel,intake valve tells the story

I had an ounce or more run out of my Road King when I took it off to do the 20k mile service. Not sure where all my oil goes, but the bike has used approximately an extra quart every 5k miles since it was new. Hasn't gotten any better or worse. No big deal, just that no other bikes I've owned used any. Well except for a ZRX1200 that once had a couple of Nikasil cylinders delaminate. That one burned a lot of oil and I am probably solely responsible for polluting the entire planet for a couple days when that happened.

Just an Afterthought, As I've now Watched and Attempted to Learn from Many a Videos and Engineering Experts in Automotive Industry I can But Rationally Conclude 1 Manufacturers don't Care what Happens after Warranty Expiry 2 No Additive can Clean the Throttle Intake or Manifold inlets Neither Heads nor Valves etc etc. While I'm Not at all Concerned bout The Current Performance of my Motorcycle , I am Concerned bout Preventing Long-term Degradation of my Intake and Engine and all related Parts thus looking at Minimizing the Carbon although I Do Not use Ethanol Only 95 Octane which here is the Midgrade Premium fuel by an EPA legal but Unique method..Check how bad some Diesels are Alf.

I could be wrong but Poor Grade Fuel especially Ethenol Additive Gasolines can cause a Black Tar Build Up on the Heads. Low Brow Customs and TC Bros make breather bolts. If a few drops drip out every couple thousand miles that is what rags are for. Sporty Spam Cans and Round OEM. They seem to use a Ram Air Technique with the hidden scoops at the bottom and HD is trying to create an air swirl effect before the engine takes it's gulps of air. The Air Intakes are fully enclosed otherwise. HD sells their special FARB with a Harley Tax in the form of Screaming Eagle Intakes outsourced from major manufacturers. They are more exposed to the air and slightly smaller than what was bolted onto the bike from the factory. So an Air Intake gives you 1 HP advantage, a exhaust gives you 3 to 5 HP advantage, and you have a tuner plus HD dyno'ed and computer mapped perfect. I BELIEVE THE BIGGEST ADVANTAGE TO SWAPPING OUT OEM INTAKES AND EXHAUSTS ARE TO REDUCE WEIGHT. Accessories even well made seem to weigh a lot less. Less weight more perceived power.

On the highway at 80mph at 3000rpm my bike vents oil..

You have stated my questions and concerns regarding external breather kits. It seems like a bad idea to port engine oil/vapor into the intake ... but SHOW ME THE DATA!

Use aluminum tape lubricant.

I simply route the breather tubes to allow the oil to drip into the air cleaner element, which is oiled anyway and cleaned every few thousand miles. Intake stays cleaner, Problem solved. I can't believe people invest so much time into such a trivial issue, but it's a trap that befalls Harley-Davidson enthusiasts particularly, in chasing tiny performance gains on a motorcycle that isn't "performance" oriented to begin with. Boggles my mind.

What about the elimination of the vaccume out of the engine when its running? External venting would be dead air when it used to be sucked out. This is holding me back from switching. Any input would be appreciated

So it’s more of a personnel preference than a tech issue.Also be careful with over use of fuel additives . It will dilute your engine oil.