Thank you for the clear and straight-forward explanation and no shaky cam. Have a 81 CB750 due carb work, this will help.

this worked flawlessly! the bike runs beautiful. no popping on decel! been trying to get this cv carbed with pods cb750 running for a while. Definitely can start the build now I know the engine is good. thanks

WOW. This is really was brilliant and after weeks of trying to understand what was going on with my carbs, this really saved me (along with the fact that I had to turn my fuel air screws in more due to my elevation - or at least thats what I think) . This is a really great technique. Thank you!!!

MATTHEW, YOU ARE GENIUS!!!

Great! Are the both the exhaust ports and spark plugs oily?

No black smoke, there is some light white smoke that looks to be expected. It did blow a big puff off black smoke once this morning after I messed around with the idle screw when I was installing the top covers on the carbs. Once I got that set back up again it started up fine and runs fairly good! One thing I did notice is if you rap on the throttle really quick the engine will stall if you hold it @ W/O. Other than that it seems to have pretty good response.

1000 thumbs up man. Congrats and thanx for not to much bla bla

Good be valve guide seals? Does is smoke when running/

excellent advice!

clever,going to try on my 94 seca2/Diversion here in Ireland :-)

Great video!

Matt, That worked awesome! after I set the manual sync I hooked up the sync gauge up and all four carbs did not need any adjustment what so ever. I noticed while the bike was running that exhaust ports 1 & 3 are very oily. Any idea why? or is this normal with these engines? Port 2 is very dry and 4 has a very little trace of oil on the out side of the port.

Great idea and technique

thanks for all your videos ive been able to do alot of work on my own bike from your videos i have a 84 CB650 with 5k miles haha its a baby.. was wondering if you could show a video how to adjust that air/fuel on these types of carbs. my bike over heats quick and i think is because when i took the carbs out to clean them must have just screwed in all the jets main jet screws with out manual procedures

Nice video. Very clear!

Hold up a sec. What year make model are you working on?

Dude awesome method better than the manual says. I'm going to do my 81 cb750 tonight. Just build a vacuum sync too.

Just done this on a Honda 400/4 but used a piano wire instead of a drill bit. The difference was incredible! A rattly unstable idle, where you could hear the cam chain and primary chain rattling; suddenly became quiet, and quite even, at about 1200RPM. This is just the bench synch, and using vacuum gauges, I'm expecting the idle to be even smoother.

bro YOU ARE THE MAN!!!!

really helpful. thanks!

81. I would try carb clean first, pinesol dip second before messing with pressed in jets.

Start with 1.5-2 turns out as baseline. Adjust to highest RPM when you are up and running.

I check a lot of bench checking yours was the best. I did mine the way you did on utube a and it runs better then it ever has .. Thanks a lot ofep up the good mechanic tips your good?

If you have the diaphragms/dash pots off for cleaning or needle adjustment you can aim the venturis at a BRIGHT light source and get a very good bench sync by SLIGHTLY opening the idle air adjustment so you can barely see light.

It will. Your #2 carb is the base carb. Insert 1st drill bit into #2 and adjust the remaining ones.

Brilliant!

Ok cheers will test it out

Is it the same with the GSXR 1100 carb? I will try to do it

Hey Matt what size drills ??

When doing that.do you turn idle up or turn it down Or slightly.which way..

If there's no base carb, from what I stated on how I synced them is that correct and what should I set the A/F screws @?

So this will not work on fj1200 carbs? since its, 1(screw between the carbs)2 sync 3(screw between the carbs)4 sync then 1/2 (screw in the middle of the set) 3/4 sync

Nice nice... I've heard guitar string for feeler gauge, about to try this with the drill bits, I like that idea. Gotta get a baseline on carbs for a V4 Honda Magna... Most annoying carbs in the world to get off and put back on, hoping I don't have to do it again..

Ok, What should the idle Air & fuel mixer screw be set @?

Thanks, hopefully it helped you out.

No prob!

81 or 82? You should post a video on how you clean your cb650 carbs Ive got 2 of the same set of carbs and am wondering how everyone else cleans the pressed in jets

Thanks sooo much!

For those carbs, adjust slides so idle screw is no longer touching the slide and slide is all the way down. Adjust idle screw so that it just touches the slide. Go to WOT and turn idle screw in 2 turns. Any further adjustments will have to be equal for both carbs.

What should the A/F screws be set @?

Nice ... a very smart way to do it... :-)

Is this the same for the vm 26mm mikuni slide carbs?

Liked and subscribed

Just curious if you have a video or advice on how to bench sync mechanical slide carbs?? Mine are Keihin PD50a style and the butterflies only seemed to be controlled by the choke, the slide itself is controlled by the throttle...any help appreciated!

I have the same carbs. Prior to bench tuning, what have you done with the throttle adjustment screw? Thanks

Lesley, doesn't matter what size. I use 1/8 or 3/16 since I have a ton of them laying around. Remember, both have to be the same size.

No. I thought you had VM slide carbs which do not have synch adjustment and are not banked together. You synch those carbs with the idle adjust. For your carbs, take 2 equal sized drill bits. Select one carb as base, and put drill bit under slide. Adjust other 3 slides with other drill bit until there is slight drag under slide. Adjustment will be under carb top cap.

Ok, The manual does not state that there's a base carb. So going back to my previous steps that I did, was this correct?

hi matt i have a 82 nighthawk 650 ,i am having a problem with the plugs going black after 10 mins of running it.but i am new at this shit ,so how do i clean the carbs the right way.thanks for your time .help please..

what is the big brass screw sticking out the top right of carb 2 i broke mine off and cant figure out what it is.

Ok, so let's see if I understand this correctly! I turn the idle set screw all the way back out.. Make sure it's not touching. Then adjust all four slides to fully closed. Then go to WOT turn the idle set screw in 2 turns any further adjustments to each carb will need to be done equally...meaning if you adjust the slide on one you need to adjust the other three the same! Is this correct? When using the carb sync on the bike does the adjustments rule still apply? If u turn one adjustment screw c

How do I tell what one is the base carb?

Ok, I just bench synced the carbs! This is what I did 1.) loosened all slide adjustment screws and turned out the idle adjustment screw until it was not touching the throttle lever. 2.)adjusted all slides in the closed position. Tightened all lock nuts. 3.)WOT turned the WOT screw in 2 turns. 4.) Turned the idle set screw in until I could slide a .075mm pin under the lowest set slide . Then set the remaining three the same. 5.) set the A/F screws! The air screw set at 1 1/2 turns and the idle s

MathewMCRepair how does it work for a snowmobile since the carbs have slides?

when is the best time to re-synch the carbs? or there are symptoms ? my unit is a cb400 S4

very easy thank you very mutch

hey Matthew should I do the same thing with my 85 kawasaki LTD 700?

I just tip them up and loosen till the drill bit drops out of the carb. Perfect!

Is this 100% ok. I like to try it and looks easy

ya sure! how can I attach them on you tube?

holy shit i would have never thought of that haha

Matt do you know what the springs are called. I am looking up "synchronization screw and spring" in google and nothing is coming up. All of the Honda parts list websites are showing that part as not available? Any help would be greatly appreciated.

tnx!!! cheers!

Cool method but still didn't understand what you were doing with the drill bits. Were you seeing when they pulled out easily or hows that go? Newbie here.

can anyone please give a make and module for them carburettors, i have a 1979 Honda cb750 with a set on it that need work.

I've ways used feeler gages at closed but this looks way easier.

i want to try it in my bike HONDA CB75cc CUSTOM

Im gonna try this on my 94 katana. My cylinder 2 and 4 are not getting hot. i clean the carburetors like 10 times

The base carb will have no adjustment. Verify in the service manual.

No problem.

Thanks

What drill bit did use?

when my butterfly valves are at rest, they are both totally closed. Does that means they are already syched?

So, why do they even have adjustung screws if all have to be the same?

OK, disregard my last comment. There might be a base carb in which you need to stick the drill bit under. Get a second drill bit and adjust other 3 slides to have same height. If there is no base carb, pick one and synch the 3 to that one.

You didn't tighten the lock nuts?

Spark plug 1 & 4 are dry 2 &3 are oily.

send them to matthew at howtomotorcyclerepair dot com

Does that work on a 95 katana?

Show. Faz menos lambança que água......

I cleaned them up and everything but those butterfly are not the same

I used to use feeler gauges. Then the last time I did it I decided to try a different method. I lay carbs in a plastic tub with butterflies facing directly upward. I poured equal amounts of fuel into each carb with butterflies in closed position. I adjusted the carbs until the flow rate of all four were equal. It appears to be the most accurate method I have tried. Better than feler gauges. I don't know if anyone has ever used this method before. I just took a notion to try it and I liked the results.

Mine are wide open at idle

Want to send me a pic of plugs?

1977 Suzy gs750

Still do not have my carbs setup. Please help!

Crack 👏🏻

why wouldnt you put the bit at the top? easier to feel and remove....just saying

Ok I just checked the plugs, very strange! Plug #1 is dry oily exhaust port Plug#2 oily dry exhaust port Plug#3 oily oily exhaust port Plug#4 is dry some small traces of oil

See me vid - "Pilot Air/Fuel Screw Adjustment Explained"

No!

Is it the same with the GSXR 1100 carb? I will try to do it