Why Do Cars Backfire?

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Why Do Cars Backfire?

Рет қаралды 759,563

Күн бұрын

Why do cars backfire? A backfire occurs when combustion takes place outside of the cylinder. Backfiring can be used to describe combustion occurring through the intake (traveling backwards) or through the exhaust, although this is also called afterfire. In this video we'll take a look at how an engine could have combustion travel up the intake.
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Afterfire (Backfire): • Why Cars Backfire - Af...
Ignition Systems: • Ignition Systems - Exp...
Carburetors: • Carburetors - Explained
Fuel Injection: • How Fuel Injection Wor...
My next video will be "afterfire." Be sure to check this out to see how combustion could occur within the exhaust.
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Пікірлер: 514

@EngineeringExplained 11 жыл бұрын

Yes, it's quite problematic if it starts coming back through the intake. Also, check out my video "why cars backfire - afterfire" which explains when flames exit the other way.

@EngineeringExplained 11 жыл бұрын

Yes, I've covered this in another video Check out the first link in the description "afterfire" to learn more about this topic!

@ps3shakes123 8 жыл бұрын

Nice job professor. learned more in the last 4min than I have in a lifetime of listening to various goofballs.

@jondi23 7 жыл бұрын

ps3shakes123 🤣🤣🤣🤣

@mustangmafia9195 6 жыл бұрын

ps3shakes123 your gay dude

@elontusk8018 4 жыл бұрын

Mustang Mafia it’s you’re

@BlizzardHockey4432 10 жыл бұрын

You need more than 189 thousand subs you deserve more great at explaining keep it up

@reuploadify 7 жыл бұрын

BlizzardHockey4432 He's at 1.24M 2 years later!

@vali69 6 жыл бұрын

Oliver Usher ye lol xd

@fidelcatsro6948 6 жыл бұрын

1.5 million now amigoes!

@MrNaufan 6 жыл бұрын

now 1.6 hell yeah

@Slossage17 6 жыл бұрын

Lmao

@gdltiii 11 жыл бұрын

Dude! I went to UTI and my favorite classes were the: drivability diag classes, electrical diag, but most of all the power performance classes. Granted its difficult to cover the material in only 3 weeks but i wish you had taught one of my classes. your videos are the cherry on top of my knowledge pertaining to these subjects. I should pursue mechanical engineering again.

@EngineeringExplained 11 жыл бұрын

Haha though I understand completely. I always wanted a channel like this to watch. Couldn't find seem to find one, so I made it. That way other people can be lazy and find out in 10 minutes rather than 3 hours how something works. From an efficiency standpoint, I think it's terrific; and efficiency is all us engineers care about haha :)

@jlopez65 4 жыл бұрын

Awesome explanation! I had a backfire problem along with rough idle, almost no acceleration power, and the engine would die on a 1987 Nissan Maxima. Problems all solved; 1.. Ignition Timing 2. Air Mass Sensor 3. #5 injector was stuck open 4. Bad Spark Plug wires.

@EngineeringExplained 11 жыл бұрын

Because the pressure may not begin to increase enough until it reaches TDC. Think about it like this. The piston is moving up VERY fast. You make the spark shortly before it reaches TDC. By the time the air fuel mixture is fully ignited and expanding, the piston has already hit TDC. It's all about timing it right so that you get the maximum amount of expansion.

@shamaYahu8635 7 ай бұрын

Hi, I have a 03 Jeep Grand Cherokee with a 4.0L that I installed a distributor to; kind of like the one you have on your drawing board. I also installed a carburetor. I don't believe that my valve timing is off because the 03 Jeeps have a timing chain and I never messed with it. I'm having backfires, and I believe it's the timing like you said in your video because the car gets ready to start but then it spits out flames or gush of are out the car carburetor, then the whole engine stops and I have to turn the engine over again.

@EngineeringExplained 11 жыл бұрын

Researching myself; check out my website FAQ (link in the description) I give a more complete, detailed answer.

@numinous4789 6 жыл бұрын

A better question: why do so many "car guys" wrongfully call afterfires backfires? Yep, they're two totally different things. As this video points out, backfires have to do with the "front" half of the engine, between the throttle plate and the intake valves, basically. Afterfires, alternatively, deal with the back side - from the cylinders and through the exhaust. Backfires are potentially far more harmful. Afterfires aren't nearly as harmful, but can damage catalytic converters. Most of the folks who have a lot of afterfiring going on are catless anyways, though.

@lukee49 9 жыл бұрын

Sooo... fuel injected cars can't really back fire?

@EngineeringExplained 9 жыл бұрын

Bayside Bluee Well, most people refer to back fire as flames coming out the exhaust, which can certainly happen with EFI. That said, the problem I'm speaking of in this video might still be able to occur with port injection.

@JohnSmith-xt7fz 9 жыл бұрын

Engineering Explained People also map in Pops and Bangs, but that's intentional over fuelling. Also have ALS and LC, that also causes 'backfires'.

@maxavatar3 9 жыл бұрын

+Bayside Bluee My saxo, has it's engine head worked on a.k.a the valves size so more gas can come in. but just a bit, before the engine heats damn it's noisy xD

@rmsvideos1335 8 жыл бұрын

+Nissan Supra AMG If its not direct, based off of what he said, it could still happen from a bent valve or misplaces spark plugs because there would still be some fuel. But even then I don't think it would be as bad because it would only be the fuel that was meant for that cylinder, whereas when its supplied through the carb there is a ton of fuel in there at any given time.

@victoraberdeen1299 7 жыл бұрын

I discovered just yesterday that fuel injected vehicles can and do backfire.The cause being faulty fuel injectors or faulty/incorrect coils.

@EngineeringExplained 11 жыл бұрын

Misfire typically refers to a cylinder not firing. For example when a cylinder doesn't fire it will throw a "misfire" code to your OBDII. The engine will be shaking.

@Sully9711 10 жыл бұрын

I'm a first year engineering student and this KZfaq channel just astonishes me with every video. I'm making all sorts of connections to knowledge I already have and it's explaining things I've always wondered. It may have helped me find my passion in engineering

@EngineeringExplained 10 жыл бұрын

Glad to hear it, thanks for watching!

@EngineeringExplained 11 жыл бұрын

You are correct in your description of detonation. It's not the same.

@EngineeringExplained 11 жыл бұрын

Great to hear, thanks for watching!

@Hanger995 11 жыл бұрын

You're A better teacher than A LOT of mechanics I know. I'm 17 and learning so much necessary information! Now I can talk 'car' with the fello motor heads on our race team.. Thanks man.

@EngineeringExplained 11 жыл бұрын

Sounds like a dream to me. Though this is done with nitrous where the mixture of N2O and fuel is sprayed together.

@EngineeringExplained 11 жыл бұрын

Delayed spark and some have extra fuel dumped into the exhaust manifold - hence the combustion goes all the way out the exhaust.

@EngineeringExplained 11 жыл бұрын

Absolutely, check out the "Automotive Careers" link on the "About" tab of my channel page.

@EngineeringExplained 11 жыл бұрын

Probably has a richer fuel mixture than on the stock tune. As far as if that's okay, not really sure. It's certainly not beneficial, but I don't think it would cause too much harm.

@EngineeringExplained 11 жыл бұрын

You're welcome, glad you enjoy the videos!

@EngineeringExplained 11 жыл бұрын

It's only 1 week away! I do appreciate that everyone is endlessly curious. I am too, but I'm just one man and have to pace my videos!

@EngineeringExplained 11 жыл бұрын

I'll go over those two in the next video. Cheers!

@Centigonos 11 жыл бұрын

You, Sir, are one of a few KZfaqrs who make this site worth visiting!

@MrAjallday91 11 жыл бұрын

Just wanna let you know that you've helped me out a lot...ive got an srt4 and there ain't a lot of room under the hood..im what you'd say "new" to cars. So you're videos really help me understands whats going on in the areas I can't see. I'm now addicted to your videos lmao HAVE A GREAT DAY!

@licarcar 11 жыл бұрын

dude, im studying engineering, your exploitations are way better than my lecturers

@EyebrowsMahoney 11 жыл бұрын

Backfires are more common on carbureted cars where vapors can sit in the intake plenum, however this can still happen in EFI equipped vehicles where timings are off or plugs are wired wrong and other situations (as explained in the video). They won't cause immediate failure, however they are liable to cause serious engine damage if you do not stop the engine and attempt to rectify the problem. Occasional backfires are common when diagnosing ignition problems and are not of an immediate threat.

@EngineeringExplained 11 жыл бұрын

There's no bad place for learning!

@EngineeringExplained 11 жыл бұрын

Rule of thumb, shift early for efficiency (as early as possible); shift late for power (as late as possible). This will probably be true for 99% of scenarios.

@oXelienanXo 11 жыл бұрын

I'm a fully qualified mechanic and I still find your topics and explanations very interesting!

@wonniewarrior 4 жыл бұрын

I have driven Dual Fuel (LPG / Unleaded) cars for decades. The older style gas injection through the carburetor would often blow out the air filter box if it backfired, which it did a lot with old style gas converters with a rubber diaphragm. Would install spring expansion clips for the air filter box so when it backfired, it would allow the air box to let the pressure out without destroying the clips, and even damaging stuff under the bonnet. I have not had the problem since I switched to cars with direct gas injection, or MPI with throttle bodies and fuel injection setup.

@gospodinkenobi9903 3 жыл бұрын

Ah yes, KZfaq algorithm keeps me up to date with new uploads!

@Psycho9263 9 жыл бұрын

Sometime raw gas fumes make their way out of the exuast valve when the timing is off or if you have a faulty ignition coil. The exaust pipe is all full if unburned fuel and when the spark returns, all the gas explodes in the exaust pipe. POW! We used to do that by turning the key off and on when we were kids.

@EngineeringExplained 11 жыл бұрын

Thanks! Glad you enjoy the videos!

@EngineeringExplained 11 жыл бұрын

Most of it in my 20's. I started getting more interested later on.

@xaviergarza9414 3 жыл бұрын

Not to much has changed in today's videos! Love it man

@aaronchristianson 7 ай бұрын

Not going to lie, I've been watching your videos for 10 years, but I especially enjoyed watching this video today. Literally a blast from the past!!

@Oblithian 7 жыл бұрын

Can you make a drawing illustrating exhaust crackle when letting off the throttle? (Not that it's a bad thing, it just sounds cool)

@gamer6654 6 жыл бұрын

Oblithian yeah that happens to mine as well, that's not considered a backfire, right?

@YachtLife 6 жыл бұрын

I believe that comes from fuel being dumped and firing off during deceleration

@mihan2d 5 жыл бұрын

@@YachtLife Why would you dump fuel on the modern EFI engine I wonder...

@YachtLife 5 жыл бұрын

@@mihan2d idk, go back a year and ask again

@jamesminner5861 10 жыл бұрын

You answered my belief that I'm trying to verify for my old dodge well. Thanks! Now on to confirm through fixing the wires. Great diagram and explanation.

@EngineeringExplained 11 жыл бұрын

Very welcome, thanks for watching!

@NellaTorre 8 жыл бұрын

Dude, you look just like George Harrison of the Beatles.

@carlosmoreno9094 3 жыл бұрын

No kidding, Dude

@david1235102 10 жыл бұрын

this doesn't explain why rotaries afterfire :)

@EngineeringExplained 10 жыл бұрын

Rich a/f mixture, unburnt fuel.

@user-by8ku4ls2o 10 жыл бұрын

Rich a/f mixture,unburnt fuel...for modern EFI rotaries ..its due to worn seals.

@TopiasSalakka 9 жыл бұрын

Γιώργος Ψευτινάκος Boost goes in, apex seals come out :D

@Slothayee 9 жыл бұрын

+David Schwab they have a 1mm gap in between the ignition and exhaust that let the compressed gas and air go into the exhaust pipe witch is smoldering hot

@65sgboogieman8 5 жыл бұрын

Right in the apex seals

@samhicks97 8 жыл бұрын

My 64 Dodge started backfiring/sputtering/no power. after a spark plug wire maintenance, found out that either my distributor cap is cracked or plug wires are incompatible. *Your video helped me where to look for problems with backfiring. Thanks!*

@Takeitlightly6 11 жыл бұрын

I am really proud we now have car nerds and engine nerds.

@sp00nix 11 жыл бұрын

I had my intake back fire in my face when i was adjusting the idle mixture. The directions had the direction reversed for turning the potentiometer so i accidentally made it super rich. This was on the crude Bosch LH 2.2 system (early 80s), it used a blinking LED to indicate mixture readings form the O2 sensor.

@dewalt607 11 жыл бұрын

Are you going to make the Redline video? By the way, honestly your such a boss, I really appreciate you making these videos, its soo simple and helpful. Thanks and keep up the fantastic work!

@Jabid21 11 жыл бұрын

Correct me if I'm wrong: a multi-port fuel injection system is less likely to backfire as air-fuel mixture is present near the intake port of one cylinder that's currently in its intake stroke.

@abdelkarimidris1130 11 жыл бұрын

What I used to know about backfire is that it is that fire coming out from the exhaust. According to what you explained it seems that this explosion happens inside the intake system, so why we see the fire coming coming out from the exhaust manifold?

@matthewisaacs7253 2 жыл бұрын

I think he referred to the out-the-muffler-fire as "after-fire" but it didn't seem to be the emphasis of this video

@SharkSugarr 11 жыл бұрын

Great videos, man. I really learn a lot! You're great at explaining things.

@custommotor 10 жыл бұрын

Actually Ziad Farghaly if the ignition is advanced too much (eg. a couple teeth off on a distributor) it can fire the spark early enough to catch the valve still open. It has to be extremely early, but I've had it happen on a 3rd gen camaro tbi injection. Lite the whole mixture up in the intake and backfired out of the intake. Newer cars would have to have the timing belt/chain put on wrong for it to happen which will blow the plastic intakes off.

@GermanGameAdviser 8 жыл бұрын

this channel is GOLD

@EngineeringExplained 11 жыл бұрын

Great to hear, thank you!

@shinzantetsu 9 жыл бұрын

OMG, i just found out about this channel. This is awesome... Love nerdy shit like this!

@EngineeringExplained 11 жыл бұрын

You are correct, most will not. And yes, I'll have the other story next Wednesday.

@oO0lechuga0Oo 10 жыл бұрын

Engineering Explained maannnn I came clicked freaking fast on this video because I thought you would explain after fire. I asked my teacher for the explanation and gave me your answer. PLEASE MAKE A VIDEO ON AFTER FIRE.

@EngineeringExplained 10 жыл бұрын

Why Cars Backfire - Afterfire - Explained

@jackthompson1382 11 жыл бұрын

Can you please make a video explaining reverse pattern cams vs. single pattern vs. dual pattern cams? With special emphasis on the reverse pattern cams (ie: the intake duration is higher than the exhaust) that are becoming increasingly popular due to better head designs like on LSx, GM push rod motors... etc. Thanks! You rock!

@EngineeringExplained 11 жыл бұрын

Thanks for watching!

@VinuraVinura 10 жыл бұрын

Can you please do a video on lift and duration and their effect on engine torque? Cheers, your videos are great!

@EngineeringExplained 10 жыл бұрын

Camshaft - High Lift and Duration - Increase Horsepower

@joripiano 9 жыл бұрын

Carbon buildup on sparkplugs can also be a problem. If the engine is used, hot, and you turn it off, the hot glowing carbon buildup can cause the engine to keep "running" while pinging/detonating. Mostly this will be 2/3 strokes and it will be all done, but sometimes the gasoline/air mixture can detonate to early, causing the engine to backfire. If your engine has a harmful amount of carbon buildup (pinging/detonating can be disastrous) it's best to just replace your sparkplugs. they don't cost that much anyway. If the new sparkplugs have to much carbon buildup after +-1000 miles, there is something seriously wrong with your engine. (burning oil, running too rich, worn out ignition system...)

@eventfulnonsense 9 жыл бұрын

Hi, I have that problem during summer time, The engine just wont shut down. And another thing happening, my idle is increasing every time I came from a long trip. Even if adjusted it down later, the same problem persist. Please help, thanks.

@youngtylerj 11 жыл бұрын

Video suggestion: Graph efficiency, horsepower, and torque vs engine RPM and explain when to shift for power or when to shift for efficiency.

@bullridermusic2054 6 жыл бұрын

Mate your channel is great, keep up the great videos!

@joshnaranjo4691 11 жыл бұрын

Backfire/after fire...correct vocabulary-learned som'th'n new.thnx

@EngineeringExplained 11 жыл бұрын

There are more collars and more gears. Check out my video "sequential gearbox." Similar idea.

@EngineeringExplained 11 жыл бұрын

To allow air to enter the cylinders.

@EngineeringExplained 11 жыл бұрын

Congratulations! Be good to her.

@Cardfold11 11 жыл бұрын

well thats quite impressive. it makes all of us seem lazy, you are doing all of the work for us haha!

@joshs6405 8 жыл бұрын

Sooooo.....my boss was telling us stories of back when when guys used to prank each other by making each others forklifts backfire. Something about revving them right up and then shutting them off, so that when they go to start em up they backfire. Idk, any explanation to this? And well, the only one that wouldn't have direct fuel injection would be the old Clark, which has 25,000 hours. So maybe not a good idea to try anything crazy....

@JohnDoe-zt3wr 7 жыл бұрын

That's because theirs a rich fuel mixture in the engine. When oxygen is added (Turning on the vehicle) the mixture combusts and causes backfire.

@JohnDoe-zt3wr 7 жыл бұрын

Revving the forklift will cause more gas mixture in the engine in the first place

@joshs6405 7 жыл бұрын

Oh I see!

@SamnissArandeen 11 жыл бұрын

Knowing how they work helps when you're trying to find the bad part(s) in the jumbled mess of a modern car.

@strungout25 11 жыл бұрын

Great videos! I learn something new every time I take a dump.

@denismorissette419 9 жыл бұрын

There is also another reason that appened with carb engine. When the engine is cold or during the warm up the fuel air mixture must be rich because fuel is not well evaporate and the droplet of fuel doen't burn well. This gives a poor mixture even if the carb deliverate the good amount of fuel. Remember, the engine is cold. A poor mixture burn slowly and during the valves overlap ( both intake and exhaust open) the flame come back to the intake manifold.(I've drive a lot of car with manuel choke a long time ago)Denis Morissette.

@lycanchimera 10 жыл бұрын

Hello EE. Thank you for putting this up!

@EngineeringExplained 11 жыл бұрын

Yep.

@CJforUSA 9 жыл бұрын

Thanks for taking time out of your day to share your knowledge with us.

@bitsurfer0101 6 жыл бұрын

what about when the engine is running way too rich?

@praneethvarma5158 6 жыл бұрын

You always make complicated things easy to explain. Thanks keep it up😀😀

@justindelvalle4361 10 жыл бұрын

@ tr3ning that is an after light or after fire from too rich of a mixture. Unplugging the rear O2 makes the ECU default to a richer Air to fuel ratio to save the engine. The rear 02 in most situation is there to monitor catalyst efficiency and be the final reference for the ecu to target stoichiometric ratio in closed loop and in open loop fueling it is ignored. Without the resistance value from the sensor it the ecu thinks its too lean and calulates a longer duty cycle to try and "correct" the issue. It adds so much fuel that it cant burn it all and it gets dumped into a hot exhaust pipe and it after lights or after fires

@blumac9801 6 жыл бұрын

I went GoKarting at Fun Depot and I had the fastest go cart cutting everyone off and drifting, and it started backfiring at the end when I had to stop, it was really really cool

@titojesusmane9540 6 жыл бұрын

Blumac5 they use gas gokarts?

@blumac9801 6 жыл бұрын

Tito Jesusmane yes, some are pretty fast too

@titojesusmane9540 6 жыл бұрын

Blumac5 that's dope, all of the karting places i've visited used little electric ones with like 15-20 horsepower max. Now that i have my beat up little straight piped 5 speed 2 door cavy i always feel like i'm in a go kart though lol

@blumac9801 6 жыл бұрын

Tito Jesusmane yeah, this one was sooo fast, I think if the track was straight it would have a top speed of 20-30H

@titojesusmane9540 6 жыл бұрын

Blumac5 sheesh

@kristibutterflykirk1 11 жыл бұрын

Oh, OK. Well, I live in the Southern US and I have never heard of a roadside mechanic. Sounds like something I might can look into.

@redliner90x 11 жыл бұрын

Unburned fuel that lights up by your hot exhaust. Notice how cars usually shoot flames out when they were flooring it and let off or flooring it and during a shift? That's when the throttle is let off and some unburned fuel gets into your exhaust.

@kiithsjet2 11 жыл бұрын

Well, if the engine is rotating at a given rpm, it's consuming a certain quantity of air. The computer injects a proper amount of fuel for that quantity of air. When rpm's drop, it takes a moment for the computer to reduce fuel delivery so the engine runs rich for a moment. during this time, theres more fuel in the engine than can combust. when the hot unburnt fuel exits the exhaust and mixes with fresh oxygen, it ignites.

@shaveendesilva189 4 жыл бұрын

now this is "teaching"

@royaldurham4417 7 жыл бұрын

idc what anyone says this dudes the GOAT

@kristibutterflykirk1 11 жыл бұрын

That's because mechanics are taught how to change out parts on cars. Mechanical Engineers are taught how the parts work and designed at how to build the parts and even come up with ways to change/improve those parts or design entirely new parts.

@EngineeringExplained 11 жыл бұрын

I'd agree.

@giorgos2710 11 жыл бұрын

you are gonna to find out in the next video,he said it in the description

@matthewisaacs7253 2 жыл бұрын

Had you considered the scenario where the carb is running lean and the air/fuel mixture ignites before the valve sending fire back to the carb ..... quite common with a pair of Dellortos in a VW Bug

@DeVoN420zz 7 ай бұрын

People also literally put spark plugs in the exhaust housing and a purge solenoid was originally used in rally racing and is installed inbetween the engine and turbo as a crude anti-lag system to create small explosions that keep the turbo spinning under the correct turbine manifold pressure with a wastegate pressure regulation device and blow off valve in the turbine air supply pipeline

@francisowa9818 4 жыл бұрын

Perfect Engineering it's quite understandable well done good lecturing

@EngineeringExplained 11 жыл бұрын

I'm an application engineer for a forklift company.

@dcaonoek 11 жыл бұрын

What you are talking about is the same as this gentleman said at the start. It's called an after fire. A "back fire" is the name given to a flame accidentally propagating "back" up the intake path. In the example you have given, it is caused by a rich situation where not all the fuel can be burned. In cars with turbochargers it is often the a fault of poor ECU mapping linked to a atmospherically vented Pressure relief Valve "Blow of valve".

@clarakoussaifi203 11 ай бұрын

Very informative! Thank you :)

@ChutneyInc. 11 жыл бұрын

Wow I finally learned an advantage of direct injection! Thanks man!

@AllenGeiger 6 жыл бұрын

Forgot to mention throttle body injection. Not very common, but has an air/fuel profile in the intake very similar to a carb engine and would also be susceptible to backfire

@Adrian_The_Great 7 жыл бұрын

Cars with electronic ignition and therefore no ignition caps, the ones of them which are not equiped with a camshaft position sensor produce a lost spark (aswell as a lost injection pulse) at the end of the exhaust stroke as the piston moves close to TDC, by the time the intake valve opens. And you dont have any backfire with them. In fact, if you remove your camshaft sensor your car should still be able to run properly. And it would do 2 sparks per cycle per cylinder as the ECU has no way to know where the engine is on the cycle.

@midlan6 3 жыл бұрын

I heard about backfire (and explosion of intake as result) when bump starting the vehicle moving forward with accidentally in reverse gear.

@Seyoum14 11 жыл бұрын

Yes please, I'm looking forward to that video.

@so1vae 6 жыл бұрын

I’m new to cars, why is it bad for a car to backfire?

@Jacrazzz Жыл бұрын

It's not bad only if it back fire out the intake that's bad

@kitty13kitty 7 жыл бұрын

Missed explanations: Hot stuff in your engine. -- Having a large enough burning ember or hot spot inside your head/stroke can cause it to sneeze when the engine is breathing in. Broken spark plug and/or wire. I do not know how many times I have personally heard an engine sneezing just to do test #1, check all plugs and wires. (normally followed by a compression check in each cylinder) It'd be nice to have a "todo:" list that goes with common car problems as people might find this video but be looking to diagnose a problem they are having.

@User-nu6km 9 жыл бұрын

for high angular speed (rpm) race cars engines like f1 engines, overlapping intake and exhaust valves cause this phenomenon

@runalongnowhoney 9 жыл бұрын

I am trying to understand why my single-cylinder (492cc) air-cooled motorcycle engine sometimes backfires through the carb. It usually happens on re-starts, with the engine at normal operating temperature. Compression checks in tolerance. Valves look fine (visual inspection through each port). New Spark Plug. Main and Slow jets have been increased in size to match free-flowing intake and exhaust modifications.