Bike Smoking when coming off revs, Rider behind said smells very rich after new

[Eric GSX1400K3]

Thanks fellas, will try the carb cleaner thing, mate across the road has a smoke tester, may borrow that. Can't see any cracks in the intakes, but worth a check.  Also agree re mechanical, as timing, comp etc is good.  I always thought popping or noise back through is a rich mixture, as its detonating too early from too much fuel during valve overlap?

[KiwiCol]

You'll be glad you don't have a Gen 2 Rocket Eric, they pop & bang on decel all the time.  I quite like it, doesn't bother me at all, just part of the bike. I know it annoys some of the guys & they can basically eliminate it by adjusting the A/F values in the custom tune.  I've no idea on that as I've never had to it (was already done on my bike),  but, if adjusting the A/F values fixes it, maybe a PC5 or PC6 with auto tune will sort it?

[Hooli]

I believe a lean mixture can cause it too as it's running hotter and the gasses are that hot they ignite the oxygen they meet in the exhaust as they leave the cylinder. Hence a leaking exhaust often backfires where the fresh air gets in.

Same reason 14's pop & crackle less on the overrun once you get rid of the PAIRs too.

[Eric GSX1400K3]

Firstly, Apologies to the op for the hijack.

Two new areas for me to check: leak from exhaust (Akrapovic headers) and inlet trumpets where the throttle bodies mount.

[Hooli]

Firstly, Apologies to the op for the hijack.

Two new areas for me to check: leak from exhaust (Akrapovic headers) and inlet trumpets where the throttle bodies mount.

Pairs plates or the blanking plates too, as they link to the exhaust ports.

[Xdiavel]

Firstly, Apologies to the op for the hijack.

Two new areas for me to check: leak from exhaust (Akrapovic headers) and inlet trumpets where the throttle bodies mount.

No problem at all Eric, If it gets everybody chatting and passing ideas around then the Forum is doing it's job imo.

The only time I have heard of popping etc back through the intake especially on carbs was the timing being way out of wack. Has that all been checked ie cam shaft marks all line up with the crank gear etc.  It hasn't been fitted with an ignition advancer etc  has it over the years?

Chat GPT has some suggestions,

A GSX1400 popping back through the intake manifold typically points to an issue with the air-fuel mixture or ignition timing. This "backfire" or "pop" can happen under load, during deceleration, or when the bike is idling. There are several possible causes for this issue:

1. Fuel System Issues:

Leaking or Blocked Fuel Injectors: Dirty or clogged injectors can cause lean conditions, which might lead to backfiring. If the fuel supply isn't adequate or consistent, it can cause unburned fuel to ignite in the intake manifold.

Incorrect Fuel Pressure: If the fuel pump is weak or the regulator is malfunctioning, it could result in too little fuel getting into the combustion chamber, causing lean running and backfiring.

Air/Fuel Ratio Problems: If the air/fuel mixture is too lean (too much air, not enough fuel), it can cause combustion to occur at the wrong time, leading to backfiring through the intake.

2. Ignition Timing:

Retarded Ignition Timing: If the spark timing is too advanced or retarded, the combustion event can happen at the wrong point in the engine cycle, causing pops or backfires through the intake. This could be due to faulty timing settings, a malfunctioning ECU, or issues with the ignition system.

Faulty Spark Plugs or Coils: Worn spark plugs or malfunctioning ignition coils can cause weak or inconsistent sparks, leading to incomplete combustion, which could result in backfiring.

3. Vacuum Leaks:

Intake Manifold Leaks: A vacuum leak in the intake manifold or any of the vacuum hoses can lead to unmetered air entering the engine, causing a lean condition and backfiring.

Throttle Body or Carburetor Issues: If the throttle body isn't sealing properly or there's an issue with the carburetor, the engine could get excess air, leading to lean misfires or backfires.

4. Exhaust System Blockages or Leaks:

Exhaust Leaks Near the Head: If there's an exhaust leak near the cylinder head, it could allow exhaust gases to flow back into the intake, causing popping sounds.

Exhaust Valve Issues: Worn or damaged exhaust valves can result in incomplete combustion, allowing fuel to pass through the exhaust system unburned, which could cause backfiring.

5. ECU or Tuning Problems:

ECU Mapping: If the bike has been tuned or modified and the ECU mapping is incorrect for the new setup (e.g., aftermarket exhaust, intake mods), it could be causing the engine to run lean or rich, leading to backfires.

Fuel Map Issue (for carbs or fuel-injected bikes): Incorrect fuel maps due to a bad tune or sensor malfunction could also be responsible.

Diagnostic Steps:

Check the Spark Plugs: Look for signs of lean or rich burning on the plugs. Replace any plugs that look worn or damaged.

Inspect Fuel System: Check the fuel injectors, fuel pressure, and fuel filter. Make sure the fuel is flowing properly.

Check for Vacuum Leaks: Inspect the intake manifold, hoses, and seals for any leaks. A simple smoke test can help locate leaks.

Verify Ignition Timing: Make sure the timing is correctly set. If you're using an aftermarket ignition system, check that it's programmed correctly.

Examine Exhaust for Leaks: Look for any exhaust leaks, especially near the cylinder head.

[Xdiavel]

Ok,

So Today's update   
i bought an iridium spark plug just to test on one cylinder and give it the best chance of combustion. I ran Her up on fast idle and let it tick over for several mins and took a look in the hole. No change seen.

I then thought lets eliminate fuelling out of the equation once and for all, so I ran the bike with the injector unplugged and no spark plug to see if I could clear the wetness off the top of the piston and yes the crown went pretty much dry.

I then put the plug back in but left the Injector unplugged and ran it for another several minutes and removed the plug. And yep the piston was wet again. Trouble is the oil is new and clear so hard to differentiate but it can only be oil at this point.

So the only option is to carry on the running in process, Prob next year now as winter has turned up with a vengeance. If that fails which I am pretty much 90% sure it will then I am lost as to what it is!!!

 

[Eric GSX1400K3]

Good elimination process.  AFAIK The only oil passages to the combustion chamber would be via the crank case vent port to the airbox and in, or via leaking pairs, past the rings or valve stem seals.  The latter two i think you've sorted (apart from the bedding in).

Are the rings gapped correctly and gaps offset to each other?

Correct size oil and compression/sealing rings (and in the right order on the piston skirt?)

Try venting crankcase to atmosphere and blocking the airbox inlet point, check for oil inside the airbox.

Maybe an Italian tune-up up after the 1000km running in?

Best of luck mate

[grog]

No more ideas either Xdiavel. Madness. A crack in head, wouldnt be all 4 cylinders.My whole mechanical life, 1972 started apprenticeship, this one has me stumped. Has to be an answer.Its oil in each cylinder from running the motor. Youve blocked the usual culprits, rings&stem seals. Cant see how pairs can possibly contribute oil. Motor breathes good? No crankcase vapour getting in? You eliminated fuel by disconnecting injector.Mate,nothing left except the mongrel thing causing the problem,mongrel thing that i cant see possible.

[Eric GSX1400K3]

Oil grade being too thin that it doesn't get scraped off the bore and ends up on the piston, rings not gapped right,but then compression would be shite, or oil getting past valve stem seals is all I can think of.

Do you see oil even when its at temperature?

[Xdiavel]

Oil grade being too thin that it doesn't get scraped off the bore and ends up on the piston, rings not gapped right,but then compression would be shite, or oil getting past valve stem seals is all I can think of.

Do you see oil even when its at temperature?

Hi Eric,

It has Mineral running in oil at the moment but before I was running 10w 50 and still did it. All the rings are OEM and spaced correctly. The valve stem seals were all OEM from Fowlers also.

Crank pressure is ok out the pipe, not as much as if you take the filler cap off but then it's not supposed to be. I have blocked the outlet out of the Airbox for the pairs to eliminate that and the airbox inside is like new.

It's all very weird

[Eric GSX1400K3]

Definitely weird thats for sure.

[seth]

Just a thought have you checked the 2 small o'rings that sit between the head but above the pairs valves as they have been known to cause problems and oil in the pairs/valves area in the past 🤔🤫

[Xdiavel]

Just a thought have you checked the 2 small o'rings that sit between the head but above the pairs valves as they have been known to cause problems and oil in the pairs/valves area in the past 🤔🤫

Hi Seth,

Yes mate that was the first bit of troubleshooting I did last year when I first noticed this issue. And also replaced them again during this rebuild to make sure.

Another test I did this weekend was to remove the oil filler cap to elliminate the crank case pressue but alas there was still wet pistons at the end of the test.

I also ran a borescope down the intake to look at the inlet valves and they were bone dry and lovely and clean,
So after all this I would now say 100% it is not coming from the Top of the engine.
All my hopes are now that the running in the oil conrol rings solves this.

To add to this when checking the throttle bodies I manually moved the flaps to get a reading and the sensor was in range. Although the flaps were 3/4 shut. Now it runs all over the place on cold start for some reason. The night before it ran ok but went out the following morning and would start up to 2k rpm the instantly drop to 1100rpm and the Fi light comes on.

My biggest worry now is that I have had the tank.plugs/panels off so many times now I am going to break something else. I mean the tank nearly fell of the bike the other day and nearly gave me a heart attack as I just caught it. (Full tank too)

I just want to sort this new issue and put it away until next year as have grown a real hatred for it atm lol.

I keep looking at other retro style bikes but nothing comes close imo I like the Kawasaki 900rs but with the 1400 you have an original and a big engine to boot.

[grog]

Mate, run it in hard,off n on the throttle,was our old story, change oil, drain cooler as well, if it still smokes, trade it in. Its a bit like marriage, if you try your guts out, you have, still doesnt work, start anew. Cost me a house but best move i ever made.