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Discussion Starter #1
See video here:


This problem started last year.. But not really a problem at the time. It only backfired/misfired very few times...

Now after 6 months of no use, it really got bad..

It sounds like it backfires / making small *poofs* into the airfilterhousing.
When engine is cold there is no problems. (cold start). The first misfiring/backfiring starts about 3-4 minutes after the engine is started from cold. Then it only gets worse, the warmer the engine gets.
Above 2000 rpm there is no problems at all. Engine runs good and pulls great. It only happens below 2000 rpm / idle.

- Problem occurs when engine is getting warmer.
- Problem getting worse, the warmer the engine gets..
- When engine is warmed up to operation temp, the engine sometimes stalls because of the bigger backfires...

I have inspected sparkplugs, coils, every single wire and plug on the entire motorcycle, meassured the resistance in every sensor, coil, rectifier, and so on. All withing specs according to the manual..
I tried disconnecting the powercommander, with no luck.
A long shot, but tried re-install the O2 sensor. No luck.
Also new vacuum hoses, and fuel lines...

What is wrong?
 

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Discussion Starter #3
Oh yeah, forgot about that... All fuel system has been inspected, tested, and cleaned. Pressure, regulator and so on are testet... New fuel filter...

I think the problem is ignition related...
When I think about it, I only tested the coils when cold. But the problem only occurs when warm.. Didn't thought about that... I will check them tomorrow again, when warm...
 

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Oh yeah, forgot about that... All fuel system has been inspected, tested, and cleaned. Pressure, regulator and so on are testet... New fuel filter...

I think the problem is ignition related...
When I think about it, I only tested the coils when cold. But the problem only occurs when warm.. Didn't thought about that... I will check them tomorrow again, when warm...
seems a logical idea, interested to see how this one pans out. Don't be afraid of taking it back to honda you know... they are pretty good at this stuff
 

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Discussion Starter #6
OK - So I it backfires on cylinder 3 and sometimes cylinder 1... Very clear to notice when the airfilter housing is removed.

- Tried to switch coils around to different cylinders; no luck

- Did the same with fuel injectors; no luck.

- Then switched the cylinder 3 spark plug to cylinder 2; Feels like it only would backfire on the left side of engine (cyl 1 + 2)

- Then tried to switch around coils again, but left the spark plugs in place; Still cylinder 1 + 2...

I think I found the issue - 2 spark plugs.. I'll order some new.

But they have only been in for about 5000 km. Thats not normal for iridium spark plugs to go at only 5K km.
What could cause this ?
 

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Heeza Y Zasch
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What could cause this ?
Blowby (low compression) and/or valves being out of adjustment.

A former riding buddy of mine had a neglected 954 and it wouldn't run on 4 during cold(er) months until it warmed up. Valves were WAY out of adjustment and compression down by 35%. After it warmed up, ran a bit smoother, but often fouled plugs.
 
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Discussion Starter #9
Blowby (low compression) and/or valves being out of adjustment.

A former riding buddy of mine had a neglected 954 and it wouldn't run on 4 during cold(er) months until it warmed up. Valves were WAY out of adjustment and compression down by 35%. After it warmed up, ran a bit smoother, but often fouled plugs.
Funny you say that... I did the valvejob on my bike this winter.. 11 of 16 valves, were way to tight... Luckily no valves were burned or damaged... I don't think this bike got the valves checked since it was build.... They are now in specs, so hope the new sparkplugs I just ordered, will hold up a little longer...

Really hope thats the only problem.. Going to Slovakia in 2 weeks for a 4-day-race... So the bike needs to be in shape :)

Last year on Anderstorp Raceway in Sweden :-D
 

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Talking to another 954 owner at Squires Cafe last year. Low power on pull-away, so he stripped the engine out with a mate, checked it all, reassembled and it still had a sluggish take-off.
Replaced the plugs (not cheap over here) and hey presto - problem fixed.
Red faces and dirty hands, but who was to know?
 
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