This bike is driving me crazy!!!

[centaurus]

First it died while riding on the other side of the city. Apparently I was riding it too soft (it's a 2 stroker) so the plugs got fowled. I change the spark plugs, and the next time I took it out, after allmost two hours of riding, I felt like the power was going away bit by bit; the bike allmost died. With superhuman efforts I managed to keep it alive (barely kicking, even in the first gear) till I arrived home (I was close by). The next day I started diagnosing and I thought I got it: one cylinder is not firing. I thought I noticed that one of the exhausts was expelling only cold fuel mixture instead of real hot smoke. I assumed I have a wiring problem at the faulty plug. Planned to fix it after the holidays.

Left for holiday for 3 weeks. Today, after I came back, I tried to replicate the problem (I forgot which was the "bad" cylinder) and it worked well. I thought I noticed one of the pipes getting a little hotter that the other and smoking more (especially accelerating hard after idle and when cold).

At this moment I'm even scared to ride it. I live up the hill and if it dies somewhere on the way, I will have to find a car with a trailer hook and rent a trailer to bring it home, even if it's two blocks away. EDIT: when it dies, it dies at idle. If it's revved it works (more or less), but as soon as it's at idle, it goes dead, and to start it I have to keep the throttle open.

Does anybody know what/how could I test or what to look for, what could it be? Or my only chance is to take to a professional? Or is any of you knowlegdeable enough and in Wellington area to have at look at it running and tell me if it runs ok or it really has some issue? I'll jump with a beer (or more )

Thanx in advance.

[SlowHand]

Mate had similar prob on his ns250r I thunk. Wanted a new CDI.

Take it to a shop?

[imdying]

Sounds a lot like a worn out and ready to pop problem. Time for a top end rebuild most likely. Do it before it blows up, if you melt a piston into the barrels, that is heaps heaps more $$$ than new pistons and rings only.

[centaurus]

I bought it in november, so I can't guarantee on it's history, but according to it's former owner, it has has a top end rebuid somewhere last year (not too many kms ago). Also I don't think it's a top end, because it can work perfectly and pull really hard for one hour or even two, and then suddenly, looses power and does not hold the idle.

[Posh Tourer :P]

Your charging system is bad? Are the headlights dim? Or flickering at idle?

[centaurus]

No. The lights are ok even when the problem apears. and it appears to be on only one of the cylinders. I was suspecting a faulty wiring to one of the plugs (a cut/loose wire that comes off sometimes). Is there any way I can check if a plug gets power?

[nsrpaul]

cylinder fowling?

check they conecters to the coils

[Posh Tourer :P]

you can take the coil in for analysis - is it twin coil or single twin output coil? Get any car mechanic to read the voltage off it....

And of course, the obvious, change that spark plug. It may be cracked or faulty.

[centaurus]

Today I started it again. As soon as the engine warmed up and I turned off the choke, it died instead of idling. I left it for 2-3 minutes and started it again (with half throttle) and revved it's neck off for 5-10 seconds and it idled correctly.

I took it for a ride for a little bit over an hour and it worked fine, but the power was not what it used to be - it was a little bit softer. After more than one hour or riding, I felt it losing power again, I pulled on the side of the road and - of course - it wasn't idling anymore; as soon as the throttle was off, it died like when without gas.

CONCLUSION: from time to time, it just loses most of it's power and doesn't idle. Most of the times when this happens (but not always), one of the pipes smokes much, the other one doesn't smoke allmost at all (expels hot air, but I am not sure it is smoke and not unburned fuel mix).

Tomorrow I will try emptying the fuel tank and changing the gas, who knows... At this point I have no ideea what to do. Until I fowled the plugs and had to change them (50-100 k ago), it ran perfectly. Now, all of the sudden it runs like shit.

[Ixion]

How did you foul the plugs. and what is "smokes much". A two smoker with pump correctly adjusted should produce a thin, just visible haze of smoke when revved hot.

[centaurus]

Apparently I was running it too soft (revving it under the power band - only 3-5k rpm). As for the smoke, when it happens, it has a visible smoke, almost all the time (revved and at idle), not just a haze (like when it has too much oil for example). But this happens only when it goes a-wall. when it's rideable, both exhausts have the normal "just visible haze" when revving.

A, and by the way - now I'm riding it in the power band: around 7-9k rpm usually.

[Ixion]

OK. So, we deduce that the problem is caused by overoiling. For some reason at times the cylinders will receive excess amounts of oil. This will cause misfiring (or no firing at all) and loss of power, and foul plugs.

So the question to be addressed, is what is causing overoiling

Possible things to check

Failing crankseals (suspect if the right hand cylinder smokes more than the left, assuming the primary drive is on the normal side)
Defective oil pump
Oil pump cable catching, or jamming, or the oil pump metering arm catching or sticking.
Defective check or non return valves

Possibly others, I'm not familiar with the Honda lube system, but I assume it follows normal two stroke lines.

Or, perhaps the lube system is set up to provide excessive oil and the excess simply builds up.(it might have always been thus, and you did not notice it before, because you were riding so gently. The oil delivery quantity varies with revs)

Anyway, check pump settings, cable (very carefully, and recheck again), metering arm operation.

If that produces no results, consider having a crankcase leak down test done.

EDIT I assume that you have double checked that you have the correct grade of plugs for the type of riding you are doing. I always reckon two strokes need three different grades for different riding occasions. Though who can be bothered changing them al the time.

[Posh Tourer :P]

Also, the problem didnt exist until the plugs were changed - If you have the old plugs, get fine sandpaper, and sand the surfaces (or get a new plug). Try replacing it, as the plug you just put in may be faulty and the insulations breaking down when it gets properly hot.

[FilthyLuka]

just in case, check the spark plug spacing (using a feeler gauge). Im not familiar with this particular ninga ninga but if the space is too small, the spark will suck, bad combustion when cold. once it warms up, combustion becomes easier (thermal effeciency blah blah, you've heard it before no doubt) and a suckfull spark will probably be enough to ignight (CRAP!), light the mixture. Its unlikely but better safe then riding an underpowered, tempremental honda (hehe...).

If you have no idea of service history you might wanna replace rings sometime soon and get the barrels honed.

out of curiosity, what fuel are you putting in? (91, 96, 98, 101 ect ect)

[centaurus]

Aparently I'm using the race plugs, and the guy at the shop told me they are the good model for my bike. Also there isn't a hotter version (I think mine are 10).

I'm putting 95 or above - the highest I can find (usually 95). I know 2 strokes don't get along too well with low end fuel.