poor running!?

[noidea]

Was thinking this also. Im pretty sure its not the head gasket... cant hear any hissing. Dont think i have intake manifold leaks. Ill have to check the exhaust. But it definantly shud run better than this even if it was an exhaust leak.

Im begining to think maybe the timing marks are out of whack? Anyone ever seen this as a problem?

cheers for the ideas linc, all helps.

 

[cranga]

You did not get your cam gear mixed up between motors? As i noticed that lifan and ducar have a fair size difference. But argh! you must be more patient than me! i would have launced it off a cliff along time ago!

 

[noidea]

Yea, its the right gear.... I double checked that. Ive tripple checked (atleast) everything elso so ill check that again lol. otherwise its 138cc time.

 

[Redstar]

When technically-inclined noidea runs out ideas, this is a genuine problem, lol..
and I'm happy to be of help although reading through the thread, Im out of ideas except one.

Just for the sake of covering "most bases", change the fuel in the tank to be sure there's no water in it.

The symptom from the vid is very similar to how my friends bike was.

This does not expalin the low compression reading though.

Just might be worth a try. I'll be on figuring it out during the day and see what else I can come up with. Cheers mate!

 

[Linc]

About a million years ago I had a VW Golf GTI Mk1.......with a head leak. It only reared it self at some rev ranges......see intake pressure out weighed volumetric pressure (i think thats how you say it) that ment that on the intake cycle the engine actually sucked the leak shut; but at some particular rev ranges where harmonics came in to play it would just die without notice then get itself going again. It sounds just like your problem......Pressure is building somewhere and its getting to a point and then shitting it's self..........I'm pertty sure of it.

Do me a favor.....over torque the head and intake manifold, take off the valve covers, place a cloth cover over both valve covers (so it can breath) and start it. I really dont think you will hear a leak but the results of this little experement may give you hint s as to what the problem is.

Linc

 

[noidea]

Just torqued it all up, to what i felt was as tight as they wud go without stripping. Did the exhaust, intake, head studs and barrel bolts. Took off the top valve cover and it all sounded fine.

Then i had a bit of a play around with the valve timing. Retarded it two notches and there was not much of difference, then advanced it one and it ran even worse.

Sprocket is the right one, the timing notch wasnt moving around.

Im stumped now, have no idea at all what could be wrong!

thanks for the idea, and keep em coming... i got nothing.

 

[mjc85]

Ok i know this sounds stupid, but you never mentioned changing the circlip to a more leaner setting. You mentioned the plug was fouled with carbon and that you tried a mates carby, but did you try a leaner carby setting ?

 

[Linc]

So to revise........

The problem is intermitant and indiscrminate.

It can't be timing.....its either out of whack or it aint.

We know it's not electrical as you have changed everything.....ummm screwy CDI??????

Your either losing compression or you didn't have it in the first place.

Not an intake,exhaust or head leak........broken ring?????

 

[noidea]

Problem: Bike has intermittant power, 90% time it seems to be misfiring badly, then will occasionally kick in to max power.

Remedies ive tried:
Spare coil
spare cdi
replacement stator
spare ignition lead
new spark plugs (multiple)
Spare carby
Timing has been set either side and dead on the timing marks.
Engine rotated one revolution then cam gear bolted back on.


So ive ruled out:
Carby, electrics and timing.



Compression is the only thing left to wonder about. I have done a compression test and got 100psi using a push on type and kicking the engine myself (not very acurate). The engine seems to have plenty of compression when kicking it over.

Broken ring? I guess it could have happened but unlikely as i reoiled the bore upon reinstalling it and did not take the rings off the piston.
Maybe i didnt put the rings in the right position? I put all three gaps at 90 degress from each other like this

l
/ \

keep them ideas coming...

 

[pugs5l]

hi im new round here and just getting into these things, is there any way the pickup timing could be 180* out? probably stupid question.

 

[cranga]

i know youve pretty much exhausted electrical possibilities, but a new loom? possible earth shortage?

 

[noidea]

will check over the wiring, but wiring faults usually expose bump related intermittance...

its the only thing left that i havent checked. cheers

 

[noidea]

pugs its pretty well pointless as i think these engines fire at tdc no matter if its a compression stroke or not (waste of spark energy??) but i did try it. You will see in my other post i took off the cam gear and turned over the crank shaft.

 

[pugs5l]

yeah sorry read that after i posted