Lifan 125cc (need help)

[Daz's Detonator]

Hi all, just need some advice as to what might be wrong...
A few months ago i had my engine put in for repairs and a rebuild. It turned out that the crankshaft had been slightly knocked off of its original axis causing problems with the clutch disengaging and making a lot of whirring noises. Anyways I got the engine back and was super stoked, the performance was better, the pickup in revs was quicker and everything was cool. Then i went riding with a mate about a week later and we came to some water crossings, it wasn't much deeper than the bashplate but three or four days later the engine started playing up by having very little compression and not being able to gain revs. on top of this there is a really strong smell of raw fuel coming from the exhaust. (at first i thought it was just running too lean but i have adjusted the carby and even swapped it with another one but still it has the same problem.) Dad said it could be the valve but we have checked and there does not seem to be any real damage.

Any suggestions would be greatly appreciated.
Cheers, Daz

 

[thump*140]

hmm... bit hard to tell whether it is all related, but it is *possible* that it sucked in some water, and "hydraulic-ed" the motor and perhaps bent rod or piston... unlikely, but possible..
the raw fuel smell coming from the exhaust, is this when the motor is running i presume?
could well be bent valve then, meaning not all fuel is being burnt in the firing stroke, and is escaping through a poorly sealing valve. would also explain sudden drop in compression...
might pay to pull the head off and have a looksee

 

[headsmess]

or a damp cdi/wiring system... remove flywheel cover, get a hairdryer. pull all plugs, get some wd40...

fuel needs spark to ignite...

but compression... blowing smoke?then the rings are stuffed(probably wasnt honed)
making a squeaky noise around the head when running? head gaskets blown or studs havent been torqued up enough...

or some fool(read apprentice cough cough ahem) hasnt retimed it properly and a valve has bent...or might just need regrinding to seat in properly...

could even just be the sparkplug has broken its ceramic or decided its time to retire...