Trouble with timing Lifan 140

[outtacontrol11]

Hey I've been trying to time a lifan 140 after replacing the head, now the bike is starting every now and then but sounds pretty terrible. I've try'd to time it with the timing marks to no avail, I've tried to move it up one tooth and then back a tooth but I am having no luck whatsoever, except flames coming out of the air filter.

Is there a way I can tell the compresion stroke from the exhaust stroke?

When the cam is at TDC it has some free play left to right, should this be in a certain spot?

Any help would be appreciated.

 

[mad mick]

you could try and work it out i dont no the engine your talking about but you will be a tell but trying to set it up buy finding when it will fire a spark some times you can do that with a test light on the coil and bu looking at where the pick up is to fire the coil that will be compresion stroke you can work out tdc of the bottom end with a pice of wire in the spark plug hole when it stops moving up and gust before it starts heading back down is tdc the can is not that hard as the strokes are suck push bang blow or intake compresion power exhaust where the valves are will tell you wher the top end is piston going up all valves closed compresion valves closed piston going down power piston up exhaust open exhaust piston going down inlet open intake also at the end of exhaust and start of intake the valves will rock if you turn the botom end back n forward

 

[pbk]

yes on TDC you can rock it back and forward slightly

also take off your valve covers and when you think you have TDC and you can rock it back and forth neither valve should move, also take out your spark plug and put a small screwdriver down the hole and turn the stator over by hand till you feel the screwdriver being pushed by the piston to find the exact TDC

 

[sean01]

yep i would recommend using a screw driver to find the true TDC, i have seen some flywheels a mile out..

the bottom end has 2 TDC's and the cam only has 1, so it doesnt matter which one it is on on the bottom end... the cam is what gives the compression stroke..

piston at TDC and the cam gear dot at 9 o'clock.. and like pbk said..to find TDC of the cam neither valves should be moving cause when its 180 degree's out one valve will just finish closing and the other starts to open..

 

[outtacontrol11]

hey, thanks for those replies, I am still having the same problems after attempting to time it a few times today. I have tried it lined up with T on the stator and lined up with F on the stator and still no closer. Would I have symptoms like blowing fuel out the carby, only firing for about 2-3 seconds and also kicking back really bad if the valves were bent or burnt out?
I am now thinking it has something to do with the valves not sealing or seating properly.
Any help on this would be fantastic.

 

[sean01]

forget the T and F marks, do as posted above to find the true TDC

and depending how bent the valves are the engine should still run..
if they are bent you will notice really bad valve clearance( it will be more)

blowing fuel out the carby means you have the timing way out, not just a tooth or 2 either

 

[outtacontrol11]

thanks for that, i'll try again tomorrow.