rd125lc mk1 not starting after rebuild

[ferret79]

hi
i have recently rebuilt my rd125lc mk1, it has a 2mm oversize piston, but a standard size head gasket, is this right or do i need a bigger head gasket?
also i have fitted hi-tech racing reeds / k&n filter, and it has an allspeed exhaust,
tried to start bike after rebuild, and did'nt go well.
it pops and splutters lots!!
will not start buy kicking over on kick start, only bump start,
then runs like a bag of nails, like its not firing correctly, will not run for more than a few seconds, and also revs very high so i have to quickly stop it using the kill switch or key. the woodruff key on the shaft for the flywheel also broke in two which i had to replace,
i know the timing cannot be adjusted but it sounds like the timing is well out.
i get lots of pops and bangs, like back fire..
could it it be anything like a cdi box?
or the pick up down by flywheel?
your help would be much appreciated
i dont know what to try or where to start,
thanks very much

[ferret79]

thanks for the info,
ive checked , checked and re checked the carb, everything in carb all cleaned and checked according to the haynes manual , and today rd sheared yet another woodruff key for the flywheel , so thats 2 keys its broke. each time stopping sparkplug sparking,
any help or advice on this woodruff key breaking would be a great help..
thanks once agian

[andysh2]

Check the taper on the crank the woodruff keys there for positioning to stop the flywheel spinning on the taper, The taper should hold the flywheel.

Cheers Andy.

[pablo]

did this bike run before the rebuild or did you buy it as a non-runner?...sounds like maybe you have the wrong flywheel? Failing that it sounds like the flywheel is not seating properly which could cause the timing to go out when the flywheel spins off your crank.It shouldnt keep breaking keys.

[ferret79]

hi ,
i brought the bike blown up, some 17 year old kid revved the nuts of it and it went bang!!
complete engine rebuild since ive had it, flywheel is the correct one.
think ive now solved the woodruff key problem, it has not broken agian,
could someone please tell me if there is a head gasket bigger then the original to go with a 2mm oversize piston kit? could not find one anywhere am using original bore size gasket.
still having problems with it not wanting to start, checked everything i can.. carb/electrics sparkplug/petrol and compression is very good..
im getting very frustrated with it now..lol
cheers

[ferret79]

right hope this works, heres a pic of bike so far ..

[ferret79]

[carlos]

Where's the oil pump cover from??

[racerd]

could someone please tell me if there is a head gasket bigger then the original to go with a 2mm oversize piston kit?could not find one anywhere am using original bore size gasket.
had the same problem i had to machine out the standard size head gasket to fit my 2mm over size piston kit do not try to start the lc with the standard size gasket with a 2 mm over size piston because the head gasket will be sitting inside the combustion chamber and it will cause the wrong squish in the cylinder head and the piston crown might touch the head gasket

[typer196]

This isnt as silly as it sounds but double check to make sure the left hand crank seal is in the correct way round as if it's a genuine one they are not always marked up correct - believe me i know, i had trouble starting mine (had to bump) went well in the powerband but would die straight away if you tried to let it tick over.
Dodgey CDI is a possibility, i brought one of ebay a while back, bike would struggle to start, would run but out of no where would go very very spluttery and also kept fouling spark plug.
Hope you get it sorted soon mate.

[racerd]

did you find the problem while your lc would not start