YBR 125 cam timing

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YBR 125 cam timing

Post by Ratchet » Sat Feb 19, 2011 4:53 pm

I'm in the process of rebuilding a 2002 ybr 125, bought it with the engine in bits as the big end bearing had seized (was going to fix as a winter bike.. but well that didn't work out)

anyway, i finally sourced a crank for it and have got it almost built up, but came across a bit of a snag, how do you set up the cam timing?

I have a workshop manual , albeit one in hilariously bad chinglish, it doesn't go into much detail though as all it says is "line up the timing marks", which is a bit of a pain, the cam one is ok as you can see it, crank one not so much, its marked on the flywheel, but there are three marks, i assume the one on its own is the correct one?

also you need to have the outer casing etc on.. which is a pain as if its wrong you have to strip it all down again.... why they couldn't mark the crank gear i have no idea, as you need to have the flywheel off to fit the chain...

i assume there must be a locking tool available for them? or some other trick, otherwise i'll have to take it apart again and make my own marks once i find tdc, no big deal really but would be nice to know what the "proper" way to do it is.

thanks :)

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Re: YBR 125 cam timing

Post by eastanglianbiker » Sat Feb 19, 2011 5:02 pm

normally on the crank where the plate is with the timing marks on it one of the lines should have a T stamped next to it that will be the tdc mark for timing or use something down spark plug hole turn crank slowly untill it is at the top of the stroke and see which mark on crank plate lines up

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Re: YBR 125 cam timing

Post by megawatt » Sat Feb 19, 2011 5:05 pm

To find top dead centre, remove spark plug, turn crank clockwise until piston approaches TDC, put a steel rule or tape measure or caliper in the hole , turn crank and watch rule rise and then fall. TDC will be where it stops rising!!! Ignition advance marks will be before TDC. Simples :mrgreen: :mrgreen: :mrgreen:
Bike work, I come to you and you can learn to do it yourself click the link below for more info
http://themotorbikeforum.co.uk/viewtopi ... 5&p=949652


Re: YBR 125 cam timing

Post by Ratchet » Sat Feb 19, 2011 6:33 pm

Thanks guys, yeah i ended up pulling off the head again to find tdc, and marking it on the bottom gear/crankcase, its only 4 bolts and i haven't torqued it down yet so it was no problem, the worst thing about this build is the fact it was half disassembled when i bought it, and finding out where everything goes is a pain, like which bolt/washer goes where..

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