rwd Posted April 21, 2014 Share Posted April 21, 2014 My YB100 wont start. When I got it it had been park in a garage since 2011 I cleaned the carb flushed the tank and it started and ran fine for about a week then decided not to start. I done a compression test and it was low so fitted new piston and rings and gaskets. The barrel looked ok. Still wouldn't start. Stripped and cleaned the carb again fitted new condenser - points - coil - plug - plug cap and done another compression test and its 100psi have a good spark. I put petrol down the plug hole and quess what ? Still wont start. Am I missing something that's staring me in the face ? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 21, 2014 Moderator Share Posted April 21, 2014 Thats confusing rwd, you have all the ingredients to start the bike...dohh! Try another plug and capacitor, they're quirky things these points ignitions I remember well from my youth (yes I know you apparently have a spark, but still) Have you had the magneto flywheel off recently...any possibility the woodruff key is sheared? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 21, 2014 Moderator Share Posted April 21, 2014 possibly the timing is out? won't get anywhere if that isn't correct Link to comment Share on other sites More sharing options...
rwd Posted April 21, 2014 Author Share Posted April 21, 2014 Woodruff key is ok. Whats the best way to set the timing ? Ive done it the old fashion way ive always done piston at tdc and set it like that. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 21, 2014 Moderator Share Posted April 21, 2014 Woodruff key is ok. Whats the best way to set the timing ? Ive done it the old fashion way ive always done piston at tdc and set it like that. There will be lines on the rotor... indicating ignition? That will be somewhat before TDC Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted April 22, 2014 Moderator Share Posted April 22, 2014 Timing, carb or airlock. Is the plug wet when you try and start it? Have you stripped and set the carb up correctly? Have you tried taking the airbox connector off and spraying a little WD40 into the back of the carb as you start it? Don't let the bike run too long with the airbox off - assuming it starts. Link to comment Share on other sites More sharing options...
dt502001 Posted April 22, 2014 Share Posted April 22, 2014 Ok bike was running and you did a top end rebuild because it stoped running why? Would be the last thing I would do unless it seized up. Check your timming markes to see if the pistion is actualy at tdc in reference to what is showing at the flywheel,you may have spun the crank shaft . Link to comment Share on other sites More sharing options...
blackhat250 Posted April 22, 2014 Share Posted April 22, 2014 [fitted new condenser - points - coil - plug - plug cap and done another compression test and its 100psi have a good spark. ] Define what a good spark is " did you gap the points to spec,, you can"t have shifted the timing , unless you slackened the stator plate screws,, More info please,, Link to comment Share on other sites More sharing options...
rwd Posted April 23, 2014 Author Share Posted April 23, 2014 I have a blue spark, I havnt touched the stator plate, and set the point to what the manual says Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 23, 2014 Moderator Share Posted April 23, 2014 I have a blue spark, I havnt touched the stator plate, and set the point to what the manual says does this mean the bike is running or that it still doesn't run but you have a blue spark? Link to comment Share on other sites More sharing options...
rwd Posted April 24, 2014 Author Share Posted April 24, 2014 does this mean the bike is running or that it still doesn't run but you have a blue spark? Doesn't run, but have a spark Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 24, 2014 Moderator Share Posted April 24, 2014 Doesn't run, but have a spark its timing then or you put the piston in backwards? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 26, 2014 Moderator Share Posted April 26, 2014 If the contact gap is changed and it's a new set (the heel will be larger) the timing will change. Happened on the gilera Sent from my RM-914_eu_euro1_280 using Tapatalk Link to comment Share on other sites More sharing options...
rwd Posted April 26, 2014 Author Share Posted April 26, 2014 Hopefully may get a chance to have a look tomorrow. Link to comment Share on other sites More sharing options...
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