Valves and timing

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Mar 8, 2019 | 09:41 AM

Lestat997

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Weekend Warrior

Joined: Mar 2019

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Valves and timing

we have an old 2000 Yamaha breeze 125 that was blowing oil out the breather so we decided to tear into it and replace the piston and rings. Followed the service manual for it and completed the replacement. Now can’t get it to fire. We have compression, but wants to keep blowing gas into airbox out of carb. I set timing chain at TDC according to flywheel and cam sprocket. When turning motor over with a socket and watching the valves, I have TDC set just before exhaust stroke, is this correct? Or should I do a 180 with it and set to just as intake is opening?
i did adjust valves while at TDC per manual specs. Not sure why I can’t figure this out, need some help here! I do have plenty of spark as well and newer carb.
thanks for any help

Mar 9, 2019 | 03:07 AM

merryman

Elite Pro Rider

Joined: Oct 2013

Posts: 7,483

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From: Lancaster England

The correct TDC is after the inlet has closed and before the exhaust opens ensuring you are turning the engine in it's normal direction of rotation. I usually just put my finger on the plug hole, turn engine by hand, when it tries to blow the finger off watch through the plug hole for the piston rising, and set valves when it is about TDC.