Yz250 ignition timingg

Acidreamer
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Acidreamer
Have an 01 yz250 2 stroke. Service manual calls for the motor to be .007" before tdc. The tool they use is a dial gauge that screws into the spark plug hole. I cant find this tool online anywhere and none of the local shops have them. Would it be safe to use true tdc or a smidge before to set it? The 3 lines on the coil make me think theres a good amount of adjustment for advancing/redarding so it shouldnt be that big of a deal if its off right?
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xnationalwrench 3/26/2017 11:14am
3/26/2017 11:14am
You can pick up a simple dial gauge at any tool shop , you can fabricate a simple arm the would attach off the cylinder head stud and then swing out to the center of the piston where you would attach the gauge. I believe that you can purchase what your looking for at either MOTION-PRO, or Yamaha special tools, but both of those are a little pricey. And yes changiing the timing can/will make the bike run way different.
Acidreamer
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Acidreamer 3/26/2017 1:21pm
3/26/2017 1:21pm
What i did since i posted was grab a dial gauge from harbor freight. I stuck it in there and just pushed it against the spark plug hole surface and went .007" before tdc. Im not sure how much its going to be off since im not threading into the hole. My main thing is just making sure it wont blow the bike up.
Wolfey
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Wolfey 3/26/2017 7:03pm
3/26/2017 7:03pm
I recently retarded mine with the dial gauge . Just made a little L bracket and removed one cylinder head nut. No more pinging and really smoothed the bike out for the better. Also you don't have to worry about blowing the bike up if your retarding the timing. When you start advancing is when you have to watch for detonation.
Acidreamer
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Acidreamer 3/29/2017 6:05am
3/29/2017 6:05am
will it matter if the timing is off by a few thou? The reason i ask is im not able to get the bike started at all. I want to think its timing related because the motor is brand new, carb was rebuilt and clean, its getting spark, gas and air. Tried putting some gas directly in the cylinder and nothing. Plug is brand new. The spark is nice and blue when i ground it out to the frame. the bike ran before the rebuild, so i wouldnt think the elec components would die from just sitting around.

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adam8781
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adam8781 3/29/2017 10:26am
3/29/2017 10:26am
but up an old spark plug, i used a dial indicator and cut up an old spark plug. works great

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