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ok im helping my friend rebuild his 2003 400 with the 440 bigbore kit after his kid locked it up by running it out of oil we replaced crank . piston , and jug and cant seem to get it to fire . we have a manual and im looking to verifiey the timing everytime we set the marks to "t" on the the crank and the marks on the cam gear with the top off the head then put in the tensioner everything looks right but after a couple of rotations the cam marks are off when we reset the crank to "t" and check we find the cam marks are off very little not even a half a tooth more like a 1/8 tooth off it there can be such a thing is this just normal after everything has seated or should it be dead on every time we check ? oh yea we are makeing sure its tdc on the compression stroke everytime as well

any input would be appreiciated
 

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The cam timing has nothing to do with firing. The ignition is triggered bt the crankshaft. It sparks (fires) at 8 degrees before top dead center (BTDC) @ 1400 +-100 rpm on both the compression and exhaust stroke.

All you have to do is make sure the cam timing is right before trying to start the engine.

I would guess you did not install a new cam chain - therefore your timing marks will be off a little (about 1/8 tooth). You should time it so the front mark is above the head surface while the rear mark is below the head surface. This allows for the normal lengthening of the worn cam chain.

Now back to basics: How much compression does the engine have (psi) after about 4 or 5 strokes (about 120 with the throttle held wide open)? Of course you are using a new spark plug and you have spark? Now all you need is fuel and air in the right amounts and it will run.
 
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