400ex not running right after ring job

[colesdaddy02]

alright, here it is. we just put new rings in my buddys 400 last night because it was smoking like crazy. everything went back together nicely and it fired rightup. it revs good until about half throttle then chokes down but keeps running good. seems to me like it is starving for fuel so he is going to check the carb and fuel line for trash. my question is would it even run at all if we were off a tooth or two on the timing chain. when we took it apart we marked the chain and the cam sproket and then assembled it back on the same marks but the two index marks didn't line up with the flat edge of the head like the manual said at top dead center. any help on this would be greatly appreciated.thanks

[dariusld]

"slowly watch the small timing window until the mark with the T aligns with the notch [figure 9] (be careful, as there are several marks on the flywheel)." Did you do this?

[colesdaddy02]

yeah we did this but the marks on the sproket did not line up with the head then. i think we are off a tooth or two on the sproket.would it still run? it fires right up with no popping or anything until about half throttle.

[rob_990]

yea itll probably run crappy though.when i took mine apart the timing was off pretty bad cause the timing chain was stretched.then i got a new crf chain and it lined up perfectly and ran a lot smoother.

[colesdaddy02]

one other important factor. he has the sparks key installed. i think this affects the tdc mark on the fly wheel so i am thinking we are right with the marks we made upon dissassembly.so why is it choking out at half throttle?stretched timing chain?but it ran good before we changed the rings except for crazy smoke.any other help

[colesdaddy02]

anybody. please help

[droppedmazda]

hey man does your 400 make any wierd noises except the part that its not running right, like and knocking noises or anything like that?

[sc400ex_rider]

yes the timing chains are known to stretch and even break over time. yes the sparks key will throw off the marks some. did you deglaze/hone the cylinder for the new rings? is it still smoking?

[rob_990]

yea the key changes tdc

[colesdaddy02]

yeah we figured out how to set tdc with the sparks key.we also deglazed the cylinder. i am going over his house after work tomorrow to work on it. i think it is fuel delivery. ill let you know how it turns out. thanks for the help