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Topend help

1440 Views 18 Replies 4 Participants Last post by  chuckrussell
my trx200sx runs and drives some what it idles fine but when I give it gas I can hear the topend I rebuilt the motor after the valves stuck and bent I put all new valves and cam chain and tensioners in it does anyone have an idea of what could be the problem I have done everything thanks
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I have had 200SX's and did an upper rebuild , the valve adjustment on that engine is kind of crazy with that lever and numbers , I would tell you to try and adjust the valves and just use the lever as a guide line and go by feel on the rockers , the rockers shouldn't be tight where they are making contact with the valve stem , and not so loose that they rattle
...I would figure if it bent a valve then the timing chain was heavily wore for that to happen ,

you might be fighting more than one demon , the carb may need some cleaning and / or have another problem

you may have missed the mark marks when reassembling ,

the sprocket could be severely worn , if you didn't already change it , and it be off from the pitch being worn

the rocker arms , rocker shafts or shaft journals could be worn out

you may have bent the connecting rod when the valve hit the piston , did you see the piston come all the way to the top of the jug deck when the head was off during your upper build ? a bent rod makes it run out of time and at a less compression , cause it won't achieve top dead center
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I don't get the bent valve thing ! Quote "they just stuck to the head and bent when i took the head off " Quote
the tank could be clogged up at the petcock or old fuel
Sounds like a valve seat has loosened up in the head casting. Thats the only way a valve can get bent without hitting the piston. I take that back... if a guide is real bad, broken or split open, a valve can get bent. I'd yank the head and have a look at the valve guides and the valve seats before starting up that motor again.

EDIT: Replace the valve springs too. They are probably junk.
another couple of ways to bend a rod or a leaking fuel float valve ,
water or fuel ingestion on top the piston , you try and start it and BAM , bent rod
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