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hey i got a ltz 400 and we just took it apart and we looked at the piston and everything it was all good and the rings were a little dirty so we cleaned them and put them back together but there was some marks on the piston where valves hit it. could a bent valve mess up ur compression ?

Edited by DirtDemon
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Yes, definately, it your vavles aren't seating properly, compression will pass by. One way to check your head and vavles for leaks, is to pour water into the intake and exhuast ports and see if the liquid leaks past the vavles, and how quickly if it does. If your vavles are adjusted too tight, it will cause the same problem. However, even if you are losing compression past the valve, the piston/rings or cylinder bore could also be contributing to the low compression. Just because the piston and rings look ok, doesn't mean that they are. You should measure the cylinder bore with a micrometer to check for wear and to make sure it is still round. The piston itself should be measured for the same things. IMO, even if the piston and cylinder don't show excessive wear, the rings should be replaced anyway if the motor is more than a few years old. Also if your vavle have hit the piston, the structural integrity of the piston could be comprimised and should probably just be replaced. If it breaks while the motor is running, the damage could be pretty bad.

We will always be happy to try and answer any questions you have, but I still strongly believe that you should have a service manual at your side when you do this type of work to the motor. I may just be beating a dead horse here, but I think you would find alot of helpful info in there. Either way, good luck, and I hope you can get your quad up and running soon. I know how much it sucks to have a machine out of commission. BTW, I edited your post, please try not to use inappropriate language in the general forums. I know alot of other sites don't have much in the way of language rules, but we try to keep this one as PG as possible. There is a forum here dedicated to more "adult" themed discussion, you can basically say what you want in there. I have also merged your "compression problem" thread into this one, please try to keep things consolidated into one thread unless the subject matter is completely different. Not only does this help cut down on clutter in the forum, but you will get better input, if everyone can see all of the responses to the same question in one thread as opposed to posting the same question in two or more threads. Once again, good luch getting your quad fixed.

Edited by DirtDemon
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Messed up when merging your threads, accidentally moved everything into the timing chain thread. I only meant to merge the two that both pertained to your compression/vavle problem. Made this new thread and left your timing chain thread by itself, since it is of a different subject matter. Sorry for the confusion.

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