ATV Florida Forum

It runs fine, has power but it smokes when it gets really hot.  I dida compression test today and got a reading of only 85PSI!!!  Its supposed to be between 100 and 128PSI.  I'm going to check it again tomorrow just to make sure I didnt have a small leak in the compression test connectors.  Anyways time for a rebuild but what to do?  Like I said it only smokes when its hot and its most noticable when its hot if you hit the gas quick.  The smoke apears to be white sometimes maybe a bluish tint which is burning oil.  So piston and rings or valve seals?   Maybe both need to be replaced not sure.  What should I do?  Where can I get a leak test done to diagnose where th eproblem is coming from?  If it needs to be bored out who locally or close will do it?  Are valve seals hard to do yourself?  Any help or thoughts would greatly be apreciated.

Thanks

if you had a bad valve seal what happens is over night the oil settles on the valve seal and leeks into the combustion chamber so that when you go to start it up in the morning it will puff a cloud of blue smoke and then go away, bad rings means it will burn oil constantly as it runs. so id say you need new rings, just get a new piston and rings and bore it a little bigger

If find a leak test and get it done and its the rings then I will open the motor up and see how the sleeve looks if its got some scratches or its egg shaped 406cc bore, wiseco 10:1 piston, cometic gaskets and I should be good to go and I will get a performance gain with an aftermarket piston

the performance gain you will see with an after market piston is only due to the fact that it allows you to run higher octane gas, depending on how high compression the piston is. a stock compression piston will have no gains. to be honest with you, the tiny gain you will see is not worth having to run higher octane gas. my buddy has a z400 just like mine(both piped and jeted) but with a je high compression piston and i still walk by him everytime...

the pistons are so much lighter than stock thats were most of the gain is.  I know Wiseco are way lighter because my borther had 1 before the valve went through it on his old motor.  The lighter piston makes for quicker revs and the little added compression gives more power all around.  I will run 10:1 which is plenty low enough to still run pump gas.  JE I have not had experience with but they appear to be pretty good.  Not sure if they are lighter than OEM or not

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