Need info on Raptor cylinder and piston

[RaptorRacrr04]

i pulled my topend off the raptor the other day due to a smoking problem..pulled it all down, cylinder is smooth with no scratchs, piston looks great with no scratchs or burns. Compression rings looked good but the oilring looked collapsed and didnt have much spring to it. but anyways i noticed that the piston looked a little sloppy in the cylinder(maybe it was just me since ive never had apart an engine before) so we checked the size of the bore and checked the size of the piston..and there is about a 18-20 thousands diffrence. I kno its not suposed to be a super tight fit but does this sound right??I cant find my owners manual to see if it has this info in it or not. So any help is needed. I just wanna make sure this is right before i put it back together and blow the rings again. It was still running very strong before i pulled it apart, just couldnt afford to put a couple quarts in it a day..So :confused:. Thanks

[mojoe2878]

the piston to cylinder clearance sounds good.
you sure the oil was coming from the bottom of the cylinder and not from the top? you could be leaking oil into the cylinder from a valve seal. did you do a compression test before you started tearing it down?

[buster369]

i had a valve seal problem on my 300 check the seals and see if they are split or the metal part of the seal spring is damaged

[Destructo]

Just because a motor burns oil won't mean its got low compression, if the oil ring is gone and the other are fine you'll get good compression but burning oil.

I would also check the valve seals, but you already got the piston out so I would put a new set of rings in anyway, they can't be too expensive.

[RaptorRacrr04]

i didnt do a compression test before i took it apart. i was gunna put a new set of rings in it when it put it back together weather it needed them or not. i already have them on order, along with the topend gasket kit and k&n airfilter. I noticed that there is hardly any carbon ontop of the piston, so if the valve seals were leakin, wouldnt there be alot of carbon and junk ontop of the piston? the valves did have alot of carbon on them but i think that came from runnin 87 in it all the time and burnin so much oil. Where can i find valve seals?? I looked on yamahaoftroy.com and looked at the diagram of the head, all i saw was the valve guides, r the seals inside the guides?? ive never had a 4stroke apart before so i really dont know alot about them. thanks for the help, i couldnt get any help on bluetraxx lol

[buster369]

mine didn't have that much on top of the piston. seals need to order from a yahama dealer. They should be inside the springs. They are like a brownish color

[mojoe2878]

look at a diagram of the valve assembly instead of the head and you should find the seal on there.
or call them and they should be able to help, you can also get them from your dealer, they should be around $9 apiece.
the top of the piston would not be anymore carboned from the valve seals leaking than it would from a bad oil ring. your seals may not even be leaking but i would go ahead and replace them since you already have the head off, its just good insurance.

[RaptorRacrr04]

ok i just ordered the valve seals...i didnt even see it where it said VALVE..i wuz lookin at the head lol. anyways, so does my piston clearance sound good??i dont see y it wouldnt be OK since i never ran it without oil and took good care of it. like i said there isnt a single scratch on the cylinder. so i figure if the cylinder or piston was wore down that much, there would be some proof on either one to show it.

[mojoe2878]

the clearance that you said you had in the first post is with in specs. you still have a good bit of wear left before you will be at the service limit.

[MIKE400EX]

Stock piston clearance is probably around .002-.004", that's two to four thousandths. Not 18-20 thousandths (.018-.020"). That thing would rattle like a coffee can full of rocks!

[mojoe2878]

what feeler gauges are you sticking in there?
i was reading the numbers on mine wrong.mike400ex is right the 18 to 20 thousandths would be to much, but i think you did like me and read the gauges wrong.
the normal clearance is .0006"-.0020" and should have no more than.004"

[RaptorRacrr04]

well i had sum1 look in their raptor manual, piston clearance is .0020-.0028...so mines right at 20thou so im as good as new!!thanks for the help guys