Pattern parts, thats the last freaking time!

[darkangel]

damn pattern parts! curse their appealing price!

Basically im having a rant because the piston kit i bought for my DT125 was rubbish, did the topend, first 1k miles all was good, the rattle i had with my old piston was gone and things were great!

After 1k miles the damn tapping noise like piston slap is back, allthough not very audible at the moment it does slowly get worse over time, i have put 2k miles on this piece of crap piston now and its doing the idle tapping noises. When i took the piston and barrel to a yamaha dealer for a rebore they mentioned how bad the new piston looked, the piston wasn't even smooth and was clearly cheaply made.
For the first 1k miles it was running reeeal sweet however, when i first fired it up after the rebuild the engine sounded good as new, as if it was really tight, smooth and in spec for the first time in years, and now its reverting back to its vibrating, tapping mess.
Im either thinking i have the oil pump wrongly adjusted and am burning through my topends (can i get some advice on how to check?) or the bottom ring has imploded like what happened with the last crappy pattern piston i put in.

Ill strip off the exhaust and have a good look at the piston when the weather allows,i dont have a garage to work on the bike in.

Why i got cheapo pattern pistons is because i was under the belief yamaha doesn't stock oversize pistons.. they do!

Anyway rant over, anyone else had similar experiences?

[Blau Zedong]

Yes.....get a rebore and piston supplied by a stroker specialist who will supply a Jap piston and have the ability to rebore to the correct clearance.

PJME in Wolverhampton are good.
____________________
18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[darkangel]

a rebore and new piston will have to wait till after christmas and i have a bit of cash to spare.
Would it be worthwhile to go for the option under the maximum rebore? seeing as the costs are the same, would i get a performance gain from the extra cc or two?

Thankfully the weather is crap and im not too bothered about taking my bike out of action for a while, however taking the bycicle is going to suck, helloo illness!

one more thing lol, has anyone tried spraying their entire bike with wd40 to keep the rust out? i've been doing it for the past few days obviously avoiding the seat and the breaks and it appears to be working, it makes plastic shine like new. Would that be okay or am i going to bust my o-rings, seals and gaskets?
I have had a look at silicone sprays and the ones i found were for protecting plastics but had no mention of water displacement or rust prevention, are they better to use?

[Kickstart]

[Vincent]

Yep - cheap pistons can quite often equal more expense, esp with Yamaha parts. How did you run the bike in?

BTW "Duck Oil" is what you need to protect the bike

[darkangel]

i heat cycle'd the bike

[Vincent]

I havn't had to do it for a while but i always used to run my bikes in over 50 to 200 miles depending on the work done. Overheating and putting the motor under too much load, (uphill, two-up etc), can cause problems. But crappy pistons are to be avoided.

[Vincent]

having said that, a mate of mine once successfully ran his RD200 in by leaving it ticking over all night with a couple of fans in front of it

[darkangel]

that would kill a 2 stroke!
the exhaust would be full of carbon

[ms51ves3]