Wiesco piston slap!

Just put my motor back together, 1075 wiseco kit no slap and just put the first 200 miles on it

crock62 wrote: I explained it to the fella who done the rebuild and assures me its only piston slap as the cylinders are bored at twice the clearance of cast pistons as to forged pistons and these expand to suit

Absolutly not true with Wisecos. You can run Wisecos tighter thasn their instructions say. If you can hear it, it has too much clearance

Thanks for your reply's...especially yours Leon.

I will pass this thread on to the owner ,don't think he'll be very happy though.

I guess its better to sought this now before any thing major happens.

531blackbanshee wrote:

Hollywoodmx wrote:

531blackbanshee wrote: i have a small engine machine shop.
i have bored and honed thousands of motorcycle engines.
i use wiseco's pistons for 98% of all cylinders i do.
if you set the cylinder wall to piston clearance up per wiseco's specs,you will absolutely never hear any piston slap.
it does not matter whether it is two or four stroke.
you set the pistons to wiseco's specs,you hear no slap.

sounds to me like your buddies"machine shop"hosed him.

this is the machine shops problem,not the pistons problem.

let them skirts slap long enough and they will fatigue and break.

leon

When I refer to the yz 2 stroke weisco slap it cant be avoided if you have the less than optimal yz jug out of the series of 4 of them. The avoidance is not to use it the next year or resleave it which no one really does other wise most of the guys just deal with the piston slap when its cold and wait to warm it up before riding.

hollywood,
when i said thousands of cylinders i was not joking.

i do not care what brand or year of cylinder.

if it is properly machined and set up with the proper cylinder wall clearance it won't slap.

if you are talking nikasiled cylinders,a bore gauge is what you use to tell the taper and egg of the cylinder.if it is out of spec you re-sleeve it or have it re-nikasiled.

you are kinda speaking in the ether here about yz two strokes can you be specific on years.

as i have machined them all at some point.

leon

I'm not disagreeing Leon. IIRC its the 2002 to today at minimum.

Basically the jug has a letter on it like "c" then yamaha makes 4 pistons; Using Pro-X pistons for example 67.95mm part # 7080B. 67.96mm part # 7080C. And 67.97mm part # 7080D. Wiseco's prolite is 66.40mm (boresize). So unless you measure first you can end up with piston slap, and its more common with the wiseco's because its the one size fit all jugs. If you have a C jug and get a C piston and don't measure you are more than likely to be ok. That's all I'm saying. If you measure and get it right with the re-boreing, sleaving, re-nikasil of course one expects no piston slap regardless of piston.

But hey the 2 strokes are pretty resilient. You can get away with a little piston slap before it gets to operating temperature and ride it for years and years. Basically search in thumpertalk in the yz forum type wiseco and countless threads upon threads of the piston slap will appear.

0Z.Z1R Mk2 wrote: Not my bike...but can you help with this question?

Z1000st

Hey guys, im hoping some of you fellows can shed some light on this subject for me. I recently had the whole top end rebuilt on me kawa, cam train, rollers everything that exists in the top end, re bore to 1075, Weisco pistons fitted. When started from cold it sounds like a truck diesel engine until it warms up which may take up to 5 minutes or shorter if warmed up for a minute or so and by the end of the road its gone. I explained it to the fella who done the rebuild and assures me its only piston slap as the cylinders are bored at twice the clearance of cast pistons as to forged pistons and these expand to suit which makes sense to me, Am i being an old woman about sounds that I've never heard come from this engine in over 32 odd years or toughen up a bit, does anyone else in the forum have this issue with these forged pistons.

deisel engines use forged pistons. :woohoo: thermal expansion occurs when the engine is warmed up

hollywood,
i understand what you are saying and that is true,especially in plated cylinders.
just another reason i prefer sleeves !

leon

I have researched this in the past, the major downfall of forged pistons is the wear and tear on the cylinders. reguardless if you use highly oxygenated fuel.

Don't believe it. But how does a forged piston create wear and tear. The obvious is that you can make way more power with them and that might contribute to wear and tear.

Yo dynodon:
Last time I checked in a wear battle between aluminum and steel/cast iron ,aluminum loses! :laugh:

0Z.Z1R Mk2 wrote: Not my bike...but can you help with this question?

Z1000st

When started from cold it sounds like a truck diesel engine until it warms up which may take up to 5 minutes or shorter if warmed up for a minute or so and by the end of the road its gone.

If you had loose pistons that were making noise, I would expect them to make just as much noise as the engine heats up and the oil thins out. It might be something else. You might want to consider:

- improper valve clearance
- Compression leaking by the head gasket (the head gasket is under A LOT more pressure when the engine heats up)
- improper piston crown to cylinder head clearance (You can check this with a piece of solder in the spark plug hole).
- Leaking exhaust header

The good news is...

With advise from you guys,his mechanic is more than happy to wear the cost if his machine shop has over bored the cylinders.

I guess the truth will be revealed when the autopsy is performed.

This would mean sourcing another set of barrels and gasket kit, but he's now happy and thanks you very much.

Will let you all know what comes of this.

Cheers....Dave

Over bored to the next size pistons maybe.... FREE piston kit from the machine shop!