Wiesco piston slap!

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.

I dont think you should hear piston slap but iam sure there will be knowledgable people here that will give you a better answer.

Sounds like too much skirt to wall clearance to me. Your friend could pull it down, measure and check it. That way he knows. Easy to change a sleeve and re-bore it correctly.

Forged pistons are more slap happy than cast cast pistons when cold. On my YZ 250 two stroke, people with Wiesco pistons always complain about piston slap when the bike is cold. Reason is Wiesco makes one typical piston for that bike where as Yamaha makes 4 and 4 different jugs so between the 4 choices you can always get a nice fit.

The slap is from the when he piston is cold it's smaller then when its warmer it expands taking up that slight variance in the cylinder wall making it normal sounding after warm.

I don't know if the piston slap is common for KZ's using forged pistons, if it was mine I would take it back because of the cost in doing it. Also try to avoid riding the bike cold if you have piston slap.

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

You definately should not hear any piston slap, hot or cold.
I have ten years and 1000's of miles wear on my everyday ride that's fitted with wiseco's and it's as quiet as the day it was done.
You mechanic messed up, don't let him fob you off with bullshit.

No piston slap here. I've known people misinterpret what is written on the box and bore to double the clearance though... :whistle:

1075 wiseco here....not a sound. Time to get it looked at before the whole engine lets go. Improper job 110% I would be pissed. Ten to one he bored the cylinder without the pistons in hand to measure first.....just went off of book - internet spec.... :S

Motor Head wrote: Sounds like too much skirt to wall clearance to me. Your friend could pull it down, measure and check it. That way he knows. Easy to change a sleeve and re-bore it correctly.

Easyer and cheaper is to buy a used cylinder and bore it...
If needed!


cheers

no slap for cold wiseco's here. :huh: maybe too much clearance........I use forged and cast.... could be bore job operator error.....not flaming though :evil:

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.

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