PLEASE HELP !! wiseco CR250 forged piston in newly nikasiled cylinder

[Elvis74]

Usually you should have more clearance on the skirt of the piston, because pistons are conical. Have you measured the diameter of the cylinder?


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[savage sausage]

Usually you should have more clearance on the skirt of the piston, because pistons are conical. Have you measured the diameter of the cylinder?
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nope, it's just the way it wasfrom when I sent it to langcourt.
but now i suppose i need to take it to be measured......4 hour drive

 

[Elvis74]

Would be the better way I guess


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[Capz85]

Sounds like your having a bit of a nightmare, hope it all comes together soon

 

[savage sausage]

understatement 1st and last gasgas

 

[Capz85]

I'm sure it will all work out, don't let it out you off.

I've been putting my 300 top end back on today aswell

 

[savage sausage]

Understatement!!
If Gas Gas spare part prices were a more reasonable cost like japanese parts, then I wouldn't be fitting honda cr250 pistons and clutches at more than 1/3 of the price cheaper.

For some people cost is no problem for others it is when its silly expensive.

 

[Capz85]

Yeah I can imagine how expensive it can get, I've been fortunate enough only to do a couple of top ends haven't had to dig as deep as you yet.

It's Saturday go and have a couple of beers and give it another look tomorrow

 

[Zman]

you can get a Wiseco 250 piston on ebay for $122 shipped.

 

[pscook]

you can get a Wiseco 250 piston on ebay for $122 shipped.

Here's one for $104-
http://www.ebay.com/itm/WISECO-TOP-...ash=item419dcb7d66:g:EbUAAOSw4HVWFHZ1&vxp=mtr

 

[barossi73]

Just remind yourself that if you were rebuilding an 18yr old 4t instead...seems cheap now dont it?
Not to mention the labour youre saving by being able to tackle it yourself.

 

[RBrider]

Ok so here's some pictures of the said clearance

On the top of the cylinder (all the way around) the feeler gauges slip down just right, not too slack not too tight about right I would say.

However turn the cylinder (jug) upside down,and insert the piston and try for the same clearance and its tight, doesnt feel right

the company who did the replate in the UK is a well respected company
http://www.langcourt.com/

They confirmed the cylinder was re-plated to the correct fitment.
does it still need honing then even if the top is fine and the piston skirt not??

thanks

Did you try a .0015 (inch) blade? Didn't langcourt say you would be safe at that clearance?



Just as a added fyi. It's been my experience that the skirt of the piston is slightly wider than the top. The top of the piston is subject to higher heat due to combustion, causing it to need more room for expansion.

If it were me, I'd use the same area of the piston to take my measurements.
Do the bottom as you've shown in your photo, the turn the piston upside down in the cyl and check the gap in the top of cyl.

If you can fit the .0015 in both area's , I think you'll be OK.

I admit, I prefer .002, but I'd certainly defer to what Langcourt says.

I don't think you need to hit the panic button just yet.

RB

 

[savage sausage]

Did you try a .0015 (inch) blade? Didn't langcourt say you would be safe at that clearance?

Just as a added fyi. It's been my experience that the skirt of the piston is slightly wider than the top. The top of the piston is subject to higher heat due to combustion, causing it to need more room for expansion.

If it were me, I'd use the same area of the piston to take my measurements.
Do the bottom as you've shown in your photo, the turn the piston upside down in the cyl and check the gap in the top of cyl.

If you can fit the .0015 in both area's , I think you'll be OK.
I admit, I prefer .002, but I'd certainly defer to what Langcourt says.

I don't think you need to hit the panic button just yet.
RB

I appreciate the help and advise you guys are offering up, .002" is the smallest increment my feeler gauges go down to so i cant try a .0015"

So I think i have what you suggested right,

turn the cylinder the wrong way up and and put the piston in the right way up and do the measurement again ....correct?

If its still tight im going to take it to be checked and honed, i simply cant afford for it to seize on the 1st time out.

 

[RBrider]

Yeah, I think you need some local, experienced, hands on help. Just to be sure that all is well.

RB