KR250s - surface in cyl.

Mirax · Post by **Mirax** » Sat May 03, 2008 1:05 pm

I'm renovating my KR250s and I can't find which kind of surface is in cylinders. Is it NIKASIL (Si-Ni-carbide), or any other??
(I'm sorry for my english grammar

).

ScottaKR · Post by **ScottaKR** » Sat May 03, 2008 2:14 pm

Welcome to the forum Mirax.
Yeah, it's Nikasil mate.
Your a lucky one to have found a KR250S (pretty rare to find nowdays).
Are you planning to have the cylenders re-plated?
Re-plateing isn't hard to have done (just a little expensive), the hard thing is finding pistons as they arn't available from Kawasaki anymore and no-one makes aftermarket pistons for the KR250 either.
There are are however pistons from other bikes that may fit. The most likely candidate so far is a 2mm oversized KMX125 piston, but no-one has tried to fit them, or if they have, confirmed that they work.
Good luck with the build, and be sure to post up some progress pics as you go.
Cheers, Scott.

Mirax · Post by **Mirax** » Sat May 03, 2008 5:21 pm

Thank you ScottaKR.
Surface looks well, but I don't have experience with it, I don't know, what is well and what is wear-out. All engines, which I was renovating had block from cast iron, or from aluminium with cast iron sleeve. I'm afraid to seizure pistons to aluminium, because i I don't know, how much is layer of nikasil strong.
One of pistons is burning-up but it isn't problem - I welding it with MIG/MAG technology.
My KR250s isn't complete. I had bought it in utterly parsed condition. I lack for any parts (oil tank, airbox, coils..).
Pics are on my www, click on "Motorky" - bikes in english

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ScottaKR · Post by **ScottaKR** » Sun May 04, 2008 10:44 am

If there's no lip at the top or obvious marks in the bore, you just need to take some measurements to make sure it isnt too worn or out of round.
The measurements can be found in the workshop manual. If you don't already have one, ask strokerboy really nicely as he may be able to help out. Otherwise, I can scan the relavent page from my manual, but your better off to have a full manual.
Never heard of anyone welding up a piston before, nor have I heard of the "MAG technology" welding either. Can you explain this a bit more please.
Parts come up on Ebay on occasion, and you can always make up a list of what you need and post in the wanted section.

Cheers, Scott.

Mirax · Post by **Mirax** » Sun May 04, 2008 10:17 pm

O.K., bore looks well, now I must measure roundness and cyl. diameter.
MIG - Metal Inert Gas (Ar, Ar+He) for welding Aluminium and Al alloy.
MAG - Metal Active Gas (CO2, Ar+CO2, Ar+O2) for welding steel, ...
I was repairing largest hole in center of piston, but it isn't look well - piston is very damaged on many positions, on the lip - it's impossible welding up

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I must buy new piston

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Bikemike · Post by **Bikemike** » Sun May 04, 2008 10:37 pm

You were even considering trying to repair that piston

Mirax · Post by **Mirax** » Sun May 04, 2008 10:51 pm

Bikemike wrote:You were even considering trying to repair that piston

YES - it isn't hard to do

O.K., you have truth, this piston is really very damaged, but i haven't other one, I must tried it...

ScottaKR · Post by **ScottaKR** » Mon May 05, 2008 11:59 am

I was wondering if you were talking about MIG welding. I wouldn't trust it myself.

Trying the 2mm oversize KMX125 pistons would be a much safer alternative I think.

kwackman12 · Post by **kwackman12** » Mon May 05, 2008 9:21 pm

Don't know if it helps but i came across this webb site for pistons http://www.procycle-online.com/wiseco/wiseco.htm they might be able to help/manufacture them?

Mirax · Post by **Mirax** » Tue May 06, 2008 9:29 pm

ScottaKR wrote: I was wondering if you were talking about MIG welding. I wouldn't trust it myself.
Trying the 2mm oversize KMX125 pistons would be a much safer alternative I think.

I'm sorry, it's my typist's error. Welding machine is same, difference is only in gas..
I want visit Kawasaki dealer in our city tomorrow for comparison KR and KMX pistons, then I'll decide for KMX125 original or KMX125 from Wiseco, etc. (thank you kwackman12 for tip)...
One more think - have you anybody electrical scheme for KR250s with marked cables colours, please?

StrokerBoy · Post by **StrokerBoy** » Mon May 12, 2008 9:31 am

Mirax wrote: One more think - have you anybody electrical scheme for KR250s with marked cables colours, please?

There's a wiring diagram for the ordinary KR250 on my site - look HERE. It doesn't cover the 'S' but that should only be one extra control box for the powervalves.