Engine arrived gonna give complete rebuild even though bottom end feels ok. New crank counterbalance bearings rod is good. Few pictures. Piston got hot but usually happens in middle? Also should I match cylinder where marked cases. Pics show what I am talking about. Piston measure 89.95

Subscribed. That thing is cool!

I guess you got this Engine from the guy I was trying to trade with. Nice. You think a Maico 490/500, 90mm+ piston will work? I think he burned it down with detonation.

I'd leave the cases alone. Looks like that sleeve can take another bore or two provided you can find a piston that will work.

Looked everywhere for piston. Isn't maico two rings on mine. Biggest yz 490 I can find is 89 mm. This one measures 89.93. Has same size wrist pin as factory fl350. Piston says .060 on top. Anyone ideas? Help please

Looked everywhere for piston. Isn't maico two rings on mine. Biggest yz 490 I can find is 89 mm. This one measures 89.93. Has same size wrist pin as factory fl350. Piston says .060 on top. Anyone ideas? Help please

Cr500 piston ??
I know there is a thread on some guy who makes oversize pistons somewhere on this site.
CO

Edit: Try this guy: CW racing (408)371-0644 another number for Chris (CW) (408) 930-1000
I got the info from this thread: viewtopic.php?f=1&t=7109&hilit=CW+Racing
The thread is about over bore Pilot engines but he may have info -- who knows, drop a dime.
CO

Looks like it is a KX500 piston.
Wossner Piston KIT #8228D400 1988-2004 Kawasaki KX500 89.93 mm

Info gleened from here: https://www.ebay.com/itm/NEW-Wossner-Pi ... 3600787105
CO

Wrist pin to big on that one.

Since I almost got this Engine but some folks ran me over, I guess I have more information for you.


Try looking up Suzuki RM500 from about 1984. Also Maico 490 and of course YZ490, but usually those stop at about 89mm. The RM500 seems to go a bit wider though.

RM500 @90mm
https://www.nwmaicocz.com/maico-parts/p ... 99p703.htm

~1984 Suzuki RM500 should actually go out to about 91~92mm and should have the right piston pin size. They are impossible to find though. At least you have a wiseco part number now for 90mm (SKU: 10820M09000)? No clue on bottom and deck heights so these could be a $200 mistake.

What is the bore actually measuring btw?

I'm quite sure you will have to take a lot off the bottom skirt, and likely window the piston also. NO CLUE about how your timings nor your squish would end up!

90.043 mm. So 90 mm should work. Wouldn't detonation be more in middle of piston? Thanks for the info. Still need a pipe though called bills in California no luck also call klem no luck.

Just checked those piston would work but all single ring this one has two rings .060 on top wiesco markings on bottom nothing else.

Number of rings shouldn't matter. In fact single ring would yield less drag and higher rpm/power.

Its detonation. Too hot melted the piston at the exhaust port.


Are you sure you know what you are getting into? btw I'm kind of upset I didn't get the chance to complete the deal and get this Engine btw.

If it were mine I would hit that cylinder with a hone first to be sure it doesn't need another bore over followed by a measurement. Currently and assuming a new 90mm piston would be 89.93mm that would give you at least 4.5 thou of clearance which is OK, but after you clean it up its going to go wider. I wouldn't use the current bore over 6 thousandths of clearance at that point you'll need to go 90.50mm, but you may not know the actual numbers until you get and measure that 90mm RM500 piston. You might waste another $200 imo.

The area at the bottom of the boost port where it runs wider near the little bridges concerns me at 90mm. These areas the hone may not touch without running through a bore machine @ (90.5mm) overbore. I can tell the piston has been rubbing the surfaces away in those areas but hey, at least that's below where the ring rides. She aint perfect.

Whats the ring end gap currently for both rings?

I hope you didn't trade out too good an Engine. The more I look at this, the more I think its going to be well over $2,500 to get this lump running.

Can't tell ring gap rings welded in piston see pics

Any chance you can mic the gap of the rings while they are still in the piston?

Call CW Racing. They might be able to duplicate the piston if you send it to them? Maybe they can go 90.25. Same with Wiseco.

Also I suggest you map the cylinder. Also you can probably degree that cylinder. To degree the exhaust install the piston backwards.

Talked to Chris at cw racing think he has found me piston. Personal friend of Micheal leckich Jerry's son. Had nothing but good things to say about them. Also was able to give me more info on Engine.

Share info ??

Just saidaybe 300-400 big bores made. Also we're 3 or 4 versions which was factory bore size. Evidently no one makes custom pipes for these machines anymore. Gonna try using power pros pipe butake new lower connection for it. Don't know how many stock bore ones were made said definitely alot more of those were produced. He is trying to get ahold of relatives so they can release rights maybe get some more cast. He said Michael has also passed away. Wish he could get Jerry's notebook on these engines!

Anyone with big bores or leckich does your engines have exhaust bridge. The big bore I just received does not. Just curious. Also called wiseco no help couldn't even look up piston off specs. Just wanted numbers real good company lol. Got 3 people searching will post results.

In the link below you will see a Leckich water cooled jug. It's one that Nuke Em has. You will see an exhaust bridge but it may not be the same cylinder you got. Your exhaust port looks strange.
viewtopic.php?t=2025&highlight=420cc
More: viewtopic.php?f=1&t=1677&view=next
More: viewtopic.php?f=1&t=8837
CO

Think it's rm 500 they don't have exhaust bridge and bore matches up with what would be .060 oversize. Now to find a 90.25 or 90.50 piston.

Map that cylinder. Post the cylinder map with measurements.

Did you map that cylinder and measure the flattened width of the exhaust port? The width of that thing scares me. Does it look like someone bay have cut off an exhaust bridge? If so this may not run the way it is depending on measurements.