Big Bore Tri-Z cylinder

[Billy Golightly]

I found this on ebay, its a 74mm bore. You can see its obviously had some damage and been repaired. I dont believe its been ran since the repairs because most of the weld on the inside around the boost port and in other areas has not been smoothed out. The largest oversize for a stock sleeve from wiseco is 70mm. The only 74mm piston I've found is from a 300cc 2 stroke Polaris Quad. I'm trying to look into the big bore 250R kits right now to see what I can get. The largest I've ran across so far is a 72mm which isn't enough. The sleeve is also a little rusty, but I think can be cleaned up with a good bore. Actually size after the bore might end up being 74.5 or 75mm. Anyone know where I might find one like that? I'm pretty sure I can use a 250R piston if I can find one the right diameter.

I dont know where the sleeve came from...I think its purpose built for the Tri-Z. All the ports seem to line up real good and their the same size as whats on the cylinder. I test fitted it on a YZ250 bottom end I have laying around that I'm saving for a PV topend conversion and the sleeve fit down in the cases fine, the piston just wollered all around in there. The piston in the pictures below is a .25 over stock Tri-Z piston and it seriously flops around in there.

[LonesomeTriZ]

Some body knew what they were doing when they repaired that thing. What size CC are you going for?

[69HemiGTX]

If there isn't a readily available piston in that diameter, I'm sure Wiseco or Nik's could make you one. Just be prepared to pay. From the looks of the sleeve, I'd say you are correct in your assumption that it has never been run. There are still tool marks in the cylidner wall from when it was bored. I can't see any evidence of a cross hatch. Plus, the bead of the weld goes slightly into the bore.

[Somekindofjerk]

Someone is very good at tig welding, hmmmm okay check this out, http://www.jbeezwatercraft.com/store/product_info.php/products_id/12310


its a 75mm or 300cc piston made for watercraft(twostroke, and probably where the sleeve came from) and made by kawasaki, so it should fit. whomever did the cillinder bore on that engine definetly had a feel for what he was doing. the price for the piston is like 72 bucks, not bad at all!



Hope this is a giant giveaway :Bounce :Bounce BUY ME BUY ME :Bounce :Bounce

[LonesomeTriZ]

Hint hint, Check into Suzuki.

[Billy Golightly]

I looked for the RM370 piston kits Louis but haven't found any. I dont believe Wiseco or Pro-X makes them anymore. Haven't tried OEM Suzuki yet though.

I'm gonna checkout that watercraft piston and see what I can find out on it. My main concern is that the wristpin diameter is the same and that its not in a whole lot of a differen posistion on the piston (IE, higher or lower then the Tri-Z). They did do a pretty good job on the welding, was a bit careless going onto the sleeve in that one place though.

[Somekindofjerk]

I found the piston your sleeve belongs too look at the above post for info!

[Billy Golightly]

I just checked out that link, thats for a Kawasaki KLF300 is the Bayou 300 which is a 4 stroke. Dont think that'll work :D

[Somekindofjerk]

OOPs so it is, i thought it was from an actuall jetski, sorry, hmmm(rubs chin) check out this wiesco website(adobe format) http://www.mpsracing.com/Instructions/Wiseco/2003_CB_yamaha.pdf

[hrc85250r]

well, idk about the 74mm bore,ut i know my friends js550 has a 75mm stock bore..i think they are all the same (js550's) up to 92...

[hrc85250r]

also i am willing to bet somewhere the is a big bore banshee piston that size, someone has got to make one.

[OldSchoolin86]

If you call wiseco tech they will glady look up a piston that has the same pin size and deck hight in the bore size you're looking for. I've called on other projects and it's not hard for them to look it up.

[hrc85250r]

HAHAHA i found it punks!!!! you can use a 92-98 yz 250 292 big bore piston, its 74mm exactly!!!! http://www.maxpower-engines.com/bb-yamaha.htm .....whats up now??? :-)


one thing you want to watch out for when using one of these different pistons is where the ring pin is, you dont want the edges of the rings where they can get caught on the ports...

[OldSchoolin86]

HAHAHA i found it punks!!!! you can use a 92-98 yz 250 292 big bore piston, its 74mm exactly!!!! http://www.maxpower-engines.com/bb-yamaha.htm .....whats up now??? :-)


one thing you want to watch out for when using one of these different pistons is where the ring pin is, you dont want the edges of the rings where they can get caught on the ports...
I'll bet the deck height is differnt on those pistons.

[Billy Golightly]

HAHAHA i found it punks!!!! you can use a 92-98 yz 250 292 big bore piston, its 74mm exactly!!!! http://www.maxpower-engines.com/bb-yamaha.htm .....whats up now??? :-)


one thing you want to watch out for when using one of these different pistons is where the ring pin is, you dont want the edges of the rings where they can get caught on the ports...


Nice! Now I need to find out if I can buy just the piston and if there is any oversizes past that.

[Billy Golightly]

As long as the wristpin diameter is the same I think I'll be in goodshape. A spacer plate can be made pretty easily to fix the deck height. I might even be able to use a 250R one thats common on the long rod engines.

[OldSchoolin86]

As long as the wristpin diameter is the same I think I'll be in goodshape. A spacer plate can be made pretty easily to fix the deck height. I might even be able to use a 250R one thats common on the long rod engines.
That will work unless it's shorter.

[Billy Golightly]

:lol: Hadn't thought of that....if that happens I'll just mill the **** out of the head. Hehe

[hrc85250r]

well, if the deck height is shorter, you can deck the cylinder. if its taller, just get a piece of alumiunum plate and mill it to the tickness you need, as far as the wrist pins they are the same diameter, and they use the same wrist pin bearing. your only obstacle is deck height, which shouldnt be to bad. i dont think there are over sizes past that though...

[Yamahondaman]

Git It Rag !!!!