Tri-Z experts, need some knowledge please

[RIDE-RED 250r]

So, Beadle350x and I got his engine together today (thanks to Mosh and 03orangeshee!). Eric bought a stock 70mm cylinder from 03orangeshee and I happened to notice his other "stock" cylinder that is a 70mm bore as well has a considerably thicker sleeve installed in it. I have a 250r cylinder with an oversized sleeve that I was told is boreable to a 295. The difference between Eric's two identically bored Tri-Z cylinders is almost exactly the same as the difference between my stock sleeved and oversized sleeved 250r cylinders.

My question is does anyone know if anything about a big bore sleeve mod for the Tri-Z? If so, what piston application would we look for to work with this oversize sleeve? You can easily see from the pics that the one cylinder has ALOT more meat than the other and they are the exact same 70mm bore.

Can anyone shed some light on this for us?? This would save Eric the cost of re-sleeving a cylinder if we can just figure out what our next available bore size is and what piston application we need to get.

Thanks!

[badass350x]

Wow that thing looks like a big bore for sure,, Is the skirt still going in the case or has the case been machined to fit it? Either way I would take it to a bike machine shop and ask for a little advice.

[RIDE-RED 250r]

Unfortunately, I noticed the difference after I installed the new topend we bought from 03orangeshee. Otherwise I would have measured the OD of the sleeve skirts to compare.

I did do some looking around here and found some results on Tri-z big bores. Seems the only big bore for the Z's is the oversize sleeve method. I ran accross a build of Mosh's if I was able to read the part number on a pic of a 310 piston he had it looks like a piston application for a Kawasaki SX650 jet ski might be the one. The bore diameter for that setup starts at 76mm and has 4 (if I recall correctly) overbore sizes available. The 76mm bore on a stock Z crank would boost it up to 308cc.

Far as I can tell, we can get that cylinder punched out to 76mm, get a cool head cut for the big bore and away we go!

I'm waiting for some info from Mosh at the moment. It was pretty hard to read the part numbers on the piston in that pic so I want to be sure.....

[volfan537240]

im interested in the OD of the big bore sleeve. sounds like it would be choking the transfers down alot to go that big.

[MTS]

Your correct on the js650 piston for the sprock bigbore, but the deck and cyl base need machined to accomodate the different piston pin height, i dont think any of his sleaves where as small as 70mm to start but could be wrong, i think you found something else, iirc someone did a bb with a rm 380 sleave back in the day also yz bb could be a possibility, did it have a tri z specific piston in it?

[Xowner]

so your telling be that the only difference between the two jugs is you noticed the sleeve was thicker? Are all the ports and everything the same? If so its just a sleeved triz jug.

[RIDE-RED 250r]

Yes, the 2 pistons seemed the same. Again, I didn't take notice to the difference till I got the other cylinder installed. And yes, all the porting seems the same as far as I can tell without measuring things with a caliper.

What makes me think it's some sort of BB sleeve is you can see the difference in material still present in the sleeves. They are both bored to 70mm. Or is an aftermarket Tri-Z stock sleeve thicker requiring boring out the cylinder casting?

Eric has the cylinder with him at his place 90 miles away. But if it would help any, I will bring my calipers with me when we go up there for Thanksgiving and take some measurements. He has a 3rd Tr-Z cylinder that is bored to 70mm. I will have a look at that one too and report back my findings. I'm hoping that 3rd cylinder has the thinner looking sleeve like the one we just installed so I can do some comparative measurments.

Thanks everyone for the replies in helping me figure out what this critter is.

[beadle]

just went out and checked the other cylinder and it looks just like the one we just put on (pic #3 one on right)




thanks for all the help guys

[zmpolaristech]

Yeah man, its just an aftermarket sleeved cylinder. NOT a BB cylinder. I have 2 of them. One is on my wifes bike. And yes, they are super thick (NOT 76mm piston thick!), and DO choke the transfers (also screws up the port timing too, due to thickness). It takes extensive porting just to get them back to a stock configuration! I Ported my wifes cylinder to basically a phase 1, and that alone was a process!

[MTS]

Man that is stupid thick for a replacement sleave, not to mention alot more work to install over just cutting it down.

[volfan537240]

I've wondered how far is too far when going with a big bore setup before the transfers are choked too much. I have been a banshee guy for a long time and the bb kit for them starts at 66mm I believe (stock bore is 64mm) and it chokes down the transfers alot. Tri-z transfers look huge compared to banshees though. I have seen one Z cylinder that had a yz426 sleeve in it (I think it was like 87mm or something like that) and couldn't help but think that there was virtually no transfer room left.

[RIDE-RED 250r]

Yep guys, an aftermarket Tri-Z sleeve is what we have. Mosh PMed me on that yesterday and filled me all in on the Sprock style big bore sleeves and what has to be done to run them.

Thank you all very much for the insight in helping us figure this out. This whole project is the first time I have ever delved into a Tri-Z. Don't know what we would do without 3WW!!

So, my next and likely final question on this subject... Is there and aftermarket replacement sleeve that is closer to OEM size available?? He has 3 cylinders now that are 70mm bore, 2 of which need resleeving. I would like to avoid the choking off of the transfer port issues if we can when he goes to get those others re-sleeved...

[volfan537240]

John tice on e2s can do any custom sleeve you want. Send him a pm over there.

[RIDE-RED 250r]

Thanks for the tip Volfan... I'm not a member there.... yet! But I will check it out.

[volfan537240]

No prob man. He has an article on the front page that shows his whole process. Top notch IMO.

http://forums.everything2stroke.com/...round-the-Shop