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Yosh Race Pistons: 2V 1000?

dardoonk

dardoonk

Forum Mentor
I just won these on fleabay. They are a set of Yosh race pistons & look exactly like the one's pictured in the Yosh Superbike article written by Ulrich, but are o/s at 73mm, compared to Cooley's bike with a 70mm bore. The specs on the superbike say a CR of 11.5:1, but these valve recesses are real deep, so I am wondering if I will be looking at the same or higher depending on what was done to the head of race bike. Anyone have any thoughts?
http://i4.ebayimg.com/08/i/001/1a/af/23a3_1.JPG
23a3_1.JPG


Here's the link for those that haven't read the Superbike article. http://slcelectronics.com/GS1000_Build/Yoshimura-specs.pdf.
 
What was the auction #? I wanted to check out the page but couldn't find it.
 
Very nice bargain. I was watching those. I think they could be or close to 11.5 cr. Those domes are alot higher than the domes on the wiseco 10.25 cr pistons. Any casting numbers on the pistons?
 
those aren't yosh piston's, sorry to burst your bubble. The yosh pistons have yoshimura stamped on the side in japanese. See the picture of the yosh pistons i have for my 1000 build. They are a 73 dia, which works out to a 1085 kit. the kit i have is about 11.2:1 stock but after surfacing the head and cylinder it will probably kick it up to 11.5 or a touch more.


3037009338_d84bc28482.jpg


those murdock piston's are probabley close to 11ish but you really won't know until you install them. You will need to check to make sure they aren't to worn out either before you install them. Check the ring grooves and wrist pin dia.

-Ryan
 
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MOST important for you to check for is collapsed skirts. If the skirts are collapsed, the pistons are junk. This reason alone is why I REFUSE to buy used pistons I don't measure myself. Even then I don't like used pistons as a rule. Ray.
 
I was sortof iffy on buying them but thought $50 bucks might be worth a shot.
I could not find any stating Yosh didn't have Murdoch make the pistons & the best picture I could find of the Yosh piston showed only two ring grooves on their race piston, but another showed three ring grooves on the "street" version from Yosh.
I figured it was a bit of a gamble, but if they end up OK, I'll be ahead of the game on my BB upgrade. If not, well... I out $50

FirstTimer, can you give pass along additional info on where you got your pistons & who I might be able to contact?

Thanks, guys.... Not exactly what I wanted to hear, but I knew I was gambling

One other thing... I don't want to put this ebay seller under the bus.. He referred to them as Wes Cooley performance race pistons. He didn't say Yosh and reading back to my first post, I appears I inferred they WERE Yosh pistons, when what I was trying to say is that they appear to be the same as those pictured in the Superbike article except 73mm rather than stock superbike size.
I think he was describing them on the up & up, but I might have been getting a bit excited actaully referring to them as Yosh, when I was really trying to find out if they are
 
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no thats cool, like Ray said check them out and you might has scored yourself a deal. If you need some more pictures and measurements of pistons I can try and measure up mine.

your not going to easily find the pistons I have, I just had dumb luck and was quick with the money. Thats how i got my yosh pistons. There was a guy who posted them for sale here on the forum about a year ago. He was a ex racer who lived in cali and had the yosh shop do work for him. He only had one set left from his race days which i bought. Your best bet is to just get the Wiseco pistons they are just as good with a touch less cr. I have only seen 1 other set of yosh pistons for sale and that was about 3 months ago on ebay and they were only a 2 ring piston which is more out dated, the wiseco would have been a better choice.
 
How about you send your pistons to JE, have them make duplicate's with a 3 ring design. 73mm should be fine. Have them blueprinted and make a set for me to buy. So it would be a JE made, Yoshimura styled big bore piston kit. It seems like only wiseco is making big bore kits for our GS1000's these days and some guys prefer a higher compression ratio piston.

If I got a used set of yoshimura pistons, this is what I would do.
 
Tarbash 27 said:
How about you send your pistons to JE, have them make duplicate's with a 3 ring design. 73mm should be fine. Have them blueprinted and make a set for me to buy. So it would be a JE made, Yoshimura styled big bore piston kit. It seems like only wiseco is making big bore kits for our GS1000's these days and some guys prefer a higher compression ratio piston.

If I got a used set of yoshimura pistons, this is what I would do.
Click to expand...
Why don't you just order some CP Pistons from me instead of copying some outdated, ANCIENT design that won't make NEAR the power of the CPs & will weigh WAAAYYYY more than the CPs?!!!! I can get you CPs, CUSTOM made to your specs with pins, clips, & rings for $675.00 SHIPPED! Let me know if you're interested in CURRENT technology instead of 30 year old! Ray.
 
Tarbash 27 said:
How about you send your pistons to JE, have them make duplicate's with a 3 ring design. 73mm should be fine. Have them blueprinted and make a set for me to buy. So it would be a JE made, Yoshimura styled big bore piston kit. It seems like only wiseco is making big bore kits for our GS1000's these days and some guys prefer a higher compression ratio piston.

If I got a used set of yoshimura pistons, this is what I would do.
Click to expand...

the ones i have are a 3 ring design so i don't really need to worry about it. It would be neet to get a copy of these but i really don't feel like paying someone to make copies of what i have since i don't need them.

I am fine with them being what they are since i am tring to do a yosh bike and the more bits i can use the better.

Ray has a point there might be better technology (forging and such) out there that would be better but i am happy with what i got.

Ray once i get a scale i am curious see how much my piston weighs compared to the cp ones.
 
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Got any info on this cp pistons or pictures? Im not no pistonologist or anything. I have a wiseco slightly used 1085 kit I planned on putting in my motor. Im not going too crazy. Its going to be a street bike daily rider and I plan on putting alot of miles on it. Web cams, lightly ported head, 29mm mikuni's. I dont know, Im sure the wiseco kit should be fine, I guess.
 
Good thought on the copies, even if I had them add a third ring. Sure, it'd be nice to have some brand new. lightweight pistons in there, but the whole point of buying these was to see if I could snag a deal. If they're nice and For $50 bucks, I should be able to spend a little extra on pins, rings & clips & still be under the cost of a Wiseco kit & get maybe another 1 point in cr. I called the tech guy at Total Seal today & explained what I dealing with having only 2 rings. Basically, he told me not to sweat it, keep my tolerances on the tight side & they can hook me up with the correct rings after I get them the measurements... Hopefully it works out better pricewise than a Wiseco kit for $429.

Ray, just so I know, whats the plus side for the added $250 I'd be looking at on the CP kit? Obviously, you could offer a higher cr than Wiseco, but other than that, can you offer some comparison? If my bargain yosh replica's fall thru, I want to be able to consider all my options.
 
The CPs are a better forging, better alloy aluminum, WAAAAYYYY tighter tolerances in the machining, narrower wrist pins so the PINS are lighter too, better pins, newer better ring style, anti-detonation grooves, lateral gas porting, & the pistons are lighter just due to the design shape & live longer & make more power! To me, for the $250.00 more to get 30 YEARS of better technology, it's a no brainer. If you can get a set of good, usable pistons for 50 bucks, go for it. Are the correct length pins available? Do they have an old style, DISCONTINUED ring groove sizing? Are the skirts collapsed? Two ring design pistons are designed strictly for RACING, not street use! They use a low tension ring set to reduce drag to free up power but on the street don't seal well for sustained mileage use. They were designed to be changed often. Do you want to replace rings often on a street motor. I know yours are a 3 ring design but I want others to know the purpose of 2 ring design pistons. My point is, used pistons are a crap shoot at best. If you get lucky & they are usable, they are still ancient in engineering respects. Way more power & durability is available with the new piston designs. Wisecos are still old design & heavy. Custom made & lighter pistons will make more power & your engine will live longer due to less weight reciprocating around inside. Ray.
 
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How do these CP's compare compression wise to the wiseco's? What size are they?
 
So, If I wanted 73.5mm pistons an 11.25:1 cr cut for 1mm os valves, or say, I wanted the largest piston I could get into a stock block (bored and sleeved of course), then you could whip up a set of 76 or 77mm pistons with a 9.5:1 cr for our bikes? (or whatever it was that fit)

Basically all a custom deal?
 
73.5 I don't know if rings are made for as it's an odd size but I KNOW I can get 83.5 rings because I have a set right now. All of your other questions, YES!:D Ray.
 
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