Topic: 64mm pistons for 750K5 ??

[Grinnin]

I have been looking for 64mm pistons for my 750K5.  Not interested in racing, but a little bump in power would be nice.  Taking the CB to 811cc would be the same percent bump as my 651-to-705 bump on a dual-sport single a couple years ago.

Using 811 would allow for a very long life and potential for 65mm 836cc later on the same sleeves.

I've seen some used pistons come up on ebay.  Really hard to judge condition with cell-phone quality photos.

Are there no new 64m pistons available? Failing to find 64mm, I'm thinking 62mm instead of 65.

[bjbuchanan]

There is an oversize for 836cc now, cycle sells it. 836 is so common and runs well that the older 811/812 have pretty much become nonexistent. Guys have them but they want nearly as much as a wiseco kit

[seanbarney41]

+1, nobody makes the 810/811/812 kits anymore, plus new rings are difficult to source for many of the old stock/used ones.  Many claim that cylinder head/valve work is gonna net you more ponies than an 836 with no other changes.  You can go to 850cc with the stock sleeves when the 836 wears out.  Also, sleeves can be replaced.

[Jerry Rxman Griffin aka MuthaF'er]

Your 812 logic is the same as I had in 1976. Since I jacked it up once I could do it again! If that were to happen to a 836 it is now easy to source a new set of cheap used cylinders and move on. My 812 Yoshi kit is still intact after 38 years and I haven't had to take it up to 836 yet. I have however done a 900, a 1000 and a 1080 but those get quite a bit more expensive.

Get one of the Cruzinimage ebay 836 kits for the price of a set of replacement rings and don't worry about it unless 'it happens'.

[PeWe]

Cruzinimage ebay 836 kit must be good and cheap. Not high CR and temperature, either. I used 836 pistons before that together with my ported head gave less compression, like stock.
Bike ran very well without pinging as my initial high CR pistons could. Now other pistons with higher CR and higher oil temperature. The hotter cam might affect the temp too.
Cheap 836 pistons with extra ring kit, ported head and moderate cam will improve the bike!

[Grinnin]

Thanks for all your replies.

[Joemetal861]

I just put 836 kit in my 78k no porting or polishing, stock cam  and I noticed a huge difference and love it! I sent my cylinders to red from Cycle one mfg and it cost me 400$ for for everything. (Boring and the kit)


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[Grinnin]

Thanks, again, for all the replies.  Ordered the Cruisimage 65mm 836 pistons.

Onward.