kz650 piston rings allocation

Mavman

New Member
recently got a sweet kz650 cafe project from craigslist and started looking into the seized engine. discovered #2 piston was completely seized and the rings are locked up. im gonna replace all the rings and hone the cylinders but not sure if i have found the correct rings

i found these (http://www.ebay.com/itm/162076951175) on ebay but im unsure of the fitment. i dont know exactly what measurements i need. its a kz650D with untouched engine so im assuming that these "standard" rings are what im looking for... just need some reassurance by the experts ;D


also while i have the top end off is there anything else i should replace while im in there? ive heard valve seals are a pretty good thing to replace at a time like this. thanks in advance!
 

crazypj

Split personality, I fake being smart
There are actually 5 pieces per cylinder. Compression ring, secondary compression/oil scraper and a 3 piece oil ring, 2 'rails'plus expander. Valve guide seals are a real good idea.
Before you take the head off, check all the valve clearances, if you lap valves you may need to fit thinner shims.The exhaust valves are likely to be close to lower limit. Kawasaki 13mm shims used to be real cheap ($0.80) last time I bought some though they had gone up to $3.75 each. (late 80's) I believe they are way higher priced nowadays so it's a good diea to check everything before and after re-assembly. Shim motors always have valves tighten up, the seats wear much faster than the shim/bucket/cam
If you have less than 25~30,000 mies you can guarantee things will get tighter with use. If you lap valves, they usually tighten up about 0.001" in first 400 miles, I always used to set 0.001" over max and put up with the ticking for 4~500 miles or so
 

Mavman

New Member
okay awesome. thanks for the info.

another question. after inspecting the cylinders it looks like im gonna need to get my hands on a new cylinder set. the rust from the seized piston ate away at the cylinder wall. its not just buildup. i have a picture to show for it. my question is do you know if multiple years of kz650's have interchangable cylinder sets?
 

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crazypj

Split personality, I fake being smart
Personally, I would bore it to 720cc. 8) ;)
Alternatively, (cheap option) find a 650 cylinder with one, two or even three damaged bores, clean it real good then put it in oven at 400f. The liners don't expand as much as the alloy so slide out. (sit spigots on a baking tray, the block will drop when it's hot enough)
Do the same to the 'good' cylinders you have and swap a good liner for the rusty one. You will need something to stand cylinders on to re-fit liner. If you do both at the same time you can use some wood blocks to hold cylinder up and spigots 'free' (at least 1/8" under them). Cool baking tray, put it on top of cylinders to hold liners down (use some weights, whatever you have lying around) then, pour iced water into tray. This causes top of block to contract and grip top of liner. You can always let things cool down without weights but then you'll have to press liners down about 0.010"
Couple of people on here have done various liner swaps, it really isn't difficult (CB360 liners into CB750 needs some work, block has to be bored before 'new' liners can be fitted to your CB920 ;D )
I'll probably be fitting Suzuki GS500 liners into Honda CB360 in the next few months, gives 420? cc)
As far as I know all 650 cylinders are the same although the seal around cam chain may be different. AFAIK, Kawasaki used a couple of different head gasket combinations over the years.
I mostly do Suzuki and Honda (pus some Yamaha) as I worked for all of them at one time or another. You will probably be better off asking on a KZ 650 specific site, someone may already have a good liner you could pick up cheap LA Sleeve used to be reasonable for new liners but I've heard they got real expensive ($120+)
 

tgcornholio

New Member
I know this is an old thread (and more focused on the sleeves than rings), but I thought I'd add my source for STD kz650 piston rings to as many of these threads as possible. Disaster Motors. (604) 779-7170.

Great customer service and prompt shipping (they're located in vancouver and shipping to the midwest took about a week) and you don't have to worry about the lottery that is ebay. This was the only reputable website i could find selling STD piston rings, and the price, ~$75, wasn't bad at all. They've got other parts for KZ's as well apparently - after the headache of searching for a ring supplier I can't recommend enough. 100% worth adding them to your supplier list.
 
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