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Author Topic: kh 400 piston /bore clearance  (Read 1125 times)

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Offline yam3narthur

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kh 400 piston /bore clearance
« on: March 08, 2012, 08:43:12 AM »
a pal is rebuilding a kh400 and has  the genuine kawasaki manual and the clearances are a bit puzzling.
the 250 triple clearance is 0.027mm to 0.037mm yet the 400 is a whopping 0.076 to 0.086mm
this is off memory so i might have the last digit out a bit. but why is the kh400 so large clearance? isnt it gonna rattle at those clearances?
with gen pistons what should you bore to?
Narrow city streets, winding country roads and the open highway belong to you astride the rugged and powerful YAMAHA RD350

------------------------------------------------------------
Yamaha RD350A 1974 uk. 
Puch M50 sports  1973
Kawazaki ZX6R 2000
Kawasaki  GTR 1400 2010 (getting old...)

Offline m in sc

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Re: kh 400 piston /bore clearance
« Reply #1 on: March 08, 2012, 10:59:43 AM »
thats approx .003" clearance, which is fine. S1 250 pistons are tiny and therefore 'grow' less when hot.
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Online JA-Moo

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Re: kh 400 piston /bore clearance
« Reply #2 on: March 08, 2012, 11:11:52 AM »
I'm in the middle of finding out myself, working on a customers 400. What pistons are you using, as I fould a few important thing sabout the mitaka's that you need to know if using them.
Just because you almost won once at Operation, doesn't qualify you to do actual surgery..........

Offline yam3narthur

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Re: kh 400 piston /bore clearance
« Reply #3 on: March 08, 2012, 03:46:27 PM »
its my pal doing the work, think he will be reusing the pistons, dunno what make they are can have a look tomorrow, they are either ancient originals or mitakas.
he just looked in the book and was amazed at the difference.
the 400 pistons are tiny compared to my rd350, they are smaller than rd250 in diameter although look a lot longer.

every 400 ive heard is as rattly as hell. even restored ones.
even wiseco dont demand that much clearance?
i'm aware the chinese copies pretending to be from japan on ebay - cruzinimage have issues with different ring sizes and wrong compression heights.
but didnt know anything about mitakas. mind you im not familiar with kawi triples at all.
let me know ja-moo and i can pass the info on. is it an issue with the skirts nearly hitting the crank?
« Last Edit: March 08, 2012, 03:47:44 PM by yam3narthur »
Narrow city streets, winding country roads and the open highway belong to you astride the rugged and powerful YAMAHA RD350

------------------------------------------------------------
Yamaha RD350A 1974 uk. 
Puch M50 sports  1973
Kawazaki ZX6R 2000
Kawasaki  GTR 1400 2010 (getting old...)

Online JA-Moo

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Re: kh 400 piston /bore clearance
« Reply #4 on: March 08, 2012, 06:45:09 PM »
Here is the "poop" on the RIK/Mitaka pistons. I just got a set in from Reproductiondecals, first over 400.

They came with Riken rings.
The wrist pin is 14 mm instead of the stock 15, but comes with a bearing to make up the difference.
The clips are a strange "G" type.
I haven't checked the rings in the grooves yet.
No directional arrow
The piston edge is approximately 1mm lower than stock.
This takes the compression from 6.5:1 to 6.32:1
Compression goes from stock 143 to 139psi
This adds about 4.4 degrees to the exhaust timing
It adds about 5.5 degrees to the transfer timing

Just because you almost won once at Operation, doesn't qualify you to do actual surgery..........

Offline yam3narthur

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Re: kh 400 piston /bore clearance
« Reply #5 on: March 09, 2012, 12:28:55 AM »
thanks for that! cruzinimage pistons must be a copy of the mitaka cos they too are a mm short
Narrow city streets, winding country roads and the open highway belong to you astride the rugged and powerful YAMAHA RD350

------------------------------------------------------------
Yamaha RD350A 1974 uk. 
Puch M50 sports  1973
Kawazaki ZX6R 2000
Kawasaki  GTR 1400 2010 (getting old...)