what is an 'A' size, 'B' size and 'C' size in mm?
Also,
what is the best shaped combustion chamber for a KR?
Hemi, Conical?
Or does it also depend on piston shape (flat or domed)?
replacement pistons
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scooble
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mj43
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I have only ever used a hemi with a domed piston. 6mm squish width, think it is 11degrees squish angle and a dome radius of 30mm.
I did try 4DP flat top pistons with a flat top hat chamber shape 98/99 TZ style. Didn't get to test it as run at Bonneville wasn't a success and the set up nuked itself at Oulton first race back from America in 2007. I think a stone got into the chamber. I have run an air filter ever since.
Details of the chamber shape are on the spreadsheet I produced a few years back.
I did try 4DP flat top pistons with a flat top hat chamber shape 98/99 TZ style. Didn't get to test it as run at Bonneville wasn't a success and the set up nuked itself at Oulton first race back from America in 2007. I think a stone got into the chamber. I have run an air filter ever since.
Details of the chamber shape are on the spreadsheet I produced a few years back.
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KR-1R
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piston size tolerances (depends on make)
why your barrells are stamped A, B , or C
A 55.95mm
B 55.96mm
C 55.97mm
D 55.98mm (not for KR)
IF your cylinders were replated, bore gauge and micrometer to measure and match piston size to achieve running tolerance stated by manufacturer.
In an ideal world you would supply pistons to the replater for them to match to.
? forged pistons require a size more clearance due to grain structure (non-unform expansion) and forging material - lots of debate ?
? high silicon content cast pistons expansion more uniform regular even content - debate ?
why your barrells are stamped A, B , or C
A 55.95mm
B 55.96mm
C 55.97mm
D 55.98mm (not for KR)
IF your cylinders were replated, bore gauge and micrometer to measure and match piston size to achieve running tolerance stated by manufacturer.
In an ideal world you would supply pistons to the replater for them to match to.
? forged pistons require a size more clearance due to grain structure (non-unform expansion) and forging material - lots of debate ?
? high silicon content cast pistons expansion more uniform regular even content - debate ?
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TwoStroke Institute
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I'll have some pics of the most modern head shape there is but suffice to say the circa 96 'top hat' shape is old hat 
Find a pic of a late KTM 125 and that is the default shape with the torriodal shape being the go for GP level stuff.
I don't think the cast/forged debate will ever end, there advantages and disadvantages of both, comes down to personal choice.
Find a pic of a late KTM 125 and that is the default shape with the torriodal shape being the go for GP level stuff.I don't think the cast/forged debate will ever end, there advantages and disadvantages of both, comes down to personal choice.
crochet & croquet