1mm skimmed head Squish Clearance Part two

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KR1 Man
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1mm skimmed head Squish Clearance Part two

Post by KR1 Man » Wed Jun 21, 2017 4:33 pm

KR1 Man calling on this topic (again)! Currently, I have a used KR1-s crank with good rods plus a lovely pair of SKE exposed ring peg pistons (which I have no intention of using). The plan is to build the engine using a pair of Mitaka Mk2s' plus a full crank rebuild . My question is this: could I use my existing crank and pistons to establish the squish clearance prior to obtaining said new items? The pistons are from my re-build of engine no 73 (Gonzohop's KR1) & (believed) genuine Kawasaki, and the crank is from my original KR1-s and again, believed to be running the original fitment Kawasaki rods etc. Is a squish clearance a standard measurement or does it vary according to different makes of con rod/piston? Please help, best regards, KR1 Man.
KR1 Sleeping Beauty/Partner.Polished to perfection.
RD350 LC YPVS. Also grandson Declan's KR1 with ZXR black/purple paintjob/ KR1-s upgrades and max polishing

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James P
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Re: 1mm skimmed head Squish Clearance Part two

Post by James P » Sun Jul 02, 2017 9:22 am

To check the squish clearance, it will be best to check with the components you are actually going to use. Otherwise, there is a chance that the components you use for testing (i.e. conrods and pistons) may each be slightly shorter than "standard", while the components you actually use for the final build may be slightly longer. In extreme cases, this could mean the difference between the squish clearance being spot-on and the piston hitting the cylinder head!

Japanese components are usually very consistent, but you'll never really know without checking. One exception may be if you can very accurately measure conrod length and piston compression height, comparing your "test" components with those you will actually be using. However, I find it a lot easier to check using the components I will be using for the final build.

If you don't want to "waste" a head gasket just for checking purposes, you can check the squish clearance without it, then add the thickness of the gasket (0.25mm I think, but measure it yourself!) to the figure you obtain. Just assemble the top end "dry" without KIPS valves, head gasket, piston rings or circlips (and no sealant or grease on the base gaskets). Measure the squish clearance, not forgetting to add the thickness of the head gasket. This way, you should be able to ascertain whether any modifications are necessary to achieve your desired clearance, which you can check again later exactly the same way, as many times as you want. Be sure to carry out a cursory check (solder through the plug hole) after final assembly to confirm your original observations.

Regards,
James

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James P
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Re: 1mm skimmed head Squish Clearance Part two

Post by James P » Sun Jul 02, 2017 9:28 am

...forgot to mention, if you're not already aware:

It will be a good idea to also measure the volumes of your combustion chambers (to calculate compression ratios), just to make sure your pistons won't melt!

Regards,
James

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KR1 Man
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Re: 1mm skimmed head Squish Clearance Part two

Post by KR1 Man » Fri Jul 14, 2017 11:18 am

KR1 Man calling, Many thanks for the guidence. Will be applying your advice upon assembling. Thanks & best regards, KR1 Man.
KR1 Sleeping Beauty/Partner.Polished to perfection.
RD350 LC YPVS. Also grandson Declan's KR1 with ZXR black/purple paintjob/ KR1-s upgrades and max polishing

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