compression test for KHK

[Coolbreeze]

What reading should we get when testing for compression? We got 25-30 psi for the rear cylinder and 0.0 psi for the front. I hope to use another testing gauge today to see if the problem is with the instrument and not the engine.

[T. Cotten]

Gosh George,..

Does it start and run at all?

If so, the apparatus, or its application, has issues.

(There's usually more than one.)

....Cotten

[duffeycycles]

start simple George..put your thumb on the plug hole & kick.Testing kickstart with a compression gauge is tricky.On E start you give it a few revolutions,hard to do that on kick statrt

[Coolbreeze]

Gosh George,..

Does it start and run at all?

....Cotten

It ran when recently reassembled; however, it fouled the front plug quickly. Now, it does not start.

[kitabel]

The usual rule of thumb is between 15 and 20 times the static compression ratio at or near sea level.
KHK 6.8:1, probably closer to 6.5 actual, so 98 to 130 psi, ideally 5% or less diff front to rear.
When boring: NEVER use 45 pistons.

[Coolbreeze]

I am sleeving back to stock and using pistons from Enfield Racing. Hopefully, this will give me good compression and oil seal - and make for stronger cylinders - and not reduce heat transfer significantly.

[kitabel]

A sleeve doesn't make the cylinder stronger.
Are they specifically K/KH replacements (22251-52/52A)?

[tfburke3]

You should be able to tell if the compression is adequate just by kicking.When you are lining up the pre kickposition and it just rolls past tdc you will get that bad feeling every flathead rider eventually gets.
Tom

[T. Cotten]

A sleeve doesn't make the cylinder stronger....

And it can never transfer heat the same, either!

....Cotten

[Coolbreeze]

A sleeve doesn't make the cylinder stronger.
Are they specifically K/KH replacements (22251-52/52A)?

No. They are whatever LA Sleeve uses.

I trust LA Sleeve to use the best materials and techniques for installing the sleeve. I know the material has to be better than what Harley used in 1956. My Chief got a set of LA Sleeves in the late '80s or early '90s and has run fine since then - at least as far as cylinder wear is concerned. Clearly, Nikasil lining would provide better wear characteristics and heat transfer. The crack in the cylinder skirt has me spooked; so, I decided to put stronger material in my engine.

[kitabel]

The sleeve itself is more durable than the original cast iron, and it's preferable to have a continuous support surface down to the lowest point of skirt travel (@ BDC). The KH castings are extremely heavy vs. 45 cylinders in many places including the flange. However, the extreme stroke length requires the spigot mouth to be relieved for rod clearance. LA Sleeve may have done this (notched the sleeve), but not accurately located the notches with your actual rod beam position - check to make sure. Just a guess: if the spigot mouth notches align with the remainder of the original notches it's OK, you only need 1/16" on either side of the beam. If the rotation is off a bit, just extend the notch wherever it's needed with a file, die grinder, etc. (milling not needed). The notch extends far up the flange inside the casting - check this also.

I would also try to juggle the gasket thickness(es) for the base flange and head (if any) to get the piston to within .035" @ TDC, or as close as possible. The original K series engines used silver paint without a head gasket and a very thin paper base gasket; using anything else is almost certain to move the piston below this @ TDC.