H low compression after rebuild

DRWNY · Jun 1, 2019

Hey guys I?ve been restoring a 45 H ( going on
about 9 years now), anyway right now it?s time to
fire it up been looking forward to this after this
project took so long. Everything seems to be good;
got gas flowing, spark, timing etc, won?t fire, finally
checked compression, I?m getting steady 60 psi in
all cylinders. I readjust valves twice to double check
set at .017. No rear wheels on at this time so I can?t
pull start to try that. I am checking compression with
a with a battery cranking, any suggestions please .
All parts bought from reputable company ( full
engine kit) valves/ seats and crank all done by
reputable machine shop. Thanks in advance, Dan

Bob M · Jun 1, 2019

Cause could be dry cylinder walls. If you haven't already done so try this: Squirt a tablespoon or so of engine oil into each plug hole, then crank the engine a few seconds to spread the oil.

You may find compression significantly improved afterward.

Carl H · Jun 1, 2019

Also be sure to have the carb wide open to let the air in, Normally you get much more compression with a freshly , fully broken in motor and when the engine is warmed up to temp. So recheck it after it has been run for a while.

(quoted from post at 15:29:33 06/01/19) Hey guys I?ve been restoring a 45 H ( going on
about 9 years now), anyway right now it?s time to
fire it up been looking forward to this after this
project took so long. Everything seems to be good;
got gas flowing, spark, timing etc, won?t fire, finally
checked compression, I?m getting steady 60 psi in
all cylinders. I readjust valves twice to double check
set at .017. No rear wheels on at this time so I can?t
pull start to try that. I am checking compression with
a with a battery cranking, any suggestions please .
All parts bought from reputable company ( full
engine kit) valves/ seats and crank all done by
reputable machine shop. Thanks in advance, Dan

Janicholson · Jun 1, 2019

Assuming the gauge is good, and accurate, (weak assumption) and that you had the throttle open all the way, that all the plugs are out, and it cranks nice and fast, it should be higher. Ig it is a distillate engine It will be in the 85-95 range. if gas only, 120 to 130 is expected. Jim

rustred · Jun 1, 2019

well if the engine has been sitting for years you need to squirt some oil in the cyl's. they are dry .also is this old sleeves in it or new ones? I have seen this before, squirt the oil in and away it goes. plus I do that anyway on any sitting engine.

H low compression after rebuild

DRWNY

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Bob M

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Carl H

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Janicholson

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rustred

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