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Proper Compression for 94 VN1500

15K views 12 replies 5 participants last post by  Dirty Dave  
#1 ·
Have to do a compression check on my 94 VN1500.

What compression should it have?
 
#3 ·
Front cylinde[
345 - 590 kPa (3.5 - 6 kg/cm2, 50 - 85 psi)

Rearc ylinder
685 - 1080 kPa (7.O - 11 kg/cm2, 110 - 156 psi)

Warm up the engine thoroughly.
Stop the engine.
Removeo ne sparkp lug and attach the compression
gauge and adapter firmly into the spark plug hole. Do
not remove the other spark plug onlyt he plug lead.
For the other cylinder remove both spark plugs

using the starter motor, turn the engine over with the
throttlef ully open until the compression gauges tops
rising the compression is fhe highest reading obtainable

Repeat the measurement for the other cylinder.

NOTE
lf the engine is well broken in. the crcnking speed may
become fastet shutting down the decompressor. This
can raise the ftont cylinder comprcssion pre\ture near
to the rcar cylindels in some engines.
 
#7 ·
NOTE
lf the engine is well broken in. the crcnking speed may
become fastet shutting down the decompressor. This
can raise the ftont cylinder comprcssion pre\ture near
to the rcar cylindels in some engines.

There is decompressing mechanism in both camsafts but they do not open exhaust valves symmetricaly. If you remove mechanism from both camsafts u get even pressure
 
#8 ·
Front (Cylinder 1) PSI was ~130, then I added a cap of oil and it measured 140
Cylinder 2 was 140, then 150 when I added a cap of oil.

I think the reason they're different is because Cylinder 1 doesn't have a muffler, so no back pressure, Cylinder 2 does have a muffler.

I'm guessing this is the difference between the 2 cylinders.

Should I be concerned if they are measuring ~140-150?
Also should I be concerned about the pressure going up 10PSI? Is this a ring/valve issue or is it normal?
 
#10 ·
The engine was just running really weak.

Oil change, new oil filter, gear shaft oil change, and 2/4 new spark plugs. Feels like its putting out about 10% more power already.

I'm guessing with a carb cleaning (and tuning), new exhaust, new fuel filter, the other 2 spark plugs it'll run great.

If it comes down to it after all that I guess I can get inside the engine and clean it out.