Cylinder compresion in old grey 138

[hkpremier]

Hi all,
Recently bought an EK manual waggon that goes O/K but struggles with a few people on board, I thought maybe I am expecting to much from an old grey.
Did a full tune with new plugs, leads, coil, points, and distributor cap and set timing but still no more power.
Got to thinking about the cylinder compression so did a compression test with the following results,

Cylinder 1 90 psi
No 2 90 psi
No 3 90 psi
No 4 80 psi
No 5 80 psi
No 6 90 psi.

The engine does not blow smoke or use oil but I was hoping someone more learned in this area could tell me if the reading are acceptable or low,
Thanks in advance,
Bibz.

[Craig Allardyce]

Compression specs are 115psi.

Did you do a dry and wet compression test? Also look at doing a valve adjustment and check the advance curve rate/function on the distributor. Looking at the 80psi cylinders you may have tight (clearances) or burnt valves. Does it have any noticeable misfire?
Pull each plug individual to check for spark quality and change in engine rpm to see if there is any misfire evident. Although probably ok if your not using oil but check how much blowby you have when the engine is warmed up.
Fuel quality and jetting could also be an issue. How old is the fuel? What carby/exhaust set up are you using? Is there a fuel filter on the set up (maybe blocked), choke could be stuck on too. Hot box flap could be stuck on (big performance killer and potential for engine damage).

Sorry for the short story but there's so many possibilities here. Post some more info and I'm sure we'll get it sorted (and pics too!)

[hkpremier]

Thanks Craig,
will check out what you have mentioned,
Cheers,
Paul