Major Compression Test Disaster? Help!

[Billy Smalls]

Hi All
I have been having trouble with my 144 for a good few months now.

It feels like a misfire, sort of. It usually happens when I ease off the throttle and then open it up, like coming out of a corner or ascending a climb. That said, it didn’t do it at all this morning on my 15 mile journey?! There is a noticeable lack of power uphill (very hilly round here) though that has only been recent. On the flat it goes along fine.

It was pinking under load recently but I twisted the dizzy 10mm anti-clockwise and adjusted the idle which cured the pinking.

I’ve carried out the following:-
set new points, fitted new condenser, HT leads, dizzy cap, and rotor arm are sound, I assume the coil is okay

Carb taken off, thorough clean, new diaphragm, needles are sound, piston drops nicely, ATF in the dashpot to correct level, float chamber is spotless and tiny filter on the valve is clean, temperature compensator is working fine, new gaskets to the manifold. Idle trim is one a half turns out (though I read that on an old engine, you might as well screw it home?)

Valves are set correctly

Now comes the disaster…..

Did a dry compression test 2 years ago, all plugs out but forgot to wedge the throttle or choke open. Got readings of (1 to 4) 150, 135, 140 & 153

Did a dry compression test 10 months ago, all plugs out but forgot to wedge the throttle or choke open. Got readings of (1 to 4) 145, 130, 130 & 140

Did a dry compression test last night, all plugs out and this time did wedge the throttle and choke open. Got readings of (1 to 4) 150, 150, 125 (but then a tablespoon of oil brought it up to 150) & a disastrous reading of 25 on cyclinder 4. Adding oil to 4 made no difference.

Oh bum!

However, I should point out that all the spark plugs can be described as having a grey brown powdery appearance on the electrodes and the gap is set correctly. The thread and ceramic insulator nose is sooty and dry. This is the same for all plugs. Would a piston fail produce an oily plug?

I am now thinking maybe the misfire is a back-fire of some kind. The inside of the carb did have a very light sooty stain, slightly more on one side of the piston, if that helps???

Is the issue with pot 4 and a misfire connected? Why such a dramatic drop in pressure in a relatively short period of time? I only do about 5000 miles a year, and don’t thrash it – much…

Am I looking at an engine out job? Mega bucks? Etc.?

Any advice folks? Thanks a lot and sorry for the long post