VF500 compression testing

Being in the fortunate position of owning multiple (OK, 3 ) 86 vintage VF500 engines I can compare their performance using that highly sensitive dynamometer known as my butt.
My OE engine has done about 22K miles and it goes well (>=177km/h). I have compression tested this engine a few times and I was always disappointed in the numbers. The cold compression test of this engine gave the following.
1-120 psi
3-125 psi
2-130 psi
4-150 psi
Not great IMO, but as I said, it goes fine. It can be a bit difficult to start but once it's going it is willing enough. Otherwise it is in very good condition, cams are unscored, uses no oil.
I have another very low miles engine I bought off Ebay (3K miles). I posted about this before when I was looking at valve springs and I now believe that mileage to be genuine.
This is the engine now in my bike. When I compression tested this engine (using exact same procedure) I got the following
1-170 psi
3-175 psi
2-168 psi
4-170 psi
As you can see, quite a big difference. However....
Out on the road my initial impressions are that the performance is the same. The only noticeable difference is this engine does start easier. It is early days and I have yet to rack up a decent mileage, so my opinion might change, but if it does, it will only be a small change. So there you have it, don't get too wound up if your engine performs badly in a compression test.

 

Mine is
150
150
150
75
When it was running on four cylinders (instead of two like it is now) it smoked a good bit, but started and ran well.

 

Sounds more like the valves are not sealing perfectly. You could pop the heads and lap the valves in. Rings seem good with no oil use.

 

Yes, could be. I did experiment and increase the valve clearances from 0.15mm to 0.18mm for cylinder 3 and the pressure went up from 125 to 135psi but that's just keeping the valve closed for longer. The problem with popping the heads off is getting new head gaskets to fit and the cost of them.