44 compression

[Dave M]

Varies Greatly

A true engine buiulder can't answer your questions without first seeing what work has been done to the inside. It matters as to that PSI you should be seeing.

Check your timing first. I think you rin a CDI ? Can't remember exactly, but you should check that as that can make your engine feel sluggish while maintaing what is the right compression. But be careful with adjusting that, to much is a burned up engine. Like I said, I am not 100% sure what you are running, so it is hard to answer.

On a side note, crush it until it starts spitting out the plugs when you rope her over.... hehehehehehe. Then back off a might. (kidding)

[Art K]

Pull the intake covers & exhaust elbows insp the pistons for scoring. Then take a small screwdriver and push on the rings you should be able to see the rings move. If they don`t you have stuck rings. I don`t know what kind reed blocks or reeds you have. But if you are also having starting problems I would suspect reeds. Aluminum reed blocks also tend to crack. Before I would put it away I would do this inspection at least. Waiting till the first race next to try correct could be a big mistake.
Art K

[blueskyracer]

Pull the intake covers & exhaust elbows insp the pistons for scoring. Then take a small screwdriver and push on the rings you should be able to see the rings move. If they don`t you have stuck rings. I don`t know what kind reed blocks or reeds you have. But if you are also having starting problems I would suspect reeds. Aluminum reed blocks also tend to crack. Before I would put it away I would do this inspection at least. Waiting till the first race next to try correct could be a big mistake.
Art K

I checked the rings last night and they all move easy and if anything the motor starts to easy compared to others..With a prime it always starts first pull

[Morris85C]

I would have to say if you had good power on that moter an now you don't you have a burnt piston or two. the comp on the moter is low. On a good 44 you should have at least 120lbs on all 4.An that is checking the comp by a starting rope by hand.If you use a starting moter the comp will go up.I would not run any of my moters if the comp was that low something is wrong.If you pull the moter down you will see that you probably have stuck rings on the top side of the pistons.The moters that Dave Mason runs are all 125 - 130 with a starting moter.I would not run them if they were less.

[PRO-MOTIONRACING]

As some of you know by now I often do things very low tech as I find looking at the numbers doesn't always win races. So, whenever I have the spark plugs out I do a no-tech leak down test.

With the spark plugs out I roll the each cylinder up on TDC by placing my finger over the spark plug hole and feeling for the top of the compression stroke. Then, while holding my finger tightly on the spark plug hole I roll the flywheel backwards against the suction about 1/4 turn. then when removing my finger listen for the "pop" no pop equals no ring seal.

I also do this after every assembly before I put all the other stuff on.

With a little practice this test can be done in about 5 seconds (after the plugs are out) allowing one to check things out between heats.



P.S. after every heat I pull the kill switch, grab the flywheel and start turning... pop pop pop pop 1 2 3 4.. good to go, let's put some gas in this thing.

[ZUL8TR]

compression

It's odd that my worn 25XS with a chrome bore and both A's have more comp than a 44xS, must be compression ratio...

It most likely is comp ratio. Per APBA inspection manual specs the calculated full stroke comp ratio numbers are:

25xs 10:21
44xs 8.82

So it would appear the 25 has about 16% higher compression psi than the 44. So all else equal 120 psi rope pull for the 44 is about 140 for the 25.