Post Number: 1
|Posted on Saturday, August 14, 2010 - 01:22 pm: ||
What should the compression be of one cylinder Dispro engine with good seals and new rings.Can a compression tester be used on a Dispro Engine?
Thanks for any help anyone can give
Post Number: 72
|Posted on Saturday, August 14, 2010 - 09:15 pm: ||
Without putting too fine a point on it, give flywheels a quick flip .... if they bounce backwards against compression you have enough compression and engine is free enough to start. If flywheel rolls thru TDC you have a compression problem. If they hang up near TDC engine may be too tight to start.
Post Number: 482
|Posted on Monday, August 16, 2010 - 10:17 am: ||
The compression ratio for the Dispro is about 4.5 to 5 :1.
That means you'll see about 60-70 psi on the compression tester.
But they'll run will leaky or worn rings any way, assuming all the other stuff is OK.
Since they are a 3 port engine , the crankcase seal should be good, i.e. give the grease cups a good twist.
The most important this to get them to run is good spark ignition. As I've said before - about 80% of carb problems are electrical.
Post Number: 1248
|Posted on Monday, August 16, 2010 - 11:23 am: ||
More and More I am seeing fuel to oil ratio causing compression problems.
A friend asked me to come look at his St L as the compression was low. He had the piston out and all looked ok so I put it back in. The compression was ok. Then I noticed he was running it on 40 to 1 gas to oil. So we ran it and lo and behold after running it for a while the compression was real poor. Just barely a bounce. Squirted some oil in the cylinder and then ran it on 16 to 1. No more compression problems. Yes the engine has some wear but not enough to put in new rings.
Hope this helps