[dwdl21]

So I got around to really checking out this engine and one of the cylinders has no compression. When I took off the carbs to remove the dead cylinder it only had three bolts in it so it's been played with. The valves are fine and the P/L doesn't have any scratch's so I'm thinking ring, hope Saito still sells them.
Dwayne

[Douglas Rosler]

if not try Frank Bowman Piston Rings he make's ring's for many engines.

[williame3590]

Ring may be fine just installed wrong. Double check valve clearances. I doubt there's much wrong.

Bill

[dwdl21]

Originally Posted by williame3590

Ring may be fine just installed wrong. Double check valve clearances. I doubt there's much wrong.

Bill

Please, how can I check if the ring is installed wrong?
Dwayne

[mikecoul]

Dwayne, be sure and double check the cam timing, I am not familiar with the twin but it looks like each cylinder runs its own cam. 1 tooth out can make a big difference.
It took me three tries to get it right on my 150 when I did the bearings and ring.

[kip51035]

Cam timing is easy:
1. Remove the rocker covers.
2. Stick a small screwdriver or allen key in the glow plug hole.
3. Rotate the engine until the piston is at top dead center and the exhaust valve is just closing and the intake valve is just opening. Rock it back and forth to make sure it is set evenly.
4. keep the engine in that position and check that the other cylinder is on compression and neither one of the valves move.
5. If the cylinders are lined up and not staggered #4 is not necessary.

[kip51035]

What size is this engine? Are the cylinders lined up? How many carbs? Is there a camshaft for each cylinder? A lot of the multi cylinder engines have ABC piston and cylinder and have to be replaced as a set. Check that hole for the missing screw, it could be stripped. I made a small clip out of aluminum that holds the cam in position while installing it.

[dwdl21]

Originally Posted by kip51035

What size is this engine? Are the cylinders lined up? How many carbs? Is there a camshaft for each cylinder? A lot of the multi cylinder engines have ABC piston and cylinder and have to be replaced as a set. Check that hole for the missing screw, it could be stripped. I made a small clip out of aluminum that holds the cam in position while installing it.

It's a Saito FA 90T

[dwdl21]

Since this engine is no good to as is I decided to swap the cylinders to see what would happen, even with swapping cylinders the side with no compression still has no compression while the side that was fine still is, so it has to be the ring, right? This would be most excellent.

[kip51035]

Try this, Take the glow plug out of the good cylinder. Remove the exhaust pipe. Turn the engine over with the exhaust port close to your ear. Do the same to the intake with the throttle wide open. There should be no air leakage. Now do the same with the rear crankcase vent and notice how much air is leaking there. Now do the same with the other cylinder. You are trying to isolate where the compression is going, A stuck valve, a stuck rocker, bad cylinder or even a glow plug with the centre seal blow out. If when you swapped the cylinders you left the pistons where they were and the leak changed sides then you have a valve problem. Did you check the piston, ring and cylinder for scoring? Does it have rings?