OS 40 problems
01-31-2003 | 11:33 PM
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From: gone,
OS 40 problems
You probably have introduced an air leak somewhere... loosly mouynted carb... bad seal on the needle valve, or bad backplate gasket are the 3 primary culprits.
Its also possible that you got the head on slightly crooked, which would cause you to see bbubbles comming out around the head...
It is also easy to put the cyl liner in offset, and fouol up the port timing. (the engine will barely run at all if the cyl liner is 180 deg out...) The hole furthest fromt he cyl head should point nearly straight at the exhaust. Then there is a key-slot in the cyl liner which on some engines points directly forward, on others directly away from the exhaust, some directly at the exhaust.... (always straght in line with the crankshaft or 90 deg off... never an odd angle)
The burn pattern on the piston top should point the cleanest portion toward the intake port.
If it was running reasonably well before dissasembly... it should run well again after proper reassembly.
Its also possible that you got the head on slightly crooked, which would cause you to see bbubbles comming out around the head...
It is also easy to put the cyl liner in offset, and fouol up the port timing. (the engine will barely run at all if the cyl liner is 180 deg out...) The hole furthest fromt he cyl head should point nearly straight at the exhaust. Then there is a key-slot in the cyl liner which on some engines points directly forward, on others directly away from the exhaust, some directly at the exhaust.... (always straght in line with the crankshaft or 90 deg off... never an odd angle)
The burn pattern on the piston top should point the cleanest portion toward the intake port.
If it was running reasonably well before dissasembly... it should run well again after proper reassembly.
02-03-2003 | 04:21 PM
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From: Towson, MD
OS 40 problems
When you put the piston back in backwards and ran it, you may have just ruined the engine as far as power goes. The metal to metal honing that occurs when an engine is running and during break in is what gives you good compression. If the piston/liner is not assembled exactly the way it came apart, more wear will occur in a different pattern and the fit will not be as tight, resulting in poor compression and loss of power. Rule of thumb: If it ain't broke, don't fix it!
Max
Max
02-05-2003 | 11:17 AM
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From: Galway, IRELAND
OS 40 problems
Fred, you were right after all!
I took my cylinder head off last night and found that the pin that lined up the cylinder liner had broken off. I had the liner lined up correctly when I re-assembled the engine, but when I put on the cylinder head, the bolts didn't line up exactly and I twisted the head approx 15 degrees to line them up. This had the effect of moving the liner slightly. I put it back together carefully and started it up today at lunch time and it ran perfectly !!!
Once again, thanks for all the ideas !!!
Ron
I took my cylinder head off last night and found that the pin that lined up the cylinder liner had broken off. I had the liner lined up correctly when I re-assembled the engine, but when I put on the cylinder head, the bolts didn't line up exactly and I twisted the head approx 15 degrees to line them up. This had the effect of moving the liner slightly. I put it back together carefully and started it up today at lunch time and it ran perfectly !!!
Once again, thanks for all the ideas !!!
Ron
