FT300 Low compresion problem.
05-21-2007, 07:55 AM
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FT300 Low compresion problem.
Hi,
i just bought a used os ft300 engine and there is low compresion on both cylinders.
i disasembled the engine and there was black carbon everywhere (except inside the crankshaft). the liner and the piston have no scraches. the rings are OK. tryed to test the compresion in every cylinder by puting the two pistons oposite on the same disasembled cilinder and push the one against the other. very low compresion.air leaking.
whats is going on?
is it posible this leaking is due to carbon deposits on the piston , ring, ring groove?piston have no scraches. the rings are OK
i will leave the pistons the liners and heads in a pot with antifreeze athyleniglycol overnight to clear everything.
do i need to change the rings althought they are ok?
the liners maybe?
many thanks guys!
i just bought a used os ft300 engine and there is low compresion on both cylinders.
i disasembled the engine and there was black carbon everywhere (except inside the crankshaft). the liner and the piston have no scraches. the rings are OK. tryed to test the compresion in every cylinder by puting the two pistons oposite on the same disasembled cilinder and push the one against the other. very low compresion.air leaking.
whats is going on?
is it posible this leaking is due to carbon deposits on the piston , ring, ring groove?piston have no scraches. the rings are OK
i will leave the pistons the liners and heads in a pot with antifreeze athyleniglycol overnight to clear everything.
do i need to change the rings althought they are ok?
the liners maybe?
many thanks guys!
05-21-2007, 08:28 AM
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RE: FT300 Low compresion problem.
first clean out the carbon from piston, combystion chambers, valve pockets and valves.
Re-seat the valves. A light valve lapping compound is needed here. I made a lapping aid by placing a drop of CA on the valve, and placing the head of a phillips screw on it. That gave grip to rotate the valve on the seat and clean it.
In general, carbon is caused by running castor based fuel in four strokes. Whilst best for wear, it will mess up the engine in many other respects as you have found out. Switching to synthetic oil will loosen carbon particles that subsequently will play havoc inside the engine. It therefor is required to clean the engine of all carbon before doing so. There is no need to replace parts if they are not worn out.
Re-seat the valves. A light valve lapping compound is needed here. I made a lapping aid by placing a drop of CA on the valve, and placing the head of a phillips screw on it. That gave grip to rotate the valve on the seat and clean it.
In general, carbon is caused by running castor based fuel in four strokes. Whilst best for wear, it will mess up the engine in many other respects as you have found out. Switching to synthetic oil will loosen carbon particles that subsequently will play havoc inside the engine. It therefor is required to clean the engine of all carbon before doing so. There is no need to replace parts if they are not worn out.
05-21-2007, 11:44 AM
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RE: FT300 Low compresion problem.
I was going to suggest running fuel with synthetic oil in order to clean the engine out without disassembly - unless it is too late. In which case, the valve lapping, etc. would be the way to go. Judging glow engines' compression via static means is not always reliable unless one has a tremendous amount of experience in said field. They do not behave the same as petroleum lubricated four-stroke engines used in other utility/automotive applications. After all, we run our glow engines on fuel that is basically a solvent.
05-21-2007, 12:08 PM
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RE: FT300 Low compresion problem.
The "solvent" fuel is not capable of removing carbon from the engine. Synthetic oil however will do just that, and it will come out in smaller or larger chunks that can embed themselves between the valve seats and ring lands. Both failure modes cause a complete loss of compression. In ABC ringless engines, the loose particles may score the piston.
Don't ask me how I know: Been there.
Don't ask me how I know: Been there.
