Posted this in another thread, appears to have slipped through the net unnoticed, so I'll try again.
I have seen a method used on rotax engines where a dial indicator is inserted in plug hole to measure piston travel. Crank is set to TDC and a pump is used to create a pressure or vacuum above piston pulling piston up and down. The measurement taken is total of the radial play in conrod bearings. From memory 5 thou max total is allowable, 3 thou for big end and 2 for small. If it is outside 5 thou both bearings are worn or one is very bad.
I checked a 2 stroke bike manual and 3-4 thou for big end only is stated.
Attached is how I do TDC pointer adjustment and my method for checking conrod bearing radial play, which uses same marks made during TDC pointer adjustment.
I have repeatedly done cyl 1 and 2 (only ones I can get at for the moment) on the 850 using above method and get consistantly the same results, they are as follows:
No1 Flat spot/bearing uptake=6 degrees, total bearing play=9-10 thou
No2 Flatspot/bearing uptake= 3 1/2 degrees, total bearing play=3 thou
Looks like No1 is suss.
Like to hear your thoughts on the method and the results.
What specs does Merc give for this?
Dave
I have seen a method used on rotax engines where a dial indicator is inserted in plug hole to measure piston travel. Crank is set to TDC and a pump is used to create a pressure or vacuum above piston pulling piston up and down. The measurement taken is total of the radial play in conrod bearings. From memory 5 thou max total is allowable, 3 thou for big end and 2 for small. If it is outside 5 thou both bearings are worn or one is very bad.
I checked a 2 stroke bike manual and 3-4 thou for big end only is stated.
Attached is how I do TDC pointer adjustment and my method for checking conrod bearing radial play, which uses same marks made during TDC pointer adjustment.
I have repeatedly done cyl 1 and 2 (only ones I can get at for the moment) on the 850 using above method and get consistantly the same results, they are as follows:
No1 Flat spot/bearing uptake=6 degrees, total bearing play=9-10 thou
No2 Flatspot/bearing uptake= 3 1/2 degrees, total bearing play=3 thou
Looks like No1 is suss.
Like to hear your thoughts on the method and the results.
What specs does Merc give for this?
Dave
