How much slack?

[Freezebear]

I am currently in the process of sealing a case leak (see previous post). Was wondering about slack in the motor. Are 2 stroke motors supposed to have some slack when turning the crankshaft. Motor was quiet and smooth while running. However, now with the case opened up, if I rock the crank back and forth, I can hear a little clunk clunk noise. There is no play in the crank, or the rods. Is this just the needle bearings I hear while doing this?

 

[G DANE]

Re: How much slack?

Hi Freeze<br /><br />Many motors will give a little sound, especially if you change direction back and forth. The 40 and 50 not much, the 60'es you have often more. You can do a test by turning motor clockwise and stopping 30 deg after TDC and thereafter pressing against piston top through sparkplughole. There must be no feelable movement of piston without movement of cranckshaft. Did this sound appear after you had it appart ? Remember splines between driveshaft and cranck/pinion gear, and impeller on driveshaft has a little play. which will be hearable if lower unit is on.

 

[G DANE]

Re: How much slack?

I forgot:<br /><br />The backpressure piston rings will produce a sound too.

 

[Freezebear]

Re: How much slack?

Thanks G Dane, I think it's probably OK too, but was just curious as to where the sound is actually coming from. The spark plugs are out and the case is still split. When I turn it in one direction everything is smooth. When I rock it, I hear the clunk clunk sound. Sounds like its coming from the pistons?

 

[G DANE]

Re: How much slack?

I think everything is fine then.