? for Techs - radial play on pto

Swannie · Feb 17, 2004

On the pto end of a crankshaft for a saw what would be a resonable limit of radial movement when measured with an indicator while moving it up or down/front to back. Saw in particular I am looking at is a 85cc Dolmar.
I'll check back after a few replies with what I measured.

Curtis

cbfarmall · Feb 17, 2004

I would say zero. Slop will quickly lead to worn seals and a burned up saw.

Chris B.

stihltech · Feb 17, 2004

play

Depends on the type of bearings in the saw.
If there are ball bearing on the crank, the answer is zero tolerance. This goes for most saws built today. If there are needle type rollerbearings, then some play will be felt. This is the type of bearing that uses the crankshaft as the inner race for the bearing.
Rod bearing, lower, zero. Rod bearing, top, very close to zero.

Swannie · Feb 17, 2004

Thanks for your replies, they should help a lot with how to proceed. Looks like I need to clear off some more space on the work bench and keep on going.

My Intertek manual shows the 133 as having ball bearings for crank support. The indicator reading on pto radial play was .002". The bearing on the flywheel side feels tight but I think I will replace both bearings and seals while I have it apart.
I checked the rod bearings closer by watching thru the exhaust port the oil film in one of the ring grooves, even the slightest movement of trying to move flywheel one direction or the other would alter the squish of the oil film. I would take this as a good indication that the rod bearings are tight.
The saw has good compression and the piston and bore look to be in good condition, all in all looks as if this should turn out to be an excellent project saw.
Again thanks for your help, Curtis.

Swannie · Jul 1, 2004

follow up

Finally made some time to do a follow up on this thread so here goes.
When I got the saw apart found that it had a ball bearing (condition ok) on the flywheel side and a roller bearing which rides on a inner race pressed on the crank on the pto side. When saw was reassembled with new pto roller bearing and fresh seals radial play went from ~2 thou" to ~1/2 thou". Put a kit in the carb, fresh bar oil pump, dressed the original 23" bar and gave everything a good cleaning while reassembling. Saw has now had 4 or 5 tanks of fuel run thru it and it performs quite well, especially in bigger wood. May need to tear the Tillotson carb back down as the high speed settings are not quite right ( very rich) and I suspect the internal govenor for engine max rpm is malfunctioning and dumping xtra fuel too early, will probably just disable that feature unless someone else has a better idea as I doubt that the govenor valve is available.
I have since picked up a couple of siblings to this 85cc saw, a (123 - 70cc), and a (143 - 95cc). The 123 is very good mechanically, just replace a Av mount and give it a good cleaning. The 143 probably will need similar work as to what was done on the 133.
Again thanks for everyones input on my question, Curtis.