Quick vac test question

[billpierce]

Have a 028 super on the bench. Just fitted new piston, as it was goosed. Cylinder cleaned up nice.

 

It runs sweet for 5 mins then starts screaming it's head off. So I suspect crank seals.

 

Pressure tests fine but won't hold a vacuum.

 

Tips on locating a vac leak please? Grease?

 

 

[spudulike]

Sounds like seals to me. Pressure tends to show splits and holes in rubber more so than vacuum. I don't think you will have a decomp valve on that saw type. Best to whip the clutch, drum etc off the saw, turn it on its side and give it some vacuum and when it leaks, run some heavy oil around the seal and see if it begins to alter the vacuum leak-down.

If it doesn't, try the flywheel side in the same way.

The classic sign of a vacuum leak is that the saw will just not snap down to idle and will hold on to revs. The saw will also have a tendency to stall after a while idling.

[billpierce]

Yup flywheel crank seal it is.....

Worth doing both or just one?

Thanks!

[spudulike]

Depends on the general condition of the saw. I usually only do one if one is buggered and once fitted, there are zero leaks but up to you really. If it is in a shocking state then perhaps do both!

[billpierce]

Ok and worth bothering with getting a puller tool or just careful wood screw technique?

[spudulike]

I got the puller tool as it was at a good price. I do however, use an awl to get most out although the smaller ones, like on the 066/MS260 flywheel side, are much easier with the tool.

[billpierce]

Thanks for the help. Did the flywheel side and holds a vac nicely now.

Was a pita. Made a little hook tool from an old tiny screw driver as couldn't find my awl. Took a while to do carefully.

[spudulike]

yup, the small ones are generally a bitch! Hope it solves your issues.