Pro Mac 700 help

[wv311]

I’ve been working on a pretty nice 700. I’ve rebuilt the carb and replaced fuel line and filter. It runs strong once it’s up and running. I have a few questions though
1 at idle is surges a little could this be an air leak ? Possibly a crank seal ?

2 I’ve noticed it sparking from the boot over to the metal on the plug. Why would it be doing this ?

3 my compression gauge shows 110 is that low for this saw ?

 

[a. palmer jr.]

It could possibly have an air leak, only way to be sure is to test it, not that hard. You might try changing the plug, electricity follows the easiest path. If it still does it you might change the plug boot. 110 is a bit low but the 700 is a reed valve engine so it can get by with lower compression than a piston port engine. I've got several older saws that have kinda low compression and I'm not even considering tearing them down. I have a Lawn Boy that runs every day in the Summer that has compression in the 90's.

 

[RandyMac]

piston ported, all 10 series are.

 

[a. palmer jr.]

piston ported, all 10 series are.

In that case the compression is a bit low. A little brain fade on my part, actually I have one apart right now..

 

[Big_Wood]

your idle surging is very likely caused by that sparking. could be a damaged plug lead or damaged boot.

 

[djones]

Do a ring job and you'll bump it up to 160 easily. Thin rings.

 

[wv311]

The carburetor gasket was boogered up and was leaking. I replaced it and the surging went away.