Dolmar 7900 Vacuum Leak Issue

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Yep. Split that case and report back to us.

I traded that saw to jacobJ for a 460 carcass. I believe he intended to use a different crank. I’ll ask him.
 
The bearing and sleeve retainer is an option, but I’ve heard of conflicting failure rates of 640 and other products.

I’ve used it exactly once to shore up an interference fit between the crank and ID of a bearing on a 660. The bearing wasn’t a slip fit, but the crank had more wear than I liked. It’s one of my own saws and is still in use today. I wouldn’t sell a saw with that fix and am 50/50 if I’d do it for a buddy’s saw.

There are machinist tricks to get a better fix, but I would go for a new crank.
 
The bearing and sleeve retainer is an option, but I’ve heard of conflicting failure rates of 640 and other products.

I’ve used it exactly once to shore up an interference fit between the crank and ID of a bearing on a 660. The bearing wasn’t a slip fit, but the crank had more wear than I liked. It’s one of my own saws and is still in use today. I wouldn’t sell a saw with that fix and am 50/50 if I’d do it for a buddy’s saw.

There are machinist tricks to get a better fix, but I would go for a new crank.
Agreed. I'd feel much more at ease about doing it around the outer perimeter
 
There should be cases and cranks out there aplenty for the OP, though. The problem with the 6400 I had was the AM p/c and other issues.

As I recall, it had a leaking case gasket, too. Someone had tried to fix it with epoxy, but that failed. Small sample size (tiny, really), but I appreciated the bottom ends of 1125s a lot more after I disassembled that saw.
 
Don't know what route to go with this one: I've put so much money into this saw recently that it seems like throwing good money after bad; but I can't get much for it now and a new Stihl costs quite a bit. I might need to think this one over before I move in on it. Looking at about $240 in repairs if the crank is the issue.
 
I hear ya. Try a wanted ad on here for a good, used crankshaft if that’s the problem. I’d split the case then make the decision.
 
I finally got time to tear the saw down, and this is what I found. The bearings slid right off of the crankshaft when I split the case.

Flywheel side of the case.
11v5g5z.jpg


Flywheel side of the crankshaft.
riygz5.jpg
 
I figured, based on my experience and your description.

Not the end of the world. You could find a good used crank, new bearings/seals/case gasket, and have a decent saw again.
Or part that sucker out and get a better project.
 
Does it matter whether or not I use a PS-7910 or PS-7900 crankshaft? The one for the PS-7910 is substantially less expensive new for some reason.
 
Back
Top