Dolmar 64xx/73xx/79xx series, smurfs and solo 665/675/681 thread

[huskyboy]

Don’t worry I’m not mad. Lol you guys are funny.

 

[old_sir_henry]

Hi,

I'm fishing for opinions.
I have a 7900 waiting for repair for about 2 years now
which has a broken crankshaft, its clutch-thread is sheared off.
The saw has a brand new 85cc top-end but with a broken crank
its of no good use. That is the state the waw is in since I bought it
as the previous owner had given up on it after the crank died away.

Since then I have been looking for a used crank in fleebay or a complete
saw to donate a crank. Last week, a PS-630 was sold for just 160 EUR and
only 12 km away from the place where I live, but I missed that one by a
few minutes (I learned that since I know the guy who actually bought the saw
and I fetched it for him from the seller).

One possibility would be to buy a new crankshaft which is about
180 EUR, maybe about 160 with discount from my Dolmar dealer.
Another option would be a SOLO 681 crank, which is new available
for about 90 EUR and it even gives a longer stroke.
However: Can that SOLO crank be installed without modifying it on
a lathe? I don't have a lathe.
I have read a thread (don't remeber if it was here or in the other forum)
where someone combined the stock top-end with the SOLO crank and I
understood some grinding in the crankcase will be neccessary in order
to make room for the larger stroke. But then I seem to remember there
had been modifications made on the clutch end of the shaft but I somehow
missed the reason for it.
What do you think: Is the SOLO crank a way to go?
Will it make sense in combination with a 85 cc top-end or is the carb
totally undersized for this combination, we will end up with 87 cc?
Is the crank replacement doable for someone not having a lathe?
Opinions welcome!

 

[huskyboy]

@Fruecrue

 

[dustinwilt68]

I believe the cases need work to get the solo crank in them.

 

[old_sir_henry]

I believe the cases need work to get the solo crank in them.

That's what I learned but I think that would be doable.
What's not possible for me is to modify the crank if that would be necessary.

 

[sawfun]

BTW, the Dolmar 7900 is the main reason I started the chainsaw weight gallery. One day @sawfun and I were chillin in Yamhill, Oregon, sat in front of a fat Douglas Fir log with a 372, an 046, a 7900, and his old 044. We were about to test them side by side(and we were both impressed by all of them). I then said to him, no freakin way that 7900 weighs a pound less than my 046. They felt nearly identical in weight. But everyone on the AS forums was saying it weighed 13.6 lbs. I shut them up about that in short order.

https://pbase.com/wyk/unofficial_chainsaw_weight_gallery

That day spawns fond memories for me. I have since sold that 7900 as I had ran it side by side with a strong running stock ms460 and found that I liked the Stihl better, with the exception of the AV. I now have a stock early 046 that cut circles around that 460 and would have done so to the 7900 as well. As far as weight goes, When I weighed that 7900, it weighed the exact same as my 460, 14.6 lbs empty, both with dual dogs and half wrap. Maybe Dolmar removed the dogs and clutch cover to get the 13.9 weight? I dunno, but mine wasn't at that number. I believe the 7900 balances just slightly better than the Stihl. We had an early 064 out to if memory serves, and with a 32" bar it was stronger than the 7900 with 28" bar. I've now found I prefer my 372's, though ported, to either the 7900 or 046. The Husky balances and oils much better than either of the other two saws, especially with a 36" bar. And while I haven't ever needed them, I carry the extra muffler bolts I've been warned to, as the penalty for running the seemingly dreaded Husky. lol

 

[brox]

I am in a similar situation with a 7900 with a bad crank. This was the stroker thread:

http://opeforum.com/threads/stroking-a-dolmar-7900.14462/

 

[dustinwilt68]

If I remember correctly he just used the a sander and smoothed the casting mark on the crank itself, should be doable

 

[mettee]

Yeah the case has to be clearanced. And then the oil pump needs to be shimmed out. And the cylinder needs to be spaced out as well. There is a stock solo gasket named in the thread Fruecrue did.

 

[Fruecrue]

I am in a similar situation with a 7900 with a bad crank. This was the stroker thread:

http://opeforum.com/threads/stroking-a-dolmar-7900.14462/

That guys a total hack.
Cases definitely require clearance work, shim out the oil pump, space up the cylinder and or cut the squish and you’re good to go.

 

[brox]

That guys a total hack.
Cases definitely require clearance work, shim out the oil pump, space up the cylinder and or cut the squish and you’re good to go.

Ha ha, I'm still too big of a chicken to try it.

 

[mettee]

Hi,

I'm fishing for opinions.
I have a 7900 waiting for repair for about 2 years now
which has a broken crankshaft, its clutch-thread is sheared off.
The saw has a brand new 85cc top-end but with a broken crank
its of no good use. That is the state the waw is in since I bought it
as the previous owner had given up on it after the crank died away.

Since then I have been looking for a used crank in fleebay or a complete
saw to donate a crank. Last week, a PS-630 was sold for just 160 EUR and
only 12 km away from the place where I live, but I missed that one by a
few minutes (I learned that since I know the guy who actually bought the saw
and I fetched it for him from the seller).

One possibility would be to buy a new crankshaft which is about
180 EUR, maybe about 160 with discount from my Dolmar dealer.
Another option would be a SOLO 681 crank, which is new available
for about 90 EUR and it even gives a longer stroke.
However: Can that SOLO crank be installed without modifying it on
a lathe? I don't have a lathe.
I have read a thread (don't remeber if it was here or in the other forum)
where someone combined the stock top-end with the SOLO crank and I
understood some grinding in the crankcase will be neccessary in order
to make room for the larger stroke. But then I seem to remember there
had been modifications made on the clutch end of the shaft but I somehow
missed the reason for it.
What do you think: Is the SOLO crank a way to go?
Will it make sense in combination with a 85 cc top-end or is the carb
totally undersized for this combination, we will end up with 87 cc?
Is the crank replacement doable for someone not having a lathe?
Opinions welcome!

I think the combo with solo crank would be cool to see.

As far as the carb, just modify it using the poleman tutorial. It's tough to get the jet out but I just drill them out and replace with a scavenged one.

 

[Fruecrue]

Ha ha, I'm still too big of a chicken to try it.

Nah, what do you have to lose?
It needs to come apart anyway.
Take it apart, think about it...

 

[mettee]

Ha ha, I'm still too big of a chicken to try it.

I have been wanting to do it myself

 

[brox]

Nah, what do you have to lose?
It needs to come apart anyway.
Take it apart, think about it...

Still need a case splitter, do the normal Husky style work? That's what I was leaning towards since I mostly own Husky.

 

[mettee]

Still need a case splitter, do the normal Husky style work? That's what I was leaning towards since I mostly own Husky.

Yes the husky splitter works perfect. I think it took me a couple minutes to split a case. Bearing were a little tough to remove, but that's good you don't want them loose in the case.

 

[Fruecrue]

Still need a case splitter, do the normal Husky style work? That's what I was leaning towards since I mostly own Husky.

I don’t own one.
Heat the case, tap the crank with a brass hammer.

 

[Wilhelm]

The saw weight comments and comparisons are worse than arguments what oil to use at what ratio.

Just so You know I have no clue how much xx lbs is and I had to look it up on Google.
For example:
13.6lbs = 6.17kg
14.6lbs = 6.62kg
To me in lbs the difference looks and sounds huge, shown in kg the difference is at 0.45kg barely worth mentioning.

If You can feel the weight difference of under 1/2kg than You must be able to feel the need to refuel Your saws tanks BEFORE the engine or chain tell You so, considering that fuel & oil tank carry over 1kg of fluids combined (Dolmar PS-7900, 0.75 + 0.42 liter).

Some of You guys must be really sensitive.
No bad thoughts nor toe stepping intended, I am just making a post as have You.

 

[dustinwilt68]

@Fruecrue stepped up and did a bad ass build.imo. lots of us had wanted to try it, but he actually did it. Now the rest of us atleasat have an idea of what to look for. From the videos I have seen, I would have to say it was a success.

 

[tickbitintn]

6401 Smurf getting an upgrade.

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