Solo 665 to 681 Conversion

Yeah the 1mm spacer would be all you'd need.

The extra for the 372 piston in the 7300 cylinder.

 

Mike, are the 675/ 7300 cylinders more/less the same?

 

Should be besides the decomp spot.

 

I'm pretty sure this is a husky piston used in a solo 675. In this picture if you look at the right front corner you can see the paint on the crankcase is rubbed off by the counterweight of the crank. In other words the crank had spread and fixin to ruin a saw.

 

Here is another view where the crank has rubbed the case.

 

Nice picture, if I'm not mistaken, it looks like the crank has also twisted, the leading edge of the counter weight on the right appears to be misaligned with the left counter weight. Could be just a optical trick but would be interesting to know. Crank could also have been misaligned when the saw was put together, I have seen this happen because no Loc-Tite 601/603 was used on the bearing cups when installed.

Both Dolmar, Solo specify the 601/603 in the WSM.

 

If you look at that thread on solo cranks this was the problem with them. Helsels couldnt keep cranks even in the stock ones the used for work. Dan even posted a pic and talked about it in the thread on CR.

 

Quote from: dozerdan on March 17, 2012, 12:13:12 am
Good luck on your quest for a good 681 crankshaft. I am not sure that they ever built a good one. I have seen 6 of the 681's that broke the crank. The first two that I had seen had port work done and ran the 272 Husky coils. I assume that the crank couldn't take the higher rpms. The next 4 that broke were on bone stock 681's.
Solo has been good about it. When I get one with a bad crank they replace the whole saw, no age limit. I have to send them the complete old saw for replacement. They will then replace the 681 with a new 675 as they have no 681's left.
If you still want the longer stroke of the 681, I would suggest sending out your Dolmar crank and have it stroked.
Later
Dan

Here is the last 681 broken crank that I had in. The crank is also twisted and you can see the big end rod pin has moved out and it also chewed up the engine case.

Question Dan, when you say twisted, do you mean that the counter weights are now not in line because one has spun a liitle more than the other due to the big end moving? Are they all failing the same?

The answer is yes to both of your questions. Solo tells me that they have corrected the problem with crank failures. The crank that I pictured above was from a 681 replacement saw for another bad crank.
Later


Dan

 

Kevin, did not some folks building race saws resort to welding the cranks?

 

Yep

 

Looks like a 371/2 piston. How much would it cost to get a crank stroked?

 

Last I knew of by Falicon 450-500 http://www.faliconcranks.com/

 

Most of the 7900 ' s I've worked on have a very loose main bearing to crank fit. As Tim mentioned locktite should be used.

Crank Works in Arizona does nice crankshaft work too.

 

I doubt I'll be getting one stroked at that price.

 

Not only is the inner race to crank fit a little on the loose side but the bearing to case fit is not that of a Husqvarna. In the case of the Husqvarna you heat the case and freeze the bearing to install, when the temps equalize the interference fit is strong enough that the bearing outer race will not spin in the case. In the Dolmars, Solos and Makitas you still have to heat the case and cool the bearing but the fitment is NOT strong enough to keep the bearing outer race stationary in the bearing recess of the case, hence the factory specifying the use of Loc-Tite 601/603. Spun bearings were also a problem with the 5100S. Once a bearing begins to spin in the case, it is only a matter of time before it goes BANG!

There are folks out there that swear they never have problems when putting in bearings by putting them on the crank, then pulling the crank and bearings into the case. They may not have had problems, that they know of, may just be luck, but they are not following the factory method. Doing this galls the bearing recess in the case and destroys the fit. You put the bearings in the case and then pull the crank through the bearings one side at a time, using a tool designed for this purpose. Using the factory tools insures that you can get the crank perfectly centered in the case and virtually eliminates any side thrust on the bearing.

I just split the case of a Husqvarna 61 to salvage the crank for a customer saw with a bad big end bearing, I'll mock-up the installation of the crank using the factory tool and how it should be used and get some pictures and post in a new thread this afternoon.

 

Both DexterDay & Dewey have completed their individual conversions of a Solo 665 to a 681.

Be on the lookout for the results coming soon.