661 Cracked Case Fix

[Loony661]

I want to pass along a cheap, quick fix to a small problem I encountered with my 661 that some of you may find helpful.

Back in December I was bucking oak logs for a buddies logging operation when the top corner of my crankcase cracked/broke where the felling spike bolts to it. Air temps were in the upper 20’s, lower 30’s if memory serves me right, and this happened after my last refuel (9th tank for the day) so the saw was plenty warm, and had been for a while. I noticed it as I was packing up for the day, but hadn’t noticed it the last time I sharpened the chain, etc, so it was fresh. I keep a good eye on my saw.. Pictures will show what happened. Following posts will show the “fix” and also how it’s holding up..

 

[Loony661]

Because of my full time job in Highway Maintenance as a snowplow operator, I did not have the luxury of being able to use my saw for a couple months, therefor the need to fix it either. So fast forward to mid February and this is what I came up with:

A trip to the local hardware store found an 8mm X 1.25 X 50mm bolt that would work perfectly. The bolt along with a few extra bar nuts was all I needed. As you can see in the pictures, I drilled a hole through the felling spikes. Now I removed them and used a drill press, and I can say that the steel is harder than I expected. I center punched, piloted, and finished with a drill bit within a couple thousandths of what the bolt diameter was to keep it as tight as possible allowing very little room to “wiggle”.
After running the bolt through from the inside-out, I snugged the first bar nut down and applied red Loctite. Next I slipped 2 more bar nuts on far enough not to interfere with the outer spike. I installed the cover and snugged it down with the bar on - this located the outer spike. I then ran the double bar nuts until they just touched the outer spike, applied red Loctite, and jammed them against each other. Lastly, installed the outer bar nut to hold the outer spike to the bolt and lock everything together. (It should be noted that I first tested without an outer bar nut, but there was still enough movement allowed that the inner spike and case piece still pulled away from the saw). After testing again, this held the inner spike in place and I could not move it. And all I need to do is remove 1 more bar nut to remove the cover for maintenance..

 

[Loony661]

Lastly, here is how it’s holding up: after a 10-11 hour day felling some good size red oaks for my buddy a couple weeks ago, you can see that it has not moved. You can see the line where it is still fractured, I suppose from vibration not allowing the dirt from building up there, but it has otherwise not moved at all - and yes I pinched my saw a time or 2 that day while limbing and pulled on it fairly hard, as well as worked the felling spikes as normal, not being ginger about any of it, throughout the day.. Not bad for a $3-4 fix! Also, I do not need to loosen the extra bar nut to adjust my chain tension - this is a plus. Only the 2 main bar nuts as usual. So I am happy with how it turned out!

 

[srcarr52]

I weld those back on all the time. It's a pretty common issue that is not unique to the 661.

 

[Duce]

I weld those back on all the time. It's a pretty common issue that is not unique to the 661.

Do you believe it occurs more on saws using large felling spikes, from added side pressure?

 

[jacob j.]

I was fairly well impressed with the 661, even as a stock saw, and it's a good machine.

The crankcase is pretty flimsy though.

 

[Vintage Engine Repairs]

Nice fix

I needed new case halves for an 034 super, both sides, new OEM from Stihl were $150 Australian dollars. If you find down the line you want to replace the case half, it may not be as expensive as one might imagine!

If it ain’t broke don’t fix it though!

Well done for an innovative repair.

 

[srcarr52]

Do you believe it occurs more on saws using large felling spikes, from added side pressure?

It happens a lot to the 064/066/660 family as well at the 044/046/440/460 and even the 461. It's not always a whole break such as yours, it's more often just the upper bolt pocket is blown out from loose bolts or from an accident.

From what I've seen it's usually from slamming the lower bucking spike point into the wood which loosens the lower bolt and eventually levers the spike around to pull the upper bolt out.
Breaks like yours are usually from an accident where the top of the case is side loaded, like a tree falling on a pinched bar or log rolling back into it.