MS661 Upgrades

[M. Kulp]

Hey, I just bought a new Stihl 661. Regular carb. Just thinking about what little things I can do to to increase power and longevity. One thing I noticed right off is that the chain tensioners are weak. Or else I'm doing something wrong. My first 661 tensioner broke 2 months after I bought it. Result of serious kickback on the 36 inch bar. OK. My fault. I replaced it. Now on this new saw the tensioner broke after the very FIRST SHARPENING. Like 2 tanks of fuel. I was cutting with the top of the bar, but no kickback, rakers were factory. Factory Semi Chisel chain. Can this system be beefed up?

What about muffler mods? I'm looking for something I can do myself, I use the saw too regularly to send it away. What's available, and will it give more power, or just that awsome noise!

Anything else you can do to these saws? Simple things? Maybe things I can do myself?

Looks like fun!

 

[huskihl]

Chain tensioners bend or break for a couple reasons. Either you didn’t have the adjuster pin lined up with the hole in the bar or your bar nuts weren’t quite tight enough.

Muffler mod and a foam air filter are a couple good modifications

 

[M. Kulp]

Must have been the nuts. Tough. Headed to southern Mississippi to help a friend knock out a 52 inch oak tree that his barn is built around. 52 inch at eye level. My other 661 blew the spark plug out, and stripped the threads this morning. What's the best fix for that? New jug? But I can borrow parts for now.

 

[huskihl]

The best bet is to have the hole welded and re-tapped. Not much else will hold for very long if it’s a worksaw that’s going to get used

 

[John Walsh]

Time-sert is a decent way to fix any stripped threads. Much better, in my opinion, than a Helicoil. Time-sert is a solid piece, while Helicoil is more of a "slinky".

 

[GrizG]

Chain tensioners bend or break for a couple reasons. Either you didn’t have the adjuster pin lined up with the hole in the bar or your bar nuts weren’t quite tight enough.

Muffler mod and a foam air filter are a couple good modifications

...or possibly you had the bar nuts too tight while adjusting the chain tension so a lot of stress was put on the adjuster.

 

[huskihl]

...or possibly you had the bar nuts too tight while adjusting the chain tension so a lot of stress was put on the adjuster.

That’s certainly possible. Probably would’ve noticed it when he was adjusting it rather than after running 2 tanks through it though

 

[GrizG]

That’s certainly possible. Probably would’ve noticed it when he was adjusting it rather than after running 2 tanks through it though

The op will have to clarify… My read was he had run about two tanks, sharpened, and it then broke while in use… and after an assumed adjustment due to stretch or after reinstalling the chain. It’s not known if he sharpened it on the saw, or off with a grinder or professionally. The order of things could by telling as well as other details…. Like a thrown chain due to looseness.

 

[M. Kulp]

Basically, just ran the saw, yeah, sharpened on the bar and tightened after about 2 tanks. If anything, it was that one nut got loose. The bar got pinched earlier in the day. I'm just surprised they broke so soon. Never had a problem on the smaller saws I've run. My father said the saws he ran 20 years ago had like a metal block with a pin for the tensioner. Y'all remember anything like it, on the 066 or similar saws. Thought I could upgrade for all the dumb stuff I might do.

 

[thompsoncustom]

You got any pictures of the broken adjuster or of a new one that shows where it keeps braking on you?

 

[rogue60]

Kick back on it's own won't break a tensioner for this to happen the bar nuts are not tight enough.
Tightening the bar nuts properly will make this problem of busted tensioners go away.

 

[M. Kulp]

I don't have a convenient way to post pictures. Sorry. It broke where it bends 90* above the screw. The screw broke also.
I'll have to pay attention to the bar nuts.

 

[thompsoncustom]

I don't have a convenient way to post pictures. Sorry. It broke where it bends 90* above the screw. The screw broke also.
I'll have to pay attention to the bar nuts.

Was just trying to think of ways to reinforce it but if the screw broke also I don't think it would matter.