The Forestry Forum is sponsored in part by:




TimberKing Sawmills




Toll Free 1-800-582-0470

LogRite Tools



Forest Products Industry Insurance


Norwood Industries Inc.


Sawmill & Woodlot Magazine



Your source for Portable Sawmills, Edgers, Resaws, Sharpeners, Setters, Bandsaw Blades and Sawmill Parts

EZ Boardwalk Sawmills. More Saw For Less Money!

STIHLDealers.com sponsored by Northeast STIHL


Woodland Sawmills

Peterson Swingmills

 KASCO SharpTech WoodMaxx Blades


Turbosawmill

Sawmill Exchange

BRUTE FORCE Authorized Dealer

Woodshax Outdoor Vending Solutions

FARMA


Council Tool

Baker Products

Forestry Forum Tool Box

Author Topic: Stihl MS661C Magnum issues  (Read 1040 times)

0 Members and 1 Guest are viewing this topic.

Offline LinuxRocks

  • member
  • *
  • Posts: 6
  • Location: Patterson, New York
  • Gender: Male
  • I'm new!
Stihl MS661C Magnum issues
« on: July 20, 2017, 03:43:01 pm »
I did a search and didn't see any Post on my Problems with the Stihl MS661cm. This is the 2nd time the engine has blown in less than 6 months. Fuel mix is correct(the same as I use on my other 2 saws along with weedwackers) They have already rebuilt it once and will bring it back to them again. Has anyone else had or heard of this happening to MS661's

BTW: I use this with a granberg alaskan mill with stihl's 36" bar

Offline HolmenTree

  • Senior Member x2
  • *****
  • Posts: 3079
  • Age: 59
  • Location: Manitoba
  • Gender: Male
  • "Been there, done that........and still learning"
Re: Stihl MS661C Magnum issues
« Reply #1 on: July 20, 2017, 08:15:07 pm »
Welcome to our forum LinuxRocks.
When all I hear is 2 rebuilds in 6 months from running it with s 36" b/c on a Alaskan mill I see lots of red flags.

Are you milling long lumber in large diameter logs?
Are  you keeping the chain meticulously sharp?

What ever your answer is, maybe you should be running a MS880.
Making a living with a saw since age 16.

Offline LinuxRocks

  • member
  • *
  • Posts: 6
  • Location: Patterson, New York
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #2 on: July 21, 2017, 01:13:16 am »
Thanks. Today was a Pine log 8' x 14". Chain is brand new Rip chain - sharp. Ya, my thoughts too I'm really not too happy about this... And it's not like I;m a newbie to chainsaws. I'm 57 been cutting with them since I was 14. Never had 1 blow on me and now this one twice in @6 months...

And before anyone else asks:

50/1 mix
chain sharp
no over revving
wasn't even 2 feet into it and it died.

There is something very wrong with this saw....

Offline joe_indi

  • Senior Member x2
  • *****
  • Posts: 1227
  • Age: 63
  • Location: India
  • Gender: Male
  • The older I get the more I learn
Re: Stihl MS661C Magnum issues
« Reply #3 on: July 21, 2017, 02:55:15 am »
Which part failed previously? And is it a repeat this time also?

Offline limbwood

  • Full Member
  • **
  • Posts: 79
  • Age: 57
  • Location: Eastern Iowa
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #4 on: July 21, 2017, 09:18:27 am »
do you know what caused the first blowup and what all was done to fix it?

Offline Texas-Jim

  • Full Member x2
  • ***
  • Posts: 236
  • Age: 60
  • Location: Texas
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #5 on: July 21, 2017, 08:14:55 pm »
Sadly a lot of mechanics repair a saw but never uncover the reason for the failure. There is a reason it failed, it didnt fail just because. If the mechanic cant explain why it failed than hes not doing his job. Make them explain it to you.
What we do in life echoes through eternity.

Offline LinuxRocks

  • member
  • *
  • Posts: 6
  • Location: Patterson, New York
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #6 on: July 21, 2017, 08:20:34 pm »
Compression release valve. but today I took muffler off to see the side of the piston, looks clean, no scoring...

Offline joe_indi

  • Senior Member x2
  • *****
  • Posts: 1227
  • Age: 63
  • Location: India
  • Gender: Male
  • The older I get the more I learn
Re: Stihl MS661C Magnum issues
« Reply #7 on: July 21, 2017, 10:17:58 pm »
Are you saying the problem is a  decompression valve that is stuck and won't go down/ won't release?
If that is the problem just squirt it with any lubricant and use a small hammer or spanner on a blunt pencil to tap it down. Pull it up and then push it down. It should be free once you do this a few times.
If the piston is clean at the exhaust side, remove the spark plug and turn the engine slowly. Does it turn smoothly? When you do it faster are there any abnormal sounds? If its a no, the crankshaft should be good.
What is the color of the deposit on the spark plug? Is it wet?

Offline LinuxRocks

  • member
  • *
  • Posts: 6
  • Location: Patterson, New York
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #8 on: July 21, 2017, 11:44:06 pm »
The stem was up when it blew the 1st time. I think it's that little black bugger M-tronic thats acting up. I could see the piston thru the exhaust port after muffler was off and its clean no gouges... They're going to get it back it's still under warranty

Offline LinuxRocks

  • member
  • *
  • Posts: 6
  • Location: Patterson, New York
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #9 on: July 21, 2017, 11:44:54 pm »
Turns easily, no grinding or sound of grit...

Offline joe_indi

  • Senior Member x2
  • *****
  • Posts: 1227
  • Age: 63
  • Location: India
  • Gender: Male
  • The older I get the more I learn
Re: Stihl MS661C Magnum issues
« Reply #10 on: July 22, 2017, 12:52:13 am »
Does 'blew' mean the engine came to a sudden stop and it was stuck,or was it like a sudden switching off. With engine turning over without starting?

Offline LinuxRocks

  • member
  • *
  • Posts: 6
  • Location: Patterson, New York
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #11 on: July 22, 2017, 01:19:51 am »
They replaced Piston, rings and pin. it would turn over when pulling but was very low compression

Offline Texas-Jim

  • Full Member x2
  • ***
  • Posts: 236
  • Age: 60
  • Location: Texas
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #12 on: July 24, 2017, 07:02:30 pm »
Not sure the compression release would cause a failure. It just make lower compression which lead less power. I have fixed many that leaked and customer used them for years. The m tronic shouldn't cause failure either, it cant lean it out to the point of damage, it could over fuel it but it has preset limit on leaning it out. You need know what rpm its running under a load, if its over revving it can fail, theres just a bunch of things can cause it.
What we do in life echoes through eternity.

Offline joe_indi

  • Senior Member x2
  • *****
  • Posts: 1227
  • Age: 63
  • Location: India
  • Gender: Male
  • The older I get the more I learn
Re: Stihl MS661C Magnum issues
« Reply #13 on: July 25, 2017, 08:36:44 am »
Last evening I was starting up a MS461 after a complete engine job. Remembering this thread I paid a bit more attention to the saw since the 461 too is a stratified saw.
Compared to its non-stratified brethren the stratified saws seem to have less compression resistance, be it the 461 I had repaired or the Husky 575 that I tried afterwards.
A 661 too wouldnt be different, I think.
A practice operators here follow is to have the decomp valve up during early morning cold starts.
 

Offline Riwaka

  • Full Member x2
  • ***
  • Posts: 175
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #14 on: July 26, 2017, 03:49:50 am »
How did you run the 661C in? The dealer around here says to use about 5 tank fuels of gas mix in them initially cutting wood through the rev range initially and going through heat- cool down cycles without getting the saw too hot.

What octane rating gas do you run, these new high performance stihls like high octane with no/ very low (less than 25percent  ethanol in the manual for m-tronics) ethanol.
50:1 might be a bit lean on the oil for heavy work, what is recommended for your area/ heavy cutting? 40:1/ 45:1 etc?

The Lucas Oil chemical engineers formulate a semi-synthetic mix oil for 2 strokes including saws.
https://lucasoil.com/products/2-cycle-oil/2-cycle-land-sea-oil-tc-w3
Stihl have gone down the full synthetic road. My old stihls lasted on mineral 2 stroke oil - the old blue color product.
https://www.stihlusa.com/products/oils--lubricants-and-fuels/oils-and-lubricants/oilhpultra/

I wonder if you don't have to carry your saw into the woods, that a Kohler 4 stroke industrial is a preferable power source rather than the new computer/ electronic chainsaws?
http://petersonsawmills.com/articles/2016/11/slabber-mill/


Offline Texas-Jim

  • Full Member x2
  • ***
  • Posts: 236
  • Age: 60
  • Location: Texas
  • Gender: Male
  • I'm new!
Re: Stihl MS661C Magnum issues
« Reply #15 on: July 27, 2017, 10:39:01 am »
Any saw should have a short break in time, im not sure it needs 5 tanks of fuel, thats a long time. I never use a compression release. Iv started 880's and never used it on them. Saws simply start better with more compression. Now to be fair I'm 6'5 and 240 pounds so im a big boy. But if you can pull it with release popped up then forget using it.

The fact a saw is stratified doesn't play a role in being hard to pull. Old saws and new ones have almost identical compression if release is popped up. But if look at rewind spools they increased size of them, that gives you a tad more leverage but also slows the rpms down when you pull on it. Not sure if its enough that you can really tell, i cant but in theory it would.
What we do in life echoes through eternity.