Stihl MS 661 having the bog blues

[Dieselshawn]

Hey guys, we have 4 661's over the past year.

The first one the guys bought ran great for 6 months until a tree flattened it.

Then another guy in same company bought one 6 months ago.

Ran like crap, always hard to start, low power and resetting didn't work.

We have great dealer support with several dealers.

So fuel filter was changed, mastermind suggested the fuel solenoid, which was changed, no luck.

This saw also had the notorious rubber washer in the intake, not one but 2 of them. This did not cause the issues.

So the m-tronic computer and carb was swapped over from the crushed saw into the poor running saw. Issue fixed.

Saw has been running great since. (Other than the piston rings sticking and carboned up pistons that mastermind and I have discussed about)

The guy that had his saw crushed bought a replacement 661.

For a little time the saw was good then had issues of low power, bogging.

Dealer replaced the computer but it doesn't fix the problem.

The guy traded the saw in for another new one with credit from the old saw going to the new one as that one was out of warranty.

The saw was traded in as the guy was fed up and didn't want to wait for the issue to be figured out.

So I think the carb itself is the issue.

We now have 4 661's all together and 2 had issues. The new one is running great so far.

These dealers have tried many things to get saw's working right and only one got fixed by having the m-tronic and carb swapped over.

These dealers also have the plug in computer to verify issues but nothing came up.

 

[backhoelover]

lol should have read up the post

 

[coltont]

That computer that they plug them into is a joke. Even when its plugged in when the issue is present it has never said that anything was wrong. Why is it that the 661 seems to be about the only m tronic with issues? What makes it the exception?

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[Dieselshawn]

Coltont: I agree that the plug in computers are useless.

I have wondered the same thing as to why the 661's have more issues than any other m-tronic saws.

Like others have said, the 661 is supposed to be Stihl's flagship model.

One of the loggers that runs a mastermind 660 in the same company that has 661's with issues, absolutely refuses to get a 661. Even if his boss says so. (So overtime they can accumulate spare parts to fix 661's as time goes on)

He doesn't care if they're smoother or whatnot, if they don't run right, trees aren't falling, no money is being made and cost to repair or replace really adds up.

 

[MustangMike]

They likely keep tweaking it to be more emissions compliant.

 

[coltont]

I have probably 300 trailer loads of logs on mine. I'm not giving up on it. That's why we have 4saws along everyday. Isn't costing any $$ for the repair work. Mostly it's just aggravating when you carry it back into the woods and and performs worse than a wild thing. I don't feel that my saw is a good representation of a stihl product.

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[Dieselshawn]

Coltont: we do have back ups which are high hour 660's but runs just fine.

We just use them while others are in shop for repair.

I agree on 661's not being a good representation of a respectable company especially when their previous flag ship saw, the legendary 660 has been around 30 years.

 

[coltont]

Almost forgot to mention this little surprise I got from it to. I'm just glad no little pieces hit me in the face. The explosion was a result of the pull cord being too dammed big from the factory and it got a twist in it and doubled over itself and its history from there.

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[Idahonative]

Keep in mind that on an enthusiasts forum, issues often seem worse than they are.

Maybe, but this isn't just an enthusiast forum. I consider myself an enthusiast but there are plenty of guys on here like the OP who make a living with their saws. Maybe his 661 problem doesn't seem like that big a deal to some but it was a major annoyance to him and I can see his point. If I paid $1400 for a saw, it damn well better run perfect...enthusiast or not. And there are very few enthusiast who would lay down that kind of cash.

 

[DND 9000]

try to change the solenoid gasket just a thought

I think this is a good idea, to try out. Normally on the m-tronic carburetors that sealing ring isn`t availible as a spare part. They sell the whole solenoid valve with the sealing ring. But from the MS 280i carburetor (HD 39), there the sealing ring of the solenoid valve is availible as a spare part. Part number is 9645 945 3001 O-ring 7x0.8

 

[Foragefarmer]

That computer that they plug them into is a joke. Even when its plugged in when the issue is present it has never said that anything was wrong. Why is it that the 661 seems to be about the only m tronic with issues? What makes it the exception?

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I have a 241 for my business that lives in a truck box and runs almost every day sometimes all day and it has had similar issues. Two solenoids and a whole new carb.. I am not so much unhappy with the saw issues as the 90 day commercial warranty and poor dealer service that didn't fix the issue. Also I had to wait 2.5 weeks for the new carb and had to call Stihl myself in order to get it that fast, they shipped it from a different warehouse. By that point I had switched dealers and was working on the saw myself. In the mean time I bought an 026 as a dedicated backup.

 

[blsnelling]

Maybe, but this isn't just an enthusiast forum. I consider myself an enthusiast but there are plenty of guys on here like the OP who make a living with their saws. Maybe his 661 problem doesn't seem like that big a deal to some but it was a major annoyance to him and I can see his point. If I paid $1400 for a saw, it damn well better run perfect...enthusiast or not. And there are very few enthusiast who would lay down that kind of cash.

You misunderstood me. My point is that we on this forum are going to see more issues than the normal Joe. Anyone with an issue on this forum posts about it, making the issue seem more wide spread than it really is.

 

[blsnelling]

Saw has been running great since. (Other than the piston rings sticking and carboned up pistons that mastermind and I have discussed about).

What fuel, oil, and mix ratio?

 

[Dieselshawn]

BLSnelling: they use 92 e-free gas, 45:1 mix, and tcw3 oil.

They've used the oil for long time in 660's but since they purchased 661's they've had 4 Pistons carboned up and stuck rings in 2 of their 661's.

 

[blsnelling]

BLSnelling: they use 92 e-free gas, 45:1 mix, and tcw3 oil.

They've used the oil for long time in 660's but since they purchased 661's they've had 4 Pistons carboned up and stuck rings in 2 of their 661's.

That's the wrong kind of oil, whether it's worked in the past or not. That's a pretty obvious place to start. Hard to put any blame on Stihl when running the wrong kind of oil. Just sayin'.

 

[Dieselshawn]

It is wrong oil in my view as well, but I couldn't argue with them as they said of was better than the stihl oils they used in the past.

They've had no crank or big end failures of any kind.

One of their 660's they just retired has about 9,000 hrs on it. Used every day since 2009. No failures. Just worn out.

The issues the 661's have isn't oil alone. It's part of one problem

 

[blsnelling]

Maybe so, but it's an obvious place to start. A base line has to be established, following Stihl recommendations. Unfortunately, there's no longer the ability to use a little orange screwdriver to tune around issues or deviations from factory. Oil and oil mix ratio can have a significant affect on how these MTronic saws run, some more so than others.

 

[Dieselshawn]

You are correct brad. I don't run those saws but the very first time I saw the piston in the 661 that had jammed rings, I said right away "oil issue".

The company president got pi$$ed and said its not the oil.

But after 4 times of cleaning and fixing their saws. Thete getting the idea.

They're using stihl oil now.

 

[blsnelling]

There's a local contractor here that runs a large lawn care operation. He went through one BR600 after another. He was using TCW3 oil from Wal-Mart, IIRC. He refused to use Stihl oil. He was too cheap to run anything else and insisted that it shouldn't matter. They finally convinced him to use Stihl oil and his problems went away. As the saying goes, you can't fix stupid, lol. I feel your pain!

 

[Dieselshawn]

It's unbelievable how hard it is to fix stupid and some are destined to remain stupid.

But I'm glad They're getting the idea.

I'll be using yamalube 2r once they arrive for my personal 660.

I was using stihl oil, Belray, and sometimes that tcw3 they used.

My 660's piston is clean.