Stihl 066M problems

[agg221]

I'm looking for some help with a Stihl 066M. I bought it about 10yrs ago for milling, and very shortly afterwards destroyed the barrel and piston on both this and my 064 in the same day, which was put down to a problem with the petrol batch, although it was never properly diagnosed (I posted the piston to Stihl UK, who had a look but weren't able to offer anything positive).

 

The 066M was rebuilt with new barrel and piston and has run happily since, but probably has no more than 50 engine hours on it.

 

I am very careful about not keeping fuel - I don't get through much so in this case the petrol was bought in January (from Murco) but only mixed a week ago, and I only mix one tank at a time, using a measure, and never keep it more than two weeks. I don't fiddle with the carb - the local agricultural dealers set it to factory settings with a tacho and I leave it alone.

 

I filled it up last week for the first time in a while and ran it for 15mins or so. Today, it was a bit reluctant to start and then cutting a log to length prior to milling it didn't 'feel right'. I wondered if it was oiling properly on the bar, so ran a quick spray check, during the course of which the power just died away and it stopped. Having pulled the piston it's completely destroyed, with all the signs of overheating.

 

I can get an aftermarket barrel and piston easily enough, but would really like to know what's going on. It could be an air leak, or carb, or fuel filter, but I would like to get it properly diagnosed as I don't want to wreck it again, or the 044, 051 or 076 while I'm at it!

 

Can anyone make any suggestions, or recommendations of someone who could go through it thoroughly for a diagnosis? I don't mind shipping/travelling to the right person. Once I'm confident as to what the problem was I can then rebuild it and take steps to avoid it recurring - - it's a lot cheaper than keep rebuilding them!

 

For the amount of fuel I get through, the reduced waste of part-used tanks (although they do get the bonfire going) and the peace of mind I am very much minded to go for Aspen - any views?

 

Thanks for any input.

 

Alec

[geoff]

I have used aspen in old & new saws with no probs,I would recomend it.

I se you are from essex,you can get aspen at does of colchester,or at the ulting (hatfield peverel) branch if you order it in.

I would have the saw checked for an air leak before rebuilding,but pump fuel over 3 weeks old is in my opinion getting sour.

[Steve Bullman]

the closest person i know of near to you would be Reg at Greens/Hadleigh...top notch chainsaw mechanic by all accounts

[spudulike]

Main reasons for the saw to seize like this are: -

 

1)Incorrect fuel mix - I always use 40:1 although Stihl state 50:1......two stroke oil 1L=£7.50 .........1 P&C non OEM - £100, OEM=£300:thumbdown:

 

2) Old fuel mix - the oil is degraded past 3-4 weeks and gets worse with age until it goes brown.

 

3) In the US they have sever problems with Ethanol being used as an additive, not so common in the UK but it will come - it also kills fuel-lines

 

4) incorrect carb H adjustment

 

5) Air leak from a bad carb boot, bad seal carb to boot, bad crank seals, loose cylinder etc

 

6) Loose Muffler

 

I would say the most common cause for seizure, without exception is neat fuel in cheaper saws followed by poor carb adjustment and air leaks.

 

I can pressure check, tach tune and compression check and have looked after a number of saws for members on this site. I do it as a hobby and a way of paying for my wifes love of shoes....I lied a bit about that last bit....just incase she reads this:laugh1:

 

If you want, I can take a look - If you look at my posts, I always recommend that the route cause for seizure is found before running up with new parts - pretty common sense but many people haven't a clue how a two stroke actually works and why a fully sealed crank-case is critcal!

 

Choice is yours - I have just done a Husky 262 for a member on the South coast, a 357 Husky for a local chap and have an 020 in bits aaiting crank bearings for another member.

 

Hope this helps - in your case I would fatten up the oil content in the fuel and run the saw a little richer at the top end plus ensure a full pressure check.

[agg221]

Just a quick follow-up.

 

I asked Spudulike to have a look at the saw, as he's relatively close (bit nearer to where I work than Ipswich) and also not a dealer, hence will use non-OEM parts where appropriate.

 

The problem turned out to be not entirely clear, but several things were wrong, most significantly a crank seal which had been incorrectly fitted during a main dealer rebuild and was causing a leak.

 

The saw is now fixed, picked it up earlier this week and took it out for a test run this lunchtime, felling an oak of just under 3ft dia. Saw behaved perfectly (once I put some fuel in it!) and now cuts properly too, the bar rails having been nipped up a bit and the chain sorted. Rakers are a little aggressive for full bar cutting, but I'll leave them alone for a few sharpenings and it will be spot on.

 

Very happy with the results - thanks Spud!

 

Meanwhile I've switched entirely to Aspen, which has cleaned up the exhaust, stopped my headaches and streaming eyes from milling and generally been a good thing. I've found that I can get it in Whittlesford, Cambs. about 5mins from work, which is perfect.

 

Alec

[18 stoner]

Really chuffed you've got it sorted, but just curious what you mean by "nipping up bar rails" and is there a tool for this?

 

Just a quick follow-up.

 

I asked Spudulike to have a look at the saw, as he's relatively close (bit nearer to where I work than Ipswich) and also not a dealer, hence will use non-OEM parts where appropriate.

 

The problem turned out to be not entirely clear, but several things were wrong, most significantly a crank seal which had been incorrectly fitted during a main dealer rebuild and was causing a leak.

 

The saw is now fixed, picked it up earlier this week and took it out for a test run this lunchtime, felling an oak of just under 3ft dia. Saw behaved perfectly (once I put some fuel in it!) and now cuts properly too, the bar rails having been nipped up a bit and the chain sorted. Rakers are a little aggressive for full bar cutting, but I'll leave them alone for a few sharpenings and it will be spot on.

 

Very happy with the results - thanks Spud!

 

Meanwhile I've switched entirely to Aspen, which has cleaned up the exhaust, stopped my headaches and streaming eyes from milling and generally been a good thing. I've found that I can get it in Whittlesford, Cambs. about 5mins from work, which is perfect.

 

Alec

[skyhuck]

A vice, I would guess.

[18 stoner]

So would you say thats an accurate way of doing it?

[skyhuck]

If you had a strip of steel a little thinner than a drive link (to allow for the spring back) and put that in the grove before squeezing, I think it would be pretty accurate.

[18 stoner]

Never seen or heard of it being done before.

 

My main concern was to distortion of the treated steel and control of the "nip". I would say the manufacturers would advise against doing it but in the real work situation I think there would be very little noticable effect.