Stihl 261 problems

[spudulike]

Most chainsaws have two carb settings, a High and Low speed as most saws generally spend their running life at idle or flat out or "WOT", wide open throttle!

 

The standard adjustment is to wind in the L screw until the saw races and then bring it out past the max revs and then set the saw to within 1,000 rpm of the max factory setting. This suits most owners who want to release the fastest cutting speed from their saw - no point in getting a 346XP capable of over 14,000rpm to tune it to 10,000rpm:confused1:

 

The exception to this is if the saw is to be used for milling - when I would make sure the top end mix is richened for when it is flat out for longer periods than used for ringing up! This will keep it cooler and better lubricated on long cuts.

 

Your problem has probably been caused by the stringent laws in the USA known as EPA laws, two strokes are dirty engines, much of the fuel mix is pumped out unburnt and the US laws are clamping down on this - I see the 125cc class of GP racer is being stopped from 2012 being replaced by 250cc four strokes - environmental laws!

 

Large manufactures have to demonstrate they are doing all they can to uphold the EPA laws so they make all our saws run lean as they possibly can, I see the latest Stihls are using two choke carbs and the US MS200Ts have a power valve on the carb to keep it lean plus all their saws have catalytic convertors - poor sods! Also see the comments about the new 201 bogging down off idle - WEAK MIX:thumbdown:

 

Your saw - my theory is that it was tuned correctly for fast running from the factory but at mid revs, due to the factory setting the low rev mix so lean to meet EPA laws, the saw leaned out and seized.

 

If I was to set up a saw for carving, I would fatten up the L setting - perhaps 1/4 - 1/2 turns out on top of standard and 1/4 turn out on the H screw - it may smoke a tad more when cold but it wouldn't seize!

 

Just got an MS200T in for the same reason -carving, went bang - seizure!

 

Let your service technician know if you are carving and get the saw set up accordingly, if he looks at you blankly - change your technician!!

[Megatron]

Adding more oil to the fuel will in fact make the fuel to air ratio leaner but I doubt 5% would have resulted in this. IMO it sounds like the saw was set up to lean from the factory.

 

Saws don't really like running half throttle, but it's more likely to cause sooting than seizing.

 

Due to the nature of design of a chainsaw carb the air/fuel ratio will be leaner at part throttle than at either idle or full throttle. However, most carbs nowadays have a part-load jet which lessens this effect, don't know if the MS261 has.

 

The other positive is that the non-OEM barrels and pistons are pretty cheap and work very nicely in my experience, even for milling (my 044 has worked fairly hard this year on one with no problems) so at least you should get a saw back together for a reasonable cost (although less reasonable if you consider the circumstances).

 

I don't believe there are any aftermarket piston and cylinders available for the MS261.

 

 

Your problem has probably been caused by the stringent laws in the USA known as EPA laws, two strokes are dirty engines, much of the fuel mix is pumped out unburnt and the US laws are clamping down on this

 

Large manufactures have to demonstrate they are doing all they can to uphold the EPA laws so they make all our saws run lean as they possibly can, I see the latest Stihls are using two choke carbs and the US MS200Ts have a power valve on the carb to keep it lean plus all their saws have catalytic convertors - poor sods! Also see the comments about the new 201 bogging down off idle - WEAK MIX:thumbdown:

 

Surley the German made saws we receive are governed directly by EU regulations as well as indirectly by EPA ones?

 

By "two choke carbs" I presume you are referring to the twin barreled carbs found on the MS441 etc. This is due to them having engines with stratified scavenging, which in itself will not make a saw run leaner.

At the start of the exhausting and scavenging cycle, fuel free air first streams from the transfer ports into the combustion chamber and scavenges the exhaust gas into the exhaust port. The head air prevents the subsequent fuel-air mixture from entering the exhaust port, thus reducing the environmental impact by reducing the fuel-laden scavenging losses and the fuel consumption.

 

What is a "power valve"?

 

Are you sure you don't mean all US saws have spark arresting screens instead of all US saws have catalytic converters?

[agg221]

Due to the nature of design of a chainsaw carb the air/fuel ratio will be leaner at part throttle than at either idle or full throttle. However, most carbs nowadays have a part-load jet which lessens this effect, don't know if the MS261 has.

 

Interesting - when I ran the 066 on the Ripsaw mill it was seriously overpowered and snapped the bands if I ran on full throttle, so it spent a lot of time at half throttle. This didn't kill it, but I ran a slightly oil-rich mix and it tended to soot up the plug, hence my comment above. A symptom of the excess oil rather than the lean mix?

 

I don't believe there are any aftermarket piston and cylinders available for the MS261.

 

Sadly for the original poster, you appear to be correct - I was posting as I was about to leave for work this morning and just presumed that it would be easier to get bits for than some of the 40yr old ones. On that basis, if it was mine I would be inclined to confine it to the back of the shed until non-OEM parts become available and buy an 026 on Ebay in the meantime, since overall this is likely to be the cheaper solution!

 

Alec

[munksapprentice]

I thank you for all your comments. When I say I add 5% extra. I have a stihl mixing bottle where you squeeze it untill the top chamber fills to 100ml. It always bothered me that if you fill it to the exact mark there is always a little oil left (ie around the sides) in the chamber when poured out. So I may be wrong but I thought by adding an extra 2mm above the line accounts the the oil left in the chamber.

I really can't say anything bad about them at the moment as i'm still waiting for a responce but i have faith. You have to don't you.

I know when my local dealer priced up my saw to repair, it would be cheaper to buy a brand new saw. Crazy I know.

I like the stratisfied saws as i'm inhaling less fumes when carving as they realy are clean running. But obviously the tolerances are really tight hence saw siezing.

This whole situation has really confused me as I can't really justify a larger saw to use just for carving. The 200 is ok with its carving bar but when doing larger pieces it would take you forever just using it. The 441's have spent hours carving and running on half throttle at times but there heavy to use and harder to control when the decide to kick back. I'm a big lad and can handle them but it still takes it out of me. Thats why the 261 was bought as its lighter and with a 13" guide bar its perfect for the job. Its also perfect for smaller jobs and logging.

Don't get me wrong i can understand in theory as to why the saw would run leaner when not flat out but in my mind it should still be able to do it. It would be crazy to run it flat out when carving as if it decided to kick back badly it may want to hurt me and happen that quick that I would not have chance to stop it. As you all know you only usually get one chance with a saw and i'm not willing to take it.

Who'd have thought it. You can only run it flat out or it breaks. Its crazy. It puts my whole carving career into the air. I can't jusify to keep losing saws when carving its not worth it. But i love doing it and can create some stunning furniture.

Anyways babble over. Thank you so much for taking the time to read and reply. It really is very much appreiated.

Thank you

[munksapprentice]

If I an suss how to do it Ill post a picture soon of the chair I made when the 261 died. It was completed using the 441's and has come out looking beautiful. Well I think so anyways lol

[spudulike]

 

Surley the German made saws we receive are governed directly by EU regulations as well as indirectly by EPA ones?

 

 

What is a "power valve"?

 

Are you sure you don't mean all US saws have spark arresting screens instead of all US saws have catalytic converters?

 

I have two 357XP EPA saws - both have decomps that push the fumes back in to the crankcase - the decomp valves cost £30, it is over engineered and they go wrong leaving you with a fried piston. My thinking is that without the US EPA laws, the saw would have a standard decomp valve and few problems.

 

Been on Arboristsite - the US one and there are many posts on there about the cats in their saws - just going on what they say - I don't mean spark arrestors.

 

The point I am making is that if you carve with your saw, running a little rich at the low and high end will protect the saw from this sort of problem and manufactures tune their saws on the lean side to meet emissions laws so using a new saw to carve with may not be a good idea - no points scoring just good advice:thumbup:

 

Oh .......Power valve -

[munksapprentice]

Sorry guys I can't upload a picture. It wont let me. I cant even upload it is a profile picture as the file size is to big. Shame.

[spudulike]

Sorry guys I can't upload a picture. It wont let me. I cant even upload it is a profile picture as the file size is to big. Shame.

 

Open the picture using Microsoft Office Picture Manager and resize it to around 45% and it should upload then. If you don't have it, use "Paint" and resize - just right click on the image and select "open with".

 

Oh - I fix PCs as well:thumbup:

[spudulike]

OK - the YPVS powervalve wasn't the one I was on about - brought back some good memories though:thumbup:

 

Some of the MS200Ts in the states have a small valve that pumps fuel in to the inlet when you open the throttle from idle, this appears to be highly problematic with the usual fix to be blocking it up with suitable sealent and retuning the L screw.

 

Just another issue caused by overly stringent US environmentalists - well thats what the US guys say!!

[munksapprentice]

Thank you. I got the picture down to 38kb but it still says the same thing when i press save "unable to save image" but gives me no reason as to why. Sorry. I will try again tomorrow just incase its feeling that way out today. Ive tried loads of times and its doing my head in.