Stihl 261 problems

[munksapprentice]

might have got it this time

[munksapprentice]

two more pics

[munksapprentice]

just the one more

[Megatron]

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.

I agree that the decomp system is over engineered but I'm pretty sure it doesn't send exhaust fumes back in to the crankcase Rather than an EPA scheme I thought it was a Husky idea gone bad. Pretty sure they stopped installing the auto decompression on later models because of all the problems and there is a tech note outlining the required parts to either turn it into manual decompression or plug the decomp.

 

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.

I suppose California and a few others might be different but I thought the majority of the US states were the same as us i.e. some model saws are available with catalytic converters but you can also get the same model saw without one. There are a lot of Stihl saws for example where catalytic mufflers are not even an option.

 

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:

 

Yes, I agree it is a good idea to run slightly richer than EU/EPA regulations permit/suggest. However, don't do it on a saw still under warranty.

[Megatron]

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!!

 

Oh, you mean the accelerator pump. Yes there are numerous accounts of the carbs getting air leaks as a result of having said pump. The pump is supposed to give the saw better throttle response by offering a solution to the different "reaction times" of the fuel vs air when the throttle plate is opened. The general concensus seems to be it wouldn't need the pump if the L screw was allowed to be richened up.

AFAIK, all MS200T carbs now have them, not just the US. A lot of other Stihl saws have them also e.g. MS361, MS362, MS441,...

[spudulike]

just the one more

 

Nice job - think I can see how the esaw seized now - you must have shifted one heck of alot of wood to make that - puts the normal owls and mushrooms in to the shade!

 

Good job and think we have come to the conclusion that running a richer carb setting will reduce the risk of premature detonation of the saws top end!

[munksapprentice]

Thank you for the complement. It is a little diseaving though. The bulk of the work was carried out with the 2 441's. 1 with a 25" guide bar and the other with an 18" guide bar. The 261 was only used to shape where your back rests on the chair and to shape where your bum sits. But it never made it that far it only did a little of the shaping of the back before it siezed. The 441 with the 18" finished the job with ease.

I will let you know what the outcome is once I know myself.

[morten]

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.

 

Spud. Did you really mean "... the L screw ...". I would think it is the "H" screw that determines the high-end (FOT) mixture. Just want to avoid someone trying to adjust high-end by fiddling with the "L" screw.

 

/Morten

[spudulike]

Spud. Did you really mean "... the L screw ...". I would think it is the "H" screw that determines the high-end (FOT) mixture. Just want to avoid someone trying to adjust high-end by fiddling with the "L" screw.

 

/Morten

 

Apologies - think my typing was going faster than my synapses:001_rolleyes:

 

This is what I meant: -

 

 

To clarify - I was talking about the L screw, if you have adjusted carbs before, you will know that if you screw the L screw in, the saw goes from normal idle, to a racing idle and then dies as the screw shuts off all the fuel.

 

The max revs I am talking about is the FAST IDLE speed caused by the weakness of the idle mixture - the same effect you get when you are about to run out of fuel.

 

Standard procedure for a rough cut tune to the idle mix is to turn the screw in until the idle races and a bit beyond to the point the saw dies and then undo the screw past the fast idle stage and about 1/4 turn past it and then adjust the idle with the idle speed adjustment screw.

 

 

This would be followed by either a tune to the H screw by ear or by tach if you have one. If you don't understand the effect of fourstroking on the max revs of a chainsaw or have experience of doing this adjustment - leave it to the experts!

 

If milling or carving, making both adjustments rich would be benificial to the saws life.

 

Hope this clarifies - any questions - just ask! Thanks for pointing out the error - I put the blame on beer:thumbup:

[munksapprentice]

I just thought i would let you know that Stihl are standing by there warranty and are going to supply me with a brand new 261. My faith in my dealer and Stihl has paid off. Perfect