Stihl MS241 NON-MTRONIC Conversion

[2strokeoil4blood]

That would certainly be a factor. You guys really get bent over on stihl parts over there.

We sure do! If I worked on more mtronic saws, I would almost be inclined to order in a bunch of solenoids from USA

 

[2strokeoil4blood]

Hey mate could you link me to a crash course on diagnosing with multimeter? Is it just testing continuity to make sure wires arent broken?

 

[lone wolf]

I would have gotten more joy from finding out what was wrong. Lol

Did you try replacing the fuel solenoid, it's the least expensive part in troubleshooting those?

 

[Doorfx]

After Spending what I spent on the rebuild, It wasnt worth it to me to take it to the Stihl shop to have it plugged in to a computer just to find out the solenoid or control units toast. I had the parts saws sitting around, so made sense to me to not over invest in the saw I'll send you all the mtronic parts i took off if you like, and you can work it out
This was also an experiment to see if it could be done aswell, some people dont like mtronic, and now the saw can be manually tuned too

I have a saw guy here that has done this dozens of times on all sizes of mtronic saws. He is old school and doesn’t understand or like them I guess. I love my mtronic 241c-m. Thanks for the parts descriptions.

 

[2strokeoil4blood]

Did you try replacing the fuel solenoid, it's the least expensive part in troubleshooting those?

No, as mentioned to another dude before, theyre $75usd over here for a solenoid, and I had all the parts here to just try it. I only made this thread incase someone else was thinking about whether it could be done to the 241, as I could not find anything online about it

 

[2strokeoil4blood]

Can you put it on YouTube, then copy and post here?

Hey mate, here is a link to a quick video of it in wood.



Was in dry blue gum wood and had already done a fair bit of cutting, will make a video of it against the mtronic one that I have on sharp chains.

Anyway, after fluffing around tuning it, I worked out that the MS251 coil is infact, limited to 13000rpm. Anyway, despite this, the saw feels amazing. I honestly think it has more balls then my mtronic one. Tommorow will confirm that!

 

[Bob Hedgecutter]

Hey mate, here is a link to a quick video of it in wood.



Was in dry blue gum wood and had already done a fair bit of cutting, will make a video of it against the mtronic one that I have on sharp chains.

Anyway, after fluffing around tuning it, I worked out that the MS251 coil is infact, limited to 13000rpm. Anyway, despite this, the saw feels amazing. I honestly think it has more balls then my mtronic one. Tommorow will confirm that!

Dude- the top fell off your hardhat!

 

[2strokeoil4blood]

Dude- the top fell off your hardhat!

Haha thats my summer chainsawing set up. Use it for ringing up when its hot, keeps head cool

 

[lone wolf]

Hey mate, here is a link to a quick video of it in wood.



Was in dry blue gum wood and had already done a fair bit of cutting, will make a video of it against the mtronic one that I have on sharp chains.

Anyway, after fluffing around tuning it, I worked out that the MS251 coil is infact, limited to 13000rpm. Anyway, despite this, the saw feels amazing. I honestly think it has more balls then my mtronic one. Tommorow will confirm that!

Can't wait to see the test between the two, thanks for posting. I find this very interesting. I just need the choke rod not throttle rod? Does the switch fit right in without mods?

 

[ammoaddict]

No, as mentioned to another dude before, theyre $75usd over here for a solenoid, and I had all the parts here to just try it. I only made this thread incase someone else was thinking about whether it could be done to the 241, as I could not find anything online about it

Thanks for your contribution. I think it's great.

 

[sean donato]

Hey mate could you link me to a crash course on diagnosing with multimeter? Is it just testing continuity to make sure wires arent broken?

Yeah, basically. The coils themselves either seem to work or not, just the same as any coil. Use a gap style tester to check them. There was a resistance listed for the solenoid a while back, but for whatever reason I can't find it quickly. (Nor do I know if it applies to the earlier solenoid(s).) Wiring harness breaks happen often enough and the solenoids like to go out from time to time. Other then that the carb is still a carb inside and all the usual components can be suspect. Hard diaphragm, fuel pump, dirt etc.

 

[2strokeoil4blood]

Can't wait to see the test between the two, thanks for posting. I find this very interesting. I just need the choke rod not throttle rod? Does the switch fit right in without mods?

Throttle rod works perfect, choke rod fit- just wouldnt actually work. Slightly different shape, could maybe be modified to work if you couldnt find one? everything was a direct fit without any modification. One thing I would note is, the 251 has a few carb variations- zamas and walbros. The Zama carb has a smaller diameter fuel inlet hose barb on it, so you need the matching fuel line for it. The 241 in question that Ive just converted already had a walbro in it so fuel line matched it, however I see my other 241 which is newer, has a Zama.
The other thing is, some of the ms251 carbs can have primers if theyre off a "easy start" model. But I do wonder, could that little black circle bit of plastic be knocked out of the top cover, and stick a primer in there? As the filter base of the 231/251s includes the bracket for a primer whether the saw it came off had a primer or not

Todays plan- see if a 261non mtronic coil I have, will work with the 241... could be a solution to the 13000rpm limiter. Otherwise, I may try the mtronic coil and flywheel I took out, apparently that may work IF i remove fuel solenoid from the mtronic carb and leave the fuel solenoid plugged in to the loom? Stay tuned

 

[lone wolf]

Throttle rod works perfect, choke rod fit- just wouldnt actually work. Slightly different shape, could maybe be modified to work if you couldnt find one? everything was a direct fit without any modification. One thing I would note is, the 251 has a few carb variations- zamas and walbros. The Zama carb has a smaller diameter fuel inlet hose barb on it, so you need the matching fuel line for it. The 241 in question that Ive just converted already had a walbro in it so fuel line matched it, however I see my other 241 which is newer, has a Zama.
The other thing is, some of the ms251 carbs can have primers if theyre off a "easy start" model. But I do wonder, could that little black circle bit of plastic be knocked out of the top cover, and stick a primer in there? As the filter base of the 231/251s includes the bracket for a primer whether the saw it came off had a primer or not

Todays plan- see if a 261non mtronic coil I have, will work with the 241... could be a solution to the 13000rpm limiter. Otherwise, I may try the mtronic coil and flywheel I took out, apparently that may work IF i remove fuel solenoid and leave the fuel solenoid plugged in to the loom? Stay tuned

Well tach an M Tronic 241 in and out of the wood first.

 

[2strokeoil4blood]

Well tach an M Tronic 241 in and out of the wood first.

Well tach an M Tronic 241 in and out of the wood first.

Oh yeah Im happy with how it goes now, im just trying to figure away around the limiter incase anyone is reading this and might want more rpm, like a saw modder I believe my mtronoc version tachos 13700 out of wood

 

[2strokeoil4blood]

Yeah, basically. The coils themselves either seem to work or not, just the same as any coil. Use a gap style tester to check them. There was a resistance listed for the solenoid a while back, but for whatever reason I can't find it quickly. (Nor do I know if it applies to the earlier solenoid(s).) Wiring harness breaks happen often enough and the solenoids like to go out from time to time. Other then that the carb is still a carb inside and all the usual components can be suspect. Hard diaphragm, fuel pump, dirt etc.

Well tach an M Tronic 241 in and out of the wood first.

Here is the piston and cylinder as it came to me from origins unknown

 

[2strokeoil4blood]

Took out the limited ms251 coil and threw in the MS261 non mtronic coil I had, annnd it works set at 13600 out of wood, and it still wants more(less)! Will try out in wood tommorow and video the results for you guys.

 

[Bob Hedgecutter]

Here is the piston and cylinder as it came to me from origins unknown

Only way an mtronic system is going to show you a piston like that is a compete and utter failure of the controlled aspect of the fuel system to deliver its promised results.

 

[sean donato]

Here is the piston and cylinder as it came to me from origins unknown

That was real lean, like air leak and kept running till she quit lean.

 

[sean donato]

Only way an mtronic system is going to show you a piston like that is a compete and utter failure of the controlled aspect of the fuel system to deliver its promised results.

I would have bet money on a bad air leak, and incompetent operator. Had a 562xp years ago i got to fix with a bad pto bearing seal. (Ended up being a bad bearing/cage.) What amazed me was it would still idle and kinda cut even though the seal was visually damaged. Fourtanlty I was able to save the cylinder, new assembled case and away it went.

 

[2strokeoil4blood]

I would have bet money on a bad air leak, and incompetent operator. Had a 562xp years ago i got to fix with a bad pto bearing seal. (Ended up being a bad bearing/cage.) What amazed me was it would still idle and kinda cut even though the seal was visually damaged. Fourtanlty I was able to save the cylinder, new assembled case and away it went.

That was real lean, like air leak and kept running till she quit lean.

Yes I would have thought the same thing if it had not run lean in wood staight after this rebuild. I never pressure tested it before rebuild but I did after with new gaskets and bearings+ crankseals.
It ran lean in cut, and heated up quick. Swap out to standard fuel system and problem solved So my money is definitely on the mtronic system being the cause originally. Showed Stihl the piston, they hadnt seen anything like it before in an mtronic saw.

Also I did pull the carb mtronic carb apart and all checked out ok visually including metering height