MS250s flywheel and recoil starter

[woodmass14]

Hello,

I was given an MS250/C 2009 from my Dad as he gave up on trying to fix it/spend more money on it. About 3 years ago a couple of fins flew off the flywheel and broke the bottom of the crankcase. He bought an new flywheel and crankcase and rebuild the saw. It started alright but after a couple of days of use the flywheel started eating away the starter system. It became harder and harder to pull before breaking and we'd end up having to change the pawls regularly as we couldn't find the source of the issue. The pulley has been replaced 3 times as the flywheel starts eating away the outer edge of it and pawls end up breaking the plastic of the pulley.

I've had this chainsaw disassembled a couple of times trying to figure out this issue but i can't find what's causing the issue. I thought it may be the crankshaft but can't see anything wrong with it, the ball bearings aren't damaged, wobbly and the piston is in great condition. I thought my dad may have bought aftermarket parts which caused the engine to sit incorrectly on the case but he pulled out the receipts and all the replacement parts were OEM.

Any ideas what could cause these issues?

 

[pioneerguy600]

I moved this post over to chainsaw forum. Can you post a few pics of the flywheel and inner parts of the recoil, that will give us something to work with?

 

[woodmass14]

I moved this post over to chainsaw forum. Can you post a few pics of the flywheel and inner parts of the recoil, that will give us something to work with?

Sorry about that. Of course! Bit dark in the shed at the moment but will upload some pics tomorrow when the sun is back out.

 

[pioneerguy600]

Sorry about that. Of course! Bit dark in the shed at the moment but will upload some pics tomorrow when the sun is back out.

No problem, the pics will help circumvent a lot of guess work.If you can find any numbers on the flywheel that also would be of great assistance, I am thinking that the flywheel may not be the correct one for your year and model.

 

[woodmass14]

Curiosity got the best of me. Brought the saw and parts in the house to take some pics. I'll happily take some more pics if you want some close ups of somewhere specific. The flywheel PN "11234001203A" Both are identical. I even had the old flywheel back on at some point but it was still messing with the starter, but that could be because the grooves in the old flywheel have worn down.

I should have mentioned in my 1st post that the replacement recoil starters we've bought are not OEM. Between me and my Dad we have purchased 3 full starter recoil pre built ready to install, all claiming to work with the MS250 along with a couple of replacement pulleys. Even tried rebuilding the original starter but ended up the same way as the rest. We were using this saw regularly before the case and flywheel were replaced and didn't have many issues with the starter, so i'm confident it's not us pulling the wrong way.

There are 4 different pulleys in the pics. The rope is loose because the spring just flew out of it. That'll be fun to fix.

 

[woodmass14]

Forgive the red paint. I had the idea to paint it a little to see where the flywheel and pulley were touching

I'm beginning to question if this flywheel is OEM. I'm comparing both but there are subtle differences. No S or N on the front of the new one and the texture of the material is rough compared to the original. I didn't notice the "warning, alteration or misuse may cause burst hazards" printed between the fins on the original that's not on the new one, yet the product numbers are the same

 

[pioneerguy600]

From your pics it appears that the nylon/plastic rotor is too large to fit inside the flywheel recess, are the recesses/cavity the rotor sits inside the flywheel both the same diameter on both the flywheels?

 

[pioneerguy600]

If you are using AM recoil setups that could be a problem, I have several, 4-5 025`s here at the moment but not a MS 250 to look at, my Media-Cat disc is in another computer at home so right now I cannot check the numbers off the flywheel but if they are both the same it probably is the correct one since they are both OEM. I have had many AM parts not fit correctly, a lot of the AM stuff is listed as it will fit many models but in reality there are times they do not correctly. I would measure the diameter of the rope rotor and compare that to the diameter of the cavity in the flywheel, the rotor must be a good bit less in diameter to clear the bumps in the inside the cavity, it appears the flywheel is rubbing the entire circumference of the rotor, not enough clearance.

 

[pioneerguy600]

Running a little search through my notes on these saws I confirmed for myself a thought I had from the outset that these saws had two different flywheels, yours with the 1123 400 1203 number and one with a 1123 400 1207 flywheel. I had to buy and service several recoils of these saws and kept a few part numbers and notes as usual for me. From my notes I do not see where I measured these, just went off part numbers not measurements at the time, the catch pawls and spacing springs seem to be the same between the two.

 

[stihltech]

I would at least get an original equipment rope rotor to compare to. AM is never a guarantee it fits.
This is why we say buy two and maybe one will work.
The crank does not have any side or end play, correct?

 

[Lightning Performance]

Seems like a different seller would have a correct rope rotor if you buy them AM complete. Many times the issues are man made not your fault. Only see this kind of destruction with mismatched bits.

 

[woodmass14]

From your pics it appears that the nylon/plastic rotor is too large to fit inside the flywheel recess, are the recesses/cavity the rotor sits inside the flywheel both the same diameter on both the flywheels?

Sorry for the wait. Removed the flywheel to get a better look at it. There's a 1mm difference. The original flywheel diameter is 1mm bigger than the newest one.

If you are using AM recoil setups that could be a problem

I would at least get an original equipment rope rotor to compare to

I may ask a friend of mine if i can borrow his entire recoil starter for testing purposes. He also has a 250 from around the same period. If it ends up doing the same i'll buy him an OEM replacement, but that will at least tell me whether its the flywheel or something else. Or better yet, ask to borrow his flywheel just to rule out the replacement flywheel, that way i'm not destroying his original starter recoil.

I would measure the diameter of the rope rotor and compare that to the diameter of the cavity in the flywheel

Hopefully i've understood your instructions correctly.
Old flywheel 36mm inner, 44 outer
New flywheel 35mm inner, 43mm outer
Rotor 51mm
The inner part that holds the pawls is 32mm which leaves 9.5mm gap on each side for the flywheel

The crank does not have any side or end play, correct?

Hi Stihltech, I couldn't say to be honest. It's something i've just learned today after googling your question. I'll look into it

 

[pioneerguy600]

Sorry for the wait. Removed the flywheel to get a better look at it. There's a 1mm difference. The original flywheel diameter is 1mm bigger than the newest one.


I may ask a friend of mine if i can borrow his entire recoil starter for testing purposes. He also has a 250 from around the same period. If it ends up doing the same i'll buy him an OEM replacement, but that will at least tell me whether its the flywheel or something else. Or better yet, ask to borrow his flywheel just to rule out the replacement flywheel, that way i'm not destroying his original starter recoil.

Hopefully i've understood your instructions correctly.
Old flywheel 36mm inner, 44 outer
New flywheel 35mm inner, 43mm outer
Rotor 51mm
The inner part that holds the pawls is 32mm which leaves 9.5mm gap on each side for the flywheel

Hi Stihltech, I couldn't say to be honest. It's something i've just learned today after googling your question. I'll look into it

I see you have been busy inspecting the parts and that is a good thing, I can not definitely say what is causing your issues but we know the flywheel is contacting the rotor when running and it should not if all parts are correct. I found out today that there are two different recoil housings for these saws also. One may be deeper in its construction, therefore it would position the rope rotor outward further away from the flywheel than the ,lets call it the thinner second version does. If you can borrow an OEM recoil from the same period saw you have then that might just clear this issue you are having up. I think the bearings would have to be totally shot to allow the flywheel to move enough to contact the rope rotor and that much movement would wreck the radial seals creating a massive air leak. Just a thought, have you checked to see if the 4 bolts holding the engine/crankcase in place are completely tight, the bolts that are on the bottom of the cylinder cradle assembly.?

 

[woodmass14]

Just a thought, have you checked to see if the 4 bolts holding the engine/crankcase in place are completely tight, the bolts that are on the bottom of the cylinder cradle assembly.?

They are tight. That's one of the first things i checked after changing the crank case originally. I do have the original recoil housing, minus the rotor. Does anyone know if the ms170 (2002) rotor is the same as the ms250? I'm looking at one currently and they look similar. I'm thinking of throwing that in the original housing with the old flywheel. I believe its a stihl made rotor. Certainly looks better quality than the replacements i've been buying.

 

[pioneerguy600]

Same part number so it should fit.

 

[woodmass14]

Same part number so it should fit.

Thanks for confirming Pioneer! I'll try that out tomorrow before asking my friend for his

 

[pioneerguy600]

Thanks for confirming Pioneer! I'll try that out tomorrow before asking my friend for his

Ok, let us know if it works.

 

[ZeroJunk]

If the cage that separates the crank bearings comes apart then the bearings can bunch on one side and give the flywheel enough room to bang around on whatever.

 

[pioneerguy600]

If the cage that separates the crank bearings comes apart then the bearings can bunch on one side and give the flywheel enough room to bang around on whatever.

It will certainly bang against the module since it is usually not more than .015 away from it.

 

[woodmass14]

I put the ms170 rotor in the original recoil starter housing and all looked good, but that is now damaged. It started well after the first couple of pulls, turned off the chainsaw and tried starting again, that's when it broke. I'll try post an image shortly. I'm going to look more into Stihltechs question and Zerojunks info as i'm starting to believe its not the starter OEM or AM. Time to take it apart again. Could probably do it with my eyes closed at this point