MS201t Problem

[Ddogwood]

Here's another wild stab. Have you taken a flywheel cover, complete with recoil, starter rope, etc., from another 201 & tried it in place of your original.
FWIW, when I bought my 201 in 2012, you could not pull the chain along the bar by hand when the clutch cover was tightened, even if the tension was loose enough to allow the chain to sag slightly. The problem turned out to be the little white plastic tabs in the clutch cover which bound the chain. Once the saw was started & revved a couple of times, the excess plastic was quickly worn away, & the problem was solved.

It is interesting that you are mentioning the chain issue, for I too have noticed that; if I adjust the chain to normal, but slightly loose tension, and then tighten down the cover; it is difficult to pull the chain along the bar. If I loosen the chain enough to sag on the bar, and then tighten the cover, it is easier to pull the chain along the bar, and it is slightly easier to pull-start.

I have inspected the clutch cover on many occasions to see if there is any apparent wear or binding occurring, either on the teflon chain guides, or on the chain brake, or if the clutch is rubbing against the cover in any manner, but there is no sign of wear or binding occurring. Also, the saw has had enough hours it to have worn away any excess plastic that may have been binding the blade, I would think.

Also, to side-step any questions regarding the condition of the clutch and bearings, there is no slop in the bearing, or wobble in the clutch or sprocket. They all spin smoothly with no play in them that might be causing them to rub against the cover when the blade is tensioned properly and the cover tightened down.

However, the chain adjustment is an issue on this saw.

I noticed that the original bar that came with the saw was in bad shape. The owner tended to over tighten the chain to the point that the bar was splaying at the tip creating burring along the outside edges of the chain channel (or chain guide), and that bar sprocket at the tip no longer spun smoothly, even when cleaned and oiled. So, I purchased and installed a new Stihl bar and chain and installed them. I thought that this would take care of the adjusting problem, but no such luck. If I properly tighten the chain and cover, it is still very difficult to pull the chain along the bar and the pull-start is harder. if I loosen the chain to sagging and tighten the cover, it is easier to pull-start. There is definitely something wrong with the chain adjustment on this saw, and it is an issue that may be design related?

Regardless; if remove the clutch cover, the bar and chain, and clutch; it is still hard to pull-start. That is, the saw would still be too hard to pull-start if up in a tree.

Thanks for your valuable input.

Ddogwood

 

[Ddogwood]

It is interesting that you are mentioning the chain issue, for I too have noticed that; if I adjust the chain to normal, but slightly loose tension, and then tighten down the cover; it is difficult to pull the chain along the bar. If I loosen the chain enough to sag on the bar, and then tighten the cover, it is easier to pull the chain along the bar, and it is slightly easier to pull-start.

I have inspected the clutch cover on many occasions to see if there is any apparent wear or binding occurring, either on the teflon chain guides, or on the chain brake, or if the clutch is rubbing against the cover in any manner, but there is no sign of wear or binding occurring. Also, the saw has had enough hours it to have worn away any excess plastic that may have been binding the blade, I would think.

Also, to side-step any questions regarding the condition of the clutch and bearings, there is no slop in the bearing, or wobble in the clutch or sprocket. They all spin smoothly with no play in them that might be causing them to rub against the cover when the blade is tensioned properly and the cover tightened down.

However, the chain adjustment is an issue on this saw.

I noticed that the original bar that came with the saw was in bad shape. The owner tended to over tighten the chain to the point that the bar was splaying at the tip creating burring along the outside edges of the chain channel (or chain guide), and that bar sprocket at the tip no longer spun smoothly, even when cleaned and oiled. So, I purchased and installed a new Stihl bar and chain and installed them. I thought that this would take care of the adjusting problem, but no such luck. If I properly tighten the chain and cover, it is still very difficult to pull the chain along the bar and the pull-start is harder. if I loosen the chain to sagging and tighten the cover, it is easier to pull-start. There is definitely something wrong with the chain adjustment on this saw, and it is an issue that may be design related?

Regardless; if remove the clutch cover, the bar and chain, and clutch; it is still hard to pull-start. That is, the saw would still be too hard to pull-start if up in a tree.

Thanks for your valuable input.

Ddogwood

PS: Oh, and Hellenger, I have replaced the whole pull-starter mechanism with a brand new OEM one. I also installed a new OEM flywheel. No change in the hard-pull issue.

 

[PV Hiker]

You have a hard time pulling and locking up, when you needed to do several back to back pulls to get a highest compression reading... how was that?

 

[PV Hiker]

The connecting rod using a different one was just checking if it was bent.

 

[lone wolf]

It is interesting that you are mentioning the chain issue, for I too have noticed that; if I adjust the chain to normal, but slightly loose tension, and then tighten down the cover; it is difficult to pull the chain along the bar. If I loosen the chain enough to sag on the bar, and then tighten the cover, it is easier to pull the chain along the bar, and it is slightly easier to pull-start.

I have inspected the clutch cover on many occasions to see if there is any apparent wear or binding occurring, either on the teflon chain guides, or on the chain brake, or if the clutch is rubbing against the cover in any manner, but there is no sign of wear or binding occurring. Also, the saw has had enough hours it to have worn away any excess plastic that may have been binding the blade, I would think.

Also, to side-step any questions regarding the condition of the clutch and bearings, there is no slop in the bearing, or wobble in the clutch or sprocket. They all spin smoothly with no play in them that might be causing them to rub against the cover when the blade is tensioned properly and the cover tightened down.

However, the chain adjustment is an issue on this saw.

I noticed that the original bar that came with the saw was in bad shape. The owner tended to over tighten the chain to the point that the bar was splaying at the tip creating burring along the outside edges of the chain channel (or chain guide), and that bar sprocket at the tip no longer spun smoothly, even when cleaned and oiled. So, I purchased and installed a new Stihl bar and chain and installed them. I thought that this would take care of the adjusting problem, but no such luck. If I properly tighten the chain and cover, it is still very difficult to pull the chain along the bar and the pull-start is harder. if I loosen the chain to sagging and tighten the cover, it is easier to pull-start. There is definitely something wrong with the chain adjustment on this saw, and it is an issue that may be design related?

Regardless; if remove the clutch cover, the bar and chain, and clutch; it is still hard to pull-start. That is, the saw would still be too hard to pull-start if up in a tree.

Thanks for your valuable input.

Ddogwood

That sounds like wrong bar and chain match! Try to start the saw with the bar chain off if that don't help take the clutch off?

 

[SteveSr]

Can’t remember, you checked squish?

I don't think so... I believe that this is an AM P&C and the OP was describing some "binding" going on as the FW was turned past TDC. So the squish might have been zero or even negative. Or it just might have been the FW magnets passing the ignition coil. We have 6 pages of speculation... Do I hear 7?

 

[SteveSr]

That sounds like wrong bar and chain match! Try to start the saw with the bar chain off if that don't help take the clutch off?

I am assuming that this saw has an outboard clutch. Any way that it can be mis-assembled to cause the center of the clutch (engine) to rub on the clutch cover?

 

[lone wolf]

I am assuming that this saw has an outboard clutch. Any way that it can be mis-assembled to cause the center of the clutch (engine) to rub on the clutch cover?

I am assuming that this saw has an outboard clutch. Any way that it can be mis-assembled to cause the center of the clutch (engine) to rub on the clutch cover?

Well I know from experience a mismatch from the oil pump drive plastic piece to the clutch sure can jam things up.

 

[boltonranger]

I have worked on small engines a long time, but I have come across a problem with a Stihl MS201t that has got me stumped.

The saw came to me in this in good condition, it wasn't too terribly dirty, the blade did seem to show signs of over tightening, but didn't seem to have too many hours on it. Anyway, I go to pull-start it and the engine turns, but extremely hard (It's like trying to start a much larger saw without first pushing in the compression release). My first thought is that there is something wrong with the pull-start, but after removing it and inspecting it, there is no problem there. Pulled the chain cover, chain and clutch, no problems there.

So, I figure that the engine is partially seized.

So I install a new after-market piston, rings, and cylinder, and put it all back together, go to pull-start it again, and the same thing happens.

So, then I think, maybe, the saw got over heated and it seized the bearings in the crank and it only becomes an issue when it is under compression? So, I found a used crankcase (Complete lower end) online that upon inspection seemed to work just just fine, and installed the new piston, rings and cylinder on to it, put the saw together, tried to pull-start it, and the same thing happens.

So, I scratch my head, pull the spark plug, and tug on the pull-starter, and it pulls easily!

So, I think, maybe I put the piston in backwards? I pulled it apart again, and find that the piston was installed correctly.

I have gone through every thing that I can think of could possibly be the problem: pulled the spark arrestor, pulled the muffler, pulled the carburetor, intake manifold to no avail.

I have pulled everything off of the motor and tried to pull-starter and get the same results; it is to0 hard to pull to get the motor to turn without really holding it down, or locking it in a vice. But, if I pull the spark plug, it spins easily!

In other words, this saw has a totally different motor in it than what came to me, but I am having the same problem!

Any thoughts?

Ddogwood

Okay, I’ve read through these excellent posts and I have a thought...

What if the crank were no longer in its original shape? I’ll try to describe what I mean. Normally the axis of the crankshaft ends is parallel to the journal where the connecting rod bolts on. Everything swings together. But let’s say for whatever reason there is a slight rotational twist on one side of crank. Slight. But there. This would create stress on one side of the crank that you might not see or feel unless you had pressure against it. Like the compression stroke. What I’m saying is that maybe the crank journal where the rod bolts on is no longer parallel to the crank axis.
The left side of the journal reaches the top of its stroke or axis from the crank center before the right side. (Or vice versa) This would create a twist on the piston and rod towards the top of the stroke. Not a big deal before the cylinder is re-installed or the plug is in.
There would be some inherent “give” in the parts. But when the cylinder is on, now there’s less room for piston to move laterally in the bore. Now add compression. Tighter clearance still.
Now the twist in the crank can’t be “absorbed” during rotation because the crankcase and cylinder bolted all together demand less lateral movement. Now there is a “fight” in the bearing loads or clearances during each rotation of the engine. You can’t “see” it. But you would “feel” it.
The tighter your clearances, the worse it would be. The more worn the bearings, the less it would be.
This would still exist if you replaced the crankcase halves or the cylinder. The more “true” they are, the more difficult it would be to pull the saw over with the plug in.

It’s just a theory that makes sense to me... the only way to prove it would be to put in a different crank or have a machine shop measure yours a few different ways.
- Might sound crazy, but it could explain the symptoms...

 

[rupedoggy]

boltonranger have you ever had a saw crank apart? Didn't think so.

 

[Ddogwood]

Okay, I’ve read through these excellent posts and I have a thought...

What if the crank were no longer in its original shape? I’ll try to describe what I mean. Normally the axis of the crankshaft ends is parallel to the journal where the connecting rod bolts on. Everything swings together. But let’s say for whatever reason there is a slight rotational twist on one side of crank. Slight. But there. This would create stress on one side of the crank that you might not see or feel unless you had pressure against it. Like the compression stroke. What I’m saying is that maybe the crank journal where the rod bolts on is no longer parallel to the crank axis.
The left side of the journal reaches the top of its stroke or axis from the crank center before the right side. (Or vice versa) This would create a twist on the piston and rod towards the top of the stroke. Not a big deal before the cylinder is re-installed or the plug is in.
There would be some inherent “give” in the parts. But when the cylinder is on, now there’s less room for piston to move laterally in the bore. Now add compression. Tighter clearance still.
Now the twist in the crank can’t be “absorbed” during rotation because the crankcase and cylinder bolted all together demand less lateral movement. Now there is a “fight” in the bearing loads or clearances during each rotation of the engine. You can’t “see” it. But you would “feel” it.
The tighter your clearances, the worse it would be. The more worn the bearings, the less it would be.
This would still exist if you replaced the crankcase halves or the cylinder. The more “true” they are, the more difficult it would be to pull the saw over with the plug in.

It’s just a theory that makes sense to me... the only way to prove it would be to put in a different crank or have a machine shop measure yours a few different ways.
- Might sound crazy, but it could explain the symptoms...

I appreciate your thoughts. Unfortunately, and this is the funny part, that I replaced the entire crankcase and crank ( or lower end) with a new used one; meaning that at this point, the only original parts left on the saw are the clutch, sprocket, oil pump (of which I have checked and found no problems) the intake manifold, carburetor, and the clutch/bar & chain cover. And, the saw is still doing the same thing. It is basically a whole new saw with the same problem that it had when I started.

Unless I happened to have two non-parallel crankshafts in relation to their journals, which is possible, I don't think that this is the issue. But, your thoughts are well taken.

I appreciate your interest!

Ddogwood

 

[Ddogwood]

That sounds like wrong bar and chain match! Try to start the saw with the bar chain off if that don't help take the clutch off?

I have done both of these suggestions with now difference. The chain an bar are correct.

 

[Ddogwood]

Well I know from experience a mismatch from the oil pump drive plastic piece to the clutch sure can jam things up.

No problem with a mis-match between the clutch and the oil pump. Checked that. The clutch is not hitting the cover or housing

 

[Ddogwood]

I don't think so... I believe that this is an AM P&C and the OP was describing some "binding" going on as the FW was turned past TDC. So the squish might have been zero or even negative. Or it just might have been the FW magnets passing the ignition coil. We have 6 pages of speculation... Do I hear 7?

Yep! Isn't it great.

Ddogwood

 

[lone wolf]

Yep! Isn't it great.

Ddogwood

wh

No problem with a mis-match between the clutch and the oil pump. Checked that. The clutch is not hitting the cover or housing

So did you try pull starting with the whole clutch assembly off yet?

 

[SCHallenger]

wh

So did you try pull starting with the whole clutch assembly off yet?

Do you suppose one or more clutch springs are weak & are allowing some contact with the drum even though the RPMs generated by pulling the start rope are very low? If that was happening, the chain trying to turn would create quite a drag.
Just a thought, & another wild stab!!

 

[lone wolf]

Do you suppose one or more clutch springs are weak & are allowing some contact with the drum even though the RPMs generated by pulling the start rope are very low? If that was happening, the chain trying to turn would create quite a drag.
Just a thought, & another wild stab!!

Could be or the wrong amount of teeth on the oil pump drive gear would jam it also.

 

[boltonranger]

Could be or the wrong amount of teeth on the oil pump drive gear would jam it also.

I once had a pull starter that was prone to jam. The cord was thin, it was braided, but could stretch slightly. When the handle was pulled, the cord on the spool would tighten and jam by sinking down into the neighboring wraps - it became stuck or much harder to pull free. I solved it by changing to different starter cord that had a good firm core. No more hard pulls. Wolf’s post about jammed teeth reminded me of it. The replacement cord I used was stiffer, more solid in the center. May have been slightly wider but not much.

Not saying that’s your trouble, but maybe something is wrong with the pull start when it is under load?

 

[lone wolf]

I once had a pull starter that was prone to jam. The cord was thin, it was braided, but could stretch slightly. When the handle was pulled, the cord on the spool would tighten and jam by sinking down into the neighboring wraps - it became stuck or much harder to pull free. I solved it by changing to different starter cord that had a good firm core. No more hard pulls. Wolf’s post about jammed teeth reminded me of it. The replacement cord I used was stiffer, more solid in the center. May have been slightly wider but not much.

Not saying that’s your trouble, but maybe something is wrong with the pull start when it is under load?

He bought a new one I thought.

 

[boltonranger]

Right you are- page 2.