Stihl MS250 - Chain Loose then Tight - Won't Run

Gotcha MM. I have only worked on Huskys.

 

I removed the clutch and found no other pieces of anything floating around. I bought a new needle cage bearing from the dealer today, and installed it with some grease -- saw runs well now. Did not have time today to cut some wood with it, so there is still that open question. Regardless, the saw is running again, and my thanks to everyone for their input and advice. I really appreciate it.

This leaves three issues. First, the chain continues spinning when idling. How do I address that?

Second, when I ran the saw today, I ended-up with a lot of bar/chain oil on the bar near the oil output, around the clutch drum, and on the cover over everything. I had cleaned out the oil hole on the bar before running the saw. Oil was getting to the chain (I could see oil on the chain, and it was spraying off the chain some as well), so it was functioning. It is cold here in CT, so I thought the simple answer might be that the bar/chain oil was cold and therefore thicker, and was not running easily into the bar hole, so it was ending up everywhere inside of the cover. Does that make sense? If not, could the oil wormgear be malfunctioning?

Third, the pull cord comes to a hard stop at least 3-4 times on the first pull, and is jerky on all pulls after that (the cycle repeats itself every time I turn off the saw). With the spark plug out, the pull is easy and smooth. Last year, I replaced the spark plug with OEM from a different dealer (who I no longer trust, which is why I switched dealers -- I'll describe that in a separate thread). The new dealer sold me a bottle of Stihl Engine De-Carbonizer (EDTA) today and suggested that carbon build-up on the piston/in the cylinder may be the cause, although his vote was that the saw is likely damaged in some more significant way. Does the EDTA make sense? Any other potential causes?

 

No, the chain does not turn when I pull the cord

When I restart the saw hot, it is less jerky -- I can start it with one pull.

It pulls over cold, with the plug removed, easy and smooth.

 

If the chain runs at idle just turn the idle screw a little to slow it down. that'll solve that issue.

Excess oil may be caused because you are not sawing and the oil builds up on the saw as opposed to the sawdust and log. Sounds normal to me.

 

Spinning chain at idle could also be weak clutch springs - worth a check if difficult to back off idle while maintaining good idle rpm. Cheers!

 

Yeah, I wondered if there was a clutch problem. It was way overheated -- all these problems resulted from me trying to do too much with a 45cc saw, which is why I will be buying a new 60cc or 70cc saw.

If the clutch springs are weak, is there something I can do to tighten them, or does that mean I need to buy a new clutch?

 

I really wouldn't say it from trying to do too much with the saw. It's designed to be used but you do have to keep up with maintenance of equipment. If you notice a change in how it normally ran to what it is doing now, investigate why it is happening before letting it continue to get worse. When I was REAL young my only saw was a 009 Stihl. Dad had bigger ones but there was plenty of times I was making full cuts from both sides of a log. Probably cut more wood with that saw than most people will in a lifetime. Sure it took longer, but at the time it was all I had. It was light enough that fatigue was never an issue either. Still run a small saw for most trimming stuff under 14 inches.

Did the clutch drum get real hot? Does it have burn or blueish color to it? It would surprise me if the springs are bad. Did you mess with the idle screw any while you were having problems? With the drag you were having to the free wheeling it has now with a good bearing you have changed the amount of force needed to spin the chain. Any change in factory setting would effect it.

 

Kevin, thanks for the responses. No, I never touched the idle screw, but I have no idea what the first dealer did with it when I had the saw there for a minor tune up last year. I will turn the idle screw to address the spinning chain. Your evaluation on the bar/chain oil makes sense.

Yeah, the clutch drum and clutch are burned/colored. Every dealer guy that has seen the saw -- looking at the clutch drum or the clutch -- says that I overheated it. One guy thought I ran it with the chain brake on. No, I did not do that -- I just buried the saw in oak too many times, which probably has the same effect.

 

I see no marks on the surface or side of the piston (looking through the spark plug hole). I note that the original dealer (for last year's minor tune up) replaced the original Bosch WSR6F R10 spark plug with a same make and model, but R6. Was that a mistake?

I just swapped back in the original R10 spark plug, and I still got the hard stops, but it seems like fewer of them at first, and it seemed to pull a little easier. Also, I still got at least one hard stop when re-starting it a second time.

I am using the small Stihl orange oil bottle with one (1) gallon of gas.

How do I evaluate when I am at 3300 rpm to determine if the clutch springs are shot? I have not yet touched the idle screw, and it seems to be idling at a low speed with the chain jerking/spinning after starting it cold. Yesterday, when I ran the saw for a minute or so, the chain spun faster at idle. Can the idle change as the saw warms-up?

 

Without a tach, you can't - but, you can usually tell a decent idling rpm by ear (you'll often hear to set idle rpm to just below clutch engagement, but I usually go somewhat lower) - on most of the saws I've had and worked on, idle set about about 2500-2700 rpm - much higher than that and you can hear that the saw is idling high. Yes, idle can change from cold to warm - my 61 will start to idle a little high after a while of cutting - these little aluminum cubes can be finicky. If you seems to be seeing the chain jerking/spinning at a low idle setting, replace the springs. Depending on the condition of the clutch, may be worth just putting on a new clutch and be done with it - if the clutch was put in a condition to stress the springs this much, may be worth spending the money on a clutch assembly. Cheers!