Stihl MS 150C - Will not rev.

[arboriculturist]

16 minutes ago, spudulike said:

Pulling the bearings and working on the crank is like working on a sewing machine. everything is super small on these saws and typical bearing pullers etc are pretty useless on this tiny engine. 

The plus point is that the saw is relatively easy to take apart.

The crankshaft should have no in and out movement as the bearings are a interference fit on the cank shaft unlike the MS200T. There should also be no up and down movement as the bearings are ball races. Don't confuse the sprocket movement as crank bearing movement.

Thankyou Steve.   I have the bare engine on the bench clutch and flywheel off.

 

There is definitely some in and out movement and up and down movement of the crank in the bearings.   

 

This saw has had a lot of use, so I would expect some wear in the bearings over 12 years of use.   I find it easy to work on.   I have a good level of engineering skill, not on your level of course.    I have no hesitation in pulling the bearings and replacing.   

 

I cannot see on any schematic of a MS150 C if there is a seal between the 2 halves of the crankcase, you would know of course.   

 

Some may say I am wasting my time, but parts are lo cost for this saw and I am happy to persist.

[spudulike]

The engine is a bit strange in the fact the crankcase is split in to two halves but has a plastic cradle a bit like a clam shell type engine.

The bearings and seals are a push fit in to the cases. 

It will be a good learning curve and it will be worth opening up the outlet hole under that muffler top cover. You will get a good increase especially if you go for the nylon air filter as well. A real simple mod, cheap and effective.

[Mark_Skyland]

This is a parts diagram, it may help with understanding how the bottom end is put together.

MS150.pdf

 

[arboriculturist]

37 minutes ago, spudulike said:

The engine is a bit strange in the fact the crankcase is split in to two halves but has a plastic cradle a bit like a clam shell type engine.

The bearings and seals are a push fit in to the cases. 

It will be a good learning curve and it will be worth opening up the outlet hole under that muffler top cover. You will get a good increase especially if you go for the nylon air filter as well. A real simple mod, cheap and effective.

Excellent ! I will change the old for a new nylon filter.   This 12 year old saw has a single piece muffler with no top cover. Yes very good learning curve.

[arboriculturist]

28 minutes ago, Mark_Skyland said:

This is a parts diagram, it may help with understanding how the bottom end is put together.

MS150.pdf 111.95 kB · 2 downloads

 

Ideal - Stihl diagram is slightly different than the L&S ones I have used. I shall post how this all pans out. Thankyou.

[spudulike]

23 hours ago, arboriculturist said:

Excellent ! I will change the old for a new nylon filter.   This 12 year old saw has a single piece muffler with no top cover. Yes very good learning curve.

So it doesn't have a small torx screw on the top like below? Every MS150 I have ever had in has had one. 

[Dan Maynard]

Think this is the rear handled one he's doing so maybe that case is a different shape?

[arboriculturist]

On 03/03/2024 at 19:38, Dan Maynard said:

Think this is the rear handled one he's doing so maybe that case is a different shape?

 Yes it is  - the MS150 C and there is no torx screw - it is 100% one piece with nothing removable. Can I still mod this Steve ?

[Dan Maynard]

6 minutes ago, arboriculturist said:

 Yes it is  - the MS150 C and there is no torx screw - it is 100% one piece with nothing removable. Can I still mod this Steve ?

I've not looked at one of these closely, the top handle has a small outlet and you get quite a bit more power from opening it up so i imagine as long as there's more hole area it'll help. Some people just drill a 6mm hole in the side of the exhaust.

[arboriculturist]

9 hours ago, Dan Maynard said:

I've not looked at one of these closely, the top handle has a small outlet and you get quite a bit more power from opening it up so i imagine as long as there's more hole area it'll help. Some people just drill a 6mm hole in the side of the exhaust.

Maybe Spud has done these mods in the past ?