stihl ms200t throttle problems

[avinit]

Hi I have 2 ms200t saws both with problems.

 

On one you can get it to fire on throttle but when you click the stitch forward onto half throttle it wont stay there ? it moves straight forward to the on position. I have opened up the handle and had a good look around but cant see which bit is worn / faulty - has anyone else had this problem and know which part is the culprit ? Apart from that the saw runs fine.

 

On my other one it has the complete opposite problem. Normally you would pull the cord on choke until it fires then move the trigger forward to half choke. But it doesn't fire once it keeps firing/running. Then flick onto half choke and it starts but then dies within a few seconds ?? Any ideas ?

[peatff]

Hi I have 2 ms200t saws both with problems.

 

On one you can get it to fire on throttle but when you click the switch forward onto half throttle it wont stay there ?

 

Choke and fast idle ? Once it coughs on choke the choke is shut off and fast idle engaged. It could be the linkage to the carb that needs tweaking, the piece of springy rod probably lost it's tension and needs bending a bit. The other one sounds like it might need to be a bit richer if the carb is alright.

[GardenKit]

Hi I have 2 ms200t saws both with problems.

 

On one you can get it to fire on throttle but when you click the stitch forward onto half throttle it wont stay there ? it moves straight forward to the on position. I have opened up the handle and had a good look around but cant see which bit is worn / faulty - has anyone else had this problem and know which part is the culprit ? Apart from that the saw runs fine.

 

On my other one it has the complete opposite problem. Normally you would pull the cord on choke until it fires then move the trigger forward to half choke. But it doesn't fire once it keeps firing/running. Then flick onto half choke and it starts but then dies within a few seconds ?? Any ideas ?

On the first saw I reckon you need to initially look at the detent. Thats the spring which fits into notches on the switch shaft. Should look like the one in this image.

With the second saw I would say you have an air leak. The choke is making the mixture just rich enough to start, but not rich enough to cause it to stop. Probably because its getting a bit of extra air from somewhere.

The fact that it won't run without the choke also qualifies this diagnosis.

But where is the air getting in? OK you could go straight to doing a crank pressure/vac test:sneaky2:, but I would first look at the inlet manifold boot. Check it for a split on the underside by looking through the gap under the air box with the handle pulled up as far as possible. You might see a split. Whilst you are there check that the impulse tube is attached (thats the black tube that looks like a smooth fuel pipe.)

 

If you have any leaking petrol it could be a lack of fuel rather than too much air, so check the wrinkly fuel pick up hose from tank to carb.

If you do have any of these problem, repair them but also check the AV mounts, they could be the cause.

If these are alright, proceed to stage 2 which Steve will surely give details on:biggrin:

[spudulike]

The first one is almost definitely the orange throttle lever, it has a little stop on the end of it which often breaks.

 

The second sounds like some sort of fuel issue so check the carb out, pumping diaphragm, gauze filter etc, if these look OK then possible accelerator pump or air leak!

[GardenKit]

The first one is almost definitely the orange throttle lever, it has a little stop on the end of it which often breaks.

 

The second sounds like some sort of fuel issue so check the carb out, pumping diaphragm, gauze filter etc, if these look OK then possible accelerator pump or air leak!

Blimey Steve, that was a nice, simple diagnosis:big grin:

Only kidding mate, all is good.

[spudulike]

Blimey Steve, that was a nice, simple diagnosis:big grin:

Only kidding mate, all is good.

 

I have done more of these little feckers than I have had hot dinners and that is what I have found, no need to elaborate, it is what it is......just had one with a welch plug made out a bit of aluminium beer can.....seen it all now:001_rolleyes:

[spudulike]

That second fault may be a split inlet manifold - it is obviously getting a big slug of air from somewhere OR the choke isn't closing properly. Check the manifold, typically the underside splits!

[GardenKit]

I have done more of these little feckers than I have had hot dinners and that is what I have found, no need to elaborate, it is what it is......just had one with a welch plug made out a bit of aluminium beer can.....seen it all now:001_rolleyes:

 

crazy init? one of the most loved saws plagued with the same small problems from the day it was launched to the day it finished. Never really rectified. Typical of Stihl. Workshops throughout the country and presumably the world inundated with the things. At least there are a lot of experts in the repair.

 

If only they had used a Walbro, they would have solved most of the issues.

[spudulike]

crazy init? one of the most loved saws plagued with the same small problems from the day it was launched to the day it finished. Never really rectified. Typical of Stihl. Workshops throughout the country and presumably the world inundated with the things. At least there are a lot of experts in the repair.

 

If only they had used a Walbro, they would have solved most of the issues.

 

Unless they fitted the same Walbro carb on the 357XP:001_rolleyes: I think all saws have their own little issues and once you know them, successful repair is relatively easy and we also only ever see the ones that have failed!

 

I now fit new accelerator pumps to ALL MS200Ts that come in for a refurb irrespective of any symptoms. It just saves all the to and fro when the thing plays up!

[avinit]

cheers guys, i'll check those out and let you know how I get on.

one question though - why would the av mounts cause a problem ? (I am not very technical with these things)