MS200T rebuild- runs to WOT, returns to idle and dies.

[Bob Hedgecutter]

Not getting any answers on my "New....... to me"thread in regards to this issue.
Saw arrived to me in parts- missing cylinder & piston.
Have rebuilt it with new Meteor top end, new OEM rubbers from impulse, manifold and fuel/vent lines, new carb kit, new plug.
Saw passed pressure & vac test.
Saw starts beautifully, open it to WOT and let it return to idle and the revs rise like it is running on the vapours from an empty fuel tank and it dies. Half choke, one pull and it is away again, open the throttle, let it return, revs rise and it dies.

Should state that these saws are not dime a dozen in my neck of the woods and a known good carb is going to be harder to find than rocking horse poop.

Is it likely to be an accelerator pump issue? Should I jump straight into the pick out the plug and epoxy the pump circuit?

 

[trains]

partial blockage in the idle circuit in the carb would be my first guess, if your metering lever is correctly set, and you have not got an air leak from the carb to the boot/ case.

 

[Bob Hedgecutter]

partial blockage in the idle circuit in the carb would be my first guess, if your metering lever is correctly set, and you have not got an air leak from the carb to the boot/ case.

Kind of thought that as well- as it seems to be the idle circuit....... but just took it out and tried to cut with it.
It will bog down while throttle held wide open during cut...... sometimes.
When it runs WOT, it is farken amazing! Would eat my modded 201 for breakfast and still be looking for more. But the way it is currently running (remember first tank since rebuild of an unknown history saw) I'd rather use the 201.
Pretty sure the air leak at manifold is a non issue- but will check it over again at near $100NZ for a genuine Stihl manifold- I was pretty bloody careful putting it on!

 

[trains]

Kind of thought that as well- as it seems to be the idle circuit....... but just took it out and tried to cut with it.
It will bog down while throttle held wide open during cut...... sometimes.
When it runs WOT, it is farken amazing! Would eat my modded 201 for breakfast and still be looking for more. But the way it is currently running (remember first tank since rebuild of an unknown history saw) I'd rather use the 201.
Pretty sure the air leak at manifold is a non issue- but will check it over again at near $100NZ for a genuine Stihl manifold- I was pretty bloody careful putting it on!

Hey Bob,
still sounds like fuel delivery issue to me, if it was a basket case, and carb left dry, the idle circuit with its fine idle, and idle progression holes, can easily block with ally dust/ corrosion/ gunk etc.
That area would be my first place looking, then if the main circuit is showing signs of fuel delivery too with the bogging, you most likely have a bit more stuff dislodged and passing thru.
Interesting to see what the inside of the carb looks like again.

Were you able to remove the limiter on the high side, and take out the needle ?

I have just looked at the IPL for the 200 carbs, and can not see a plate that covers the idle circuit drillings, is this open to the chamber, or is there a cover pressed into position covering the idle circuit.

Go easy on carb cleaner, and air, dont want to damage the poppet valve in the main jet nozzle.

My money is on ally fuzz, grit, etc causing your issues, might take a few repeat cleanings to get it all moved thru, and as your running, with fuel and vibration and heat cycles, you just move a bit more each time to add to your current symptoms.

T

edited to add,
Looks like the c1q series does have the welch plug over the idle circuit drillings for the C1Q series.
https://www.zamacarb.com/page/disassembly_servicing_1

 

[Hdtoolmkr765]

Have you confirmed your impulse hose isn’t pinched?

 

[Bob Hedgecutter]

Yep, impulse hose is not pinched or overbent.
Could very well be a dirty corroded crud filled carb. It was in pieces in a bag with lots of the other small bits belonging to the saw, did spend a long time cleaning as best I could before rebuilding the carb (no ultrasonic cleaner). Have read elsewhere to stay away from compressed air gun cleaning of these and was pretty lenient with the aerosol carb cleaner.......... but it could well be still dirty internally, some pretty small galleries in there!
It is the carb with the accelerator pump- but no limiters on the adjustment screws? I thought those were on the 201 (now missing on mine! ) and not the 200T?

 

[trains]

Can you get the accelerator pump kit from stihl ? Not sure on the O ring size.
the IPL shows a cap on the high screw.
Should be able to get a complete ohaul kit from zama/ stihl with the welch plugs in it, my thoughts are that area under the welch plug needs a proper clean.
when you spray cleaner thru the idle side, do all the idle ports in the venturi flow, or is one of them blocked ?

On my old 015l I could not get the main jet mesh screen or carb kit thru stihl for it anymore, got a fleacebay chinga one that had everything in it for a few dollars, even the gasket material had printing on it saying made in USA, quality appeared very good which surprised me.

 

[Bob Hedgecutter]

Can you get the accelerator pump kit from stihl ? Not sure on the O ring size.
the IPL shows a cap on the high screw.
Should be able to get a complete ohaul kit from zama/ stihl with the welch plugs in it, my thoughts are that area under the welch plug needs a proper clean.
when you spray cleaner thru the idle side, do all the idle ports in the venturi flow, or is one of them blocked ?

On my old 015l I could not get the main jet mesh screen or carb kit thru stihl for it anymore, got a fleacebay chinga one that had everything in it for a few dollars, even the gasket material had printing on it saying made in USA, quality appeared very good which surprised me.

For all the hassle, I think it would be easier to pull the welch plug and epoxy the accelerator circuit (as shown in various posts here), used the carb kit that cane with the welch plugs etc, new mesh screen etc.
Seriously thinking about one of the chinga AM carbs as a known good OEM will be hard to find over here, be easier to find an old 020 and hope it has the two bolt carby.
All ports appear clean when the carb was rebuilt- but as you said earlier- maybe crap is dislodging as the saw runs and becoming lodged in amongst the tight places within the carb body.
When I get a bit of time (middle of calving) I will pull the carb and inspect again for new filth and grime.

 

[trains]

For all the hassle, I think it would be easier to pull the welch plug and epoxy the accelerator circuit (as shown in various posts here), used the carb kit that cane with the welch plugs etc, new mesh screen etc.
Seriously thinking about one of the chinga AM carbs as a known good OEM will be hard to find over here, be easier to find an old 020 and hope it has the two bolt carby.
All ports appear clean when the carb was rebuilt- but as you said earlier- maybe crap is dislodging as the saw runs and becoming lodged in amongst the tight places within the carb body.
When I get a bit of time (middle of calving) I will pull the carb and inspect again for new filth and grime.

Yeah, if you take the carb apart completely, and get into those galleries, you have a much better chance at it working correctly, so you cant get the pump kit locally then ?
You have cleaned it, so I would not expect to see something initially obvious. It dosent take much to upset them.

 

[Bob Hedgecutter]

Okay, managed a couple of hours away from farming duties- after all it is the first official day of Spring over here.
Pulled the carb, cleaned it again, checked the gasket and diaphragm were in the correct order (have goofed that before!). Pulled the manifold checked and refitted (whoever thought up that square squeeze fit manifold sealer...... needs lined up against a wall........), checked impulse and fuel lines, breathers, tank cap o-rings.........

 

[Bob Hedgecutter]

And.......
It still runs like shite.

 

[trains]

Until you take off that welch plug for the idle circuit, you cant rule out ally corrosion dust/ fuel resin, all sorts of gunk causing issues with those fine idle drillings.
Even if your seeing fuel pass thru those fine idle drillings in the throat of the carb, there is a few of them, it may be a flaky bit that covers it when running.

And can you get the accelerator pump kit for it ?

We will get it sorted.

 

[Bob Hedgecutter]

Until you take off that welch plug for the idle circuit, you cant rule out ally corrosion dust/ fuel resin, all sorts of gunk causing issues with those fine idle drillings.
Even if your seeing fuel pass thru those fine idle drillings in the throat of the carb, there is a few of them, it may be a flaky bit that covers it when running.

And can you get the accelerator pump kit for it ?

We will get it sorted.

Yeah, been there done that with the welch plugs. Not sure about the accelerator pump piston and o-ring being readily available. I go into my local dealer and ask for bits and bobs for either the 200 or 201 and they kind of screw their faces up and look at you kind of funny with that "WTF" look on their faces. Had to go around to their side of the counter to point out the bits on the computer screen I wanted when buying OEM rubber bits for the 200........ so guessing the accelerator pump parts might be well above their pay grade. Personally, next step might be to eliminate the pump circuit with epoxy.

 

[trains]

Yeah, been there done that with the welch plugs. Not sure about the accelerator pump piston and o-ring being readily available. I go into my local dealer and ask for bits and bobs for either the 200 or 201 and they kind of screw their faces up and look at you kind of funny with that "WTF" look on their faces. Had to go around to their side of the counter to point out the bits on the computer screen I wanted when buying OEM rubber bits for the 200........ so guessing the accelerator pump parts might be well above their pay grade. Personally, next step might be to eliminate the pump circuit with epoxy.

Ah sorry, didnt realise you had already taken the damn thing out and replaced it, what was the gallery and the underside of the plug like ? did you use some nail polish to seal them up ?
Before you fill it up with gorilla snot, see if you can get the pump kit, you need to take the throttle shaft out, only the E clip, and the center screw that holds the butterfly.
From what I can gather, its the O ring that fails, then cants the pump, and it gets scored = new pump kit, not sure on the O ring size, or what O rings are available your way, some ag dealers are great for odd ball sized stuff, and others dont want to know you unless your rebuilding your header and spending bank loads.

Not had the time to do a search on common fixes yet, but assume you have done that already.

pump kit # is 1129 120 9700

 

[Bob Hedgecutter]

Ah sorry, didnt realise you had already taken the damn thing out and replaced it, what was the gallery and the underside of the plug like ? did you use some nail polish to seal them up ?
Before you fill it up with gorilla snot, see if you can get the pump kit, you need to take the throttle shaft out, only the E clip, and the center screw that holds the butterfly.
From what I can gather, its the O ring that fails, then cants the pump, and it gets scored = new pump kit, not sure on the O ring size, or what O rings are available your way, some ag dealers are great for odd ball sized stuff, and others dont want to know you unless your rebuilding your header and spending bank loads.

Not had the time to do a search on common fixes yet, but assume you have done that already.

Common fix around here seems to be JB weld the piston in the bore of the accelerator pump.
I am beginning to wonder just how bad the AM carbs could be.......
Looked pretty good internally to tell the truth, didn't nail varnish them in- used head cement (I am a fly tyer ) besides- head cement sounds far more manly than nail varnish!

 

[trains]

Common fix around here seems to be JB weld the piston in the bore of the accelerator pump.
I am beginning to wonder just how bad the AM carbs could be.......
Looked pretty good internally to tell the truth, didn't nail varnish them in- used head cement (I am a fly tyer ) besides- head cement sounds far more manly than nail varnish!

Not sure what head cement is, not a term I am familiar with.
hah, used to have a bottle or 12 of nail varnish for painting the metal from holes before fitting grommets for wiring, snorkels etc surprising how close you could match paint with them at times .
Got a few odd looks from people, especially my female customers, until I explained it was basically enamel paint, and it saved their car from rusting where the wiring was routed etc.

just had a bit of a search, seems there is quite a discussion re carb issues for the 200t

Pity you didnt take the plug out for the pump, and see if its the body of the carb thats scored, or the o ring, good project for post mortem of it. See there are other non pump carbs that will fit.

 

[Bob Hedgecutter]

Not sure what head cement is, not a term I am familiar with.
hah, used to have a bottle or 12 of nail varnish for painting the metal from holes before fitting grommets for wiring, snorkels etc surprising how close you could match paint with them at times .
Got a few odd looks from people, especially my female customers, until I explained it was basically enamel paint, and it saved their car from rusting where the wiring was routed etc.

just had a bit of a search, seems there is quite a discussion re carb issues for the 200t

Pity you didnt take the plug out for the pump, and see if its the body of the carb thats scored, or the o ring, good project for post mortem of it. See there are other non pump carbs that will fit.

Head cement is just a hard clear (sometimes coloured) nail type varnish that comes in a very similar bottle to nail varnish, complete with the same kind of applicator brush and is used to coat the fine thread at the head area of fishing flies so the thread does not unravel.

 

[Bob Hedgecutter]

trains, thanks for the help and suggestions through this, good to see someone taking the time.
But, problem solved. Picked out the accelerator pump welch plug and epoxied the circuit closed as per Lonewolf's method.
Saw runs perfect now.

 

[lone wolf]

trains, thanks for the help and suggestions through this, good to see someone taking the time.
But, problem solved. Picked out the accelerator pump welch plug and epoxied the circuit closed as per Lonewolf's method.
Saw runs perfect now.
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I was gonna say but I just got here. I keep spare carbs to troubleshoot saws it saves hours. Glad its running.

 

[Bob Hedgecutter]

I was gonna say but I just got here. I keep spare carbs to troubleshoot saws it saves hours. Glad its running.

Cheers.
But, unlike over there- 200T's in my neck of the woods down here are a bit like rocking horse poop....... so spare carbs are not laying about like flies on a turd.
But, thank you Sir for taking the time to share your knowledge regarding this very simple fix.
I did not use JB Weld, but a two pot Loctite product- designed as an aluminium repair.