ms200 carb

[openspaceman]

What options do I have for replacing the carburettor on a MS200, I take it this will be them same as the ms200t?

 

The Stihl part appears to be 85 quid plus VAT

[Andyhope1977]

I've used the farmertec ones off ebay with no issues... or a good ultrasonic clean and new carb kit

 

Sent from my SM-G900F using Arbtalk mobile app

[Graham]

You can do a repair to the original carb by blocking off the accelerator pump. Fixed all the issues on two of mine.

[openspaceman]

I've used the farmertec ones off ebay with no issues... or a good ultrasonic clean and new carb kit

 

Sent from my SM-G900F using Arbtalk mobile app

 

It's a cracking little saw and I don't know why it got taken to a dealer for repair. If it comes back in pieces I'll clean it but the dealer is adamant the carb is "all over the place" .

[openspaceman]

You can do a repair to the original carb by blocking off the accelerator pump. Fixed all the issues on two of mine.

 

Any more info about this?

[Graham]

Any more info about this?

 

This pic shows a carb cut in half which is of no consequence. The aluminium welch plug shown is removed and the small chamber is filled with epoxy putty or glue.

 

Leave it 24hrs to cure and make sure it's not proud. It blocks off the leaky pump which causes the problems. Saws run just as well after but you'll need to alter carb settings to suit.

[GardenKit]

I don't want to be too critical, or damning of others methods, but, in my opinion blanking off the accelerator pump is not so much a 'mod', as a 'bodge'. (I must admit I too have done this bodge in the past)

 

The pump is there for a reason, and that is too overcome the 'flat spot' which occurs in the transition from running on the idle jet, to running on the main jet as the butterfly is opened.

At idle the flow through the carburetor is low. Some of the fuel is evaporated and some remains liquid at the bottom of the intake pipe.

Suddenly opening the throttle will give an immediate air flow increase to the cylinder. The evaporated fuel follows the air flow, but the liquid fuel takes longer to increase its speed. This means that the first second after opening the throttle, the engine will get a lot of air but very little fuel and the response is bad.

This is compensated for by the acceleration pump in the carburettor.

Remove this pump and you need to compensate to some degree by richening up the idle L screw, which sort of works but cannot be done in production because of emission regs.

Why not simply repair the accelerator pump?

[Graham]

Personally I've not found it creates a flat spot and if it does it can be tuned out anyway.

 

If you replace the accelerator pump it will only wear out again fairly quickly. The nature of the saw's use ie constant on/off throttle sees to that.

 

This mod is a one off fix unlike a pump repair.

[openspaceman]

Personally I've not found it creates a flat spot and if it does it can be tuned out anyway.

 

If you replace the accelerator pump it will only wear out again fairly quickly. The nature of the saw's use ie constant on/off throttle sees to that.

 

This mod is a one off fix unlike a pump repair.

 

I accept Barrie's point but as I will end up with a spare worn carb I can at least try blocking it, thanks for the tip Graham. The guys are determines to keep the ms200s going rather than have newer saws.

[spudulike]

I don't want to be too critical, or damning of others methods, but, in my opinion blanking off the accelerator pump is not so much a 'mod', as a 'bodge'. (I must admit I too have done this bodge in the past)

 

The pump is there for a reason, and that is too overcome the 'flat spot' which occurs in the transition from running on the idle jet, to running on the main jet as the butterfly is opened.

At idle the flow through the carburetor is low. Some of the fuel is evaporated and some remains liquid at the bottom of the intake pipe.

Suddenly opening the throttle will give an immediate air flow increase to the cylinder. The evaporated fuel follows the air flow, but the liquid fuel takes longer to increase its speed. This means that the first second after opening the throttle, the engine will get a lot of air but very little fuel and the response is bad.

This is compensated for by the acceleration pump in the carburettor.

Remove this pump and you need to compensate to some degree by richening up the idle L screw, which sort of works but cannot be done in production because of emission regs.

Why not simply repair the accelerator pump?

 

Of course, Barrie is correct in what he says. Blanking off the pump does cause this flat spot issue that needs a bit of careful tuning out to mask it, after all, Stihl didn't fit an accelerator pump for no reason and the pump is there to give the saw a bit of grunt from low revs!

 

I have done this mod, there are potential risks in doing it but if done well, it does make a bad running saw in to a good one again IF the pump is the route cause of the fault!

 

I stopped doing this mod and now simply replace the accelerator pump giving the saw a return to how it should be. If I ever had the repair fail then the blanking off of the welch plug would be the next option as it will get the saw useable again even with slightly less ZIP off the line.