MS200T bogging down when warm

[BrucetheSpruce]

I did use the saw yesterday. It was a 2 hour smash down so the saw was in use for the majority of that time and it ran absolutely spot on....until the two very last cuts, when the bogging returned. Unfortunately had to get on with other work so couldn’t tinker with it but will update on Monday.

[Khriss]

On 11/11/2020 at 20:03, spudulike said:

Nothing wrong with 200s, it is just people have high expectations of 10-15 year old saws and feel a £20 new top end will sort out any issues.

My approach is to get them in bits, replace anything worn with OEM parts, rebuild, set up and then test.....pretty simple and have done more than I can remember- must be a thousand or so by now!

I find them remarkably simple to work on but guess others don't judging some of the disasters that I have seen!

Appart from the throttle and deadman, god wot a stupid setup  ?  K

[Paddy1000111]

11 minutes ago, Khriss said:

Appart from the throttle and deadman, god wot a stupid setup  ?  K

I've had mine apart so many times I can strip back to the crank and re-assemble in an evening now ?. I do have to take a photo of the throttle linkages every time though! 

[Khriss]

Baffling Paddy , why do they use 5 parts on Stihls when 2 will do     K

[spudulike]

The throttle linkage is fine, they even colour the throttle linkages in a bronze colour. 2 part linkages only work on saws with a direct to choke control like the MS150! The MS200T is pretty easy to strip and reassemble!

 

The earlier "High Jet" comments are about the "Check Valve" which is a one way high speed valve. If they go bad, they can be driven out and replaced but it isn't that simple for the uninitiated. They can fail by going open and the saw will be very rich, smokey and boggy if this happens with no idle.

 

I would try a known good carb or just bite the bullet and fit a new one, probably a better option than waiting for a dealer to pull his finger out and fix it and chances he will be lazy and fit a new carb as most won't take my approach in fixing carbs!

 

Not being funny but, you have checked the impulse line is connected to the union on the bottom of the air box? It is a rubber hose (Like a fuel line) that comes out of the top cover just under the air box - like in the pic. If it is loose like below then it shouldn't be!

 

 

Edited November 14, 2020 by spudulike

[Paddy1000111]

I would say that it has something to do with German engineering and having the perfect feel but I think it's more to do with frightening consumers into using service centres. The extra £0.20p of wire used to make all the links probably brings them in a good few thousand in man-hours on repairs!

[Darkslider]

I've got an MS200t that is behaving very similar, revs need coaxing up and will bog down and die if you just grab a load of throttle. Air filter is full of fuel too. I've fallen at the first hurdle a bit because I wanted to start off by adjusting the mixture screws back to factory settings, but the Stop is missing from the H screw and I've no idea where it's meant to be ( the L was a lot more than one turn off its seat, compensating for whatever the fault is I guess?) And now I can't get it to start at all.

 

Any pointers? I've checked a few other things, fuel filter is clear, no holes in the fuel pickup line, tank vent is clear, I've checked both diaphragms in the carb and no splits in them. 

 

Edit: also found it was fitted with an ngk  bm6a plug, whereas Stihl and everywhere else I can find recommend the bpmr7a which looks fractionally longer putting the electrode further into the cylinder. I'm always wary fitting a longer plug than the one I've taken out but it still pulls over with it in so I'm going to have another attempt at starting it once it's reassembled to see if there's any difference.

 

Edited November 15, 2020 by Darkslider

[spudulike]

It should be the BPMR7A plug. The standard carb settings should be 1 turn out on the L&H screws but take care the saw isn't screaming at WOT on these settings as I have seen many on 1.5 - 2 turns out and you may need another 1/4 turn on the L screw but start with 1&1.

The air filter being covered in fuel may be the dodgy carb settings, leaking needle valve or wear on the inlet side of the piston/cylinder causing blow-by.

 

[Paddy1000111]

Spudlike knows more than me on this but I had similar issues with my 200t. Turns out I was tuning it like a mug and not having a high enough LA setting. It was flooding on idle/didn't have enough airflow to vaporise the fuel properly meaning it would bog. Should be a BPMR7A for NGK or a WSR6F in bosch. Maybe they got confused 

[Darkslider]

1 hour ago, spudulike said:

It should be the BPMR7A plug. The standard carb settings should be 1 turn out on the L&H screws but take care the saw isn't screaming at WOT on these settings as I have seen many on 1.5 - 2 turns out and you may need another 1/4 turn on the L screw but start with 1&1.

The air filter being covered in fuel may be the dodgy carb settings, leaking needle valve or wear on the inlet side of the piston/cylinder causing blow-by.

 

I think I left it on 2 turns out on the H screw as that was where it seemed happiest, it was running and revving up nicely at that whereas any less and it would cut out if the revs were left to drop. Perhaps I should have given it another 1/4 turn on the L screw too, it seemed to be inconsistent I thought I'd fixed it as it was idling and revving nicely for a period but then it cut out and was a pig to start again so I carried on tweaking.

 

I've had to hand it back as it is and admit defeat as it's needed tomorrow, but i checked the needle seat while the carb was off and I couldn't blow through it while it was held shut by the spring so I don't think that's the reason for it flooding, the 'tang' had a slight bend in it that would have limited how much the float needle could open too would have been interesting to compare that to a new one and see if that's the shape it's meant to be or if it's been modified in the past. Also checked the impulse pipe was still on the airbox, filters and lines clear with no holes, compression was 150 psi after a few pulls-all the normal stuff. 

 

It's had plenty of use so a bit of blow by isn't unlikely, when it does run it has loads of power reportedly. I'll try and get some feedback on how it does this week, if it's no good it could be coming your way ?