ms200t air leak?

[3dogs]

One of my ms200 starts fine ticks over for about 30 seconds and then picks up revs and dies as if its run out of fuel (tank is full) ive swapped the carb, new spark plug, (checked diaphram and gause filter in both carbs) the replacement carb is from an older saw but i know its good. Ive not swapped thefuel filter as it looks good (and to be honest dont have a spare to hand) and the tank is breathing. Anyone got any ideas:thumbup1: cheers dave.

[Marc]

One of my ms200 starts fine ticks over for about 30 seconds and then picks up revs and dies as if its run out of fuel (tank is full) ive swapped the carb, new spark plug, (checked diaphram and gause filter in both carbs) the replacement carb is from an older saw but i know its good. Ive not swapped thefuel filter as it looks good (and to be honest dont have a spare to hand) and the tank is breathing. Anyone got any ideas:thumbup1: cheers dave.

 

Sometimes the boot between the carb and engine can get damage or loose you checked that?

[3dogs]

Sometimes the boot between the carb and engine can get damage or loose you checked that?

 

seems ok but will double check. cheers.

[spudulike]

Possibly a split carb boot, cracked impulse line - have you pushed the impulse line fully home on the handle. Allignment of the boot has caused issues in the past, fuel filter, fuel pipe, crank seals etc.

 

If you get stuck, I can sort it - Just PM me and we can talk.

[Marc]

seems ok but will double check. cheers.

 

Also fuel line damage, this can happen when conifer or something other gets into the gap, rare but can happen.

 

How old is the saw and how much use has it seen?

 

Crank case seals can leak also rare, but if symptoms are same with 2 different carbs you got to look along these lines as chance of 2 duff carbs are slim.

[Stihl4Life.DK]

tank vent??

[GardenKit]

As others have said ,along with other very valid faults, one cause could be a misplaced or split inlet manifold (boot) so just a little more info on that.

If you have duff AV rubbers, especially the rear one, extra strain is placed on the boot.

It may not be the case here, but its always wise to replace AV's before they fail completely.

 

Seeing a split boot can be difficult, they usually split on the underside, you may be able to see it using a pencil beam torch, looking through the gap between the handle assy and tank, whilst pulling the handle gently upwards to increase the gap and open the split. Check fuel pick up hose at the same time.

 

Occasionally the boot will pop off the pot flange, flick out the square retainer plate to check. ( and old boots will often not reseal here, even if they look good, they harden with age)

 

Good luck.

[Marc]

tank vent??

 

Thats a good shout for the symptoms as after 30seconds a vacuum would be created in the fuel tank:thumbup1:

[Al Smith]

I just went through this ordeal with both an 020T and an Ms 200T .

 

Here's what I found .These series of saws use roller bearings instead of ball bearings for main bearings .They relie on a fiber thrust washer to keep things in alignment .Given enough time they develop some side to side slop in the crankshaft which will ride the edge of the seals up over accumulated carbon on the crankshaft left by pyrolited oil residue .The seals heat up then they leak .The seals appear to be Viton which is very resilliant but will swell when heated .

 

After I got home from work this afternoon I'll post some pictures which will clear this up .

[Al Smith]

Okay here's what pictures I have of this thing .Note on the pic of the crank where the black spots are .This is the carbon build up I spoke about .Both saws I worked on had perhaps 1/8" of side to side movement in them .

 

I changed the bearings and seals on one saw which I got from a doner case that was cracked .The other saw I used a thin socket which fit perfectly with the outer race of the bearing and tapped it inward to tighten the bearings up and replaced it with a good seal .Note this is only a temporary fix but it worked .

 

I'm not certain if you can see the thrust washer built into the roller bearings but that is the only side to side thrust preventaive this type bearing has .Unlike a ball bearing which affords thrust control .