Nicholas
ArboristSite Operative
Well guys I ran into a good one today. A gentleman, who is also a local chainsaw carver brought in his Stihl ms 200T to have looked at....again. This gentleman must have brought that saw in at least a dozen times. No one can seem to figure out why it starts so extremely hard, cold blooded, and starves for fuel/loses prime a w.o.t.
Our lead mechcanic who recently certified to Stihl's gold level put that saw through just about every test in the book, compression tests, pressure tests, vacuum tests, etc, and the saw checks out fine. He tried cleaning the carb body and installing a carb kit in it, new fuel pick body, removed the limiter caps, tried adjusting the saw, and still can't get it to run quite right. He got frustrated with it and passed it off to me to look at it.
Well, I when I looked at it, I couldn't get the thing to even pop. Pull and pull and pull, until your arm is ready to fall off. So I reset the carb settings to 1 1/4 turns out from the needles lightly seated. Finally got the thing to start, tuned in the idle and low speed needle. The saw seemed to accelerate and return to idle decent. Then I proceded to tune in the high needle, rev the saw to w.o.t. touch the needle with the screw driver and the thing just dies. Start it up again, rev to w.o.t. starve for fuel and dies. I brought back into the shop, disassembled the carb to find everything was fine exept the inlet needle lever was set too low. I reset the inlet needle lever, reassembled, and reset the carb setting to 1 1/4 turns out from lightly seated needles. Restarted in 2 pulls, tuned in the idle, and low needle. Now the saw accelerates and returns to idle nice. Now I go back to the high speed needle. The will rev and hold w.o.t. for 5 sec starve for fuel and die. so I open the H needle another 1/4 turn and restart. Now the saw revs to w.o.t. for 8 sec and starves for fuel and dies. So I restarted held the saw a w.o.t. and kept turning the H needle open until the saw kinda quit starving for fuel. But that point was about 2-2 1/4 turn out from a lightly seated needle, and the saw would sort of blubber along at 7,500rpm w/little or no exhaust smoke. Any leaner and the saw would immediately starve for fuel and die.
I also found the saw would idle fine when tipped/turned right, left, nose up, nose down, but would die if turned upside down. One other thing I found is the crankshaft seem to have a significant amount of side to side end play, as well as a small amount of radial play.
Okay, here's what I am thinking. In order for this behavior to occur there must be an air leak and or fuel delivery issue somewhere. I was thinking a cracked rubber carb manifold/boot, loose manifold clamp, cracked/broken/disconnected/rotted impulse hose, cracked fuel line. Possibly, a cracked crankcase, leaky cylinder base gasket, loose cylinder base screws, crank seals (But if that was the case it would not have passed the vacuum/pressure tests.)
This saw has me absolutly puzzled. If anyone has any advise, ideas, or information please post it. I'd really appreciate it.
Thanks,
Nick
Our lead mechcanic who recently certified to Stihl's gold level put that saw through just about every test in the book, compression tests, pressure tests, vacuum tests, etc, and the saw checks out fine. He tried cleaning the carb body and installing a carb kit in it, new fuel pick body, removed the limiter caps, tried adjusting the saw, and still can't get it to run quite right. He got frustrated with it and passed it off to me to look at it.
Well, I when I looked at it, I couldn't get the thing to even pop. Pull and pull and pull, until your arm is ready to fall off. So I reset the carb settings to 1 1/4 turns out from the needles lightly seated. Finally got the thing to start, tuned in the idle and low speed needle. The saw seemed to accelerate and return to idle decent. Then I proceded to tune in the high needle, rev the saw to w.o.t. touch the needle with the screw driver and the thing just dies. Start it up again, rev to w.o.t. starve for fuel and dies. I brought back into the shop, disassembled the carb to find everything was fine exept the inlet needle lever was set too low. I reset the inlet needle lever, reassembled, and reset the carb setting to 1 1/4 turns out from lightly seated needles. Restarted in 2 pulls, tuned in the idle, and low needle. Now the saw accelerates and returns to idle nice. Now I go back to the high speed needle. The will rev and hold w.o.t. for 5 sec starve for fuel and die. so I open the H needle another 1/4 turn and restart. Now the saw revs to w.o.t. for 8 sec and starves for fuel and dies. So I restarted held the saw a w.o.t. and kept turning the H needle open until the saw kinda quit starving for fuel. But that point was about 2-2 1/4 turn out from a lightly seated needle, and the saw would sort of blubber along at 7,500rpm w/little or no exhaust smoke. Any leaner and the saw would immediately starve for fuel and die.
I also found the saw would idle fine when tipped/turned right, left, nose up, nose down, but would die if turned upside down. One other thing I found is the crankshaft seem to have a significant amount of side to side end play, as well as a small amount of radial play.
Okay, here's what I am thinking. In order for this behavior to occur there must be an air leak and or fuel delivery issue somewhere. I was thinking a cracked rubber carb manifold/boot, loose manifold clamp, cracked/broken/disconnected/rotted impulse hose, cracked fuel line. Possibly, a cracked crankcase, leaky cylinder base gasket, loose cylinder base screws, crank seals (But if that was the case it would not have passed the vacuum/pressure tests.)
This saw has me absolutly puzzled. If anyone has any advise, ideas, or information please post it. I'd really appreciate it.
Thanks,
Nick
).
