Hi All,
My best guess where to post this. My years reliable 200T, perhaps only fault may take extra pulls to start at beginning of day, just idled up enough to start moving the chain. So I thought I had neglected the gas and dutifully went to top it up only to find 1/4 tank still there. I topped it up anyway, same fast idle maybe even increased a tad. Definitely much faster than my backup 200T, so not weak clutch springs fooling me. I pop the tank vent line (remote style) and it holds pressure and lets vacuum pass correctly. Carb inlet holds pressure correctly. I make a block plate for the exhaust, sealing with a strip of inner tube and rejig an adapter onto the carb studs which enters to the carb bore opening but blocks/covers the pulse port. Spark plug in, it first holds 1/2 bar vacuum just fine and also holds pressure even as I jiggle the crank. I could even induce a small wiggle on the needle turning the crank by hand during the pressure test. Muffler's clean, no screen. Plug looked good, tan not whited or fouled.
Wouldn't the usual suspects impulse line, cracked manifold boot, gasket leaks and crank seals all be given a green light by the above?
The carb is an accelerator pump C1Q S126 005A which might be original with intellicarb snorkel. Is it possible for a worn out accelerator pump to be this dramatic in air leak effect through the accelerator pump? The engine response had that lag of not having an access pump whereas normally you squeeze a 200T trigger and it instantly responds.
My plan is first swap a known good carb and then possibly the fuel filter or a crack in fuel pickup line inside the tank could cause that much lean condition? I've never had any filter suddenly crud up in a 5 second span.
Any one been down this road and can confirm or deny the fault cause? thanks
edits:
mods - please move to chainsaws and such, my bad, too tired
Can anyone confirm 11291209700 Pump Piston Kit has been changed to 11291209701 and is still the right PN for C1Q S126?
Can anyone confirm C1Q S126D versionD is the current latest replacement carb ($130 Can)
Letting grain of rice JB Weld Marc-Antoine method cure tonight, can't hurt to try and avoids trusting throttle plate reassembly to not come undone and eat the saw innards.
After the first 1/4 turn lowering the idle there was no further difference and was still way too high.
Also figure 100% full tank would eliminate effects of cracked portion of fuel line inside tank - idle stayed high.
edit2:
Add one more endorsement for Marc-Antoine. Idles like a kitten, has a bit of hesitation if you stab the trigger. Yes, the accelerator pump can cause that much havoc. Noted the back up saw was in worse shape than expected, showing some symptoms, may spring for carb to get a definitive evaluation of the Marc-Antoine fix and to have one saw bona-fide.
edit3:
Pulled another carb apart, S126 version no A or other letter version, accelerator pump piston and spring shot out when I removed the plug (warning). Bore was 5.45 mm and no out of round or scoring to the naked eye. Piston was 4.95 mm o.d. chrome covered brass wore through a bit on one side, piston groove was 3.16 mm od and the O ring was visibly worn and so hard it cracked when I pried it out of the groove. Note the throttle plate screw is staked so it can't get eaten by the engine so I'll have to re-stake it on assembly and the service manual states this too. O rings are Viton 3 mm id by 1 mm thickness. I put a hole in the plug to extract it so I'm going to try soldering the hole before I press the plug back in.
more info: fresh O ring on piston just binds in vernier jaws set to 4.98 mm, it also doesn't fall into the deeper bore so the bore has 5.45 mm at the welch plug and smaller where the piston moves.
My best guess where to post this. My years reliable 200T, perhaps only fault may take extra pulls to start at beginning of day, just idled up enough to start moving the chain. So I thought I had neglected the gas and dutifully went to top it up only to find 1/4 tank still there. I topped it up anyway, same fast idle maybe even increased a tad. Definitely much faster than my backup 200T, so not weak clutch springs fooling me. I pop the tank vent line (remote style) and it holds pressure and lets vacuum pass correctly. Carb inlet holds pressure correctly. I make a block plate for the exhaust, sealing with a strip of inner tube and rejig an adapter onto the carb studs which enters to the carb bore opening but blocks/covers the pulse port. Spark plug in, it first holds 1/2 bar vacuum just fine and also holds pressure even as I jiggle the crank. I could even induce a small wiggle on the needle turning the crank by hand during the pressure test. Muffler's clean, no screen. Plug looked good, tan not whited or fouled.
Wouldn't the usual suspects impulse line, cracked manifold boot, gasket leaks and crank seals all be given a green light by the above?
The carb is an accelerator pump C1Q S126 005A which might be original with intellicarb snorkel. Is it possible for a worn out accelerator pump to be this dramatic in air leak effect through the accelerator pump? The engine response had that lag of not having an access pump whereas normally you squeeze a 200T trigger and it instantly responds.
My plan is first swap a known good carb and then possibly the fuel filter or a crack in fuel pickup line inside the tank could cause that much lean condition? I've never had any filter suddenly crud up in a 5 second span.
Any one been down this road and can confirm or deny the fault cause? thanks
edits:
mods - please move to chainsaws and such, my bad, too tired
Can anyone confirm 11291209700 Pump Piston Kit has been changed to 11291209701 and is still the right PN for C1Q S126?
Can anyone confirm C1Q S126D versionD is the current latest replacement carb ($130 Can)
Letting grain of rice JB Weld Marc-Antoine method cure tonight, can't hurt to try and avoids trusting throttle plate reassembly to not come undone and eat the saw innards.
After the first 1/4 turn lowering the idle there was no further difference and was still way too high.
Also figure 100% full tank would eliminate effects of cracked portion of fuel line inside tank - idle stayed high.
edit2:
Add one more endorsement for Marc-Antoine. Idles like a kitten, has a bit of hesitation if you stab the trigger. Yes, the accelerator pump can cause that much havoc. Noted the back up saw was in worse shape than expected, showing some symptoms, may spring for carb to get a definitive evaluation of the Marc-Antoine fix and to have one saw bona-fide.
edit3:
Pulled another carb apart, S126 version no A or other letter version, accelerator pump piston and spring shot out when I removed the plug (warning). Bore was 5.45 mm and no out of round or scoring to the naked eye. Piston was 4.95 mm o.d. chrome covered brass wore through a bit on one side, piston groove was 3.16 mm od and the O ring was visibly worn and so hard it cracked when I pried it out of the groove. Note the throttle plate screw is staked so it can't get eaten by the engine so I'll have to re-stake it on assembly and the service manual states this too. O rings are Viton 3 mm id by 1 mm thickness. I put a hole in the plug to extract it so I'm going to try soldering the hole before I press the plug back in.
more info: fresh O ring on piston just binds in vernier jaws set to 4.98 mm, it also doesn't fall into the deeper bore so the bore has 5.45 mm at the welch plug and smaller where the piston moves.
Last edited:
