Cub Cadet BC490 4 cycle trimmer

[Jwilson22071]

Gas trimmer will not run once you take off choke. Changed the fuel lines, fuel filter , carburetor, gaskets, plug and checked the exhaust. Fires up 1st pull on full choke, as soon as I move to the mid choke position it dies. Starting at wot like the manual says but even at full choke it only runs at just above idle. Valves at set at spec. Coil works fine. Will run all day at full choke as long as I hold the throttle open. Compression is at 115. Any ideas?

 

[slomo]

Leaking fuel tank, carb issue or bad vent on fuel cap. Chinese carb installed?

slomo

 

[Jwilson22071]

New walbro carb, fuel tank is good, runs the same with different caps and cap on or off. Ran like this with old carb also.

 

[slomo]

Get a pressure tester and test the tank. Tank can leak both ways.

How did you test the tank? Wasn't leaking fuel so it's good?

Test for vacuum leaks and fuel line leaks.

slomo

 

[StarTech]

The carburetor probably needs adjusting but all are not fine tuneable any more. Which Walbro model number is it? Also waht is the 41 model number of the brush cutter trimmer?

I have also seen where the metering lever is set too low on new carburetors from the factory.

 

[fixit1ddh]

Pull muffler off and see how it runs.

 

[slomo]

Pull muffler off and see how it runs.

Good call, might be a clogged spark arrester.

slomo

 

[Jwilson22071]

All ready checked the spark arrestor but will pull the muffler again and try to run without it. Good idea , thanks

 

[Jwilson22071]

So a little update. Pulled the muffler off- no change still dies when start to open the choke. Unhooked the shaft (grasping at straws). Same result. Pulled the carb off and the insulator block to check the gasket to the head. At this point I noticed some oil in case under the crankcase hose that runs to the air filter housing. Checked the hose and it was split. Replaced the hose and put everything together. Pulled the rope and oil shot out of the housing and hit me in the chest. Pulled the hose again and cleaned it out. Pulled the rope again ( i did move this time) and I can get 30w oil to shoot across the shop about 10' lol . Also noticed somebody has been in there before. Orange silicone around the base of the cylinder lol.

 

[slomo]

So a little update. Pulled the muffler off- no change still dies when start to open the choke. Unhooked the shaft (grasping at straws). Same result. Pulled the carb off and the insulator block to check the gasket to the head. At this point I noticed some oil in case under the crankcase hose that runs to the air filter housing. Checked the hose and it was split. Replaced the hose and put everything together. Pulled the rope and oil shot out of the housing and hit me in the chest. Pulled the hose again and cleaned it out. Pulled the rope again ( i did move this time) and I can get 30w oil to shoot across the shop about 10' lol . Also noticed somebody has been in there before. Orange silicone around the base of the cylinder lol.

Oh no, silicone bandits strike again. RTV is the worst crap you can make gaskets from. OEM gaskets with some high tack spray sealant is the ticket. Prefer the brush-on to the can junk. Much easier to control when applying. Canned stuff is messy.

Knowing it's got gobs of silly-cone, I would tear it all down. See what the heck was put back incorrectly or broken. Amateur hour......

slomo