04 switchback 800 low rpm bog on acceleration

[Cweber5156]

Just picked up a 2004 switchback 800 VES

New plugs, valves cleaned. Was told it had the carbs rebuilt end of last season.

Anyways it will sometimes have trouble starting. But will start and idle eventually. 3 or 4 pulls. But rpms seem low. Then when you tap the trottle it will bog and die sometimes. If you feather throttle sometimes it will accelerate then pick up rpms.

Carbs adjusted improperly? Dumping 2 much fuel?

Both plugs wet.
Took valves off and under bellows was a lot of I believe fuel.
Also when idling its blowing out fuel or oil from exhaust.
150psi in both cylinders

 

[BeartoothBaron]

Definitely too much gas from somewhere. First thing I'd do is swap or rebuild the fuel pump; if the diaphragm is ruptured or leaking, gas can feed right into the crank-case. Best way to find that is to unscrew the crank-case drains (at the base of the block in front, underneath the y-pipe). You'll normally get a tiny dribble of oil and fuel, but if you get a bunch of gas pouring out, it's probably the fuel pump. I have an old sled that had a bad pump, and when I unscrewed the drain, several ounces of gas poured out. Next, if the choke is over-adjusted, you'll get too much fuel. Could also be bad needle and seat in the carbs or choke plungers going bad, although that would tend to be noticeably worse on one side or another. It's also good to check the jetting and adjustments of a new-to-you sled, but as much gas as you describe is probably leaking constantly, either from a bad fuel pump or the needles and seats in the carbs.

 

[Cweber5156]

Definitely too much gas from somewhere. First thing I'd do is swap or rebuild the fuel pump; if the diaphragm is ruptured or leaking, gas can feed right into the crank-case. Best way to find that is to unscrew the crank-case drains (at the base of the block in front, underneath the y-pipe). You'll normally get a tiny dribble of oil and fuel, but if you get a bunch of gas pouring out, it's probably the fuel pump. I have an old sled that had a bad pump, and when I unscrewed the drain, several ounces of gas poured out. Next, if the choke is over-adjusted, you'll get too much fuel. Could also be bad needle and seat in the carbs or choke plungers going bad, although that would tend to be noticeably worse on one side or another. It's also good to check the jetting and adjustments of a new-to-you sled, but as much gas as you describe is probably leaking constantly, either from a bad fuel pump or the needles and seats in the carbs.

Just took the screw out. Good stream of gas came out. Any way 2 test the fuel pump? How do I determine if it's carbs or pump?

 

[Cweber5156]

I took fuel pump off. Blew into the crank case vent and it holds pressure. Took it apart and as far as I can tell it looks good. Diaphragm does not look ripped. Guess needle seats in carb?

 

[Snocat3]

i would try replacing the o rings on the float bowl assembly . they do fail . I picked up a 0-ring kit from harbor freight that had the proper size.

 

[Snocat3]

NAPA part # CRB 2-18416

 

[Cweber5156]

NAPA part # CRB 2-18416

Is that a whole kit? My local poo dealer has the o rings in stock like $2/ea

 

[Snocat3]

if you can get the o rings go for $2 go for it . or use the NAPA ones

 

[whoisthatguy]

In the 2004 800 Liberty engines with mikuni carbs, the needle is normally set with the clip in the #2 position from the top, which includes the little shim below the clip. For 2000 feet to 8000 foot operation, 400 jets seem to be about right. The problem with older fuel pumps is that they require more pulls to start when the engine has been sitting overnight, for instance. The defect in the fuel pump is the nickel size semi-clear diaphragm gets all roughed up on one side, which causes it to lose it's seal. You can either carefully flip that diaphragm over or get the $16 fuel pump repair kit on EBAY, and use those new diaphragms and rubber center plugs. Hesitancy from the start and failure to reach maximum rpm, is often caused by the choke adjustment that does not have enough freeplay at the carburetor end of the cable.

 

[whoisthatguy]

Stator or CDI.