Wb3a

sundog

Member
Air leak at the fuel hose, pumper on the wrong side of the gasket, old pumper gasket, lever arm smashed down, pulse tube leaking, screen clogged with dirt, gas cap vent on tank clogged....
 

flattop1

Dawg 89
Thanks . Not hands on , so diagnosing from afar .
Had not considered gasket on wrong side .
New carb kit .
 
Instead of starting a new thread I thought I would pose this question here. I have experienced and witnessed just the opposite problem. Why would this carb on a kt100 pump too much fuel? I have had this problem recently and I have witnessed other racers this season have a situation where the motor will not start without completely closing the needles because it is flooded, or they have to run much leaner settings just to get it to run. It appears as if the needle isn't closing and there is enough syphon/pressure effect from the fuel tank that it is completely filling the carb with gas. When you go to start its already flooded. I can't speak for others but I usual run around 10-12 psi for pop off which should be enough to close the needle, no? Any thoughts?
 

spincycle

Member
Instead of starting a new thread I thought I would pose this question here. I have experienced and witnessed just the opposite problem. Why would this carb on a kt100 pump too much fuel? I have had this problem recently and I have witnessed other racers this season have a situation where the motor will not start without completely closing the needles because it is flooded, or they have to run much leaner settings just to get it to run. It appears as if the needle isn't closing and there is enough syphon/pressure effect from the fuel tank that it is completely filling the carb with gas. When you go to start its already flooded. I can't speak for others but I usual run around 10-12 psi for pop off which should be enough to close the needle, no? Any thoughts?
I have a similar issue with my kt100 with a Wb3A on 110 with a mix of 8oz burris hirev, kinda of a pita at times to get it started, when it does, it runs extremely rich (gauging by the exhaust smoke), ive tinkered with the fulcrum arm height a little, cant seem to find a happy medium, though I guess I would rather it be on the rich side than too lean and ending up seizing it....I run in the Midwest on dirt and this summer, the humidity has been atrocious, not a master tuner by any means, but I suspect that is part of equation that maybe isn't being taken into consideration enough.....
 

Don K

Member
A lot of guys like to set the pop-off as low as 7-8 pounds. I found 11 worked best for me. 8 was just to finicky to find the sweet spot. Here is the routine we use.

High needle 1/8 to 1/4. You can find the best setting by revving on the stand. Tiny changes until the high end gets crisp and quick.

Low needle. Start motor at 3/4, hit the track at 1 1/4, pace laps at 1 1/4, start race at 1 1/2, open 1/4 after each two or three laps till 2 1/4 out. Back down to 1 1/4 on yellows and start all over. This was for dirt speedway. The 2 1/4 is judgemental or best EGT. I really never could see the display so mine was always by the seat of the pants.

DK
 

flattop1

Dawg 89
Crank seal leaks can cause starting issues .
I kept a can of either on the starter zip tied a Gatorade bottle for holder .
PSST , VROOM VROOM
 
The common tuning on these carbs is with the low open 2+ turns when racing. When you come off the track or are under yellow this is very rich and just loads the engine up. As you roll into the pits close the low down to about 1 turn or so and it won't load up. Blip it a couple times so you know it's clean and let it die. If you do this and your other components are good it should fire right back up when the time comes. It works for me.
 
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