I am an experienced licensed mechanic. This thing is kicking my butt.


When you first start it up, it will run well for about 30 seconds. It then acts like it is running out of fuel. Blowing in the gas tank vent tube will keep it running or get it to start again when it dies.
I have,
1. Disassembled the gas cap, cleaned, reassembled. Ensured air flows into cap from vent tube.
2. Emptied and cleaned gas tank.
3. Removed petcock and cleaned primary and reserve filters. Verified flow through both.
4. Replaced fuel line to carb.
5. Removed filter in carb fuel inlet and cleaned.
6. With float bowl removed you can blow through fuel line and get little resistance through needle and seat. With float bowl installed there is much resistance.
7. Replace needle, seat, and float.
8. Cleaned carb. Am able to spray carb cleaner through all orifices and see it come out other end.
9. Removed obstructions from float bowl vent lines. Also tried with lines removed.
10. I can blow into vent for float bowl in carb body and air passes freely. I do not understand why flow into the fuel inlet is restricted. Loosen the float bowl and flow is free.


I have had this carb off at least 20 times. It is improved since I started but still not good enough to ride normally. Any help would be appreciated....

 

"When you first start it up, it will run well for about 30 seconds. It then acts like it is running out of fuel. Blowing in the gas tank vent tube will keep it running or get it to start again when it dies."
Sounds like that's the area you need to concentrate on. I've found tank vent lines along with atmospheric vent lines on carbs that were pinched or partially collapsed that would cause one to have a vapor lock condition. Get enough air to run for a tad,then die.

 

I have tried loosening the gas cap and no change. I have seen the tank vent cause this on other machines. Have also seen the vent lines that hang off the carb clogged with dirt. Still stumped....

 

Nice, detailed "write up"....good job!
I know you have cleaned the petcock but have you verified good fuel flow from the petcock, meaning disconnect from carb, turn petcock to the "on" position and let the fuel run into a jar?
In regards to the small filter located on the carb fuel inlet.....have you removed the filter and tried running without it ( I know you cleaned the fuel tank as well )? It doesn't require much trash/sediment to clog/partially clog that little screen. When I get the 220/250's Kawies in....I remove that little screen and add an inline filter as that little screen has caused me problems similar to what you are having.

NOTE: and you are sure the float is set high enough...to the proper level? I mean no offence in saying that but I make that same mistake every now and then myself...

 

I did check flow from the tank and it is good. I have not tried it without the filter yet. I will try that. Float level was set to the manual spec. Main thing I don't understand is why flow is obstructed when blowing in the fuel inlet, but flows free with the float bowl loosened. There is a vent above the float chamber that goes overboard to a tube that I can blow into easily. No way to test flow out of the chamber though.

 

There is a vent above the float chamber that goes overboard to a tube that I can blow into easily. No way to test flow out of the chamber though.[/QUOTE]

^^^^^^I don't understand this either, there is no "one way" valve that I know of, or have ever seen on any of these...just an atmospheric vent. Question, with the carb on the bike, can you open the carb bowl drain screw? They are often stripped ( the head ). Open it if you can, let some fuel drain out of the bowl....then try it again. I do recommend checking the filter screen tho.

 

Then sounds like a carb problem itself if you can loosen the bowl and inlet pressure will pass. Bowl somehow obstructing operation of the float assy,some how needle may be sticking in the seat?? Can you shake the carb up and down and hear the float move? Plus have you rigged up an auxiliary tank to see if it runs that way? Also you should be able to open the drain screw with a clear hose attached to see if fuel is passing good and fuel level is ok.

 

It will be a week or so before I get back up to it but I will try it. It is possible the float is being held up by the bowl somehow. Did not think of that. Thanks, I will follow up when I try it.