Monday, May 25, 2009

Why does she stall?

video
Before I can determine if the lights and electrical are working correctly I need the bike to be running. Today is the second time I have ever run it and both times it has stalled as if it lost fuel or something. I need to determine what the problem is soon so I can complete the bike. I did have the choke on in this video and had held the throttle a hair back to keep it from stalling, which only bought me some time.

Suggestions?

Possible reasons:

"Sounds like it's a fuel starving issue. Make sure that the fuel line is down and under to the carb. I had a similar problem once because my fule line was going strait into the carb w/out a j-bend going under then into the carb. Also check to make sure the air hole in the gas cap is not clogged and that the gas tank filter is not clogged. May also be your carb jets are clogged." -Scott

"Air leak. Explains the high rev as well. Carb basket base gaskets and crank seals are the places to look. Start it again and spray some carb cleaner at the base of the carb (inside the air cleaner), then at the bottom of the basket and if the idle drops at all, then you have an air leak there." - Derek

5/27/2009 Update

It is possible that my fuel line is too long. The correct length (stock) is 25 inches and the fuel line is clear on stock bikes. The other to make sure is that there is a "J" bend in the line going up to the carb. It should not feed straight to the carb.

I will measure the length of my fuel line. I suspect that it is too long for the gravity feed fuel system to work properly, hence the stalls from fuel starvation.

I also need to confirm the correct diameter of the fuel line. The black one I am currently using is 5/16". I was under the impression that black was the stock color, but clearly clear would be easier to use since you can determine that the fuel is actually flowing correctly.



Other possibilities to trouble shoot:
1) Air leak. Explains the high rev as well. Carb basket base gaskets and crank seals are the places to look. Start it again and spray some carb cleaner at the base of the carb (inside the air cleaner), then at the bottom of the basket and if the idle drops at all, then you have an air leak there. -- Derek G.

2) You said you have the choke on? I only use choke for the very initial start up, then I turn it off right away and use the throttle to warm up a bike.

The length of your fuel line from the tank to the carb is very important. I usually measure the length like this:

Lift the gas tank out of the bike. The fuel tap should not be allowed to come above the plane of the frame. The fuel line should pull tight not allowing the tap to come up above the frame. Basically you want the fuel line to be as short as possible without making it too hard to reach the bottom of the fuel tap.

I've had this same symptom when my fuel line was too long. This is a gravity feed system. You don't want to have the fuel travel too far "up hill". -- Michael C.

3) Make sure "clear" tubing you use is fuel-compatible. If you're not interested in a 100-point restoration you may want to use the transparent fuel tubing available via mail-order from Aircraft Spruce and Specialty. We've been using it on our race bikes and it works great. Let me know if you want specific part #s. -- Dave S.

4) As everyone said before, the gas line needs to be the correct length. Clear fuel line is not a problem, as long as you get fuel line, and not some other type of clear tubing. First Kick has the stuff you need.

As for the clogged breather hole, it is unlikely that is your problem. However, it is easy enough to check. Simply try to run the scooter with the gas cap open. If it still dies, then the breather hols is not the source of your woes. -- Paul S.

5) Here’s a quick way to check if your fuel line is too long:

Get a second person to help. Have that person lift the gas tank up as high as it will go. Now you kick over the bike. If the bike keeps idling while the gas tank is held up that high, then your fuel line may be too long.

What you are doing here is increasing the potential energy of the system buy making the petcock that much higher than the carb. Increasing the potential energy will help the fuel flow. -- Michael C.

6) Make sure to have a "J" bend in the fuel line going to the carb. The line should not go directly to the carb. -- Scott

2 comments:

Anonymous said...

after 500 miles try checking the airbox is "square" onto the carb top (the ones I have run over the ears have had a tendency to vibrate loose as the air box base hasnt cleared the cylinder cowl leading to lean air /fuel and heat seizur) A little dremmel work on the air box base where it fouls will prevent this and make sure the two bolts and springs do there job holding the base down

Anonymous said...

if this problem happens only once the engine is warm then replace your condenser