This started happening when I recently changed the jets on my Mikuni pumper. I used to be able to go about 80 miles before the bike would start to sputter and I would flick over to reserve and the bike would start running again.
Now the bike sputters and dies at about 55 miles. The bike will not start and act like it has completely run out of gas. Putting it into reserve will not work. The puzzling thing is, there is still plenty of gas left in the tank (about one gallon); yet the bike acts like it has an empty tank. It will not run until I put more gas in the tank which at that time will restart instantly.

What do you guys think is causing this situation?

 

May be a venting issue. Do you hear air suction when you open the gas cap? You can pull the fuel line off at carb, put into an empty gas jug, then open the petcock and see if all the fuel drains from tank. If it stops or slows flow at any point, you have a clogged vent, pinched hose, etc. Worth testing. Or take it for a ride and when it happens again, open gas cap, then try to start. If it does, venting issue.

Or, your hitting reserve, but your reserve pickup is clogged. Try starting your ride on reserve. Or while draining tank into gas jug, switch to reserve to check flow.

 

I did open the gas cap to see if it would start but that did not help and I did not hear any suction noise.

I will try the other things you mentioned. Starting out in reserve with a full tank is a good idea; I will try that first. Thanks Werloc!

Werloc, I think I remember you from the Ducati forum...you have or used to have a gen one Hyper?

 

Yes, That was me.....







Small world....

 

The only thing I can think of is that there's a blockage in the petcock or the fuel filter inside the tank is clogged. Gas will flow to the point of blockage, but then will not flow after that. It's easy enough to remove. That's what I would look at.

 

Sorta sounds like an issue with the Reserve portion of the system. No obvious reason for the Reserve pickup to have become blocked as a result of carb work, but maybe you pinched or crimped the hose from the reserve pickup on the tank to the petcock when working on the carb?

Side note, did you range on your primary supply pickup really go from 80 to 55 miles from the jet change?! Was that a huge change in jet size?

Good luck,
TC

 

If you removed the carb to do the jetting changes there is a chance that in taking off the fuel tank that you messed up or pinched the fuel lines. Check that. It seems the most obvious.

If you have compressed air you can try forcing air into the tank (with the cap open) from the supply line to the carb. This will force any obstructions out of the lines. Otherwise you need to disassemble and inspect.

 

No the fuel consumption did not change. I am getting the same mileage. At 55 miles, there is still about a gallon left. It would not go to reserve that early. It just acts as it had run out of gas and reserve is not useable. So basically the remaining one gallon of gas not useable...not very good in a bike with a 1.9 gallon tank lol!

 

Yeah I will take another look at the fuel lines.

I just remembered an incident that occurred right after I put the pumper in. The bike ran out of gas in main (at the normal 80ish mile mark). I flicked it to reserve, and it would not start. I tried it several times and it would not start at all. I started to push the bike and after pushing it for about a half an mile, just on a whim, I hit the starter button and it started right up. Not sure if this info would help anyone decipher this mystery?

 

Werloc, do you still have yours? Mine is the first year 2008 and I still have it. Here is the most recent pic from earlier this year