strange jetting question

[oilspot]

I've still slowly been working on leaning down my jetting to get it correct. I've started rich and am leaning it out till it's correct.
My next step was to drop down one main jet size and I think that will be just about perfect.
Then I ran into a strange situation yesterday. I ride a little before work every sunday and am able just to ride to work. I ran for a few seconds at WOT and when I dropped off the throttle the engine surged a few times like it was running lean, which was a total supprize thinking that I was about to go to a leaner main jet.
I carefully made it to work because I was close. I ran at low rpm's incase my main was too lean. I know I'm not running too lean in the lower rpms so that's where I kept it. After I got off of work I checked and changed the plug. It's hard to see down into the plug but I could see a healthy ring indicating that I'm not too lean.
After kicking several times I figured out that I was low enough on fuel that I had to switch to the reserve on the tank..... which started me thinking.....

Was the bike just starving for fuel because it was running out of gas, making it run lean. It ran great home! I even did a WOT run once I got close to my house to see if it would surge again. No problems.

Has anybody had a bike act like this when running out of fuel.
I would like to catch any problem that would run my bike lean before I fry a piston.

 

[Rich Rohrich]

It's hard to see down into the plug but I could see a healthy ring indicating that I'm not too lean.

You aren't too lean SOMEWHERE in the fuel curve but where specifically is still in question. You didn't do a wide open throttle chop on a clean plug, so don't assume the main isn't too lean because you see a ring. The ring is likely there from the part throttle running you were doing.

 

[2strokerfun]

I have had one do exactly that a couple of times. Once when I was extrememly low on fuel and once when my gas vent was clogged. Add fuel and do the chop test, as advised.

 

[oilspot]

You aren't too lean SOMEWHERE in the fuel curve but where specifically is still in question. You didn't do a wide open throttle chop on a clean plug, so don't assume the main isn't too lean because you see a ring. The ring is likely there from the part throttle running you were doing.

So I'm guessing I should get the bike fully warmed up, change the plug, and do a WOT throttle chop to read the main.
Does the bike need to be under load?

 

[TimberPig]

Yes, it does need to be under load. An engine that is not loaded requires less fuel to be correctly jetted than the same engine when loaded. You can't jket a bike correctly without having adequate fuel supply, fully warmed up, free of mechanical issues, and being ridden in the conditions you ride in. The rider and the conditions the bike is used in are crucial pieces of the puzzle in correctly jetting a bike.

 

[oilspot]

Sounds like I need take some plugs next time I go out for a normal ride, and something to label what's what.
I've got a little antique craftsman lathe that I should clean up so that I can cut the plug for easier viewing.



I'm thinking that I was just running out of gas/ starving for fuel and that's what created the lean situation yesterday afternoon. Not that I've got the jetting dialed in yet! It was just so differant that the norm that I've got from the bike.

 

[kx125412]

When I forget to turn my gas on sometimes the bike will fall on its face stuttering and I'm pretty sure it's surged a little bit. Mostly just stutters.