Float Height Help

[apolloant]

Carb troubles gallore. I live at 3700 feet. Bike ran great at 2000 feet with 137.5's, K&N, after market exhaust. Moving here, it began to cut out at 5000 rpm, bad. Couldn't get past it. I moved the needles down 1 notch to 2 lean side. It cleared up the 5000 rpm trouble, but now stumbles hard at low rpm. Does o.k if I pull the enricher out 1 notch, so I know it's a lean prob. I'm gonna try 135 mains, needle back to the middle. But, what about the floats? I ride from 3700 to 100 feet elevation. They are stock at 25.6mm? I am running pods now, which does seem to help a bit. My mileage was 26-ish, now 40-ish m.p.g. Pipes are bronze, not blue, so showing rich still. Runs rough bottom to 3000 rpm, clears out to 7000 or so, has a stumble, then hold-the-hell-on. Did a 2nd gear wheelie by accident yesterday.

[TopCatGr58]

Hey ApolloAnt,

Had to look at your profile to see that you have a 79SF, would be good to edit your signature to include it with every post!?

I didn't search your previous posts, so I can't remember anything about what you've done to the bike. Although your symptoms needing the choke does sound like a lean condition, things don't add up!? And you said you were talking about going to 135 mains vs. your 137.5's.....or did you mean to say 145 mains?

When you go to higher elevations, the air thins out, and so a good fuel/air mixture can become RICH due to less air density. SO...when tuning for higher elevations folks usually have to go leaner on the jets.

Have you done the Pickup Coil wire check or repair? The stumble at 7krpm doesn't sound carb related. Once you get to around 3-4krpm, you're getting into the mains, and it's just a matter of increased supply as the vacuum slide rises to clear the main. In the lower rpms, the timing plate flexes a lot with varying rpms and vacuum input, but around 3500 rpm, it usually hits the max POWER timing advance of about 36 degrees BTDC, max cent. advance point. The timing plate and wires shouldn't flex much at that point on up. Many folks have chased what they thought were carb problems, just to find out that their PU coil wire fix didn't hold!?

Your increased mileage after your needle adjustment also points to having made a leaner adjustment, which affects the mid and upper rpms. You didn't say what your pilot jet size was. Since it seems to behave better with the enrichener out 1 notch, I would try turning out your pilot screws 1/2 turn each, test, if still stumbling but not as much then another 1/2 turn out. This will help richen the low rpm circuit similar to what you are doing with the enrichener. But doesn't necessarily make sense for running at higher altitude than what you were originally running!? The enrichener helping it may or may not be diagnostic, it may cause it to idle higher so that when you are giving it throttle, you are already starting out at a higher rpm, getting more air to handle the increased fuel/throttle input.

So...you might also need to try turning IN the pilot screws to lean out the low rpm mixture a bit, because it might be stumbling due to too much fuel when you first open the throttle, but once it gets going, it then is able to suck in enough air to handle the eventual increased fuel input!?
T.C.