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Discussion Starter · #1 ·
I have been a long time follower of this thread and really enjoy getting new tips and hints from you all.

So, now I am asking for some advice.

My bike is a 2006 Scrambler with the following mods

AI Removed
Bellmouth w/unifilter
120 main jets

The bike was stored home in the barn over the winter and seafoam was added to the tank. Just prior to storing the bike we changed the oil, new brake fluid, new tires (Michelin Anakee's),balanced the carbs, re-oiled the air filter...I believe thats it.

This spring the bike was a little tough to get warmed up, although nothing alarming.

What is strange is that the bike dogs out and sputters when going over 55 into the wind! Seems like that going with the wind its ok. We brought it up to 90 no problem going with the wind, but turned around to head home and it dogged out at about 55 again.
Even seems like when riding if you stick your knee out (create wind resistance) the bike wants to sputter and dog on me!

I have been unable to locate anykind of fuel filter, havent noticed at loose vacuum lines, etc.

I have about ran all the gas that had the seafoam out of the tank, will fill with high test and keep trying.

Any suggestions? Seems like when I need all the fuel it can deliver, it fails?

Thanks for reading the long post


2,453 Posts
Check the carb breather tube. Follow it from the carbs down to the bottom of the engine. If the tube sticks out under the engine, cut a short length off so that the end of the breather tube is a couple of inches up from the bottom of the engine.

A few people have suffered from winds blowing across the bottom of the tube and creating a vacuum in the float bowls with the effects you're describing. Just a long shot.

258 Posts
Ahh... good old high speed stalling...

Carb breather tube is one thing to check, or chuck, depending on your preference. The center nipple of the T-fitting between my carbs is running bare (carb breather hose completely removed), and has been for the last ~6000 miles. Lots of rain. No problems from it.

Another is the vent in the gas cap. You could be partially vacuum locking the tank, which would cause the fuel to drain into the float bowls much more slowly than it should. With the wind, fuel demand is low, so you can get speed. Into the wind, you need a lot more fuel to maintain the same speed, so you're running out. Suck on the bottom of the gas cap (wipe the gas off first, or use an ear syringe) to see whether the valve is working. If not, suck harder, and you'll get it unstuck.

Some tanks (mine included) seem to also breathe through the overflow tube. The tip valve can get gummed up. Make sure yours isn't. It's along the front side of the vertical frame member that the airbox wraps around. Follow the tube from the bottom right of the tank, and you'll find it. Keep following it, and see whether you have the California emissions equipment on the bike. I ended up removing mine as part of the tank vacuum lock fix, and it solved the problem.

Another possibility, though rather unlikely, is that you could be creating low pressure over the bellmouth going into the wind and starving the bike of air. Reinstall the snorkel and see whether the problem persists.

If you determine that the carbs and the tank aren't vapor locking and the bellmouth isn't starving the engine of air, pursue other options. There are fuel filters on the pickups for the petcock, so you have to remove it from the tank to check them. They're designed to not get clogged easily, so they're not likely to cause problems unless you have rust or a serious amount of crud in the tank, and the bike probably wouldn't behave like you're describing if that were the case. Beyond that, it's a lot of taking stuff apart and fiddling to find the problem and fix it.
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