Bonneville America Forums Forums Technical Forums General Tech Please Help!!!!

I have a rather curious, and infuriating problem. Around town, even under hard acceleration, my bike runs fine. When I get on the highway, above 60mph or so, the bike falls flat on its face. The more throttle I give it, the slower it goes, sputtering the whole way. I can slow back down to around 55 or so and the problem goes away. Sounds like mixture/needle/carb problem right?
Here's the twist. It only seems to happen when I'm riding into a headwind. Downwind runs are just fine, in my few experiments thus far.
The problem started before I replaced the stock air box and re-jetted. Here's what I'm running now: K&N pods (Freak), 152.5 mains (from jet calculator), 2 baffles removed, no shims, AI removed.
I'm at a block here, I'm beginning to think maybe electrical/ignition, but that doesn't account for the apparent headwind issue. I've also replaced the stock turn signals and installed a load equalizer in the headlight bucket, but I don't see what, if anything, that would have to do with it. ANY HELP would be GREATLY appreciated.
Some more observances: High rpm's, such as 4th gear acceleration onto the interstate doesn't seem to have this problem, only in 5th gear, at around 60-65 mph. Also like I said earlier, around town hard starts are also no problem, the bike has plenty of ooomph. Please lend me your ideas/thoughts/magic wands......

pull the spark plugs and check the color.
check all the connections on the coils.
check all the rubber vacuum caps on the carbs and intake.
check the hidden fuel filter in the "t" between the carbs.

get back to us with the findings.

As you are checking those electrical connections, hit em with some dielectric grease.

Thank you and thank you. I have checked all the coil/elect. connections, vacuum caps/intake rubbers, and I removed the hidden filter at the carbs. Just came back from a test run, 3-3 mile runs up and down the interstate, and the bike ran fine, couldn't get it to cut out. I'm wondering about the throttle position sensor, what exactly does/can it do to the performance? Maybe it's just mixture, with the air being pretty cool right now (50). Anyway, keep the ideas coming, I appreciate any and all help.

far as I know , the throttle position senser is useless.
some have changed to other carbs that did not have the senser
and they just took it off and the bike runs fine.

was the little hidden filter crappy?

You could have a fuel restriction problem check vent hose and fuel line from tank to carbs a small pinch in fuel line could do this

Sounds like a tank vent issue.

tank vent line is fine, I thought same thing and popped the gas cap going down the road to no effect. I left the little filter out, don't really see the use when the petcock filter is 6 inches away.

Ok, a friend of mine at work has suggested the only plausible answer to my problem, and as strange as it sounds, it's the only solution that fits. It's basically a matter of fluid dynamics. As an object travels through the air, positive air pressure builds in front of the object, and negative air pressure develops behind it. NASCAR calls this drafting, airplanes call it lift/drag, and my bike calls it vacuum choking. Essentially as I ride into a strong headwind, the negative pressure forming behind the motor is creating an air "void", causing it to basically choke itself rich, thus the "flat" throttle response. This may sound very obscure, but it explains why this problem is not constant, and town driving is unaffected, because of the relative slower speeds. This very effect is why ram air induction faces INTO the direction of travel instead of away from it, the vacuum formed would literally suck the air OUT of the carb.
So now the problem is in the fixing. I'm imagining some sort of air dam/guide to force more air toward the filter pods. It will have to be hidden under the seat, possibly attached to the downtube, I'll just have to get creative, but at least I have a direction now. Thank you all for your suggestions, maybe if someone else develops this problem they can use this info too.

I think you buddies theory is hypothetically possible, but not probable. First, hunderds of us are running pods with nothing to report but better performance. I've had my bike into the triples many times. It sounds like fuel loading either from too much fuel, too little air, or too little spark. <P> You mentioned you are running the FREAK, but then you mentioned two baffels removed. Are the baffels from the exhaust? What exhaust, needels, and mains are you using? <P> Aside- I'd start at the electrical. Disconnect the load equalizer and take it for a ride. Wire those away fromthe electrical system of the engine. In fact, isolate it with a relay. Ohm out your plug wires- bad plug wire? Get new sparkplugs. Check the coil outputs.

The baffles are of course out of the exhaust. Not to sound snooty, but where else would they come from? Stock needles, no shims, mains are as listed, 152.5. Too little spark would hardly make a difference riding into or with the wind also. I'm not denying the performance boost of the pods, this problem started after I (unknowingly) blew out the stock airbox during a cold start backfire. It continued after installing the freak, but only into strong (30+) mph headwind. So far it's the only plausible explanation that covers all the parameters. I have thoroughly checked all electrical components, so it's all that's left.

When your ride stumbles, try pulling the choke out. Your friend's theory is a good read. From reading the first post of yours I guessed that you were running rich or having a fuel starvation problem. Thus the plug chop at full throttle. And now the enricher when stumbling. You could have something blocking one of your mains periodically. Like maybe perhaps just might be a tenny weeny piece of paper towel. Or something sucked up into an internal port. If you pull the choke while the sickle is stumbling and you about get thrown off the back, start at the fuel tap and work to the carbs re fuel delivery. All else left is lectric. Greybeard's cheap timing light procedure will confirm an issue there. Hook it up and see if the light acts erratic while the motor is stumbling...

Also, check your bat'try connections and the 30amp fuse. Odd how the symptoms appear apparently only in a head wind! You must hail from the bayous.

Edited: Since this arose after your engine hiccuped, you very well could have sucked some debris into a carb internal passage.