Strange Loss of Power

[cowboyup3371]

For a few times this summer (latest being today), I've experienced a sudden and fairly unexplained loss of power on the ride home from work. Essentially, the bike will run fine for about 20 of my current 34 mile ride home and then suddenly start to cut out. It won't do this at any other point in the ride nor will it do it in the morning, in town (if I ride around town during the day), even not everyday on the same ride.

Here are the circumstances as I see them:

• The ride home is a straight 70 mph shot down that highway 94 I've mentioned several times once I get out of town (4 miles of intown 55 mph riding).
• In town riding consists of buildings, homes, businesses, and other cars while the highway is open with no obstructions (especially after the 17 mile marker) but with one long steep hill and cutouts from smaller hills the highway travels through. It's two lane pretty much the entire way after getting out of town
• Only times I lose power is if I'm facing a strong SE to NE wind (today's wind was SSE at 15mph gusting to 22mph but felt more like it was coming from the east).
• It acts like a vacuum leak but I can reduce speed, downshift, throw petcock over to prime and still have the problem. Vacuum line, intake boots, and airbox side boots all look good - read no cracks that I can see.
• When I do reduce speed I can swap back over to "on" and the bike runs but I'm at a slower speed and will experience surges that sometimes helps to clear out the issue and sometimes not.
• Temperatures outside today were mid-90s which has been about the same during the other episodes.
• Only happens in the afternoon, no other time so far
• I wasn't out of gas (odometer was at 70 miles and I normally swap to reserve around 100 miles)
• Does not do this every day but almost always if I'm running into a wind coming from the east (I drive east in the afternoons, west in the morning).
• I think my air filter needs changing but I've only put 4000 miles on it so I'm not positive if it's time
• Fuel flows perfectly every other time and I don't have a problem if the wind flows from the west on the way home (sometimes does) or directly from the south or north as best I can tell
• I sealed the air box this winter and those screws are tight.

Any suggestions on what to look at to figure this one out?

Thanks

[cowboyup3371]

One other thing to add, once I get out of the wind by turning down my road (runs south), I get all the power back with no further problems.

[mike_of_bbg]

Where are the ends of your carb vent tubes tucked away? I put mine behind my side covers. They should be away from turbulence.

[cowboyup3371]

I don't have any hoses on mine but I think they are pointed up. I'll take a look at them tomorrow

[tom203]

Does it do this, no matter where the fuel level is in tank- i.e., if you fill tank on ride home, would it behave differently? Maybe tank filter is gummed up around bottom portion and 90 degree heat makes it worst. Sounds like it's running out of gas.

[Suzuki_Don]

While I was reading your initial post I was thinking exactly the same thoughts as Mike. You should have two rubber breather tubes coming from between the carbs and these need to be directed rearward and tucked inside the framework of the bike somewhere. Mike has his in behind the side covers, I have mine going rearward over the airbox. If you don't have these breather tubes then that could be the problem as well.

[cowboyup3371]

Does it do this, no matter where the fuel level is in tank- i.e., if you fill tank on ride home, would it behave differently? Maybe tank filter is gummed up around bottom portion and 90 degree heat makes it worst. Sounds like it's running out of gas.

Yes, it happens no matter the fuel level.

[cowboyup3371]

While I was reading your initial post I was thinking exactly the same thoughts as Mike. You should have two rubber breather tubes coming from between the carbs and these need to be directed rearward and tucked inside the framework of the bike somewhere. Mike has his in behind the side covers, I have mine going rearward over the airbox. If you don't have these breather tubes then that could be the problem as well.

I'm going to try something today if it happens again and will probably get the hoses put on by this weekend. I appreciate all the advice. Thank you all.

[Windsmile]

I read your questions and replies today (7/21/11) and thought that you had described my problem exactly. See my post titled "is this surge scenario common?" Judging form your original post I'd have to say its not unheard of. Your problem is so much like mine that the only difference is in the direction we're going when it happens.
I have yet to figure a solution out yet but I'm working on it in bits and pieces. My next try is to add Techron to the fuel and see if that makes a difference. If you would like to talk about the surging problem we're having on the phone I would be pleased to give you a call at a time that is convenient.

[cowboyup3371]

I've seen your post but I don't believe it's the same Windsmile. Mine was a loss of power but as I get it back it will surge. Based on what I've seen in the last couple of days, Steve's comments to me privately as well as the recommendations above make a lot of sense. I'm having an airflow issue based on the direction of the wind, the lack of vent hoses (I have the tubes but no hoses), and low air pressure. If I have a tailwind I don't have any issues because the low air pressure can't develop since the air flows through the bike. The headwinds are hitting the front of the engine and sliding around causing a low air pressure area in my carbs. I intend to add the vent hoses but am waiting until I have some money for other repairs I want to make. This will save me the trouble of taking the carbs off more than once.

I really think you will need to step back and take another look at your carb cleaning and maybe redo it.

[Windsmile]

Thank you for your reply. I've check the lines and mine look to be in good order and routed correctly. Since the surging I have is occurring in one direction on the interstate and not the other, perhaps I should experiment with the hoses.

[Jason the terminator]

Have you changed anything before this happen? Did this start out of no where?

Maybe want to check your tank vent as well.

[cowboyup3371]

Yea, pretty much out of nowhere Jason. Thanks though, i'll take another look at it.

[cowboyup3371]

I think I figured out the fix for this and it's extremely simple - ALL bits and pieces to the bike must be put back on to let everything work correctly. Although I still don't have any hoses put back on my vent lines, I did put the chrome caps back on my side covers two weeks ago. Since then, I have not had any problems with the stalling even in the same wind conditions as before.

I'm not quite sure how, but I think there's too much wind getting to the boots; by putting the side covers back on correctly it's doing its job. At least, in my estimation that's what has fixed it. Course, I'll put new vent hoses on after I return from Ohio.