Crosswind hesitation

[scratch]

Sunday, on the way back from Infineon, while pacing with 70 cam guy at 75mph in the rain, I noticed whenever I passed a car the bike would suddenly start to hesitate. Stock '94 with 2.5 turns out on the mix screws, 40 non-bleed pilots, one .5mm washer and 125 mains, 40 tooth rear.

Anybody else experience this, or can someone verify?

[mwdbruno]

I don't know that I feel a "hesitation", but a strong wind has slowed me up on a rare occasion.  I've gotten in the habit of anticipating the winds I can (like around semi trucks, SUVs etc) and when necessary kick it down to 5th to bring the revs into the powerband and motor through it.

[scratch]

We had a couple of crosswinds, on the way up, that did cause me to slow down and Andy mentioned it too, but on the way back it definitely was carburetion because I could hear the chain go slack and feel the rear wheel drag, like in coasting.

Another thing I should mention is that I have an aftermarket foam air filter of unknown origin. Spiral wire frame, plastic top with rubber velocity stack (if you can call it that).

I usually cruise at a steady 69mph (better fuel mileage), and have had no probs. I have kept up with a CBR954 in 5th at 85mph with no probs, too, but that's in 5th gear and at 85 not 6th at 75. So, that is why I have concluded that it is carburetion. I guess I need to do a plug reading.

I also have the stock petcock, and I know I have set the float level level with the gasket.

I guess another question is, am I going rich when the crosswind hits?

I had a freind with a SRX600 that was very suseptable to crosswinds, and he would go rich, because the crosswind wouldn't allow any wind into the airbox or suck the wind out of the stillair pocket before the airbox.

[newbieone]

i theory if the engine was suddenly starved of air, it would hesitate notably. For example, take a your home a/c, cover up the intake vent; it will still produce air, just not cold air and the velocity is significantly decreased.  You might just need a new air filter. I do not have any experience with your situation, and I have no clue as to your carb setup, but if you want to know if a lose of air will cause a hesitation, i'd say so if it starved that much. hope this helps

[ash999]

THis probably has been asked b4, but i dont know if my bike has been rejetted, but it does have a KandN filter. Is there a quick way of telling if it has been rejetted!! cos want to do another mod!!!!!!!!

[scratch]

Yes, feel under the front of the carbs for a smooth brass plug covering on the mix screw towers. The plug may have a tiny hole in the center. This is usually the first indication that someone has messed with the carbs, but it does not nessessarily mean that they have changed anything internally.
I'm also guessing I have the K&N drop-in foam filter, which I like, because it's easier to clean than to replace.

Also, the crosswind could also mess with atmospheric pressure to the float bowls. Something to think about how to cure.

[Kerry]

Yeah, what scratch said!  The brass plug he talked about is labeled "Air/Fuel Mixture Screw" in the photo below:



This photo shows a pre-2001 model carb that has NOT been rejetted.  If that brass plug with the tiny hole in the center is missing, it's a pretty good bet that someone has monkeyed with the jets and then adjusted the mixture screw to fine tune the change.  (Although it's technically possible that someone adjusted the mixture screws without rejetting ... like scratch said!)

However, just because the brass plug is still there doesn't mean someone hasn't changed the jets inside.  To be SURE you would have to drain and remove the float bowl and unscrew the jets.  This usually requires taking the carbs off the bike.   :x

PS (for scratch) - As far as I know, K&N only makes filters with a layer of cotton between a sandwich of fine metal mesh.  I have a foam filter made by UNI lying around somewhere, but I think other folks make 'em, too.

EDIT: Changed link from sisna.com to bbburma.net.

[scratch]

Thank you, Kerry, for a picture! (for future reference, too)

O.k., so it's not a K&N drop-in, so it must be a UNI or other, cool, thanks! As long as it's the foamy-type.