Carb Cough

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mkunert

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Jul 10, 2006
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Location
Minneapolis, MN
I bought a 2001 two years ago with 750 miles. Ever since that time, the carbs will "cough" every now and then. I've had the carbs rebuilt, tuned, run Sea Foam every now and then, and have never run oxygenated fuel. I rode today in very cold weather (25 degrees), and it was coughing like crazy. Does anyone have any idea what is going on?
 
Sounds lean. But, check for exhaust leaks, intake boot leaks first. How do the plugs look? When's the last time you checked float level and sync? Have the mixture screw plugs been removed? Vmaxes come with a lean idle mixture from the factory.
 
No leaks. Plugs look good and clean. Not fouled or buned. I synced the carbs every year, so that should be o.k. I bought the bike after it sat for 3+ years with stale gas. I had all the carbs professionally rebuilt. Not sure if the mixture screw plug have been removed.
 
mkunert said:
No leaks. Plugs look good and clean. Not fouled or buned. I synced the carbs every year, so that should be o.k. I bought the bike after it sat for 3+ years with stale gas. I had all the carbs professionally rebuilt. Not sure if the mixture screw plug have been removed.
Click to expand...
I talked to Shawn Kloker the other day.....both of our does it....once in a while....(I call it a burp....lol)
My screws are out 3.5 turns now.....and still does it the same.
200.00 tuning and cleaning job too.
 
Mark is right.You are lean.I always richen mine in the fall and lean it after spring.
 
FYI- when cold outside, I set the Vboost to 1,800 rpm, and that eliminated the cough. When it warmed up, I set it back to 4,500 rpm, and it's been running fine.
 
Yep, my 97' does the same thing when cold. I just attribute it to the normal goings on of the bike as it's continues after being tuned and such.

Also, I know there are plenty of ways to lower the rpm that boost kicks in at, but does anyone know of a setup that would set Vboost to kick in at 7k rather then 6.2? Highway running where I live means you run around 90-100mph unless you want to get your ass run over. Problem is, thats right in Vboost territory and it's a pain in my ass to keep dealing with the boost surge. Not to mention the ding on fuel milage.

I thought discconecting boost all together, but then realised that would almost be suicide on the highway.
 
I've got the SASY, and I am constitantly adjusting it. When riding around town, I have it on the low range. Before I get on the freeway, I bump it up to 6000. There is no 7000 setting, but you can turn it off. I don't think that will work for you, though.
 
Well, if I end up keeping the vmax (I might be trading it in on another bike) I will look into this issue. Mainly since there are obviously ways to set vboost to kick in quicker, so there has to be a way to set it for a tad later.
 
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