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Old 04-16-2012, 12:06 PM   #1
lmyamen OP
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Joined: Nov 2011
Location: Des Moines, IA
Oddometer: 332
Carb issues or something else? (R90/6)

Hey guys/gals thought I would ask here. I am noticing a problem when accelerating on the interstate. When traveling at 60-65mph and I accelerate it starts out fine but then it kind of cuts out almost like a feeling of the gas being restricted and not flowing. It does not show any symptoms of this at lower speeds under 50mph when traveling through town and the clutch is definitely not slipping when I am accelerating. I am wondering if this could be caused by dirt carbs? I was talking with my father and he said maybe something has gotten into the carburetors after having the tank off and doing all the paint work. Going to take a further look at it tonight though, any other options of what could be causing the hesitation?


my bike


lmyamen screwed with this post 04-16-2012 at 01:17 PM
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Old 04-16-2012, 12:18 PM   #2
robsmoto
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Joined: Jul 2001
Location: Columbus, Ohio
Oddometer: 328
check the vent for the tank (in fuel cap,I've used B-12 to clean, replace cork or rubber gasket afterwards)
check the in-line fuel filter, if present - replace or clean
drain gas from tank, remove petcock, check screen and tube for crud - clean and/or replace
check diaphrams at carb tops, if torn will give poor top end performance, replace if needed
remove bottom bowl from carb, check for water, crud, gas varnish. If necessary remove jets, clean with B-12, replace o-rings (I find it easier to just remove carbs at this point for a proper cleaning).
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Old 04-16-2012, 12:38 PM   #3
supershaft
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Location: San Francisco Bay area
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It could be about anything but the first thing I would do is pull the floats and look very carefully for water in your bowl. If the water is clean, it is very hard to see. Then check and make sure you floats are adjusting right and the fuel shut off is working. First things first! No need to tear it apart just yet. Good luck!
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Old 04-17-2012, 01:22 AM   #4
chasbmw
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My betting is that the float height is set too low, unlikely to be diaphragms at this speed.

Cheap and easy cure
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Old 04-17-2012, 07:25 AM   #5
lmyamen OP
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Joined: Nov 2011
Location: Des Moines, IA
Oddometer: 332
We will find out more when I take the interstate this evening, but last night opened up the carbs and one of them had some debris of some sort in the float bowl, cleaned it out and seems to be running great. Took it for a quick ride on the interstate last night afterward and no signs of missing.
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Old 04-17-2012, 07:59 AM   #6
cycleman2
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Joined: Jan 2010
Location: Alberta, Canada
Oddometer: 514
Put a dose of Sea Foam into the tank. It really helps to clean out the carb orfices and is a good treatment to use once and a while.
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Old 04-17-2012, 01:10 PM   #7
sigpe57
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Joined: Oct 2005
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The fuel-cut-out happened to several of my BMWs. One bike it cut out at 70mph or higher. One bike cut out at 10mph. It's all caused by weak rubber diaphram. I replaced the diaphram. The cut-out problem goes away.

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Old 04-17-2012, 02:18 PM   #8
bmweuro
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Location: Chico, California
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Quote:
Originally Posted by chasbmw View Post
My betting is that the float height is set too low, unlikely to be diaphragms at this speed.

Cheap and easy cure
I agree. Make sure your points and condenser are good and your getting full advance.
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