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Old 02-14-2011, 07:15 AM   #1
Uncle Pollo OP
happy cachiporra
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Joined: Jun 2006
Location: Albuquerque, Neue Messico
Oddometer: 48,548
Full throttle = bike chokes mono r80 bmw

The bike runs fine going on slower speeds, open throttle full at highway speeds and the bike "chokes" (like it is not sucking gas), then back off a bit and it is allright. It bothers me because I don't know what it is, it is not a safety problem (au contraire, it prevents me from running the ton every day) but I want to fix it!
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Old 02-14-2011, 08:04 AM   #2
Sniper X
De Oppresso Liber
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Joined: Jul 2006
Location: Central New Mexico, 7420ft above sea level
Oddometer: 33,349
I still think there are pinholes in the diaphrams....lets throw a set of mikunis on that thing!
" The people who cast the votes decide nothing. The people who count the votes decide everything."
Straight Out Da Trailah!
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Old 02-14-2011, 08:14 AM   #3
Boon Booni
Red Clay Halo
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Joined: Aug 2003
Location: Richmond, Va
Oddometer: 13,916
My first guess would be holes in the carb diaphragms.

Also fuel flow restriction, or leaky float bowl gaskets sucking air. Improper float height. Maybe the spring on the floats is sticking, keeping things too lean in the bowls.

Also could be weak spark breaking down under full load. charging system OK? Battery Good? Ignition switch in good working order? I had one that would miss under full load because the ignition switch was going bad the the extra vibration would cause an intermittent miss as the contacts arc'd.

Why not throw a carb kit at it? You get diaphragms with BMW kits so you can eliminate that possible issue, and verify that everything is clean and well sealed in the carb.
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Old 02-14-2011, 08:46 AM   #4
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Joined: Apr 2008
Location: Road Island
Oddometer: 6,068
The primo suspecto would be fuel delivery, a classic case of fuel starvation when fuel is most needed...

As above, check float levels, check fuel flow from each petcock. Both easy checks, and likely to be the problem... if not, then go for the diaphragms.

XS650 becomes a VT BackRoadRunner
Loving the 80ST
I love projects that take twice as much effort as should be needed. Should be an Airhead motto. (disston)
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Old 02-14-2011, 09:46 AM   #5
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Joined: Feb 2005
Oddometer: 1,041
Make that "secondary," as clearly diaphragms are first.

Cracking the throttle open does nothing directly in terms of fuel flow, but it sure does want to cause the diaphragms to raise the needle jets.
Kent Christensen
'12 R1200RT, '02 R1100S, '84 R80G/S
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