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Carb Identification Help

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nchirikos
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Carb Identification Help

Post by nchirikos »

My 1981 R80 G/S has carb numbers 64/32/323 and 324. Per the Bing manual, these numbers are associated with the R80. The numbers for the R80 GS are 64/32/357 and 358. the differences in the chart are:
Slide R80: 906-1 GS: 907-3
Main Jet R80: 150 GS: 135
Idle jet R80: 40 GS: 45
Jet needle R80: 241 GS: 251
Float bowl: R80: 60 GS: 66

Also, there are two separate lines for the R80, the other having the numbers 64/32/353 and 354! My question is: do I have the correct carbs for the G/S or have they been changed or altered by the previous owner?

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schrader7032
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Re: Carb Identification Help

Post by schrader7032 »

I think the 357/358 carbs might be for the post 1985 GS bikes. There is a distinct difference in calling a bike a G/S and a GS bike. G/S was the label prior to 1985, and the Bing manual doesn't do a good job distinguishing that. I don't know what was happening on the assembly line when they were building 800cc bikes. Without knowing about the bike's history, I would say that your carbs are correct for an 800cc engine and that getting it tuned to run the best possible - starting, idling, performance, gas mileage - should be your goal.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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schrader7032
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Re: Carb Identification Help

Post by schrader7032 »

I tracked down info from BMW's Profiles publication for 1969-1998 bikes. Here's what they report for the 800cc models prior to 1985:

R80/7 -- 1977-1984 -- 201/202
R80G/S -- 1980-1987 -- 305/306
R80ST -- 1982-1984 -- 305/306
R80RT -- 1982-1984 -- 305/306
R80 -- 1984-1995 -- 353/354 [this is the mono-shock bike]
R80RT -- 1984-1995 -- 353/354
R80GS -- 1987-1996 -- 349/350

Can't this is all inclusive, but it's what they publish.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

chrishea
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Re: Carb Identification Help

Post by chrishea »

What matters are the jets and needles. Post 81, the carb physical configuration didn’t vary too much, except the slide and needle. The needles and slides changed from the “twist” style needle to a needle with a circlip. However, BMW also changed the needle taper, needle jet, enrichener jet in the float bowl, idle jet, and main jet to meet tighter emissions standards.
BMW also specified different jets for high altitudes (leaner).
The early 80s R80s came with two “large” snorkels on the air box. BMW issued a service bulletin that changed one of the snorkels to a smaller one and changed the jetting at the same time to improve mid-range performance.
If your bike has two large snorkels and you don’t notice a midrange flat spot, keep the stock 150 main jet. If you want to experiment, get the one smaller snorkel and try 135 mains. There’s room to experiment here.
Chris
Seattle

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