Boxerworks.com

So the carbs on my 71 /5 have a serial number 64/32/328. Now are these carbs post /5 carbs? Also i noticed that these carbs have no spring but many of the diagrams indicate a spring. I called bing and they told me carbs with the serial number ending 1-20 did not have springs but my carbs end in three digits. The bike runs good but i just need to know what model and year did my carbs come off of and should i install a spring?

also i just took a lok at my main jets which are 145 and my slow jets are 45. that seems to large, so what are the correct jet sizes for a 1971 r75

Hawksley says that the only R75/5 carbs were 64/32/4-3 or 64/32/9-10, that /6's used 64/32/9-10 or 64/32/13-14, and /7's used Bing 64/32/13 - 64/32/14. BUT, he doesn't always have all the alternatives that were used during a run. Regardless, yes that is the correct size (32mm), but correct carb? Maybe not.

The carb you have (64/32/328)is listed in a couple places as being for a 82 - 83 U.S. Triumph (a "Bing Amal" carb built by Amal in Spain under license from Bing). I don't know if that's 100% correct, or if it means it does or doesn't belong on your bike. I also don't know if there's pure Bing 64/32/328's, and Bing Amal 64/32/328's. There is some ebay ad that says they also work on BMW's. No one seems to have ever mentioned them before on Boxerworks except you in another string.

Hucky's shows 45 idle jets for the R75/5, and different years had 135, 145, and perhaps 140 mains.


Here's correct carbs:




Here's the only pic I find of yours:

well the bike runs well and the spark plugs are brown so in theory i can run these carbs on my bike but do you think there is anything that i should change or just leave as is

If it ain't broke....


It's quite possible they have a different slide cutaway than the stock carbs, but, if the linkage is the same as stock, and they're working, I'd leave well enough alone.

The 328 carb (and whatever it's mate is) has to be from a 1980s or later bike...I don't have my Bing book around right now. Probably an R65 or maybe an R80 or something. My /7 has 19/20 carbs on them.

Kurt in S.A.

lelocp wrote:So the carbs on my 71 /5 have a serial number 64/32/328. Now are these carbs post /5 carbs?

Yes, I'd say they're post /5 carbs, but the BING book doesn't list the 328.
325-326 is the closest in the BING book...for the R65.

1 and 2 were very early and did poorly. next were the 3 & 4, they were better. The 9 & 10 came out for 72 and finally we had carbs that worked well, were stable and idled nicely.

The early ones can be modified to perform better at low rpm, but they still weren't as good as the 9 & 10.

I have never heard of those numbers.

Steve's right. I also have "The BING Book" and there's no 328's listed for any BMW.
I also have an R75/5 and put /9 and /10 carbs on it. They are just fine.
The jets listed (BING Book) for R75/5 are 135 (for 9&10s) or 140 for the earlier models. Idle jets are 45 for all.
The carb design - cutaway - might be the factor in deciding to use the 145, OR it might have been changed by someone, OR they used those as that is the size listed for an R75/6.
IF you are satisfied with the mpg and have got the idle adjusted, and it runs good, DON'T mess with it.

what would be a symptoms of the main jets if they were to large?