Forum bmwbike.com

My R50/2 has a large, non-choke air cleaner housing. The Bing manual say to use a
jet size of 120 with this type of filter and it works quite well. I want to add a repro Hoske sport muffler system. The Bing manual says that a lower back pressure exhaust like the Hoske would require a richer mix. So I've conducted a little test. I put the exhaust on and took the bike out for a short ride and it seemed to have more power, as expected, across a broad rev band, but at full throttle it LOSES power. This is also expected and is mentioned specifically in the Bing manual, so I'm assuming that it's running to rare at full throttle. Not a good thing!

My question is: 120 is the largest jet size in the Bing manual, so what jet size/needle combination should I be using to avoid running rare? How should I adjust the carbs? Help anyone!?

hallo,
are you sure that your Hoskes has a lower backpressure?
never the less, you have to adjust the carb by trial and error.
I do not know the biggest size of Bing mainjets, my biggest size (which I tried) was 155.
Buy a handful of mainjets(115,125,130,135) fit them,what highspeed?Higher?next bigger mainjet, " ? " ? "
and so on, until the speed did not raise(and also not lower) then "finetuning" by the jetneedle(the needle fills the gaps between the mainjetsizes)
Short: right mainjet:as rich as possible at best highspeed
If the highspeed did not raise by the 125, try to take the 115( see the first sentence) or only change the needleposition.
rolf

My Capital Cycle catalog lists jets up through #175, here are a few part numbers that may help.

13 11 0 039 147 #125
13 11 0 039 141 #130
13 11 1 256 612 #135
13 11 1 336 877 #140
13 11 1 337 889 #142
13 11 1 261 703 #145

Drew

Apparently the jets listed in the Bing manual are the ones provided as stock. A
little further investigation revealed that Bing produces sizes up to 280!

Anyway, thanks for your help!