Forum bmwbike.com

I have a 68 r50 /2 with carbs 124 131 and 124132 my problem is the bike starts fine but will back fire out the left side exhaust . the plug wires are new non resistor type and so are the caps the right side plug is chocolate brown the left is wet black . I have taken the carbs apart and cleaned them and put new gaskets in ??? the floats are new the air filter is the choke type any adjusting tips ?? what is the tiny screw in the end of the mixture screw ??,needle settings ?? thanks for any help Frank

Frank,

Backfiring in the exhaust is caused by a rich mixture--your plug indicates that too. Does
the float in the left carb have a leak? If so, replace them both. I also suggest replacing
the main jets, needle jets, jet needles and idle jets. Mark has all these parts.
Buying the tuning manual from Bing in Kansas is also a good idea. Email me if you want
their address. It contains a good tuning guide, all jet sizes and needle positions for all
models.

Tom