No leaks from the carb, float needle in position 2, air mixture screw at about 1 1/2 turns.
This bike is new to me. I owned a 1954 R25/3 25+ yrs ago and had to sell; replaced with the '55 just this past spring. Any thoughts? Appreciate any and all....
I'm having some issues with my R25/2 not nearly as persistent as you. I do get some surging after I've ridden the bike for a while. At one point, I thought my air mixture screw was the wrong kind...there's a short on and a long one...the long one has a hole drilled in the side to allow air to get in. But that didn't help. Plus, whenever I screw the mixture screw in or out, it makes no difference on the way the bike runs. The latest suggestion for me is to get the bike warmed up again and spray something like carb cleaner around the carb and its connections. Somehow air is getting into the carb at low throttle settings but not through the air mixture screw. You say there are no leaks, but I'd do something like that just to be sure.
'78 R100/7 '69 R69S '52 R25/2
Coil failing after warming up?
Have you check the obvious, fuel lines, spark plug and sp cable, jets, key vibrating out of contact...
'58 R26 '76 R90S '94 R100GS/PD
Thank you for the welcome! When I got the bike, it had a Mikuni carb... The reproduction Bing carb is made in Germany and it claims to be to exact specs as the Bing 124/41. I haven't check the jets themselves. Thanks for the suggestion re the air getting into the system; I'll try that next - makes sense.schrader7032 wrote: ↑Thu Sep 03, 2020 7:11 pmWelcome to the forum! What was wrong with the original carb, do you know? I wonder about the reproduction carb. Is there a carb number that is similar to Bing? What about the other parts of the carb...the idle jet, the main jet, etc.
[...] The latest suggestion for me is to get the bike warmed up again and spray something like carb cleaner around the carb and its connections. Somehow air is getting into the carb at low throttle settings but not through the air mixture screw. You say there are no leaks, but I'd do something like that just to be sure.
It doesn't seem to die when riding - higher rpms keep it going. Within 1 minute or so of stopping, same surging pattern then dies. I have checked fuel lines, flow from petcock, have not checked jets since carb was a repro with no time on it but didn't look to see what was in there.
I would look at the petcock flow and the screen in there. Take the fuel line off the carb and put the end in a clear glass jar. Turn the petcock on and make sure the flow is consistent and fast.
I have seen the following items do this:
- Gas cap not venting properly.
- Dirty fuel filter
- Someone put an EXTRA filter in the fuel line. Don't do it!
- Rubber in the petcock has swelled. It happens.
1967 R69S, 1966 R50/2, 1965 R27, 1963 R27, 1952 R51/3 and 2018 R1200GS