Boxerworks.com

Hi all,

I have newly rebuilt Bing carbs, pod filters, and low restricted mufflers with baffles. I am having a difficult time getting it tuned. (I know pod filters are hated on, but It's too late to go back). I'm also sure this has been discussed but I can't find an answer applicable to my situation.

I started off with the factory settings (150 main, 2.66 needle jet, needle clip in position 3). The bike idles fine and revs fine if you roll on the throttle slowly. When quickly revving, it cuts out until you let off. I tried a 155 main jet, needle clip in position 4, and no change. Should I try a 160 main jet and perhaps a 2.68 needle jet?

Any help is appreciated.

P.S. The bike is an R80/7.

Suggestion 1 -
Do a quick road test without the pods and see what happens. Be sure your pant legs are tucked in your boots not to get sucked in.

Suggestion 2 -
Have the diaphragms been inspected/replaced, and are they installed correctly?

I will try without the pods. I have just been testing in the driveway and have yet to ride it after the carb rebuild because I've been working on other issues as well. The diaphragms have even inspected and are perfect. They are installed correctly. I am very meticulous.

One thing comes to mind...

If you are testing on the drive, the bike is never becoming fully warmed up. With an airhead, the engine really does need to be fully warmed before the carbs can be properly tuned and that means riding the bike preferably for at least ten miles before even attempting to tune.

That being said, if the symptome persist, my advice would be to go back to stock... temporarily at least. The symptoms are complex and could be caused by a number of things. If possible, refit stock exhausts and air filter. If the symptoms are still there, then the problem probably isn't with the carbs (or the exhausts for that matter). If the symptoms go away, then swap back the non stock items to see which one(s) is causing the issue. You will need to bo some tuning between each test but that's the joy of messing with things that affect breathing on an old school engine.

On after market parts... be sure of what you are getting. There are (for example) pod filters that are suitable (for a given value of suitable, and you're right I do dislike them intensley for various reasons) an R60 that would upset a R100... and vice versa. There are exhausts that are suitable for - say - Triumphs, that won't work on an airhead. If you mix and match parts, you have to be willing to experiment again and again to get the engine running satisfactorily.

Rob