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Old 07-04-2013, 09:27 PM   #91
bmweuro OP
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Originally Posted by Beemerguru View Post
Chris,,never saw if this was a new build or if you had some miles on the engine?
Greg this was a motor that Bob G built many years ago and has not had the best life since he sold the sidecar it was in.
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Old 07-05-2013, 04:38 AM   #92
StephenB
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Originally Posted by bmweuro View Post
Problem solved. It seem to be a combination of things. Once I got a stethoscope I could here a noise in the carburetor like the slide was rattling. I replaced the carburetors with another set of 40mm Bings and the noise mostly went away. Secondly I rejetted the carbs to a European R100GS spec, retarded the timing and now I have no strange knocks at all.
So it was pinging after all? A rattling slide inside the carb could not produce a mechanical sound like the knocking under load you describe. Since you changed 3 parameter (different carbs, rejet, retard) at the same time, you still don't know what your root cause was exactly. That wouldn't satisfy my curiousity. How do you know it's not coming back?
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Old 07-05-2013, 06:28 AM   #93
villageidiot
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Originally Posted by StephenB View Post
So it was pinging after all? A rattling slide inside the carb could not produce a mechanical sound like the knocking under load you describe. Since you changed 3 parameter (different carbs, rejet, retard) at the same time, you still don't know what your root cause was exactly. That wouldn't satisfy my curiousity. How do you know it's not coming back?
A rattling slide can make noise under load. I got a buddy with a BSA chopper that never had a filter on the carb since it was built in 71. That slide is so loose you can push it from side to side and front and back, and it makes hella noise throughout the range.
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Old 07-05-2013, 11:30 AM   #94
StephenB
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I woudn't have thought that, given the size of the "resonating" body (aka carb body). I assumed a knock being lower frequency emitting from a larger body (e.g. engine block). Glad you got it finally sorted.
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Old 07-05-2013, 12:35 PM   #95
Plaka
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Originally Posted by StephenB View Post
I woudn't have thought that, given the size of the "resonating" body (aka carb body). I assumed a knock being lower frequency emitting from a larger body (e.g. engine block). Glad you got it finally sorted.
That part of the problem; the word "knock".

One mans knock is another mans rattle is another man buzz is another mans ping, etc.
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