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First start on '73 R75/5, Idles too high.

Posted: Sun Jan 03, 2016 10:30 pm
by drcollie
Rebuilt both of the Bing 32mm Carbs - they were a mess. Went slow and took my time, replaced the diaphragms, all o-rings and gaskets, cleaned out the sludge from the bike sitting for almost 10 years. Started up tonight for the first time and immediately went to 4,200 rpm and would not idle down. Quick video:

https://youtu.be/p0e6rTVDTyY

Cables are slack, slides run free, good butterfly action. No idea why its hung up so high on startup. Any quick ideas what to look for?

I'm thrilled that it started. The rest will come with time and more work, I'm sure.

TIA
Duane

Re: First start on '73 R75/5, Idles too high.

Posted: Mon Jan 04, 2016 12:08 am
by Bamboo812
Have you checked the timing with a strobe? Could be too far advanced or a sticking advance unit.

Re: First start on '73 R75/5, Idles too high.

Posted: Mon Jan 04, 2016 3:21 am
by Major Softie
For an idle that high, the first thing I'd do is pull off the intake tubes, look inside the carbs, and make sure the butterflies are actually closing all the way.

Re: First start on '73 R75/5, Idles too high.

Posted: Mon Jan 04, 2016 5:46 am
by SteveD
Have you backed off the throttle screws?

Re: First start on '73 R75/5, Idles too high.

Posted: Mon Jan 04, 2016 10:35 am
by Duane Ausherman
A simple quick test will show where the problem lies. A simple search with Google would have taken you to http://www.w6rec.com/duane/bmw/advance/index.htm where you would have a plan for diagnosing and fixing it.

Re: First start on '73 R75/5, Idles too high.

Posted: Mon Jan 04, 2016 2:54 pm
by Major Softie
Duane Ausherman wrote:A simple quick test will show where the problem lies. A simple search with Google would have taken you to http://www.w6rec.com/duane/bmw/advance/index.htm where you would have a plan for diagnosing and fixing it.
Hes BACK!

Re: First start on '73 R75/5, Idles too high.

Posted: Mon Jan 04, 2016 10:31 pm
by Duane Ausherman
While on the road, I often don't have the time, or Internet in order to post.

Re: First start on '73 R75/5, Idles too high.

Posted: Tue Jan 05, 2016 3:23 am
by Rob
Duane Ausherman wrote:While on the road, I often don't have the time, or Internet in order to post.
Coffee at McDonalds.