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Registered
Join Date: Jun 2010
Location: Arizona
Posts: 2,117
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BMW Airheadz
I rebuilt my 75 R90S engine a year ago. I put in the 286 cam and had the flywheel lightened.
The results is an engine that has noticeably more power but has a stumble when cruising around 40 mph with the throttle barely cracked open. The stumble makes the bike annoying to ride so I want to fix it but I don't know if the real problem is the cam or the lightened flywheel. I suspect the cam but the flywheel is a lot easier to replace. Cost wise its probably about the same, unless I find a used flywheel somewhere. the jetting is slightly rich according to my KN air/fuel meter that I installed temporarily any opinions? |
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01-18-2013, 09:56 PM
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Registered ConfUser
Join Date: Aug 2006
Location: Waterlogged
Posts: 23,934
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Probably not the answer you're looking for, but why not go back to stock? It's not a lightening fast bike by any modern standards anyway and BMW engineers likely knew what they were doing when they designed it as they did.
I had an HD many years ago that was a slow pig. Spent a bunch of money on tuning/cam/exhaust, etc., to make it very slightly less of a slow pig. The result was a very choppy low rpm ride which was 90+% of my riding anyway. Lesson learned.
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Mike “I wouldn’t want to live under the conditions a person could get used to”. -My paternal grandmother having immigrated to America shortly before WWll. |
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01-19-2013, 05:02 AM
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Virginia Rocks!
Join Date: Oct 2003
Location: Just outside the beltway
Posts: 8,497
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Might the carbs be gummed up a bit? I found my R65 had a lot.of trouble at one specific rpm. It was the point when the jets switch over. I had to run some cleaner and just ride it a bit for it to go away. Comes back sometimes. Ah, carbs.
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01-19-2013, 06:10 AM
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Registered
Join Date: Dec 2001
Location: Ky, USA
Posts: 1,134
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If you changed the cams you will have to change the carb jets.
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01-19-2013, 01:11 PM
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