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Post by jeepster1 on Feb 24, 2008 21:02:32 GMT
Has anyone tried it or have any advice for suitable carbs for the job?
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Post by amorti on Feb 24, 2008 21:21:10 GMT
Whatever for? You want to reduce your power and fuel ceonomy in on fell swoop? Apart from which, car carbs are quite big.
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Post by jeepster1 on Feb 24, 2008 23:08:08 GMT
I'm just gonna play around but the point is to improve economy as one carb per cylinder is awful for economy and smooth running, on the flip side their perfect for high perfomance at the expence of low end tractability.
If done right not only would I expect to get 70+ mpg on a run but improved torque and low to midrange performance.
I've worked out that the 900 motor should flow around 150 cfm at full throttle at 90% volumetric effciency, so 34mm carb should be perfect for the job, say an SU carb from a mini.
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Post by Reaper on Feb 27, 2008 7:53:06 GMT
Whatever for? You want to reduce your power and fuel ceonomy in on fell swoop? Apart from which, car carbs are quite big. Ive seen this done on a GL1100 Gold wing and the performance acceleration wise wasn`t drastically affected, however the torque and fuel consumption were greatly improved. He used an SU carb as it was an easy carb to match to his newly made 1 into 4 manifold. Yes car carbs look big but compared to a bank of 4 motorcycle carbs a single SU is small and would take up less spae than the entre 2 of a bank. Lets face how often in real life do we need the full power a bike offers and to loose the edge but gain in the pocket would be more sensible. |
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Post by CD on Mar 5, 2008 20:31:08 GMT
It would have to be an older type SU carb. The ones used on BL Metros were huge great things and not easy to tune. Back in the 1970's a bloke called Dave Vizard (I once had his book long gone now  ) wrote about tuning the BL A series. He was getting 130bhp from a 1275 with a single 1-1/2" SU. The carb and head were gas flowed and it had all the top exhaust and fancy cams etc. It shows what can be done and that was 30 or more years ago. At 90bhp, the Divvie 900 is probably at about the same state of tune as that souped up mini engine. BTW Car engine type fuel injection would be fun to try. |
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Post by CD on Mar 5, 2008 20:44:38 GMT
BL Metro SU carb with MZ 250 for comparison.  |
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) wrote about tuning the BL A series. He was getting 130bhp from a 1275 with a single 1-1/2" SU. The carb and head were gas flowed and it had all the top exhaust and fancy cams etc. It shows what can be done and that was 30 or more years ago.