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Old 03-05-2013, 02:00 AM   #36
Rob Farmer
Beastly Adventurer
Rob Farmer's Avatar
Joined: Aug 2002
Location: Loughborough, Leicestershire. England
Oddometer: 5,821
Originally Posted by supershaft View Post
Which top did you have. It sounds like the one with both horns being the same size? My 8.5:1 Dell/sport cam setup had a big flat spot in the midrange with that top on the box. One large/one small horn fixed that perfectly with almost no penalty on top but the cap with two large horns killed midrange with absolutely stock setups as well. IMO, the GSPD types are too heavy but the G/S's are light. Tires and brakes issues are easily fixed. The single biggest thing I did to my bike which had the same engine as yours excepting lower 8.5:1 CR pistons (I think your came with 9.5:1 pistons?) and coming stock with 32mm Bings was putting a 336 cam in it. Huge step in the right direction! If I was going to go back to 32mm Bings I would rather instead go back to 36/38mm Dell's or Mikuni's. 32mm Bings are great at what they do. My only problem with that is that they don't do much at all to start with!

Bing makes mains for our CV's from 70' to 300's. I keep them at my shop from 120's to 170's. I keep needle jets from 260's to 274's. You can't get 260's and 262's through BMW.
I tried no horns, cut down horns and different sized ones but they all still had the vacuum depression mid range.

The standard pd engine has 8.5:1 pistons (mine are standard in the pd).

I have another gs running high comp, moorespeed oversized valves, guides etc but is running 81 heads, which richie isn't keen on due to the port size. It has a standard air box on at the minute and still has the stumble on the midrange where the mixture goes way too rich. You can barely feel it on the road but it shows in the dyno.
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