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Mikuni HSR42 vs HSR45
  #1  
Old 03-13-2006, 09:00 PM
deejay-2k
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Default Mikuni HSR42 vs HSR45

Recently I had my 80" Evo motor rebuilt by Jerry at your shop. With 10.5:1 compression from forged SE pistons, a Woods W6H cam, Baisley modified SE heads, and Baisley roller rockers the end result was 87HP and 87TQ. The TQ peaked at 2700 rpm then dropped to a gently increasing 80-84 from 3300-5500 rpm. Is my Mik 42 (160MJ) the cause of the dip? Would a swap to a Mik 45 prevent the dip?

If the Mik 42 is the right carb for maximum torque, would adding a Forcewinder or Hypercharger help?

Other info:
1993 FLHS Electra Glide Sport
SE ignition
Barnett Extra Plate Clutch Kit
SuperTrapp True Dual Slip-ons
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RE: Mikuni HSR42 vs HSR45
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Old 03-13-2006, 09:00 PM
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Mike Mike is offline
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Default RE: Mikuni HSR42 vs HSR45

I reviewed your dyno chart and believe your torque curve is a function of the exhaust. Too few dics in the mufflers will produce this curve and adding more would be a way to test. As we add discs we may start do develope a dip around 2700 rpm, which is not always wanted on a touring bike. Also, some true dual head pipe systems can contribute to a drop off of hp above 4k rpm due to their lenght and lack of staging. We do not normally make exh changes as part of dyno tuning unless instructed to do so by the owners. This adds to dyno time and therefore cost to the customer and the setup on exhaust, as we recieve them, is often what the owner has established through their own riding impressions and does not want changed. Last, changing discs in an older high milage system can be problematic in that screws break off and threads in the baffle gaul or strip out.
As an exhaust issue, adding more carb will not help. The 42 should be ideal for your application and can support up to 100hp. Up to 90hp the Force or Hyper-Pro would be OK. The standard Hypercharger is too restrictive and both become restrictive above 100hp.
I would like to see your bike back on the dyno to investigate this issue. If you are up for it, we can work something out with our service manager to make sure your bike is as good as it can be for your riding style and the investment in perfomance upgrades.
Please let us know if you would like us to revisit the tuning or discuss options, we would be happy to do so!
Regards, Mike
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RE: Mikuni HSR42 vs HSR45
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Old 03-19-2006, 09:00 PM
deejay-2k
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Default RE: Mikuni HSR42 vs HSR45

Mike,

I got the Supertrapp slip-ons new about 8 months ago. Each muffler came with 12 discs. Looks like I need to put in an order for another 18 (9 more for each)? I think the screws can handle a max of 21 discs. Anyway.... thanks for the carb info. I think I will stick with the Mik 42. I will bring my bagger in soon for some exhaust work and more dyno time.
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RE: Mikuni HSR42 vs HSR45
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Old 03-20-2006, 09:00 PM
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Mike Mike is offline
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Default RE: Mikuni HSR42 vs HSR45

Thanks for using our forum! Mike
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