Triumphrat

BadMouth

Ok, I'm a cheap bastard, but I couldn't pass on the opportunity to get a dyno run at a local bike night for $20. (actually won $50 because there was nobody else in my "class", so I'm $30 up + plus some knowledge gained). Unfortunately they didn't run an O2 sensor, so I'm not sure what is going on. The guy running the machine said that I should raise the needles up a notch, but when I did, I barely made it back home on the test ride. Is there any obvious adjustment for the RPM range where I have the dip? The current setup is: K&N in factory airbox, adventurer ORs, 100 mains, factory pro needles on center notch, 40 pilots, AI screws 2.25 turns out. Any comments/suggestions would be appreciated.

tri-900

jim's 5 hole drill job on air cleaner, 142 mains, 42 pilots, with the rest the same will, shood give you 83 hp to rear wheel :-g

BadMouth

Any sacrifice in low end torque?

jimmyj900

There's something wrong with that dyno run. Torque and horsepower should be equal at 5252 rpm but the lines on your dyno run don't cross until about 6200 rpm.

The formula for horsepower is HP = (Torque x rpm)/ 5252, so when the rpm is 5252, the 5252 conversion factor in the divisor cancels out and HP = Torque.

The horizontal compression of the graph also makes it look worse than it really is. If it was full-page instead of half-page the curves would look a lot better.

Peak torque on these engines with the stock exhaust is around 4000 rpm with a dip at about 5000. The torque then rises slightly to around 6000 rpm and then rolls off continually as rpm increases. Since horsepower is a multiple of rpm and torque you'll see the peak horspower above 7500 rpm despite the decrease in torque.

The extent of the torque drop above 5000, the retention of the stock airbox and your observation that it ran poorly after raising the FP needles suggests to me that you're running too rich at higher rpms. The FP needles have a sharper taper than stock so I'd suggest you put the stock needles back in and see how it runs with the #100 mains. If it's better, either leave the stock needles and try them with a shim or try the FP needles with the stock #98 main jets. The FP needles were designed for the higher performance 885s with the bigger airbox so don't be surprised.

Did you use FP main jets? If so, they may be cut a bit differently than the Keihin jets and causing some additional richening.

Jim

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BadMouth

Thanks Jim.

I'll swap out the needles tomorrow and see if there is any seat of the pants improvement. I am using FP mains.

I've been torn for a while between going back to stock for economy/touring or opening up the airbox for power. I think I just need a scoot for each purpose.

[ This message was edited by: BadMouth on 2006-08-22 16:40 ]

tri-900

NO PROBLEM WITH LOW END TORQUE, pull smooothly from 2000 RPM in the big hole. It did cut my fuel mileage 10 mpg when you gouge on it.

[ This message was edited by: tri-900 on 2006-08-24 12:48 ]