Shift light setting? GS1150 for drag racing

[CivilRock]

Before I go and sort this out by trial and error, where should I set the shift light?
My drag racing mentor told me to set it at 10500.
I don't have a stock tach, but I believe the stock one redlines at 9000.
I just saw a dyno chart for a bone stock 84 1150 and the peak power is at just below 7500.

When I shift at 10500, I honestly don't know how far the RPM drops for the next gear.
If it only drops to 8000, aren't I missing the peak power of the motor?

Should my shift strategy straddle the peak power? Or do you want to stay in a gear as long as possible (without blowing up the motor)?

There's a local Dyno Day coming up where I can get a baseline run for $50. Do I need this info to figure out my shift strategy?
Is there a formula? Should I rely on trial and error? (not opposed to that!)
My motor is stock, but I have carbs and a pipe. Does the configuration change the optimum shift point?

I know I spouted off 8 questions here, sorry about that, and Thank you for your thoughts in advance.

-Kevin

 

[posplayr]

trial and error? Ever heard of multivariate optimization (numerical search)?

 

[Guest]

In a perfect world you would set it at the RPM where your bike builds it's peak power but if you don't have the dyno info then I would start at 9,000 rpm. 10,500 rpm is to high for a stock motor.

 

[trippivot]

your cams / head flow / lobe center dictate where most effective shift point is. the final gear ratio also has a percentage effect too.

you are only doing a quarter - not half - not whole mile - so hitting your redline at the stripe in 3 or 4 or 5 gear is the goal, whichever it may be . nothing wasted. no wheelie no spin get it all done in 1320 feet. in a perfect run - like dragracers try to do starts with WOT at the hit and redline at the stripe.

- I know about my combinations and what stock will do and usually the acceleration is over by 8500 rpm - holding on to 10K is wasting time if you don't have your cams timed for it. so launch at 3000 or 3500 and shift at 8000 or 9000 as a starting point until you see where you need to adjust . shift point or gear ratio or both

don't concern yourself too much with rpm drop - unless you shift right into the torque dip. then you have to make a choice to short shift and hold your highest gear - or rev up higher and time hitting redline at the stripe in 4th or 5 . my stock runs with stock gearing have me finishing midway in 3rd gear and I shift at 9 - launching at 3000 slipping the clutch trying to get my foot ready for 2nd gear shift. I totally had to practice launching with my left foot on the peg - not easy to have both feet on ground and still try to foot shift.

 

[CivilRock]

This is great stuff. Thank you.

I need to change my gearing. Right now I'm either hitting the rev limiter 200 ft. before the stripe, or barely shifting into 5th. I think I'm going to raise the gearing so I'm still in 4th at the line.
I'm fighting a wheelie through all of 1st, and I think I was doing better with taller gearing off the line. My best runs were with the front about 1" off the ground from the start and into 2nd, and it would just touch the ground while I shifted into 2nd. Just enough time to correct my aim down the track.

I think another change I need to make is to put a hump or strap across my seat to keep my butt forward on the seat. Right when I launch my butt slides back on the seat 4-6 inches and I have to do a pullup/crunch to get my body over the tank, and get my feet back on the pegs to try and make the 2nd gear shift. It just adds to all the things I need to do in that short time that's so critical to getting a consistent start.

I'm going to set my shift light at 9k and bring a couple rear sprockets to the track with me so I can play around with gearing.

Thanks for all the advice.
-Kevin

 

[CivilRock]

I was digging into my bike and found the Rev limiter set at 9500 and my shift light set at 10500 . Not sure if I messed with it earlier, but that could have been why i was having so many problems.

Kevin.