sprocket ratio asssistance

Doing some searching on here and I come across this post ! Just wondering if you got the bike ready for this season ? I looked at my sprocket and I'm running a 42 tooth but I do mostly 1/8th mile tracks and I'm at about 100mph crossing the line on top end of 4th gear 
.  What part of the country are you in and post a few pics of your bike if you get time I'm just curious..kinda new to racing myself I raced last half of season b4 last and some broke parts kept me out last season but we are about 2 weeks away and I think I'll be ready this year !!! 

Almost have the bike ready. I did change the final drive ratio from 15/40 (2.66:1) to 14/42 (3.0:1) see what that does. Added a dynatek two step launch controller, upgraded the rear brakes to Performance Machine rotor and caliper which saved me nearly 6lbs of weigh. Built and aluminum battery box. Built a fiberglass seat and currently getting her painted will post a few pics when its done. I race at Lebanon Valley Dragway in upstate NY

wrote:

Almost have the bike ready. I did change the final drive ratio from 15/40 (2.66:1) to 14/42 (3.0:1) see what that does. Added a dynatek two step launch controller, upgraded the rear brakes to Performance Machine rotor and caliper which saved me nearly 6lbs of weigh. Built and aluminum battery box. Built a fiberglass seat and currently getting her painted will post a few pics when its done. I race at Lebanon Valley Dragway in upstate NY.       15/40 sounds like a good combo., bottom and top.  Keep the rpms up and the rubber down. Let the good times roll.
 

Dr. Gamma wrote:

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First off, I have no experience racing motorcycles.   

For reference, I think all 73-80 big-fours use the same gear ratios.  There was a factory close-ratio transmission available, but they are hard to find and expensive now.  Here are the ratios (I'm pretty sure the close-ratio numbers are right, but not positive).  As you can see, 1st and 4th are the same, but 2,3,5 are spaced closer to 4th.

Stock             Close-ratio
1: (12/38)       1: (12/38)
2: (16/35)       2: (19/37)
3: (21/35)       3: (22/35)
4: (21/29)       4: (21/29)
5: (23/28)       5: (23/29)

Are you still running the stock cams?  It seems like with the stock cam you don't want to go too short, as most of the power would be closer to the mid range.

One other thought is that is seems like the ideal setup would be very dependent on the track.  A setup using 15/45 puts you at about 104mph at 8500 RPM in 5th gear (depending on your tire OD).  That seems like a good setup for a tight track without a long straight, but not a track that's more open.

""I have run that close ratio gear set in my Superbike motors since back in the late '70's. The part number for the "mission assey" was 13254-001.

First gear is way taller than the stock Kz trans. I have the correct ratios listed somewhere, but I ain't going to go dig for it.

First gear in the close ratio box is closer to a stock gearbox second gear!!!! My first gear is good for almost 60MPH in my Superbike. I ran like 15/34 gearing most of the time. When I took it to the drag strip I ran a few more teeth on the rear. With a 1015cc motor it would run anywhere from 11.20 to 10.80 at like 128 to 131MPH.  That was doing a road race start and no powershifting!!!

If the bike has a close ration trans, you can't run the stock kickstart gear. Unless your motor has one of the rare Andrews Products kickstarter gears they made for the close ratio trans. Most folks just left out the whole kickstart shaft and gear when running the Close ratio trans. ""



Question for all from Australia.
getting enthused to start  over on my Z1R.
i have the aforementioned CR box in my motor, no kickstarter shaft because i remember it wouldn't work (remember i built the motor 30 years ago and it's all a bit hazy).
Anyone got more info on this fabled Andrews products starter gear/ one to sell/ even one to measure up ? I certainly never heard about it BITD so curious is all.
I have a good machine shop now and might be interested in making one/some.