Track Gearing

[JFMNINJA400]

What gearing are you guys running on the track? I see that 14/45 is stock. That seems to work for the streets. Seems to give the bike good grunt to pass cars on the road. I see some like a 15 front sprocket for lower RPMS for more relaxed highway riding and better gas mileage. I have an aluminum 43 rear sprocket, I may try. Would like to get over 105mph without a problem. I do like the pull of the 14/45 gearing.

[DannoXYZ]

Going to taller gearing (43t), will actually slow you down at track. That’s because you’ll end up with lower torque at rear-wheel and less linear thrust at contact patch and slower acceleration. Unless you’re already redlining top-gear on fastest straight, you don’t want taller gearing. If anything, you’ll want to use lower-gearing (46t) to give quicker acceleration and faster lap-times.

I adjust gearing so that I just barely kiss redline in top-gear at end of fastest straight at each track. Here’s relevant mods on my ‘09 250 race bike and gearing for each track.

- 315-lbs with 1-gal petrol (-60 from stock)
- full Tyga exhaust
- dyno-tuned by Spears for +22% more power than stock (DynoJet stg2)
- 428 chain conversion with alloy rear sprockets

This is gearing I use at various tracks:

18x60t - tight tracks like Laguna Seca, Sears Point Sonoma, Streets of Willow Springs, Thunderhill West. Gearing lower than 520 14x46t for maximum acceleration. I might go to 18x61t next season at these tracks (other than Laguna) as I’m not redlining top-gear at any of them.

18x59t - same as 520 14x46t for longer tracks like Buttonwillow and Willow Springs

18x58t - still lower than factory 520 14x45t and just balances extra 22% power with top-speed @ redline at end of 10-sec straight at Thunderhill East. Hits actual 103mph on calibrated TrailTech Vapour digital dash (114mph on factory speedo).

This is also calculated extra top-speed over factory 96mph top-speed with 22% more hp. Also helps to put chin on tank, tuck in elbows and hands with only pinky-finger on throttle to keep it WOT.

[AwDang]

It should be noted 428 tooth counts are different from 520.

[JFMNINJA400]

Thanks Danno. Pretty much what I figured. I plan on using the 250 on the more technical tracks with shorter straights. I agree more grunt will help on the more technical tracks coming out the turns. I will probably get an aluminum rear sprocket in the stock size just to lighten things up a bit. If I find a good deal on a full exhaust I will pull the trigger. If not I will just go with the current slip on and a stage 2 jet kit.

What is a 428 chain? Stock is the 520, I knew there is a 415 size.

[DannoXYZ]

I tried 415 chain once in beginning. Without O-rings, it didn’t last more than single season. That’s with cleaning and oiling 2x per day at track. A 428 chain is same pitch as 415, but can be had with O or X-rings. Has wider rollers than stock 520 with less weight and more durability. I’ve gotten 3-seasons out of 428 chain set-up, and that’s with 45-48 days at track each year. It only saves 2.5-lbs over stock compared to 3.5-lbs for 415, but well worth it for more durability. Read all about 428 conversions on Cramer or Sprocket Specialties site.

http://web.archive.org/web/201704230...x250/428.shtml

Sticking with stock front sprocket & 520 chain, you may want to try 46t or even 47t rear sprocket on tighter tracks for faster acceleration. Watch out for wheelies!

[JFMNINJA400]

Originally Posted by DannoXYZ

I tried 415 chain once in beginning. Without O-rings, it didn’t last more than single season. That’s with cleaning and oiling 2x per day at track. A 428 chain is same pitch as 415, but can be had with O or X-rings. Has wider rollers than stock 520 with less weight and more durability. I’ve gotten 3-seasons out of 428 chain set-up, and that’s with 45-48 days at track each year. It only saves 2.5-lbs over stock compared to 3.5-lbs for 415, but well worth it for more durability. Read all about 428 conversions on Cramer or Sprocket Specialties site.

http://web.archive.org/web/201704230...x250/428.shtml

Sticking with stock front sprocket & 520 chain, you may want to try 46t or even 47t rear sprocket on tighter tracks faster acceleration. Watch out for wheelies!

Ok thanks for the info, I have been educated! I will try the 46t aluminum rear and see how I like it! I have a +1 rear aluminum sprocket, with a few other mods, and I can power wheelie my 400 in 1st! I am sure with the same mods on the 250 and a +2 rear, I should be able to power wheelie in 1st.