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Discussion Starter #1
What’s everyone running for “all around” gearing?!

My Z is street legal, I use it for mini moto track/ race days, only street time it sees really is when I take it out to eat or run out quick when I’m racing big bikes so I don’t need to unhook my truck from the toyhauler. Majority of it’s life is spent towing a cart around the paddock for pit bike duties.

I’d like to get alittle more acceleration out of the bike at the kart track and no sacrifice to much top speed ( yes I know it’s to complete opposite things just want a nice middle ground if there is over stock).
Bike is stock motor wise other then a exhaust system and I don’t want to do any motor work.

Thanks
 

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A few guys at a local Kart track go -1 on the frontand +3 on the rear on their z125 track bikes, but our track is very slow/technical not much room for big mph.

I would start with -1 on the front and see how you like it.

the serious mini guys at the track also run ceramic low drag wheel bearings and “speed spacers” along with lightweight tires like the PMC’s- every little bit helps 8hp get down the track quicker
 

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This is my second post. This is what I have been looking for. So which is easier to swap out, the front or rear sprocket ?? I just want a few more rpm's in 4th gear. I'm getting about 8 thousand rpm's at full throttle. I think with the right sprockets I can get that up to 10,000 rpm's and a couple more mph's with a little quicker start from a dead stop. Mine is a dead stock bike with 650 miles on it. I don't plan on doing anything else at this time. Maybe a less restrictive muffler at some point. It's my putzing around town bike so I don't need much. I have a 650 Yamaha for the road and if anything get's traded it will be the Yamaha.
kwg
 

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Front sprocket cheaper and easier install, Use a 13T
It may allow to hit the rev-limit now, but the lower gearing will put your "actual GPS" top speed at 58mph .
The stock speedo reads 3mph faster than your really going

GEAR RATIO CHANGES.JPG 1 TOP SPEED OPTIONS.JPG
 

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If it comes other bikes they might have one in stock, Or they should be able to order it for you if that's where you prefer to get your parts

Or find one on this page...
 

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I do not know the results of testing this theory, but one caution: it may well be that the Z125 is reaching its maximum possible speed with the current gearing. Sometimes a taller gear will result in too much drop-off from peak power that the bike will actually be slower. I remember the days when 5-speed (4+overdrive) transmissions were new (OK, now you know how old I am) and I was surprised to see that many cars reached their maximum speed in 4th, not 5th.
 

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My Z seems to run out of torque around 53 or 54 mph and 8000 rpm. I'm thinking dropping 1 tooth off of the front sprocket will get me up to 10,000 rpm and 58 or 59 mph. Plus a little more pull at the bottom end.
 

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I ended up going with a Driven brand +2 sprocket in the rear and really like it. I have a 19 Z plus I'm a bigger guy (225lbs). With the stock tires and gearing on a loooong straight I could hit 67mph on the speedo which I know isnt accurate, they run a couple miles fast, but none the less. Shortly after I bought it this summer, at roughly 200 miles I put Kenda Big Blocks on it. Although I love the tires I lost quite a bit of top speed because it seemed like the bike just couldn't rev out with the tires and my fat *** on it. Now with the +2 rear sprocket it feels like stock again or maybe a touch quicker but also Rev's out much better. I have no problem cruising at 58-60mph via GPS.
 

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I have found a 13 tooth front sprocket from Drive Systems. Has anyone done business with Drive Systems and were you satisfied with the product ?
kwg
 
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