Yamaha Junior Sportsman

[David Young]

Putting together a Yamaha Jr Sportsman for my daughter (8 yrs) to run. Any thoughts on where I should be starting on rear spocket size before I go out and purchase a selection of gears in the wrong range? 219 chain and 10-tooth clutch drive.
Thanks.
David

[ajhaun]

the best time to decide taht will probably be on sunday. this is a brand new track so no one really knows what to expect. and more than likely you will need atleast 2 diffrent sizes one for counter clockwise and one for clockwise. and if she is just starting i migt suggest investing in a kevlar sprocket. they flex and wont bend if or when you go off the track. but for the size. it will be close to what they run in oklahoma, i dont race yamaha so i cant give you numbers. just wait till sunday. i will promise you 3g will have the size you need.

[Gary Percival]

I had the same problem when I was trying to get my sons Yamaha going. I was at the Austin Iron Rock track website and there was a page in there listing the gearing on karts for Typical Kart Classes.

http://www.ironrockraceway.com/kartages.php

It said Yamaha Jr and Yamaha Sr gearing was 10/80. Figured that would be a good place to start. I imagine now with the new long straight we will have to go up or down a tooth or two. Just have to play with it.

When I bought my sons Birel/KT100 kart from a guy in Fort Worth it was a Junior with the small 55 carb and can and single disc 11T Tomar clutch and 89 gear. I got the bigger 3A carb and several pipes and a Horstman Steel Nytro 10T clutch off ebay and will expeiment. Just bought another Emmick/KT100 kart for my younger son. It has a can, Tomar 2 disc dry clutch and 91 gear. Will keep that for now but will change to an 82 gear or so and experiment.