Gearing question

[wildbob]

So, if you change your final drive gear, do you have to change all the gearbox gearing? This may be a stupid question, but wouldn't changing it require all the gears that mate with it to change size as well?

[2SlickNick]

I don't think so. I thought when people talked of changing the final gear - they were referring to the sprocket at the gearbox.

[x-bird]

He may be referring to swapping to the pair of gears in the trans. IIRC the 13/41?? set is the one that was in Carters and some others at some point that provided excellent bottom end and gave you an overall ratio that didn't need the 39 T on the axle for climbing. To make the change would require two gears.

(Tom/SYC and CKAU probably know the numbers better than I off the top of their heads even though it was in the engine i had on the Rockhound.)

[wildbob]

Yeah, with my new motor build, It'll have a lot more torque, but I understand strokers don't like the high rpm's, so I was thinking maybe I should make the gearing a little taller in the gearbox. Of course then there's the question over finding compatible gears for the trailmaster tranny. I see all sorts of racing gears cut for different ratios, but I'm unsure whether they'll work in the trailmaster gearbox. I ride mostly on trails with gentle inclines, but I don't want to completely sacrifice low end. I could always try to not get too mental on the straightaways, but that darned lead foot of mine always get's the better of me.

[jmansracerocket]

wildbob with the setup ur going with the 31 tooth sprocket gearing should work well. Also go with a heavier roller/slider around 16 gram roller or which ever u prefer.

[SYCARMS]

You need to determine the gearing after the build. I have the long rod stroke in my 150 but I recently went with a 9000rpm CDI. My and your buggy differ however where as I can change out my gears since I have the basic scooter GY6 with the final drive gears. The trailmaster uses the internal reverse transmission and no gears are available to change the ratio.

[wildbob]

Ok, well that makes things easier. So basically that leaves the sprocket on the motor and the sprocket on the axle. I might just leave the gearing alone then. Things get scary as it is. There are very few open straightaways where I ride (mostly curving trails or dirt roads)No sense over complicating things. Might look for different sprocket sizes for the motor if it looks like it's getting wound out too much. Although, there is an air strip that would be nice to test top speed once it's broken in..

[SYCARMS]

You really need to check the sprockets after the build in other words don't get ahead of things. My RPM's are so high after I installed my custom camshaft in the buggy along with a 34mm Mikuni slide carb. Prior to the carb and cam I was at about 8200 RPM at top speed so I doubt you will have issues with to high RPM. With the long rod stroke you will have much more torque at the wheels so with the winding curves or climbing I think you will be happy with the results as compared to if the short rod was used rpm's would be much higher. You could compare the difference between a long and short rod to a big block and small block engine. The small block spools up much higher whereas the big block will give you the torque. After the build drive it than upgrade to a 26mm Mikuni VM series round slide carb and you won't believe the difference in performance over the cv carb but you will either have to make a spacer or new intake for the slide carb to work but well worth the effort in performance gains. If you do go that rout spend the extra money and purchase from carbs unlimited for they are the US distributor for Mikuni and he will help you dial the carb in to that motor since a slide tunes much different than a cv carb and if you have never done one from scratch he will be a great source of help when you purchase from him.

[wildbob]

Yeah, I've got a VM26-606 on it now. I love that carb. I had such issues with jetting until I realized my needle was bent and my gas cap wasn't venting. I had bought two by accident so I threw the spare on and got it jetted, swap the gas cap and couldn't believe the difference. It should go with this motor better than the last, of course I'll be re-jetting again...