Changing Gear Ratio

[Eric1204]

So, now that we got the Manco 606 to go, we want it to go faster... This is the current set-up:

Robin-Subaru EX17 6.5hp
Comet 30 Series TC
60T axle sprocket
9T jack shaft sprocket
420 Chain
18" Rear Tires

Based on what I've been reading, my understanding is that if I change to an 11T sprocket I will reduce my gear ratio from 6.67 to 5.45 which should result in better top speed, but slower out of the gate.

Is that theoretically correct and any thoughts on how much of a practical difference it would make?

Thanks!



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[landuse]

With 18" tyres, you will probably eat through belts at a rapid rate. Your ratio now is at the borderline of what the clutch can handle

 

[itsid]

I agree...

my calculator says that even on the lowest end of possible weights (175kg // 385 lbs)*
11T JS sprocket will not work (5.45:1)
5.75:1 is the absolute minimum it'd accept as "could work" (11 js and 63-64 axle)
(100 lbs more and it requires 6.45:1 to not throw an error message)*

* 606's curb weight 301 lbs... gross vehicle weight 551lbs; just to add some perspective

still, you'll eat through belts much faster than today, since that's always the weak spot, and it will see more abuse...

if you insist... maybe a 10T JS sprocket (6:1) will do already;
personally I wouldn't even try that.

To me it seems like you have to tweak the engine (or cheaper, buy a predator 212 to tweak and keep the expensive-replacementparts-robin-subaru untouched and as an emergency backup )

'sid

 

[Eric1204]

Thanks for the feedback guys!

I like the way you think 'sid, maybe I'll pick up a predator when there is some extra cash laying around. Then we'd have an extra engine for when we find the next great deal on a second kart.


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