What sprocket size is best for top end speed

[MancoGX390]

I have a comet 40 series torque converter and I am wondering what sprocket size is best, my currant config is a 9 tooth jackshaft sprocket and a 54 tooth axle sprocket, now I've had a reply from another guy on my other thread saying that the more teeth you have on your jack sprocket the higher end speed you get and the more teeth you have on your axle sprocket the less top end speed you get but having more teeth on the jackshaft sprocket the low end acceleration will suffer. I have a Honda GX390 so no shortage of power. Now what would be the best config?

12 tooth jackshaft sprocket and 54 tooth axle sprocket

12 tooth jackshaft sprocket and 48 tooth axle sprocket

Same config: 9 tooth jackshaft sprocket and 54 tooth axle sprocket

14 tooth jackshaft sprocket and 48 tooth axle sprocket

14 tooth jackshaft sprocket and 54 tooth axle sprocket

Which is best? Help would be much appreciated!

 

[2SlickNick]

http://www.bmikarts.com/Gear-Ratio-Speed-Calculator-MPH_ep_84-1.html

 

[itsid]

those calculators are pure BS to find a good ratio!

Why?
because the calculate the wheelrpm based on ratios and that's all

with a calculator like that you can get a top speed of ~215mph by entering 1:1 ratio and 20" wheels.

And we all know that it wouldn't even move with a 1:1 ratio.

So for a good guess,
we need much more than just a ratio..
what series 40? (40 driver or 44?)
wheel diameter?
weight of that contraption with you in it?
frontal area and wind coefficient of your Dingo with you in it?
what wheels (knobby, street, slick?)
what terrain? road, offroad; hilly, flat?

shall I go on?

I think it's safe to get a ten tooth TC sprocket,
12 I wouldn't try (4.5:1 ratio)...
that might already ruin your belt on a very regular basis. (reads will be expensive)
14 is plain nuts.. might ruin the belt in an instant.
(depends a bit on how big your butt is )
So change your ratio carefully.. one tooth at a time;
a sprocket is cheaper than a belt

'sid

 

[Half-breeder]

... Which is best? Help would be much appreciated!

I'm NOT tryin to be an 'intelligent posterior'... but...

A. Like Sid... not quite enough info given to give 'others' personal preference in gearing.
B. This kinda question is best answered by you... it's like as if you were to ask us... "... Which girl is best?"... best for what?... and remember not everyone has the same tastes in 'best'... hence the phrase... 'One man's garbage, is another man's treasure'.

 

[MancoGX390]

Thanks Sid, great help! I will now consider a 10 tooth jack sprocket and a 48 tooth axle sprocket and it's a 40 series 5.5 inch clutch. I am going to be using this with 16 inch wheels and on flat grassy terrain (field) thanks for the help everyone!

 

[landuse]

I would stick to the 9T and 54T setup that you have. With your engine it will work nicely. Anything with a higher ratio you are going to suffer

 

[MancoGX390]

Yeah but surly going for a 10 tooth jackshaft sprocket with a 48 tooth axle sprocket at gear ratio of 4.800 would be ok? Plus more speed which i am wanting out of the kart?

 

[landuse]

Yeah but surly going for a 10 tooth jackshaft sprocket with a 48 tooth axle sprocket at gear ratio of 4.800 would be ok? Plus more speed which i am wanting out of the kart?

Like we said, 4.8:1 could more than likely be too high for you. You are looking at the theoretical speed you could reach, not what you would practically get.

Read all the posts from the members in both your threads

 

[MancoGX390]

I have then theres sid saying a 10 tooth jack with a 48 tooth axle would be ok then there you landuse saying i should stick with a 9 and 54, im really confused.

 

[MancoGX390]

I think ill just stick with the setup i got now and just tweek the engine then maybe upgrade to a comet 780 series TC. Thanks everyone!

 

[Hambone]

I run a 12 tooth jackshaft sprocket to a 60 tooth axle sprocket with 18 inch tires, a 30 series torque converter, and a 6.5hp predator (212cc).

Take off is okay, but it does take a while to get top speed.

I'd say you could get away with the 10:48 sprockets.

 

[MancoGX390]

How quickly does it go when it reaches top speed Hambone?

 

[Hambone]

It goes about 40mph, according to the speed calculator on this site.

With rhe extra power from your bigger motor, you "could" get away with 4:1 gearing.

It depends on personal preference really. Try one, and if you aren't satisfied, new sprockets aren't that expensive

 

[MancoGX390]

I think ill just go for a new 9 tooth jackshaft sprocket and a new 54 tooth axle sprocket same as I got now because it's been running fine now and has not shredded a belt infact it's still running on the belt it came with when I had the old briggs 8hp on it. I think I will upgrade my torque converter to the 780 series with the bigger clutch and pulley and get a new belt to suit it then I will tweak the engine and add new part and take the governor off and so on, anyway thank you guys so much for the help!

 

[landuse]

I think ill just go for a new 9 tooth jackshaft sprocket and a new 54 tooth axle sprocket same as I got now because it's been running fine now and has not shredded a belt infact it's still running on the belt it came with when I had the old briggs 8hp on it. I think I will upgrade my torque converter to the 780 series with the bigger clutch and pulley and get a new belt to suit it then I will tweak the engine and add new part and take the governor off and so on, anyway thank you guys so much for the help!

That sounds good

 

[MancoGX390]

Would a 10 to 54 be ok or is that asking too much? At gear ratio 5.400???

 

[Hambone]

I just changed my jackshaft sprocket to a 14 tooth and my axle sprocket is a 60 tooth.

That's a 4.2:1 ratio it has plenty of low end still, and when you get to top end it really flies (~42 mph)

I'm sure you'll be happy with anything above a 5:1 (buy good quality belts or they'll wear out quick)

 

[landuse]

Would a 10 to 54 be ok or is that asking too much? At gear ratio 5.400???

Go for it and see what happens

 

[MancoGX390]

I've ordered a new 10 tooth jackshaft with a 54 tooth axle sprocket and a new manco 2344 belt so I'm gunna see how it works and if it doesn't ill swap back over to the 9 tooth I have now! I also ordered the bolt on kit one from Affordable Go Karts with the new straight through exhaust and bigger more direct air filter, then I will remove the governor so should be really great!