Roketa 200cc engine.. any input

[1992suburban]

•Gear Ratio: ◦1st Gear: 2.769 ◦2nd Gear: 1.882 ◦3rd Gear: 1.400 ◦4th Gear: 1.130 ◦5th Gear: 0.960 ◦Primary Reduction Ratio (IP): 3.333 ◦Final Reduction Ration (IF): 2.706

 

[1992suburban]

makes me wonder what sprockets to run...

if I can gear it for 60mph in 4th

 

[oscaryu1]

Imagine a wheel falling off at those speeds

 

[1992suburban]

they are held on with NUTTTZZZZ

 

[Rickracer]

Sounds like it might be worth the risk. With a 12 tooth front sprocket, I think I'd be looking for a 25 to 28 tooth rear sprocket. QRC has em, on up to about 33 or down to 23, got their 23 on my kart now. I'd also find out what range of sprockets are available for the front, one tooth up front is about the same as 2 or 3 teeth on the rear. Might wanna go up on the front.

 

[1992suburban]

what kinda speeds can I expect rick??

 

[Rickracer]

Did you say it will turn 8000? And what size tires? Rollout that is...

 

[1992suburban]

rated peak HP @ 8500

 

[Rickracer]

12 and 28 will give you 123 mph with a 38" circumference tire (same as a 12 x 8 x 6 Maxxix HT3), IF you can pull 8000 in high gear. Sounds like a lot, but if you go much lower, you'll be shifting constantly. Here's a little something to play with: http://www.gokartracing.org/Calculate.htm ,

 

[1992suburban]

rick.. its got a 3.33:1 gear reduction

 

[Rickracer]

That counts the bike rear sprocket, which was probably 39 to 45 teeth, and it had a much taller tire.
I'm at 13 and 23 and I'm thinking I may need to go higher, like up to a 13 or 14 tooth front sprocket, 23 is as low as I can go in the rear unless I make something, but I can buy up to a 15 tooth front for like $10. I don't think the chain would clear my shift shaft with a 15 tooth front on it unless I redo my tensioner (maybe make it adjustable?), or redo my motor mount to change the angle. My kart seems to launch way better in 2nd gear than it does in 1st.

 

[1992suburban]

no thats the primary... not the final

I dont know.. either way

I am cornfused

 

[Rickracer]

Primary is in the trans, final is sprockets,

 

[1992suburban]

OK rick so in 4th gear your tellin me that your motor on your cart turning 8000 rpms the sprocket is turning 8000 rpms ???

NO SIR I disagree

 

[1992suburban]

My math tells me I will need a 20 front and 23 rear in 4th gear to go 64mph @ 8500 rpm since it prolly wont pull that much in 5th

 

[1992suburban]

http://home.earthlink.net/~gellett/mph.htm

USE this formula

 

[Rickracer]

That one puts my top speed about 70, no way that's correct. Try this one: http://www.gearingcommander.com/ , you'll have to put in your ratios and tire sizes, (unless they have that Roketa in the database already), but it should be VERY accurate that way.

 

[1992suburban]

i found an 18tooth. 520 chain with hub!!

with a 15tooth drive sprocket

thats 58mph in 4th gear with 11 inch tire PLENTY FAST

 

[1992suburban]

looks the same to me rick


3.33 Primary 1.13 4th gear 15/18 sprockets.. 8000rpm what you get

 

[Rickracer]

Doing some more reading on Gear Commander, it seems that primary is actually the difference in crankshaft and clutch shaft ratios, which I assumed would be 1:1. Looks like I gotta do some more investigating even for my own kart, No way I'm only doing 70 in fourth though, I was doing 55-60 on the race course with the old Honda motor, and I'm way above that now.
My primary must be different....... :rolleyes3:
Where did you find an 18 tooth rear sprocket and hub? And what's the bolt pattern? I wonder if it would fit my current hub?