Tire size vs. gear ratio + TAV

[nerfo]

Ok, I'm brand new to this forum, but I've been using it as a resource for MONTHS... so, take it easy on me. I'm new.

I've wanted to build a go kart for years... now I have the time, a few extra bucks and Comet closed their doors, so I hopped on ebay and bought a brand spankin' new TAV before the prices went completely through the roof. Besides, I always wanted to use one! Also took advantage of the 99 dollar HF 6.5 clone coupon and picked myself up a shiny new turd I MEAN clone motor! I'm still in the planning stage and getting ahold of parts and the like... but theres one area I've been struggling with...

Gear ratio.

In my head and using go kart speed calculators I've found on the internet, I've come up with using the TAV with a 12 tooth #35 sprocket (wanted 10 tooth for a 40 or 41 chain, but, hey... beggars can't be choosers) and a 72 tooth axle sprocket. And I want to put an 18" tire on it. Am I nuts? Will I just completely toast the belt on this poor little converter?

The kart will primarily see "yard" type use. Grass, some tame ATV trails behind the house with a few rolling hills. It'll also hit the street (dead end country road with ZERO traffic) from time to time. Will what I plan on doing work with a converter and 6:1 ratio, or am I going to be way, WAY better off going with like... a 96 tooth sprocket for an 8:1 ratio?

Any personal experiences would be awesome. What's worked for you guys? What hasn't? Between my fat A$$ and the weight of the frame, I'm probably looking at about 350 TOTAL lbs.

Side note... not looking for max performance from this engine, but with the stock carb, air cleaner, and muffler in place and the governor guts yanked... what kind of risk am I running for blowing up this 99 dollar gem?

 

[nerfo]

Any ideas? I know Asuza makes sprockets up into the 100+ tooth count. Leaning toward the higher tooth count... seriously, this thing is going to be zipping around some small trails. I doesn't NEED to go 50 some odd miles per hour... but man, wouldn't it be cool?

 

[newrider3]

You really don't need some gigantic sprocket; plenty of people run 18" tires with a 60-72t final sprocket with no problems.

 

[Jdominique]

I'm a 210 lb dude and 6:1 works great for me.

 

[NJOHC]

The best gearing I've found is 6:6. But that is with my engine revving to 4500RPM. You can safely let yours rev that high and you will get the top speed of a 6:1 ratio with worlds better take of speed. If you dont trust yourself with completely taking of the governor then just add another spring to the existing governor spring. Stiffer springs make the governor kick in at a higher rpm. You can find a pack of those springs at autozone or some place like that. It'll take some testing to see which one is right but it is a very cheap and useful mod. It saves you the worry of over revving it. And the valves usually float at like mid-high 5k range so with stock valve springs blowing it up is usually not a problem.

 

[Kenny_McCormic]

I had an older wimpier TAV on a manco dingo with 21 inch tires and I believe a 12:54 final drive, not sure on the driver. It was underpowered and it wouldn't climb a hill without a rolling start, but it was alright otherwise.

 

[nerfo]

Thanks for the input guys! I've actually decided to go with sprocket somewhere around 84 tooth. That'll give me a 7:1 ratio between the driving and driven sprocket. With 18 inch tall tires, it outta be a good compromise between decent acceleration and top speed. It definately will be a larger than ordinary sprocket, but I'm ok with that. Oh, and about the governor... it's long gone. I ripped it out about two hours ago! I'll probably toss some 18lb springs in the motor to keep the valves from floating. I'm going to start a new thread in the projects section as I've taken some pictures marking the begining of my little project.