Setup Advice

4 Stroke Kart Engine Forum
21

This may be kinda obvious but ill ask anyways. How old are your tires and are you running the same compound?

22

The clock at the end of the straight doesn’t matter. If you’re losing on the straight, and keeping up IN the corners, you’re getting beat badly on exit.

There’s a fine line in 206 setup between loose, free, and tight. If you’re a hair tight, it’ll feel ok but you’ll drag the engine down so bad your lap times will be horrendous. If you’re too loose and sliding the rear, you’ll rev right but be slow.

Most fast 206 guys will roll the corner. You get off early to slow the kart a bit, get the rotation started, and get on the gas. I’m normally off the gas and back on by the time I’m turning the wheel. You look like you’re jamming it in and scrubbing all your speed. You dont have power to do that in a 206. Back your corners up.

On a twisty track like that, I eat the chip way early on the long straight. You gear high for the tight section to stay in the powerband and sacrifice the straight speed on the long stretch. There’s a layout at our local track where I chip the entire straight.

23

I finally got around to pulling off the sprocket to see what I have. Of course my chain breaker broke while I was removing the chain… Anyways, I have 21 in the front and 70 in the back. Sounds like a lot of people run a 3.5 ratio, but I think that is with the #35 chain. Anyone know how much RPM one tooth will add for 219?

24

Use the same ratio. Bump it up to a 73 or 74. I personally would go to the 74.

25

I’ll give it a try. Thanks!

26

21/70 = 3.33-1
Add/subtract one on the engine equals about an 300 RPM.
Add/subtract one on the axle equals about 75 RPM.
That’s assuming 6000 RPM at the end of the straight.

27

We race 4-strokes in SA and sounds like the gearing is pretty long but not sure what your specific series allows in gearing.
As an example we running Honda 390’s and changed tires and adjusted gearing for 2020. What we found is that we were always around 0.6 faster then our rival series who supposedly run a more standard engine spec compared to ours where we advance the timing and skim the head.
2020 we running the same tires and gearing they running 45/15 = 3 ratio versus us on 45/17 = 2.81. Our fastest qualifier on a relatively speed ordinated circuit was 53.8 versus their best qualifying of 55.8.
What is important is torque on the engine and the longer the gearing the more effect we find on performance. I.E. my engine was dyno tested and our spec is below 24hsp, my engine had to have an additional thin 0.2mm gasket fitted which over 5 runs dropped from 24.3hsp to a of 23.8hsp which you would say is pretty decent. Not the torque level is 3nm down which is worth around 0.5 tenth plus.