First go kart build, questions

[Toobam757]

So first go kart I’ve ever had, found this thing on the side of the road with a “free” sign on it. See before pictures, had no engine, no brake, no cables. Did have a rear 54 tooth sprocket, tires, steering, manco hex axle. Painted it, put a predator 212 on it, wired a kill switch to the front, put a clutch with 40 chain, mechanical brake, replaced a tube in one of the tires, new pedal springs and throttle cable and new brake disc. Was a cheap Amazon clutch so it ran crappy but did get up to about 40mph on flat, returned it and got a cheap Amazon torque converter 65$ doesn’t slip at all accelerates amazing top speed of around 33mph with on flat or 40 downhill.

The mechanical brake does suck, doesn’t have much stopping power but I’ve learned to drive with it, bought a hydraulic brake but haven’t rigged up a bracket for it yet. Recently had the idea that “oh this thing sat outside forever I should probably lube all of the untouched components” like steering column, wheel bearings etc.

well lubing the steering caused it to become more loose, too loose for my liking, is there any way to tighten things back up as far as that goes. Also is it normal that I lost top speed when switching to a torque converter? Also any suggestions for a better brake setup? This mechanical brake straight up sucks I’ve tried adjusting it but I’ve had to tighten it so far that it’s basically full engagement when you press the pedal, even then it doesn’t stop very well, is that because of the weight and speed of this thing or? Will this hydraulic brake bridge the gap im looking to fill?

also what is this thing? My best guess after research is some kind of manco dingo that’s been modified in a backyard to look like this? The steering column you can see has been cut and moved forward which creates its own issue, it stops the pedals after a certain point which I guess isn’t that big of a deal only losing like half and inch or inch of pedal movement but still.

 

[ezcome-ezgo]

It has a "dingo" look to it in parts, so good call on that. But at this point I don't see where it matters. Thing about that brake disk is it is so small with those big wheels, you have very little leverage. Play with the linkage at the pedals and see if you can gain some clearance and leverage too.

 

[Toobam757]

N

It has a "dingo" look to it in parts, so good call on that. But at this point I don't see where it matters. Thing about that brake disk is it is so small with those big wheels, you have very little leverage. Play with the linkage at the pedals and see if you can gain some clearance and leverage too.

No doesn’t matter to much what it is, was just curious about that. It has a 6” brake disc, the only thing larger I can find is 8”, would it be worth switching to that? Or should I try the hydraulic first? Also I’m thinking a new brake rod because the one I have now flexes a little bit which is part of the reason I have the mechanical brake so tight.

or maybe get a hex hub and buy a larger brake disc and put it on there ?

 

[bob58o]

18” Diameter Tires?
Old clutch was 10 tooth?

Does it seem like the engine rpm is lower?
Perhaps it was around 4k RPM with the clutch and now only revving to 3K RPM?

you might want to try a smaller front sprocket or larger rear sprocket if only revving to 3k rpm now. There are losses that come with using a belt drive. 10% of the power you had with chain is gone. also the 30 series with 6” driven unit has an over drive that reduces mechanical advantage by 10% … which might put too much load on the engine which means it can’t rev as high. The buggy is fairly heavy with large tires. Small engines have limited torque. We might be at a place where we need to tune the gear ratio to match the engine TQ output to the buggy.

Maybe 60T on the rear.
And 9T on the front.
6:1 in overdrive.
36MPH at 4000 rpm…
Maybe can even get a bit higher than 4k rpm with that gear ratio?

Or try an 8T front with the 54T rear and see how it works. Many ppl hate on the 8T sprocket. It’s a cheap optio to test gear ratio.

3rd option is replacing 6” driven with 7” driven unit. There is no overdrive with the 7” driven unit…. Giving the full mechanical advantage of the sprocket ratio. 54:10 stays 5.4 : 1 instead of the over drive ratio of 4.86 : 1 with current set up.



54 : 10 sprocket ratio
40 mph with clutch
4.71’ per axle revolution

4000 engine rpm
4000 / 5.4 = 741 axel rpm
741 x 4.71’ = 3940 feet per minute
3940 x 60 = 209,400 ft per hour
209,400 / 5280 = 40 mph

30 Series TAV (with 0.9 : 1 Over drive)
54 : 10 sprocket ratio
4.86 : 1 overdrive ratio
33 mph (with clutch)
4.71’ per axle revolution

3000 engine rpm
3000 / 4.86 = 617 axel rpm
617 x 4.71’ = 2906 feet per minute
2906 x 60 = 174,360 ft per hour
174,360 / 5280 = 33 mph.

 

[bob58o]

Check that. High gear with 7” driven is 1.12 : 1.
When fully shifted, 54:10 becomes 6 :1.

All three options above end up giving 6:1 when fully shifted, which is more than the 5.4 :1 you had with clutch. Top Speed might be slower, but will be better for belt life, acceleration, hills, stop and go….

 

[Toobam757]

18” Diameter Tires?
Old clutch was 10 tooth?

Does it seem like the engine rpm is lower?
Perhaps it was around 4k RPM with the clutch and now only revving to 3K RPM?

you might want to try a smaller front sprocket or larger rear sprocket if only revving to 3k rpm now. There are losses that come with using a belt drive. 10% of the power you had with chain is gone. also the 30 series with 6” driven unit has an over drive that reduces mechanical advantage by 10% … which might put too much load on the engine which means it can’t rev as high. The buggy is fairly heavy with large tires. Small engines have limited torque. We might be at a place where we need to tune the gear ratio to match the engine TQ output to the buggy.

Maybe 60T on the rear.
And 9T on the front.
6:1 in overdrive.
36MPH at 4000 rpm…
Maybe can even get a bit higher than 4k rpm with that gear ratio?

Or try an 8T front with the 54T rear and see how it works. Many ppl hate on the 8T sprocket. It’s a cheap optio to test gear ratio.

3rd option is replacing 6” driven with 7” driven unit. There is no overdrive with the 7” driven unit…. Giving the full mechanical advantage of the sprocket ratio. 54:10 stays 5.4 : 1 instead of the over drive ratio of 4.86 : 1 with current set up.



54 : 10 sprocket ratio
40 mph with clutch
4.71’ per axle revolution

4000 engine rpm
4000 / 5.4 = 741 axel rpm
741 x 4.71’ = 3940 feet per minute
3940 x 60 = 209,400 ft per hour
209,400 / 5280 = 40 mph

30 Series TAV (with 0.9 : 1 Over drive)
54 : 10 sprocket ratio
4.86 : 1 overdrive ratio
33 mph (with clutch)
4.71’ per axle revolution

3000 engine rpm
3000 / 4.86 = 617 axel rpm
617 x 4.71’ = 2906 feet per minute
2906 x 60 = 174,360 ft per hour
174,360 / 5280 = 33 mph.

Yea 18” tires, both 10T on old clutch and running 10T sprocket on the TC.

also this thing gets up to speed in seconds, don’t see a problem with the acceleration after the TC I put on it. And yes might have seen a drop in rpms maybe slightly.

 

[bob58o]

Yea 18” tires, both 10T on old clutch and running 10T sprocket on the TC.

also this thing gets up to speed in seconds, don’t see a problem with the acceleration after the TC I put on it. And yes might have seen a drop in rpms maybe slightly.

Well IMO the drop in speed could come from 3 things.

1. The power loss from converting a chain drive to a belt drive. Maybe 10-15% power loss from introducing the belt.

2. The system struggles to fully “shift out.” The CVT is an automatic transmission and if the load is too much for the engine, the CVT stays in lower gear. It’s possible that the engine revs high but the transmission stays in a “lower” gear.

3. The system does fully shift out, but the combination of TQ output from the engine multiples by gear ratio doesn’t allow the buggy to accelerate any further.


If it’s #2 or #3, I believe the 69:9 with 6”, 54:8 with 6”, or 54:10 with 7” will help.

Clearance for a larger rear sprocket needs considered. Clearance for 7” pulley might require raising the engine. Smaller front sprocket doesn’t require any more space.

 

[Denny]

Yes you will loose a little top speed switching over to a cvt from a clutch. You can’t help that but you gain reliability and acceleration. Yes, that was a 285 Manco Dingo at one time. Great kart! Align that front end and you may pick up 1 or 2 mph. I would also go to an 8” rotor for the brakes. More leverage. It will help with the hydraulic brakes too. No stainless steel rotors though. They suck!

 

[bob58o]

If it’s #3, it depends on what max rpm is and where it falls on the TQ / HP vs RPM curves.

If my engine isn’t reaching RPM where it makes max HP, my gearing probably needs fixed.

 

[bob58o]

These things are junk, but good enough for me needs most of the time. I like to keep an eye on RPM.

 

[bullseye670]

I put a tach on every build. I've always gone with the battery powered one. Only one wire to run to your plug wire. Only thing is it's only good as long as the battery lasts. No changing it. Supposed to last about 10 years. Have't had one die yet.

 

[panchothedog]

The mechanical disc brakes are not very good. I have them on a similar sized kart, and much like yourself have learned to drive with it. The hydraulic system you have will be a night and day difference. Don't waste any more time messing with the mechanical one. It will never be good. As stated by Denny, it is very normal to loose a little top speed when using a torque converter. The acceleration and drive ability is well worth it. A 10 tooth drive sprocket and a 60 tooth axle sprocket is industry standard. Almost every large tired kart came with that ratio and there's a reason why. It works. For all around driving, it's perfect.