Torque Converter experiment.

[bbrewer2005]

Has anyone attempted to put a 40 series driver and driven unit on a 30 series backplate?
I'm running a stage 1 predator 212 that I've got dialed in very well (on a minibike). Its got a 30 series ebay tav2 unit on it now. The thing runs great. My only issue is that with how much it gets ridden, I'm going through these cheap belts. Its not shredding them, its just wearing them down and stretching them. I tried an actual comet belt and it did last a decent bit longer, but still. All my buddies are having the same issues with theirs. They have similar setups, or are fully built (rod, flywheel, cam, and mikunis). Id like to go with a 40 series as it is a bit bigger. My issue is the $350 price. I see all kinds of 40 series pulley sets for 80 bucks on ebay, but no complete kits. If it is possible to use the 30 series back plate, id just get the 40 series pulleys. If not, is there a complete ebay kit for 150 or less for the 40 series for a 3/4in shaft?

Thanks for any help.

 

[bob58o]

I think this is as cheap as it gets for a 40 series with a backplate.
https://www.ebay.com/itm/Go-Kart-To...em4d6dc011af:g:euMAAOSwCglag0u6#shpCntId#shId

But how do you plan to adapt the 3/4" shaft for the 1" bore of the 40 series?
The typical shaft adapter uses a stepped key. Seems like it would be an issue when trying to install the driver pulley (which has a built in key).

---------- Post added at 06:50 AM ---------- Previous post was at 06:41 AM ----------

The TAV-2 backplate sets you up for 6-5/8" pulley center to center spacing.
The smallest 40 series belt I know of is for 7-1/4" pulley center to center spacing.
Meaning you would have to modify the mounting holes on the backplate to make up that extra 5/8".

Also to use a 40 series driven with a backplate, you need to mount the driven unit outboard and need a reverse wound driven spring. This will cause the pulleys to be out of alignment at some point (probably better to be crooked at idle, then straighter when shifted) I'm not sure if the 40 series driven unit will fit on the TAV-2 jackshaft. They make a 5/8" bore driven unit for the 40 series, but not sure the shaft is long enough.

 

[bob58o]

To be honest, the 30 series should be fine on your stage 1 predator. How quickly do you run through belts? You probably have alignment or gearing issues. What is the count on your sprockets? What size are your tires? How much total weight (you plus minibike)?

 

[anickode]

Even IF you could find a belt short enough, the 40 series running mounted outboard on a backplate relies on the belt to eat up the massive offset that happens at high gear. The closer the pulleys are together, the more likely it is that your belt won't hold up for long, or will just simply roll on its side and be useless.

Running a 40 series even on a backplate meant for a 40 series is a less-than-ideal setup.

Plus the weakest part of a tav2 setup IS the backplate, so setting it up with an even bigger torque converter and feeding it more power is a recipe for failure IMO.

 

[bbrewer2005]

To be honest, the 30 series should be fine on your stage 1 predator. How quickly do you run through belts? You probably have alignment or gearing issues. What is the count on your sprockets? What size are your tires? How much total weight (you plus minibike)?

They are starting to be noticeably worn (can tell while riding) after about 10 or 12 HARD hours. The thing becomes much easier to control the front end coming up from a dead stop. This is when I normally start wanting to change them. They sit down inside the driven pulley instead of flush or slightly above the driven when the engine is off. This is when I typically change them.

I think it's only fair to mention that we BEAT on these things HARD. I'm talking 20-30 dead stop drag races at a time, hot lapping them one after another. (We all have actual drag cars so it only makes sense)

The alignment is spot on, it's not that. It's not shredding belts, just stretching them out and wearing them thin. They still look new when pulled off, just not the same dimensions anymore. Lol

My setup is a Coleman ct200eux with a 212 hemi predator. Full stage 1. I'll be putting a tillotson tct carb on today. It has a 9t jackshaft gear and a 50t drive gear. 19in tires. The bike weighs about 120lb and I'm about 210lb.

I tried a 10t/60t and it was too much. I mostly drag race/top speed run with this and it made it WAY too hard to keep the front end down.
My personal best is 52mph on flat road with a long straight stretch. This is with a new belt. With a worn belt I can manage about 47-48ish. I feel like it's geared fairly well but i could be wrong.

I guess I'll just stick with this 30 series for now.

 

[anickode]

You may have answered this and I missed it, but are you buying genuine comet belts, or cheapese clone belts? It makes a big difference on longevity.

 

[bob58o]

If you are happy with the gearing now, you might just have to accept that you are going to run through belts. If you can get 12 hours out of a cheap belt, $20 gets you 36 hours of enjoyment.
$0.56 per hour in belts.
$2-$3 per hour in gasoline.

I'm not aware of any cheap 40 series driver options that come with a 3/4" bore.

 

[bbrewer2005]

I'm using the cheap belts, but I've used the actual comet belts as well. They did last longer, but not 4 times longer( they cost 4 times as much).

Bob, that's what I was afraid of. I ordered a 10 pack of cheap belts for 55 bucks. Those should last a while. As for fuel, I get probably 4 hours out of about 2 bucks in gas. Not too shabby. Lol

 

[KartFab]

Has anyone attempted to put a 40 series driver and driven unit on a 30 series backplate?

yeah and it it didnt work. check center to center distance.

Might want to use the 30 series backplate and just use the jacckshaft on it for gear reduction, then use a centrifugal clutch or race clutch on the engine shaft. Thats what a lot of guys do when racing mini bikes and drag racing.

 

[landuse]

I tried a 10t/60t and it was too much. I mostly drag race/top speed run with this and it made it WAY too hard to keep the front end down.
My personal best is 52mph on flat road with a long straight stretch. This is with a new belt. With a worn belt I can manage about 47-48ish. I feel like it's geared fairly well but i could be wrong.

You still haven't answered what gearing you have at the moment. Could you give tyre diameter too?

 

[mckutzy]

Post 5.
He says 9-50toth count 5.56:1 , 19" tires.

 

[landuse]

Post 5.
He says 9-50toth count 5.56:1 , 19" tires.

Dang! Missed that. Thanks

No wonder the belts are getting ruined. That gear ratio is too high for optimum belt usage.

 

[bbrewer2005]

Dang! Missed that. Thanks

No wonder the belts are getting ruined. That gear ratio is too high for optimum belt usage.

What should I be running? I've heard as high as 7-9:1 with 19in tires. I'll say it now that that won't happen. 6:1 is as short as I'd go. I'd say the bike would be pretty well useless with anything higher than that imo (for my uses). If that's the case then I'll just have to accept the fact that I'll be using up belts more quckly like bob58o said.

Might want to use the 30 series backplate and just use the jacckshaft on it for gear reduction, then use a centrifugal clutch or race clutch on the engine shaft. Thats what a lot of guys do when racing mini bikes and drag racing.

It came with a 10t clutch with a 2:1 gear reduction jackshaft to the 50t drive Sprocket. It was an absolute pig. In both low end acceleration and top end.

 

[mckutzy]

On my bike I use a 7:1 with a maxtorque cent clutch, with a jackshaft, 24" car spare tire.. Reasonable acceleration and good top end(but I haven't the space/area to really test)..
If say about that in ratio, and use a good quality race clutch...

 

[landuse]

What should I be running? I've heard as high as 7-9:1 with 19in tires. I'll say it now that that won't happen. 6:1 is as short as I'd go. I'd say the bike would be pretty well useless with anything higher than that imo (for my uses). If that's the case then I'll just have to accept the fact that I'll be using up belts more quckly like bob58o said.


It came with a 10t clutch with a 2:1 gear reduction jackshaft to the 50t drive Sprocket. It was an absolute pig. In both low end acceleration and top end.

The lower the gearing number (5:1), the higher the gear ratio. The higher the gearing number (10:1) the lower the gear ratio. With a 5.73:1 ratio, you are relatively high, which means worse acceleration but higher top speeds. It also means premature belt wear. Lower gear ratios like 7:1 or 9:1 would mean a lot more torque and acceleration, but slower speeds. Belt wear would not be as bad.

You have to find that happy medium that works for you between the two. There is always going to be a trade off.

Why do you say the kart would be useless if you went with a lower gear ratio? Just curious.

 

[bob58o]

Why do you say the kart would be useless if you went with a lower gear ratio? Just curious.

He mentioned how easily the front wheel of the mini comes up off the ground.