Need setup advice

[BaconBitRacing]

I understand that 6:1 is ideal but what's the missing piece to the equation? From the factory, most carts don't come with tiny front sprockets and huge rear sprockets. This cart once pulled well on a smaller motor with 43/13 sprockets.

I'm not trying to be a smart @$$. I'm generally curious. I know, on a car 4.10 gears are great for the track but you'll cruise on the highway at super high RPM's (reduced top speed).

So what's the in between ratio? One that won't smoke the tires but still takes off reasonably well, cruises fast enough, and doesn't each up belts?

The one video you sent, the guy swapped his red spring for the yellow. If I did that, it would allow the engine to spool up more before engaging, right? So essentially faking a higher ratio?

The stock kart had internal gear reduction in the engine, the predator does not. If you look at old karts, you’ll see big rear sprockets, because they didn’t have internal gear reduction. These modern karts are a lot less bolt on.

 

[Thepartsguy]

you list the kart up for sale are you gonna let the buyer know about all the research and work Needed to make it usable? I know it sucks... but just like me... if you want this done your gonna have to do it from scratch. If I had to guess the factory put small sprockets on these china karts on purpose specifically so you cannot update/upgrade them easily later... like even the people who built them don’t want the engines upgraded... that’s why it worked so well with the original engine. That’s all the snot the factory wanted it to have...

 

[joshw0000]

you list the kart up for sale are you gonna let the buyer know about all the research and work Needed to make it usable? I know it sucks... but just like me... if you want this done your gonna have to do it from scratch. If I had to guess the factory put small sprockets on these china karts on purpose specifically so you cannot update/upgrade them easily later... like even the people who built them don’t want the engines upgraded... that’s why it worked so well with the original engine. That’s all the snot the factory wanted it to have...

Yes. I don't have the heart to rip people off. Again, if it'll run fine as-is I'll keep it. Even if I have to replace a belt or 2 every year. I have girls and they get bored riding in 20-30 mins. They won't run it at WOT for hours like a boy would.

Honestly, this is probably my first build of at least 2 or 3. Now that I know what to look for when buying one I'll probably build a bigger one for me that won't require tons of cutting/welding. But that won't be this summer. Too many other projects to finish and this one is delaying them all.

 

[Thepartsguy]

Yes. I don't have the heart to rip people off. Again, if it'll run fine as-is I'll keep it. Even if I have to replace a belt or 2 every year. I have girls and they get bored riding in 20-30 mins. They won't run it at WOT for hours like a boy would.

Honestly, this is probably my first build of at least 2 or 3. Now that I know what to look for when buying one I'll probably build a bigger one for me that won't require tons of cutting/welding. But that won't be this summer. Too many other projects to finish and this one is delaying them all.

You do not need any adapters just to let you know... not even grade 8 hardware... I bolted a 40 chain 60t sprocket to a 35 chain 58t sprocket by drilling four new holes in the 35 chain sprocket. I then stacked three Nuts on top of each other between both sprockets and tightened it all down to the point the china hardware I was using just almost about snapped.. it worked for years... as long as the hole in the new sprocket will slip over the old hub I would try to drill and mount a sprocket to a sprocket. You at that point notch that frame and use any sprocket you please? Edit: you can see the 35 chain sprocket welded to the hub.. and You can just see the four holes I drilled into the sprocket. I had a brand new 40 Chain sprocket and there was no way I was buying a new hub.. I had a drill laying right there.. I had to dig through buckets to find bolts/nuts of course.. but it got me on the road with a drill..

 

[BrownStainRacing]

Where does the x .9 come from?

I've studied this cart for hours and spent three times as many online searching for parts. I don't know any other way to get this thing going without throwing away everything and starting over. There's no combo of sprockets for 35 or 40 that will fit my setup and provide any benefit over what I have.

Looking at my axle more yesterday and the threads are smaller than 0.75 on the end and the the center of it is thicker than 1-1/8". I didn't have enough washers on hand to check against. But that's just one more complication to face if I decided to replace the axle. It's a 35" inch axle. Nothing about it seems standard.

The x .9 comes from the tav when the 6" driven goes into high. It's a power killer on stock engines with the wrong gearing.

Heres what I've learned with 30 series tav's over the years.
With a 6" driven, it will have a low gear somewhere around 2.4 - 2.7:1. high gear will always be .9:1.

Now a 7" driven changes the ball game.
2.9 - 3.15:1 low
1.12:1 high

It's simple math, the 7" will pull more weight at same rpm compared to the 6" with the same setup. Of course we can change gear ratios and tire height to get the 6" to work like the 7". But we can't do it here with this bulid.

41t/8t = 5.125:1
5.125 x .9 = 4.6125:1 final drive w/ 6"

41t/8t = 5.125:1
5.125 x 1.12 = 5.74:1 final drive w/ 7"


I found a 41t #420 sprocket, with the bolt pattern you posted earlier. I don't see it now. I'll post it when I come across it again.

 

[BrownStainRacing]

Here it is. 64mm is 2.51"

REAR SPROCKET FOR 420 CHAIN 41 TOOTH FITS STOCK CRF50 XR50 DIRT BIKE RS03 | eBay

Find many great new & used options and get the best deals for REAR SPROCKET FOR 420 CHAIN 41 TOOTH FITS STOCK CRF50 XR50 DIRT BIKE RS03 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[BrownStainRacing]

7" driven, when using a tav backing plate will need 203591 belt

6'' Inch Slim Pull In Electric Radiator Cooling Fan 650CFM Mount Kit Universal | eBay

Description: 100% Brand new radiator cooling fan blade for Universal use. Slim Design Making it Great to Install in Small,Tight Areas ; Bring More Space for Engine Modification. Pull Type Fitment / Replacement. OE Fitment or Replacement, Pull Type Diameter: 6 inch (Blade to Blade) Maximum Fan...

www.ebay.com

 

[BrownStainRacing]

I understand that 6:1 is ideal but what's the missing piece to the equation? From the factory, most carts don't come with tiny front sprockets and huge rear sprockets. This cart once pulled well on a smaller motor with 43/13 sprockets.

I'm not trying to be a smart @$$. I'm generally curious. I know, on a car 4.10 gears are great for the track but you'll cruise on the highway at super high RPM's (reduced top speed).

So what's the in between ratio? One that won't smoke the tires but still takes off reasonably well, cruises fast enough, and doesn't each up belts?

The one video you sent, the guy swapped his red spring for the yellow. If I did that, it would allow the engine to spool up more before engaging, right? So essentially faking a higher ratio?

No, he changed to the yellow spring( stiffest) so it stays in low gear longer allowing the engine to build power before the tav started shifting. This will work good for your build.

To "spool up more before engaging", you need to "stall the driver" by installing higher engagement springs. I use 3000 on my mini, 3600 on my son's and 3100 on my grandsons buggy.

Replacement Springs for 20 & 30 Series Driver | 011188

www.bmikarts.com

 

[Thepartsguy]

No, he changed to the yellow spring( stiffest) so it stays in low gear longer allowing the engine to build power before the tav started shifting. This will work good for your build.

To "spool up more before engaging", you need to "stall the driver" by installing higher engagement springs. I use 3000 on my mini, 3600 on my son's and 3100 on my grandsons buggy.

Replacement Springs for 20 & 30 Series Driver | 011188

www.bmikarts.com

I have also seen people use straight up spacer bushings to keep the tav from shifting out of first.

 

[joshw0000]

No, he changed to the yellow spring( stiffest) so it stays in low gear longer allowing the engine to build power before the tav started shifting. This will work good for your build.

To "spool up more before engaging", you need to "stall the driver" by installing higher engagement springs. I use 3000 on my mini, 3600 on my son's and 3100 on my grandsons buggy.

Replacement Springs for 20 & 30 Series Driver | 011188

www.bmikarts.com

You simply refuse to let me do this wrong, huh? I like it!

Ok, the sprocket should work. I think the bolt holes are off a little bit but since the bore is right I can bolt whichever holes fit and easily drill out the others. I just double checked and the 8T I posted earlier is compatible with a 420 chain, so all of the sprockets/chain I feel good about. Being 41T I don't see how I'd have clearance issues. The 30 series TAV I ordered will be in tomorrow so I can bolt it on backwards and see where it falls. If it's too low I'll get the riser I found, if it's not, I'll order one you sent to keep the motor as low as possible plus I like the left/right forward/back adjustability.

I had no idea about 6" to 7" but you posted a direct link so I think I can handle ordering / installing it.

Springs....this is a little new to me. The red / yellow, I watched the video and I could manage changing that out but I have no idea what to do order or if I even need to. Same with the springs in this link. You seem to have a good understanding of what is what so make a recommendation if you think I need it and I'll order it. I may also need some instructions.

Thanks!

 

[BrownStainRacing]

You simply refuse to let me do this wrong, huh? I like it!

Ok, the sprocket should work. I think the bolt holes are off a little bit but since the bore is right I can bolt whichever holes fit and easily drill out the others. I just double checked and the 8T I posted earlier is compatible with a 420 chain, so all of the sprockets/chain I feel good about. Being 41T I don't see how I'd have clearance issues. The 30 series TAV I ordered will be in tomorrow so I can bolt it on backwards and see where it falls. If it's too low I'll get the riser I found, if it's not, I'll order one you sent to keep the motor as low as possible plus I like the left/right forward/back adjustability.

I had no idea about 6" to 7" but you posted a direct link so I think I can handle ordering / installing it.

Springs....this is a little new to me. The red / yellow, I watched the video and I could manage changing that out but I have no idea what to do order or if I even need to. Same with the springs in this link. You seem to have a good understanding of what is what so make a recommendation if you think I need it and I'll order it. I may also need some instructions.

Thanks!

Yea, I don't give up ez, lol.

The yellow driven spring is the stiffest spring, works great for heavy loaded vehicles, but is a big pain to install in the tightest hole. I can't change it by myself, even the middle hole is a pain, but manageable. I would get the 7" driven and move the red spring over to the next hole ( most resistant), this again will keep the tav from shifting too fast. Not as good as the yellow spring, but it's worth a try. You can always order the yellow spring, and try it. My grandsons buggy has the yellow spring in middle hole, and I showed you already, it leaves black marks on the concrete. It's the same 212 pred non hemi that you have.
Those garter springs are for the driver( small pulley that goes on the crankshaft). The stock springs engage at 2200 rpm, they suck. You need to rev the engine a little higher before engaging the belt. Stock pred 212's peak torq around 3000-3200 rpm. They make crap torque at 2200, so getting rpm up near where the engine makes peak torque will get the weight of the vehicle moving faster outta the hole. The white springs (3100) will get it there. You can mix a stock spring with a white spring and have 2600 rpm engagement, but you will be happier with the white springs. They are super ez to change.

Go back and look at that earlier post about what you need. Those parts, with the 7"driven, that belt that matches, and those white springs will put you on the road. And smiles per hour is more important to me then miles per hour.

Take you time and make sure you are ordering the right parts.

 

[BrownStainRacing]

Here's the yellow spring.

Comet Yellow Spring for 30 Series Driven | 216168 | 216168A

www.bmikarts.com

 

[BrownStainRacing]

I have the best luck with Bando belts. I jus replaced the 1 on my mini bike back around Thanksgiving time. The old 1 had been on there for 3 yrs or so. and I lost count on how many different test engines, gear ratio changes, springs changes, hard dead stop launches, hill climbs it's been thur.

My grandsons buggy has a comet belt, it's been on there well over 2yrs and I'm sure it's got 2-3 more yrs to go. Its been thur more abuse then my mini bike, pulling 2 people up crazy steep hills, countless mud holes, and gravel dust every day.

Point being, if it don't say bando or comet on the belt itself, go find 1 that does.

Search

Belt Palace, Replacement belt Store

beltpalace.com

 

[joshw0000]

Yea, I don't give up ez, lol.

The yellow driven spring is the stiffest spring, works great for heavy loaded vehicles, but is a big pain to install in the tightest hole. I can't change it by myself, even the middle hole is a pain, but manageable. I would get the 7" driven and move the red spring over to the next hole ( most resistant), this again will keep the tav from shifting too fast. Not as good as the yellow spring, but it's worth a try. You can always order the yellow spring, and try it. My grandsons buggy has the yellow spring in middle hole, and I showed you already, it leaves black marks on the concrete. It's the same 212 pred non hemi that you have.
Those garter springs are for the driver( small pulley that goes on the crankshaft). The stock springs engage at 2200 rpm, they suck. You need to rev the engine a little higher before engaging the belt. Stock pred 212's peak torq around 3000-3200 rpm. They make crap torque at 2200, so getting rpm up near where the engine makes peak torque will get the weight of the vehicle moving faster outta the hole. The white springs (3100) will get it there. You can mix a stock spring with a white spring and have 2600 rpm engagement, but you will be happier with the white springs. They are super ez to change.

Go back and look at that earlier post about what you need. Those parts, with the 7"driven, that belt that matches, and those white springs will put you on the road. And smiles per hour is more important to me then miles per hour.

Take you time and make sure you are ordering the right parts.

Thanks. Posting for future reference.

 

[BrownStainRacing]

Thanks. Posting for future reference.

Yeap, ez pz.
You're gonna need a GOOD pair of snap ring pliers when changing that driven spring.
I recommend changing or moving the driven spring while the driven is new. A little wear will cause burrs and be a pain to get apart and put back together.

 

[joshw0000]

I got impatient and ordered everything expect the mounting plate (may need riser or may just need adjustable) and the yellow spring (I'll see how the setup feels before I order it).

So, pending delivery:

30 series torque converter
41 tooth rear 40 series sprocket
8 tooth front 40 series sprocket
420 chain w/ breaker and 5X master links
2X white Comet garter springs
7" driven for 30 series torque converter

What am I forgetting?

 

[joshw0000]

Yeap, ez pz.
You're gonna need a GOOD pair of snap ring pliers when changing that driven spring.
I recommend changing or moving the driven spring while the driven is new. A little wear will cause burrs and be a pain to get apart and put back together.

Thanks. I have some.

Re-reading posts after placing an order. I need a 203591 belt when upgrading to 7" driven, right? The belt that comes with the kit standard is no good?

 

[BrownStainRacing]

I got impatient and ordered everything expect the mounting plate (may need riser or may just need adjustable) and the yellow spring (I'll see how the setup feels before I order it).

So, pending delivery:

30 series torque converter
41 tooth rear 40 series sprocket
8 tooth front 40 series sprocket
420 chain w/ breaker and 5X master links
2X white Comet garter springs
7" driven for 30 series torque converter

What am I forgetting?

That's a good start. You can mock up the engine and tav and see how far you are off from the axle sprocket. If you can turn the clutch around on the crankshaft where the sprocket is on the inside, will show you where the tav sprocket will line up with the axle sprocket, jus for measuring, not running, jus mock up.
I'll check today on how much wider the 420 chain is compared to the 40 and 41, I should have some old some where. I'm concerned about the space between the back of the driven and the backing plate where the tav sprocket goes on the shaft, this area is narrow, ive had the chain hit the back of driven and backing plate causing the master link clip to break or pop off, same with 1/2 links. That's why I only use #41 chain and no 1/2 links. I have no problems at all with the narrower #41 chain when using a tav with backing plate. I'll let you know what I find.

 

[BrownStainRacing]

Thanks. I have some.

Re-reading posts after placing an order. I need a 203591 belt when upgrading to 7" driven, right? The belt that comes with the kit standard is no good?

Yea its crap, but too short for the 7" driven anyways. Jus save it for now. Might use in the future or some one in the neighborhood might need 1 some day.

 

[BrownStainRacing]

I got impatient and ordered everything expect the mounting plate (may need riser or may just need adjustable) and the yellow spring (I'll see how the setup feels before I order it).

So, pending delivery:

30 series torque converter
41 tooth rear 40 series sprocket
8 tooth front 40 series sprocket
420 chain w/ breaker and 5X master links
2X white Comet garter springs
7" driven for 30 series torque converter

What am I forgetting?

Now here. is tav for a 3/4" shaft?? And driven for 5/8" shaft????? Your crankshaft is 3/4 and the jackshaft coming with your kit is 5/8, make sure you have ordered the right kit and driven.