How to make 212/224 more tame for kids?

[ebrammer252]

I have a doodlebug with a 212 on it, 12T clutch, 65T rear. I also have a motovox frame that I'm going to be putting a 224 in, I have a 12T clutch for it, and it currently has a 75T rear, will probably change that to a 65T as well.

I want to make these tame enough for my nieces and nephew to ride when they come to visit. They're ages 8-14 and have never ridden anything with a motor, but have experience on bicycles. Right now the Doodlebug with the 212 and 12T/65T runs great, but it's abrupt on throttle and will pick up the front wheel with my 220lb self on it. Even with the throttle stop screw set ALL the way in, the on/off throttle is still pretty abrupt.

Are there any good ways to make these more tame for kids? I was considering a much smaller rear sprocket, maybe a 12T/50T clutch/rear combo, but I know that's a low ratio and I understand that might toast a clutch quickly?

I've seen some people on FB mention adding a spring to the throttle, essentially adding more force to close it and they say it makes it more docile for kids to ride. Thoughts? Input?

 

[ole4]

There is a screw on the throttle mechanism to adjust the governed speed and you can adjust it to limit the RPM of the motor. It will still accelerate the same but will not go very fast and you can actually adjust it so low as to not engage the clutch. Do not lower it so much that the clutch does not completely engage or you will burn it up due to constant slipping.

 

[ebrammer252]

There is a screw on the throttle mechanism to adjust the governed speed and you can adjust it to limit the RPM of the motor. It will still accelerate the same but will not go very fast and you can actually adjust it so low as to not engage the clutch. Do not lower it so much that the clutch does not completely engage or you will burn it up due to constant slipping.

Even with the throttle stop screw set ALL the way in, the on/off throttle is still pretty abrupt.

 

[ole4]

You are correct the way it works is the throttle just pulls a spring on the linkage that whacks open the throttle until the govenor arm pulls another spring to pull it back. The throttle stop works by limiting how much you can pull on the spring that opens the throttle, but until the govenor starts pulling back against it the gives a lot of throttle.

 

[BrownStainRacing]

Are those 14"- 14.5" tall tires???
If so, you can go to the 50t for the kids and not hurt the clutch.

75/12= 6.25
65/12 = 5.41
50/12 = 4.16

When the clutch engages (2200-2500) , you could easily be hitting that SMALL back tire with 35-40 ft/lbs tq. That's with the stock pred 212 and 4.16:1 gear. assuming around 8.5-9.5 ft/lbs from the engine. But you can see the weight to power ratio will be around 2:1 for a 80lb rider. 2.5:1 weight to power, would calm them down. But might still be a bit much for a 80lb rider.

The 224 box says it makes 10.23 ft/lbs tq outta the box, my butt dyno says it's closer to 11 then it is 10.

If you get a new 224, check all the bolts, including the rod bolts, and flywheel nut. Nothing was torqued to spec on the 3 I checked.

 

[DaddyJohn]

I don’t think there’s really a good way that’s practical for easily switching back and forth. It might be just as easy to swap a GX160 or GC160/190 on there for when the kids come by.

 

[SAT]

We re-powered two of our bikes with 2hp eze-spins and 8:1 jackshaft set-ups.
The 8 year old can check the oil, start it and run pretty safe with a standard bike helmet. The top-end is pretty slow. No danger of wheel stands.

 

[sparkwizard]

I had to find another frame and put a 79cc Predator on it for the visitors. Rookies and Predator 212s are not a safe combination.
There are great suggestions here, but SAT has the best one, so far. Good luck and be safe.

 

[SAT]

I had to find another frame and put a 79cc Predator on it for the visitors. Rookies and Predator 212s are not a safe combination.
There are great suggestions here, but SAT has the best one, so far. Good luck and be safe.

Unfortunately, I’ve misplaced the images.
Both are good runners.

 

[SAT]

Unfortunately, I’ve misplaced the images.
Both are good runners.

A more modern design could be a 79 or 97 cc engine with the bolt-on jackshaft plate.
No frame welding.
Just a thought.

 

[ebrammer252]

Are those 14"- 14.5" tall tires???
If so, you can go to the 50t for the kids and not hurt the clutch.

75/12= 6.25
65/12 = 5.41
50/12 = 4.16

When the clutch engages (2200-2500) , you could easily be hitting that SMALL back tire with 35-40 ft/lbs tq. That's with the stock pred 212 and 4.16:1 gear. assuming around 8.5-9.5 ft/lbs from the engine. But you can see the weight to power ratio will be around 2:1 for a 80lb rider. 2.5:1 weight to power, would calm them down. But might still be a bit much for a 80lb rider.

The 224 box says it makes 10.23 ft/lbs tq outta the box, my butt dyno says it's closer to 11 then it is 10.

If you get a new 224, check all the bolts, including the rod bolts, and flywheel nut. Nothing was torqued to spec on the 3 I checked.

I thought they were 16? They're 145/70-6

 

[BrownStainRacing]

I thought they were 16? They're 145/70-6

They are small. It don't take much torque to turn little tires.

 

[ebrammer252]

They are small. It don't take much torque to turn little tires.
View attachment 300326

So I could run a 50T rear sprocket when they come to visit and swap back afterwards.

 

[BrownStainRacing]

So I could run a 50T rear sprocket when they come to visit and swap back afterwards.

It's worth a try. It shouldn't hurt the clutch at all. Try it with your weight too. It might be alright. You will know fast, if it won't pull you.

 

[ebrammer252]

Are those 14"- 14.5" tall tires???
If so, you can go to the 50t for the kids and not hurt the clutch.

75/12= 6.25
65/12 = 5.41
50/12 = 4.16

When the clutch engages (2200-2500) , you could easily be hitting that SMALL back tire with 35-40 ft/lbs tq. That's with the stock pred 212 and 4.16:1 gear. assuming around 8.5-9.5 ft/lbs from the engine. But you can see the weight to power ratio will be around 2:1 for a 80lb rider. 2.5:1 weight to power, would calm them down. But might still be a bit much for a 80lb rider.

The 224 box says it makes 10.23 ft/lbs tq outta the box, my butt dyno says it's closer to 11 then it is 10.

If you get a new 224, check all the bolts, including the rod bolts, and flywheel nut. Nothing was torqued to spec on the 3 I checked.

Any harm in doing a higher tooth count clutch as opposed to replacing rear sprockets?

 

[BrownStainRacing]

Yea that's another choice. I was gonna mention it earlier, but you already had sprockets. Some clutches you can buy jus the sprocket, some sprocket and drum combo. The El cheapo clutches you have to buy the whole clutch to get a specific sprocket teeth count.
I think they sell a sprocket adapter for that mini, that uses split sprockets for quicker gear changes and not remove the rear tire. But still gotta change the chain length.

 

[BrownStainRacing]

Even with the throttle stop screw set ALL the way in, the on/off throttle is still pretty abrupt.

I jus realized something. You CAN control how far the throttle opens before the governor pushes it back Its ez, under the fuel tank you will see a arm and spring, move that spring to the holes going left, until you feel comfortable the kids can handle it. Then you can fine tune it with the throttle stop screw. Far right is more rpm, far left is less rpm.
Sorry bout that. Most people are looking for more rpm. Here's a pic.

 

[ebrammer252]

I jus realized something. You CAN control how far the throttle opens before the governor pushes it back Its ez, under the fuel tank you will see a arm and spring, move that spring to the holes going left, until you feel comfortable the kids can handle it. Then you can fine tune it with the throttle stop screw. Far right is more rpm, far left is less rpm.
Sorry bout that. Most people are looking for more rpm. Here's a pic.
View attachment 300327

Ah good to know! Thank you!

 

[BrownStainRacing]

Ah good to know! Thank you!

No problem.
Let us know how it turns out.