Mini Bike Gearing with TC

[jdschwass]

Heyall, I'm new to mini bikes, and I have to say this is quite a slippery slope!
I picked up a Coleman CT200U-EX less than two weeks ago. I have installed a stage 1 kit so far along with a 30 series torque converter. I'm running the stock 50T rear sprocket with a 10T drive sprocket.
Hisun 198cc engine. The engine is stock internally.
The bikes performs very well, but I feel I am being limited on my top end. Flat out on the road I can't break 40MPH, and I'm only 170lbs. My revs at full speed are maxing out at about 4000, maybe a bit higher with a tail wind. Even with stock internals, I should be able to go higher in the rev range than this.

Setting a goal with a 5500rpm red line, and fully understanding the limitations of a stock engine, I ordered a 60T rear sprocket. My theory is that by reducing the gearing will allow me to rev higher at speed, and provide more torque down low, gaining me both torque and speed. In theory. I was hoping someone has run into the same issue.

I won't have the new sprocket until next week, so in the meantime I plan to move the spring over on the driven clutch so that it takes a little longer to go into OD. If the 60T sprocket ends up being too tall, I also have a 12T sprocket for the front that I could swap in. But based on the ratio calculators, going to a 60T should put me back into a realistic top speed range of 45-50MPH, rather than 60MPH currently, giving me more useable range within the available engine operating speeds.

I think my logic checks out, but purely theoretical based on lying awake at night thinking about it. I was hoping someone might have some real world experience to substantiate my theory.

Much appreciated. Cheers.

 

[Possom Point]

You can change your clutch weights to Aluminum and switch out the garter springs to a higher RPM rev, will help spin the clutch faster, I did this on my Murray and broke 52 mph on the street, but dealing with “Death Wobble” was a sketchy outcome. BUT my motor was not stock.

 

[BrownStainRacing]

Heyall, I'm new to mini bikes, and I have to say this is quite a slippery slope!
I picked up a Coleman CT200U-EX less than two weeks ago. I have installed a stage 1 kit so far along with a 30 series torque converter. I'm running the stock 50T rear sprocket with a 10T drive sprocket.
Hisun 198cc engine. The engine is stock internally.
The bikes performs very well, but I feel I am being limited on my top end. Flat out on the road I can't break 40MPH, and I'm only 170lbs. My revs at full speed are maxing out at about 4000, maybe a bit higher with a tail wind. Even with stock internals, I should be able to go higher in the rev range than this.

Setting a goal with a 5500rpm red line, and fully understanding the limitations of a stock engine, I ordered a 60T rear sprocket. My theory is that by reducing the gearing will allow me to rev higher at speed, and provide more torque down low, gaining me both torque and speed. In theory. I was hoping someone has run into the same issue.

I won't have the new sprocket until next week, so in the meantime I plan to move the spring over on the driven clutch so that it takes a little longer to go into OD. If the 60T sprocket ends up being too tall, I also have a 12T sprocket for the front that I could swap in. But based on the ratio calculators, going to a 60T should put me back into a realistic top speed range of 45-50MPH, rather than 60MPH currently, giving me more useable range within the available engine operating speeds.

I think my logic checks out, but purely theoretical based on lying awake at night thinking about it. I was hoping someone might have some real world experience to substantiate my theory.

Much appreciated. Cheers.

Ahhhh, you mean that stage 1 kit didn't add 50hp and 12,000+ rpm?????

J/k.

Stop wasting your money on those crap kits, I'm not j/k.

You at 170, is putting a load on the t/c with that low compression engine. It's only making 8.5-9 ft lbs tq.
More gear will help, but the complete tune will help more.

Thats a good idea to tighten that driven spring, it'll slow that shift into high down for you, letting the engine build up more power before that overdrive shift, if it's even going into o/d.

Jus make sure you mark it before pulling that snap ring off. Those marks will be where you need to preload the spring when you get it back together.

Post pics of the gov arm and spring, under the tank. They are usally not set for mini bikes and karts.

You also probably need a lil more stall (rpm engagement) in the driver.

What rpm is it at when the bike starts to move from a dead stop??? When it gets hot, up to temp. Tuning things cold does nothing.
Lmk, and I can show you how to up it 200-300 more rpm. It'll cost way less (nothing) then that stage 1 kit, and make it come outta the hole faster, .

 

[BrownStainRacing]

You can change your clutch weights to Aluminum and switch out the garter springs to a higher RPM rev, will help spin the clutch faster, I did this on my Murray and broke 52 mph on the street, but dealing with “Death Wobble” was a sketchy outcome. BUT my motor was not stock.

You know what I'm talking about.

It's funny, how that stall engagement makes the high side hit higher rpm from the regular 30 series drivers.

I don't understand why people don't do this 1st,

 

[jdschwass]

Thanks for the replies.
My stage 1 kit includes a 22mm Mikuni and header pipe, so there is no more governor. I have not yet removed the internal governor components. I didn't buy a kit, just a carb/intake and a pipe, and a jet kit. I can't even justify upgrading valve springs, flywheel, rod etc if I can't even get to red line as it is. Hoping the larger sprocket will give me more ceiling.

From dead stop I'd say the primary it's engaging around 2500 rpm. I know if the choke is on, bike idles around 2200 as it warms up and the clutch is not quite grabbing. I know I am limited by the power of the engine, but I also feel that I should be able to wind it up a bit more. Just now moved the spring over on the driven and went for a ride. No noticeable difference, other than I never broke 3800 rpm...

I read one post where someone added an additional collar ring to the driver that prevented the belt from dropping down all the way, thus raising the engagement speed... not sure if that would help me or just hurt my bottom end. But as you said, raising the stall speed may add to the top end.

I would absolutely love to buy a 212 and build it up, but money is a bit tight right now. My goal in the meantime is to work with what I have to make it the best it can be.

I will definitely look into clutch weights, seems simple enough. I attached a couple pics of the bike after I did my custom work. Made the back rack myself. It's been a fun project so far, but as I said... slippery slope!

 

[jdschwass]

Question about the driver clutch weights: my TC is just a chinese 30 series, will any of the comet parts, or other brand, fit these knockoff units?

 

[BrownStainRacing]

Thanks for the replies.
My stage 1 kit includes a 22mm Mikuni and header pipe, so there is no more governor. I have not yet removed the internal governor components. I didn't buy a kit, just a carb/intake and a pipe, and a jet kit. I can't even justify upgrading valve springs, flywheel, rod etc if I can't even get to red line as it is. Hoping the larger sprocket will give me more ceiling.

From dead stop I'd say the primary it's engaging around 2500 rpm. I know if the choke is on, bike idles around 2200 as it warms up and the clutch is not quite grabbing. I know I am limited by the power of the engine, but I also feel that I should be able to wind it up a bit more. Just now moved the spring over on the driven and went for a ride. No noticeable difference, other than I never broke 3800 rpm...

I read one post where someone added an additional collar ring to the driver that prevented the belt from dropping down all the way, thus raising the engagement speed... not sure if that would help me or just hurt my bottom end. But as you said, raising the stall speed may add to the top end.

I would absolutely love to buy a 212 and build it up, but money is a bit tight right now. My goal in the meantime is to work with what I have to make it the best it can be.

I will definitely look into clutch weights, seems simple enough. I attached a couple pics of the bike after I did my custom work. Made the back rack myself. It's been a fun project so far, but as I said... slippery slope!

You really need to get that governor out before it flys apart and destroys the engine.

Better yet, put the stock carb back on and hook the governor back up. I guarantee it'll hit 4200 rpm, if tuned right.

The reason it can't rev higher is because it's so low compression, it's only 7.3-7.7:1, there's no external upgrades worth justifying without more compression. It jus can't happen.

That spring adjustment, put more pressure on the engine, it jus don't have enough torque to pull it.

As you can see that bigger carb and header done nothing for you.

That muffler comes with a plug in it and very restrictive.
Did you remove that plug yet ????

Do you have a tach, so you can see exactly what kinda rpm you have to start with???

Gotta know where you are at, so you know which direction to go.....right???

I understand with working with what you got, I like a 196 they are so simple to build and can make plenty of power with the right compression ratio and tune.

No need to buy a predator, it's jus a bigger '"roto-tiller motor". You gonna have to turn around and do the same to it, .

A few years ago the 196 engines came with a 18cc head. This bumped the CR up to around 8.3:1. And made really good usable power, a simple head gasket swap made them over 9:1 CR. But those 18cc heads are gone now and expensive to buy from race shops.

Nowadays, they use a 20cc and 22cc head and that killed the power of the 196, dropping CR down to 7.3-7.7:1

14cc heads are cheaper nowadays, and make much more power without so much useless unneccessary parts and money.
I think the last 1 I bought was $35-$40 bare and I used all the parts outta the 20cc head to build it.

You can clip coils off the stock driver springs, but without a tach, you can go too far and the springs will stretch.

 

[jdschwass]

Thanks for the great reply. I do have a tach, so I know where I am at.
I have two mufflers, one plugged, the other not. I have been playing with both. It's a real tradeoff between power and scaring the neighbors on the next farm over!
I wouldn't say the mods have done nothing. My brother has a stock BT200x with governor tied back partly, and throttle stop removed, and I am out running him constantly on all terrain.

I am more than open to modding this engine down the road once I have the resources. I also want to keep driving my new bike in the meantime! I will look into getting a head. I agree on compression 100%... but once i'm in there, it would mean a lot more fancy parts and mods... where does it end? I know, preaching to the choir here...

I saw the 212 Tilly knockoff for sale locally at $160... figured if I am going to start doing internal work I should start with another motor... then I can swap over in an afternoon without down time.

Really appreciate the info. Such fun.

 

[BrownStainRacing]

Thanks for the great reply. I do have a tach, so I know where I am at.
I have two mufflers, one plugged, the other not. I have been playing with both. It's a real tradeoff between power and scaring the neighbors on the next farm over!
I wouldn't say the mods have done nothing. My brother has a stock BT200x with governor tied back partly, and throttle stop removed, and I am out running him constantly on all terrain.

I am more than open to modding this engine down the road once I have the resources. I also want to keep driving my new bike in the meantime! I will look into getting a head. I agree on compression 100%... but once i'm in there, it would mean a lot more fancy parts and mods... where does it end? I know, preaching to the choir here...

I saw the 212 Tilly knockoff for sale locally at $160... figured if I am going to start doing internal work I should start with another motor... then I can swap over in an afternoon without down time.

Really appreciate the info. Such fun.

I live in the country, but I know about the noise factor.

The 196 is a great lil engine. A really good 1 for a beginner to learn on.

Don't have all the clearance problems like the 212 and 224. The 212 is not bad, some rod to cam clearance issues, but overall not bad.

The 224 is a freaking nightmare. I advice a few 212 builds before building a 224 or 236.

A few yrs ago I had so many 196's from where everybody was swapping to the preds.

I built a few, gave some away, some wasn't worth building, but I was searching for that 18cc head, that sucka works good on a 212, .

If you do decide to put the 196 on the bench and build it later, save your penny's and get a real engine.

The Ducar 212 is the best out there, outta the 212's. It comes with a pvl flywheel and governored at 5300 rpm.

It don't need no upgrades. Right outta the box, it'll put a spanking on them preds.

In the Box Stock Racing class, they have to turn the Ducar down, and turn the preds up to race together. Uhm, wonder why????

That tells me which 1 might be the better engine.

The Ducar 224 is the nastiest lil engine I have every seen for a stock engine. It comes with no governor, and you have to get a throttle assembly and safer flywheel. Its a beast.

These are Kart Racing engines, not utility engines. They dont need all the fancy, dancy stage this, that crap kits.

Racing Cams and Parts | DUCAR 212 Engine | 212-1000 | DynoCams

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[jdschwass]

Thanks for that, some great engine info. Somehow I prefer the idea of building up an engine... buying one already done you only get to have half as much fun. Some good stuff to consider though.
Cheers.

 

[BrownStainRacing]

Thanks for that, some great engine info. Somehow I prefer the idea of building up an engine... buying one already done you only get to have half as much fun. Some good stuff to consider though.
Cheers.

Yeap, I can understand that.

 

[Rat]

I'm old school, I don't do stage kits. I upgrade part by part and fabricate any parts I can to reach a common goal.