Diagnosing an Issue, Coleman B200R with Tillotson 212

[Boss302]

Hello All-- new to the forum and hoping to get some input from more experienced folks.

After wanting a mini bike since I was a kid, I was at Tractor Supply and couldn't resist the urge to take a Coleman B200R home with me (I'm almost 40 now). Knowing nothing about mini bikes, I figured this would scratch the itch in factory condition. After realizing it only went 23-24 MPH though, I couldn't resist modifying it.

Flash forward to 2 months later, it now has a Tillotson 212, predator stage 1 carburetor, cone filter, header pipe, 30 series torque converter with 12 tooth sprocket, and 42 tooth rear sprocket. It'll now hit up to 50 MPH on a slight downhill grade.

Here is the issue: I bought the Tillotson 212 Stage 1 through GPS, and it was supposed to have the governor removed. I always felt that even at top speed, the engine barely sounded like it was breaking a sweat, so I installed a tachometer and sure enough, it will not rev past 3500-3600 RPM. This engine was a bit suspect from day one (it had a defective carb right out of the box, and was missing an oil dipstick), so I'm thinking that GPS charged me for the engine with the governor removed, but sent me a totally stock unit (I'm assuming accidentally). In it's current form, I have the carb dialed in nicely. It fires up on the first or second pull, idles perfectly, and cruises without issue, so I know its not an air/fuel issue.

Am I off here? Is there any way the governor on this motor is actually removed, and something like the torque converter is limiting my RPM from getting above 3600? It seems suspicious though, given that I believe the governor on these motors is meant to limit revs from exceeding 3600 RPM exactly.

Any input is greatly appreciated.

 

[ezcome-ezgo]

Evidence of the presence of the governor is external. This linkage:

 

[Boss302]

Evidence of the presence of the governor is external. This linkage:

View attachment 150318

It's a little trickier than that-- they state on the product page "Some of the external "governor" linkage is left for ease of use with stock style carb." so the only way to really tell would be to open the engine up I believe.

 

[Grizzlymi]

It's a little trickier than that-- they state on the product page "Some of the external "governor" linkage is left for ease of use with stock style carb." so the only way to really tell would be to open the engine up I believe.

Correct. The only way to truly tell would be to open the side case and look. Make sure there are no loose parts (governor gear and arm is completely removed) and I would recommend removing the external arm and taping and plugging the hole with a bolt and lok-tite.

 

[Grizzlymi]

On a side note, you will have to reconfigure the throttle with the external arm removed.

 

[bob58o]

I assume you attempted to rev the engine with the rear lifted off the ground. Just to make sure the engine still can’t rev over 3600 rpm with minimal load?

I’ll look into your gearing. You’re getting 40-50mph with a small engine. Your sprockets might be limiting your rpm’s because you are already going near top capable speed when engine is making peak horsepower.

You might not be baking enough beans at 4000 rpm to increase spreed from 45 mph to 50.

 

[bob58o]

19” Tires ? = 4.97 foot circumference
42T / 12T = 3.5 :1 Gear Ratio
30 series TC has 0.9 :1 Overdrive Ratio

If fully shifted into overdrive, you gear ratio would be 3.15 : 1.

At 3600 RPM and 3.15 :1 gear ratio with 19” tires…
64 MPH

3600 RPM and 3.5 :1 Ratio…
58 MPH

3600 RPM and 4.5 :1 Ratio…
45 MPH

Not getting into overdrive. Staying partially shifted at ratio around 4.5 : 1. TC Ratio of 1.3 :1 , instead on 0.9 :1

Seems you are geared for too much speed.
I’d go 60T on the back instead of 42T and see if you can’t get that TC to shift into high gear. It appears that the engine is making too little torque with really big tires and an unfriendly gear ratio to fully shift out the TC into high gear.

 

[Boss302]

Correct. The only way to truly tell would be to open the side case and look. Make sure there are no loose parts (governor gear and arm is completely removed) and I would recommend removing the external arm and taping and plugging the hole with a bolt and lok-tite.

Thanks

 

[bob58o]

With 60T and 12T ratio is 5 :1.
With 0.9 :1 overdrive, final ratio would be 4.5 :1.
At 3750 RPM, speed would be 47 mph.

Just about same rom and speed as before, but now the TC is fully shifted. And the ratio gives you a better chance to increase rpm above thst. Although spending your time in the rpm range above peak HP isn’t ideal either.

This gearing will give you best shot at top speed near peak HP…

 

[Boss302]

19” Tires ? = 4.97 foot circumference
42T / 12T = 3.5 :1 Gear Ratio
30 series TC has 0.9 :1 Overdrive Ratio

If fully shifted into overdrive, you gear ratio would be 3.15 : 1.

At 3600 RPM and 3.15 :1 gear ratio with 19” tires…
64 MPH

3600 RPM and 3.5 :1 Ratio…
58 MPH

3600 RPM and 4.5 :1 Ratio…
45 MPH

Not getting into overdrive. Staying partially shifted at ratio around 4.5 : 1. TC Ratio of 1.3 :1 , instead on 0.9 :1

Seems you are geared for too much speed.
I’d go 60T on the back instead of 42T and see if you can’t get that TC to shift into high gear. It appears that the engine is making too little torque with really big tires and an unfriendly gear ratio to fully shift out the TC into high gear.

My previous set up with the 30 series TC was a 10 tooth sprocket up front and a 60 tooth rear sprocket. With that set up I was topping out at 36-37 MPH, which is why I went down to the 42 tooth rear and 12 tooth up front. That picked up about an additional 12-13 MPH.

I put a Tillotson 196R ignition coil on tonight, already has an AutoLite 3910X plug, and I've got the Tork-Zilla driver in the mail. Hopefully those help out. It's a heavy bike, about 175lbs with a full tank, and I'm about 200lbs, so it may just need more power. We shall see.

 

[bob58o]

Maybe you are only revving to 3600 RPM limit?
6:1 ratio you had before would put you right around 37-38 mph at 3600 RPM with a fully shifted TC.

Did you test if it revs past 3600 RPM when the rear tire is off the ground?

 

[panchothedog]

If you already have the sprockets ( 10 & 12 tooth, and a 42 & 60 tooth ) you should try a different combination. At 12X42 your gearing is way too tall for the engine to get wound up very good. Regardless of gearing ( low with high engine rpm, or high with engine lugging along ) there is a maximum top speed. You are probably putting out about 9 horse power. 50 mph is probably all she's got. Actually that's darn fast for a mini bike. I have a similar sized and weight bike with a pretty hopped up 196. Probably 11 to 12 hp. 10 X 60 gearing. I'm about 215 lbs. It tops out at 44 mph, but will get there pretty quickly and climb just about anything. Very happy with its performance. How much do you think you need? How thick is your wallet?

 

[Boss302]

Maybe you are only revving to 3600 RPM limit?
6:1 ratio you had before would put you right around 37-38 mph at 3600 RPM with a fully shifted TC.

Did you test if it revs past 3600 RPM when the rear tire is off the ground?

It does seem to rev higher with the rear tire off the ground. I'm going to install a Tork-Zilla driver and a Tillotson 196R ignition coil this weekend to see what that does.

 

[Boss302]

If you already have the sprockets ( 10 & 12 tooth, and a 42 & 60 tooth ) you should try a different combination. At 12X42 your gearing is way too tall for the engine to get wound up very good. Regardless of gearing ( low with high engine rpm, or high with engine lugging along ) there is a maximum top speed. You are probably putting out about 9 horse power. 50 mph is probably all she's got. Actually that's darn fast for a mini bike. I have a similar sized and weight bike with a pretty hopped up 196. Probably 11 to 12 hp. 10 X 60 gearing. I'm about 215 lbs. It tops out at 44 mph, but will get there pretty quickly and climb just about anything. Very happy with its performance. How much do you think you need? How thick is your wallet?

I've had different combos on it before (10 and 60, 10 and 42, and now 12 and 42) and the current setup is the best.

The Tillotson Stage 1 motor is rated at 11.5HP, and I've got a couple extra add-ons beyond that, so definitely pushing more than 9HP. As for how much I need...that is a good question. I'd like to be able to cruise around 55 MPH and get up to 60 MPH if I really want to. My wallet can handle it.

I'll see what this Tork-Zilla driver and Tillotson 196R ignition coil do once I get them on this weekend or early next week.

 

[panchothedog]

What other add-ons do you have on your engine? Just curious. I hope the ignition coil helps you find some extra rpm. I have a juggernaut driver on one of my karts with a very built predator 212. I'm fairly certain it and the tork-zilla are quite similar, ( sold by different shops) but they both advertise the same thing. Frankly I'm not impressed. Would never spend that much money on another one. A stock driver with lighter weights and different springs ( big selection to choose from ) can be done for about half the price of the zillas or the jugas. Save your stock driver and look into what I'm talking about. I like my tweaked stockers A lot better than the juggernaut. FWIW, I have 4 karts. All with built engines and modified drivers, or the one with the juggernaut. Just trying to help you find some more top end speed.

 

[Boss302]

What other add-ons do you have on your engine? Just curious. I hope the ignition coil helps you find some extra rpm. I have a juggernaut driver on one of my karts with a very built predator 212. I'm fairly certain it and the tork-zilla are quite similar, ( sold by different shops) but they both advertise the same thing. Frankly I'm not impressed. Would never spend that much money on another one. A stock driver with lighter weights and different springs ( big selection to choose from ) can be done for about half the price of the zillas or the jugas. Save your stock driver and look into what I'm talking about. I like my tweaked stockers A lot better than the juggernaut. FWIW, I have 4 karts. All with built engines and modified drivers, or the one with the juggernaut. Just trying to help you find some more top end speed.

Not much-- just an upgraded carb over what came on the motor and header pipe. I've heard people rave over the juggernaut/tork-zilla, and other people say it was a waste of money. I figured it was worth it to just try it out to see what happens. Worse case scenario I'm out $80.

I put the 196R ignition coil on last night. Although I didn't get to test drive yet, I did notice a big difference in the idle. Idles much smoother and at a lower RPM than before.

 

[Boss302]

Some data points for anyone considering a Tork-Zilla/Juggernaut:

I got the Tork-Zilla installed today and took the bike out for a drive. My bike makes maybe 11.5-12HP, so not the more heavily modified motor these drivers were intended for. First observation was that it did increase how high my motor revs-- from topping out at 3600 RPM with the standard 30 series driver all the way up to 4900 RPM with the Tork-Zilla. What's interesting though is that while the Tork-Zilla seemed to deliver power in a smoother fashion, the bike felt actually less torque-y from a stop, and I lost about 5-6 MPH in top end power (44-45 MPH with the Tork-Zilla vs. 50 MPH with the standard 30 series driver).

I swapped my standard 30 series driver back on just to confirm, and sure enough I was back to touching 50 MPH on a slight downward grade. I plan to buy a Predator 212 motor to fully build over the winter, so I'll keep the Tork-Zilla and try it again once I have a motor that it's meant for.

Also, some notes on the gearing-- these are the results I've had with different set ups and the same Tilltoson 212 motor:

Factory Jackshaft Setup and 60 tooth rear: 32 MPH
30 Series with 10 tooth and 60 tooth rear: 38 MPH
30 series with 10 tooth and 42 tooth rear: 48 MPH
30 series with 12 tooth and 42 tooth rear: 50 MPH

 

[panchothedog]

That seems very strange, to increase top end rpm by 1300 and loose 5 mph in speed. Just out of curiosity ( because I don't have a tach ) on any of my stuff, when you posted different gear ratios and speeds was your engine at the same rpm when it topped out? Put a set of light weights ( aluminum, $35 ) in your stock driver, even if you don't change springs. Takes maybe 15 minutes. It will raise the engagement rpm by about 800 rpm and keep it there. At the increased rpm the engine is making more horse power and will pull harder and very likely increase your top speed.
Have fun with your build this winter. I enjoy building them as much as riding them.

 

[Boss302]

That seems very strange, to increase top end rpm by 1300 and loose 5 mph in speed. Just out of curiosity ( because I don't have a tach ) on any of my stuff, when you posted different gear ratios and speeds was your engine at the same rpm when it topped out? Put a set of light weights ( aluminum, $35 ) in your stock driver, even if you don't change springs. Takes maybe 15 minutes. It will raise the engagement rpm by about 800 rpm and keep it there. At the increased rpm the engine is making more horse power and will pull harder and very likely increase your top speed.
Have fun with your build this winter. I enjoy building them as much as riding them.

Yeah, I'm not sure how to explain it. The engine was definitely revving higher, it just didn't seem to want to go any faster.

I didn't have the tach for those first two setups, so I'm not sure. I think the engine revved higher with the factory jackshaft setup though, judging by sound alone.

Where do you get those weights from?

 

[panchothedog]

Go Power Sports sells them. I think O M B Warehouse also has them. Just go to the section for torque converters, and then parts. The stock ( heavy ) ones are Zinc, the lighter ones are aluminum.