212cc swap, torque converter, top speed only 32?

Mini Bike & Go-Kart Parts

#1
So after having some issues with my coleman 200cc I decided id just swap a new engine in it, picked up a ducar 212cc, swapped in fairly simple, got everything back up and running, bike has no issue ripping wheelies at low speeds, lots of torque, but just seems like it should have more top end?

Tried some top end runs and just seems to stop at 30-32 mph?

Could this just be the design of the torque converter? belt seems to reach its limit and thats it, need a new belt? Do they stretch out over time?

Seems like the engine should have plenty of power to go much faster so thinking has to do with the torque converter/belt maybe
 
#2
The Ducar is governed at 5300 rpm whereas the original engine would have been governed at 3600 rpm. In theory, that swap should have provided a significant increase in top speed. If you don't already have one, get a tachometer to know what rpm the engine is reaching. Also make sure the throttle is opening fully.

I'm not an expert on torque converters but I know of members exceding 40 mph on stock Mega Moto MM-B212 Pro Series bikes with the stock (3600 rpm) 7.5 HP Lifan 212, the only mod being the removal of a speed limiting spacer/bushing in the driver (a MM exclusive thing, aftermarket torque converters don't have one).
https://www.oldminibikes.com/forum/index.php?threads/pro-series-mini-bike.166130/page-5#post-1214087
 
#3
The Ducar is governed at 5300 rpm whereas the original engine would have been governed at 3600 rpm. In theory, that swap should have provided a significant increase in top speed. If you don't already have one, get a tachometer to know what rpm the engine is reaching. Also make sure the throttle is opening fully.

I'm not an expert on torque converters but I know of members exceding 40 mph on stock Mega Moto MM-B212 Pro Series bikes with the stock (3600 rpm) 7.5 HP Lifan 212, the only mod being the removal of a speed limiting spacer/bushing in the driver (a MM exclusive thing, aftermarket torque converters don't have one).
https://www.oldminibikes.com/forum/index.php?threads/pro-series-mini-bike.166130/page-5#post-1214087

Gotcha, ordered a tach off amazon so will see what its showing.

Checked the throttle, seems to be opening fully to me as far as I can tell.
 
#4
Looked at it again and noticed I spaced out the one side more than the other to align the chain so added a washer to the other side and seemed to help, got it to register 38 mph top speed on my phone GPS that time.

Still seems kinda on the low side to me but not sure what to expect.
 
#5
Looked at it again and noticed I spaced out the one side more than the other to align the chain so added a washer to the other side and seemed to help, got it to register 38 mph top speed on my phone GPS that time.

Still seems kinda on the low side to me but not sure what to expect.
Another thing you could check: remove the chain, prop the wheel up and spin it to check for drag. The brake or bearings could be dragging.

Even the chain could hold you back a bit if it's not in good condition and/or lubricated.
 

toomanytoys

Well-Known Member
#6
Is the throttle stop screw backed out? Out of the box mine would only hit about 4000rpm. Backed the throttle stop out to get maximum pull on the linkage and hit 5800rpm with the back wheel off the ground.

I let off the throttle around 50mph.

Now ill say this. I tip the scale at 180. My buddy is around 230-240. He can only get 40 out of it.
 

SAS289

Well-Known Member
#7
Is the throttle stop screw backed out? Out of the box mine would only hit about 4000rpm. Backed the throttle stop out to get maximum pull on the linkage and hit 5800rpm with the back wheel off the ground.

I let off the throttle around 50mph.

Now ill say this. I tip the scale at 180. My buddy is around 230-240. He can only get 40 out of it.
What gearing are you using?
 

SAS289

Well-Known Member
#9
Yeah I can't put GPS speedo on my work phone so I have to use max RPM and a speed calc. With the belt shift you should be lower than 4300 at 50 mph. More like 4K.

Here's the numbers I put in. Can someone correct me if I'm incorrect?

19 inch tire.
60 tooth rear sprocket---- With 9/60 gearing if the torque converter shifts all the way to high. 6.6 x .9=6.0 (5.94)
10 tooth---- Used this number to get the 6/1 from the overdrive calculation.
5000 RPM---- The max RPM at top speed from the tach. (At least where I backed off at). Engine is a 196 governed to around 5K.
Top speed should be around 47 MPH according to the speed calc.
 
#10
Cvt + gear calculator? Never seen one
Some things i know about cvts.
Cvt is 3/1 ratio variable inside of mechanical gear ratio / final drive
You cant rev engines to max rpm with cvts while back wheel is in the air..
Cvt itself is a governor
Cvt work better with more load (weight)
The aluminum washer that goes over bronze washer in cvt drive pulley is a speed limiter remove it forever
Thats all i can think of at the moment. .maybe this helps
P.s. cent clutch direct drive is boss...for many reasons cvts blah.
Cvts are for electric motors they dampen instant power ♻ or do opposite move heavy loads slowly with tiny motors i.e. 1.2L cars that weigh 4000 lbs use cvts
Im drunk lol
With smooth (er) transition


https://www.bmikarts.com/Go-Kart-Gear-Ratio-Speed-Calculator
 
#11
The Ducar is governed at 5300 rpm whereas the original engine would have been governed at 3600 rpm. In theory, that swap should have provided a significant increase in top speed. If you don't already have one, get a tachometer to know what rpm the engine is reaching. Also make sure the throttle is opening fully.

I'm not an expert on torque converters but I know of members exceding 40 mph on stock Mega Moto MM-B212 Pro Series bikes with the stock (3600 rpm) 7.5 HP Lifan 212, the only mod being the removal of a speed limiting spacer/bushing in the driver (a MM exclusive thing, aftermarket torque converters don't have one).
https://www.oldminibikes.com/forum/index.php?threads/pro-series-mini-bike.166130/page-5#post-1214087
Ducar is governed at 5k ..dang didnt know that...
 
#13
Yeah I can't put GPS speedo on my work phone so I have to use max RPM and a speed calc. With the belt shift you should be lower than 4300 at 50 mph. More like 4K.

Here's the numbers I put in. Can someone correct me if I'm incorrect?

19 inch tire.
60 tooth rear sprocket---- With 9/60 gearing if the torque converter shifts all the way to high. 6.6 x .9=6.0 (5.94)
10 tooth---- Used this number to get the 6/1 from the overdrive calculation.
5000 RPM---- The max RPM at top speed from the tach. (At least where I backed off at). Engine is a 196 governed to around 5K.
Top speed should be around 47 MPH according to the speed calc.
10tooth on front slowing you down
Circle to small .
Plus i think thats theoretical. .doesnt account for weight, wind, rolling resistance
If you had heat sensor that front sprocket is hot from tight chain cirlce,
all the load is there....i bet front crank seal leaks?....they melt.
Im just spit ballin..who knows
https://www.bmikarts.com/Go-Kart-Gear-Ratio-Speed-Calculator
 

SAS289

Well-Known Member
#14
10tooth on front slowing you down
Circle to small .
Plus i think thats theoretical. .doesnt account for weight, wind, rolling resistance
If you had heat sensor that front sprocket is hot from tight chain cirlce,
all the load is there....i bet front crank seal leaks?....they melt.
Im just spit ballin..who knows
https://www.bmikarts.com/Go-Kart-Gear-Ratio-Speed-Calculator
The 10 tooth is a standard that comes with the CVT for a 420 chain. This is what most people run. Never heard of anyone using larger than 10 tooth with a 420 chain.

My gearing choice is 9 tooth 60 tooth. The 10 tooth came off before the CVT was bolted on. I use 10 in the speed calc to satisfy the 6/1 gearing that I end up with once the CVT shifts to high.
 

toomanytoys

Well-Known Member
#15
Cvt + gear calculator? Never seen one
Some things i know about cvts.
Cvt is 3/1 ratio variable inside of mechanical gear ratio / final drive
You cant rev engines to max rpm with cvts while back wheel is in the air..
Cvt itself is a governor
Cvt work better with more load (weight)
The aluminum washer that goes over bronze washer in cvt drive pulley is a speed limiter remove it forever
Thats all i can think of at the moment. .maybe this helps
P.s. cent clutch direct drive is boss...for many reasons cvts blah.
Cvts are for electric motors they dampen instant power ♻ or do opposite move heavy loads slowly with tiny motors i.e. 1.2L cars that weigh 4000 lbs use cvts
Im drunk lol
With smooth (er) transition


https://www.bmikarts.com/Go-Kart-Gear-Ratio-Speed-Calculator
10tooth on front slowing you down
Circle to small .
Plus i think thats theoretical. .doesnt account for weight, wind, rolling resistance
If you had heat sensor that front sprocket is hot from tight chain cirlce,
all the load is there....i bet front crank seal leaks?....they melt.
Im just spit ballin..who knows
https://www.bmikarts.com/Go-Kart-Gear-Ratio-Speed-Calculator
I ran the tiniest 8 tooth on my mb212 pro with a 50 tooth rear. It would fly. 20" tires, 8/50, 5000rpm on the tach and 46mph on the GPS speedometer. Never had an issue with the sprocket. It was 5 dollars vs 50 for the rear sprocket. I figured I'd try it out.

I've read all this before. Wind resistance, tire compound..... We are building minibikes not 200mph super bikes.

How is the front sprocket going to melt your crank seal when it's mounted on the behind the driven pulley 12" away from the crank shaft?
 

SAS289

Well-Known Member
#17
I don't get the obsession with top speed. Are you guys running these bikes at Bonneville?
I agree about the top speed thing. I only figure it out and post it as a reference to others of what my combo gets.

When I did a ride trip in June 99% of the ride was under 35 mph. I did one top speed run just to get a max RPM on my tach. To me what happens in between 0 and 30 is much more important than top speed.
 

SAS289

Well-Known Member
#18
I ran the tiniest 8 tooth on my mb212 pro with a 50 tooth rear. It would fly. 20" tires, 8/50, 5000rpm on the tach and 46mph on the GPS speedometer. Never had an issue with the sprocket. It was 5 dollars vs 50 for the rear sprocket. I figured I'd try it out.

I've read all this before. Wind resistance, tire compound..... We are building minibikes not 200mph super bikes.

How is the front sprocket going to melt your crank seal when it's mounted on the behind the driven pulley 12" away from the crank shaft?
While waiting for my 60 tooth to come in I ran 8/50 and it worked nice. Was thinking about putting a TAV on my other bike and run 8/50 with the stock 196 governed to around 4500 or so.
 

toomanytoys

Well-Known Member
#19
I don't get the obsession with top speed. Are you guys running these bikes at Bonneville?
As long as I can hit about 40 I'm happy. I use my bikes to travel around town. Down to the dollar store, down to my parents, or just cruise the gravel roads. Speed limit around is 40. That let's me keep up with traffic and not be a nuisance. Small town. No one cares and just about every one uses some sort of non-legal bike, atv or sxs to get around town.
 
#20
Is the throttle stop screw backed out? Out of the box mine would only hit about 4000rpm. Backed the throttle stop out to get maximum pull on the linkage and hit 5800rpm with the back wheel off the ground.

I let off the throttle around 50mph.

Now ill say this. I tip the scale at 180. My buddy is around 230-240. He can only get 40 out of it.

Yep backed that out.

So I got the tach on it today, with wheel in air, no load, revs to 5k and governor kicks in.

With my riding the bike full out it would settle around 3600-3700 RPM.
 

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