212cc predeter question

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kolomootro

New Member
May 24, 2011
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Hi i was just wondering if the HF 212cc would need some kind of torque inverter
to drive the wheel.I have seen some minibikes and things on youtube with that engine without a torque inverter but maybe they work cause they have small wheels so they are geared low.
or do you think it would work with just a centrifugal clutch?
 
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BeaverRat

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Jun 27, 2011
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Lots of people use torque converters such as the TAV2 or the clones, but lots of people also just use jackshafts and centrifugal clutches...
 
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5-7HEAVEN

Well-Known Member
Aug 2, 2008
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kolomootro said:
Hi i was just wondering if the HF 212cc would need some kind of torque inverter
to drive the wheel.I have seen some minibikes and things on youtube with that engine without a torque inverter but maybe they work cause they have small wheels so they are geared low.
or do you think it would work with just a centrifugal clutch?
Click to expand...
I think that with the proper gearing, a torque converter would not be necessary.

Even if you DO install the converter, you'd still need the correct gear ratio for cruising speed and running up hill.

I liken gears only as a one-speed transmission. If gearing is too high from a standstill, acceleration is sluggish and you overheat the clutch. If gearing is too low, acceleration is brisk, you don't damage your clutch, but your top speed is lower.

The torque converter is like a two-speed transmission. Acceleration is VERY brisk with a much lower gear from a standstill(2.7:1), with a high gear(.9:1) for cruising. Multiply those ratios to your jackshaft gearing for the effective gear ratio. The .9:1 is overdrive; it will raise your jackshaft gearing for cruising speed. However, if your jackshaft gearing is too high, you can't cruise up a steep hill and you lose speed and torque. I think this is especially so if the engine governor is still on. If climbing the hill is really bad, ya might have to lower your speed and crawl up the hill using the 2.7:1 assistance.

I hope this helps.
 
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BeaverRat

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Jun 27, 2011
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5-7HEAVEN said:
I think that with the proper gearing, a torque converter would not be necessary.

Even if you DO install the converter, you'd still need the correct gear ratio for cruising speed and running up hill.

I liken gears only as a one-speed transmission. If gearing is too high from a standstill, acceleration is sluggish and you overheat the clutch. If gearing is too low, acceleration is brisk, you don't damage your clutch, but your top speed is lower.

The torque converter is like a two-speed transmission. Acceleration is VERY brisk with a much lower gear from a standstill(2.7:1), with a high gear(.9:1) for cruising. Multiply those ratios to your jackshaft gearing for the effective gear ratio. The .9:1 is overdrive; it will raise your jackshaft gearing for cruising speed. However, if your jackshaft gearing is too high, you can't cruise up a steep hill and you lose speed and torque. I think this is especially so if the engine governor is still on. If climbing the hill is really bad, ya might have to lower your speed and crawl up the hill using the 2.7:1 assistance.

I hope this helps.
Click to expand...
Yes - and luckily the CVT's do this switching automatically based on the load of the rear tire! There are an infinite amount of ratios that can be accessed by the CVT between 2.7:1 and 0.9:1.
 
wayne z

wayne z

Active Member
Dec 5, 2010
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The 212 definatly has enough power for a bike, to not need a torque converter. Even my 99cc takes off quite briskly from standstill, geared for 38 mph at 5000 rpm.

These engines have a lot of torque and power for what we are applying them to. The standard centrifugal clutch is designed to take the intermittant slipping abuse to allow the engine to get some revs to make power, similar to an automobile's hydraulic torque converter.

What you do loose with a direct drive though is the ability to slow cruise without constantly slipping the clutch. This may or may not matter much, depending on how and where one rides the thing.
 
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kolomootro

New Member
May 24, 2011
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ohio
ok thanks beaver and wayne
im not shure if ill ever get to making it though lol
but ill see if i can make it work whithout inverter so it will be simpler that way
 
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5-7HEAVEN

Well-Known Member
Aug 2, 2008
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kolomootro said:
ok thanks beaver and wayne
im not shure if ill ever get to making it though lol
but ill see if i can make it work whithout inverter so it will be simpler that way
Click to expand...
Use this as a jackshaft:

http://www.ebay.com/itm/Baja-Motors...Parts_Accessories&hash=item4cff5f65c3&vxp=mtr

Install your 10t engine clutch and 20t driven sprocket. Lengthen the 5/8" shaft and secure it to the down tube. A 10t jackshaft sprocket chained to a 36t rear sprocket will get you 7.2:1.

When you're done playing with gears only, you can re-use this jackshaft plate. Install the Comet driver/driven pulleys and belt. You will now have the Comet Torq-Verter system.

That's what I'll be doing.
 
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