What is safe RPM for predator 212cc and which TAV is best?

[JoePapa]

Hi. I need your expertise.

RPM related questions:
----------------------------------------------------------
I've read multiple articles on here and it seems like the HF 212cc Predator is a good motor for the price and it looks like there are a few upgrades out there to crank up the power a little. A few posts mention removing the governor to get more RPM but what is the safe RPM of the factory flywheel and what is the safe RPM of the rod?

Eventually I'll get this - 6625 ARC Billet Flywheel, Predator, Non-Adj.

However, what is my safe RPM for the mean time and will I need to update the rod when I get a new billet flywheel?


Converter related questions:
----------------------------------------------------------
Concerning Torque converters, do different torque converters offer different low and high end ratios? So instead of 2.7:1 down low and 1.10:1 up top, can I get one that is in the 3range down low and a little more up top? Probably a silly question but I thought I saw one that was in the 3:1 range for low end and I can't find it again. Last - any brand preferences?

I plan to upgrade the Predator 212cc motor by doing what seems to be the common mods of carb jetting changes, valve springs, ratio rockers, air filter, and header - possibly bump compression by using a thinner head gasket. If I get close to 9hp out of the motor instead of the factory 7, does this change my converter choice?

I don't know if this is needed but the rear sprocket is 60 tooth and the chain appears to be a 420 chain.


My other hobby is drag racing and I need to kick up the power a little to make sure I have one of the quicker pit bikes out there but it's got to be reliable because my son will be riding it too. I think these mods will be a good balance.

 

[JoePapa]

Any feedback on this?

If it was a V8, I'd know but I'm new to hot rodding single cylinder motors...

 

[zipseattle]

Just my 2 cents...

The safe rpm for your engine, without any changes to the rod or flywheel, is the governed one.

Torque converters are approximately 3 to 1 (crankshaft rpm to output rpm) auto adjusting to about 1 to 1. The springs in the driven pulley can be adjusted to change the engagement rpms, but I've never done that.

On a minibike, a predator with a TC will have plenty of low end torque - sounds like with your rear sprocket it would be a wheelie machine.

On my mini, I went with a smaller rear sprocket, a bone stock motor (6.5 HP) and a Torque Converter. It accelerates nicely, and will do just under 50 mph.

OldMiniBikes has torque converters.

 

[JoePapa]

Thank you for the info.

On the RPM - if I replace the flywheel do I need to also replace the rod? I've read some threads where folks are talking 6k rpm which seems rather high to me for this type of a motor. If normal RPM is 3600 and I can get to 5k with a flywheel change that will probably be good enough to kick bootie and provide a decent top end speed and save some reliability.

I hope you're right on the torque. I was disappointed with the lack of torque this original motor had with just a clutch. I put a used jackshaft on there and that made a nice difference but I lost top end so I'm hopeful the converter will step it up a notch and return some of the top end.

Thanks for the help. Please let me know the thoughts on the rod. I may be able to up the governor to a desirable RPM - I'd be happy with that.

 

[zipseattle]

If it was me, I'd get the torque converter, and leave the predator stock to start. Ride it for a while that way, then decide if you want to mod the motor. Especially if my kid was riding it.

I've never had the desire to crack the motor and make a bunch of changes, so can't help there.

Food for thought, but its your call...

http://www.oldminibikes.com/forum/h...nor-your-engine-OldMiniBikes-please-read.html

 

[JoePapa]

Thanks. That video says a lot! They're lucky nobody got seriously injured, especially since you're sitting on top of that thing. In the drag racing world, that looks about like trying to race a stick shift car without a scatter-shield - not a smart idea. So warning understood and will be adhered too.

I'd much rather use the governor like a rev limiter but increase it to say 5k once I get a new flywheel if I still need to increase the power level once we get the new motor and converter on. I'll start slow and motor and converter at first and go from there. Having said that - does one converter have more gearing affect than another? It seems that they're all pretty close and they're all about 200 dollars.

 

[zipseattle]

The Comet 30 Series is the only one I am familiar with. The 30 Series includes front and rear pulleys and belts that can be bought separately based on application (which is what I did), as well as the original Torq-A-Verter (TAV) which is everything in a self contained assembly with steel backing plate that bolts on to the engine. The TAV was replaced by the TAV2 which had a cast aluminum backing plate. There are also Chinese copies.

I'd go with the Comet TAV or TAV2 if you can find one. They can come with a #35 chain sprocket, or a #41. The #41 will be compatible with a #420 chain/rear sprocket - that's what I have. You can also change them from one to the other if needed.

TC's are the way to go for driveability, love mine. Here's a link to my mini, it will spin the tire in gravel, cruise all day at 35, and tops out just under 50.

http://www.oldminibikes.com/forum/project-logs/8323-zipster-build-8.html

 

[JoePapa]

Thanks man.

I found a converter that appears to be specific to the Predator 212 motor.

GTC Torque Converter Kit for Predator 6.5 engine TAV2


Nice ride you have there. There's more go fast goodies for these things than I realized.

 

[Harleys Papa]

Its a few more dollars but I would go with the proven Comet TAV2 - Torque Converter - 3/4" 10T #40/41 - 218353A you will need to modify the backing plate but its not a big deal :thumbsup:

 

[JoePapa]

Thanks. I'll check it out. Why the preference - is it name brand vs generic or is there a functionality aspect or reliability advantage?

 

[funky ole]

comet usa is no longer. all went overseas as i know it anyway.
that said,the tav series with the metal backing plate won't fit flat on a clone engine,it must be angled down to clear the cylinder. the tav is 3 to 1 start, then goes to .9 overdrive. if your frame alows,i definetly would put a tav on it.makes for great riding.

 

[Mark G]

Thanks. I'll check it out. Why the preference - is it name brand vs generic or is there a functionality aspect or reliability advantage?

The main reason you should go with the actual Comet is it is the real deal. Some people have had the knockoffs work ok, but many more have had problems. poor quality being the most common complaint. You are better off spending a few more bucks on a genuine Comet, less frustration:thumbsup:.

comet usa is no longer. all went overseas as i know it anyway.

This is not true. After they went bankrupt Comet was purchased by a company in Wisconsin and had moved operations here, they even got some of the Comet employees- and they are back in business, making genuine Comet parts here in the USA:thumbsup: