9 hp mini bike, is it possible?

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Johnnyboy

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Hey guys,
Over the past few weeks, I've been formulating some potential plans for a high powered mini bike. However, I've encountered some serious issues that might impact the design. My plan is to buy 6.5 predator engine and mount it to the frame of a baja doodlebug/warrior. However, I plan on doing some modifications to he engine (ie. new air filter, exhaust, spark plug, etc.) that would push it over the 8hp mark. I also plan to use a torque converter on the bike, but from what I understand I would need a comet 44 series to RELIABLY run the bike. And here are where my questions come in:

1. I know I kneed a jackshaft for the driven assembly, but how would I know where to mount it so that it is the correct distance away from the drive unit?

2. Would I have to make any significant modifications to the frame to accomodate for the TC?

Thanks in advance!
Johnnyboy
 
2SlickNick

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You can use the 6.5hp engine and mod the heck out of it. You do not need a 40 series TC.
A 20 or 30 series will work with a backplate you can get the whole TC ( with backplate and JS included ) for $150 or less. I have not added TC to my doodle bug yet, but you shouldn't have to do anything to the frame.
 
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jdblood202

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Johnnyboy said:
Hey guys,
Over the past few weeks, I've been formulating some potential plans for a high powered mini bike. However, I've encountered some serious issues that might impact the design. My plan is to buy 6.5 predator engine and mount it to the frame of a baja doodlebug/warrior. However, I plan on doing some modifications to he engine (ie. new air filter, exhaust, spark plug, etc.) that would push it over the 8hp mark. I also plan to use a torque converter on the bike, but from what I understand I would need a comet 44 series to RELIABLY run the bike. And here are where my questions come in:

1. I know I kneed a jackshaft for the driven assembly, but how would I know where to mount it so that it is the correct distance away from the drive unit?

2. Would I have to make any significant modifications to the frame to accomodate for the TC?

Thanks in advance!
Johnnyboy
Click to expand...

What style doodlebug frame are you using? I have a predator 212cc swap in a older style doodlebug frame. Are you planning on pulling the motor apart/taking out the governor, or just mainly bolt-ons? Are you dead set on using a comet 44 series tc? I'm running a jackshaft setup that hotrodminibike.com sells and it's been great. What all do you plan on doing to the motor? I found that with just bolt-ons, (intake, header, jetted carb), the bike would get up to it's top governed speed fast, then bounce off the governor the rest of the time, making the ride a bit choppy. I pulled the governor, replaced the rod and flywheel with billet parts, (along with some other mods), and now it's pretty much perfect. Smooth strong pull all the way up the power band and scary fast for a bike that small! Also, good plan on the hydro brake. Great upgrade and awesome stopping power, although I highly recommend swapping the pads to some heavy-duty pads, the stock pads it comes with do not stand up to repeated high speed stops. Good luck with your build, if you have any questions about what I did with my build just shoot me a pm. Here's a couple pics of my bike:



My entire mod list: Non-hemi predator 212cc, 1" header pipe, air filter, jetted carb, ARC billet rod and flywheel, dyna mod 2 camshaft, gx160 14cc cylinder head with some porting/milling work done with 18lb valve springs, high compression head gasket, jackshaft kit with 60 tooth rear sprocket, 8" Azusa tristar front wheel with street tires on both wheels, and hydraulic brake setup.
 
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Johnnyboy

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2SlickNick said:
You can use the 6.5hp engine and mod the heck out of it. You do not need a 40 series TC.
A 20 or 30 series will work with a backplate you can get the whole TC ( with backplate and JS included ) for $150 or less. I have not added TC to my doodle bug yet, but you shouldn't have to do anything to the frame.
Click to expand...

So you're saying that the 30 could stand up to the beating?
 
supermanotorious

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I put 30 series on 13hp (420cc) engines for wakeboard winches and they stand up just fine. That being said, we only run them at full RPM for 45 second intervals or so.
 
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I modded my gx200 (Predator 6.5 equivalent) to 10-11hp, governor removed,stock springs... and I use a TAV2 (30series 'kit'). I travel alil over 50mph. The frame/power train/myself weight right at 300lbs total weight. The axle spins a set of 16" wheels w/ a 4.5:1 ratio.

... so it IS possible... just gotta ensure the wheel(s) dont hinder the continual rotation of the 'driven'... which will burn up/dent a belt, if it does.
 
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Johnnyboy said:
So if I use 10 inch wheels I should be fine?
Click to expand...

I'd say yes:thumbsup:. BUT... it 'does' depend upon your gearing...

Lets hypothesize... you remove governor, leave springs, boost hp = 8-9hp at 5k rpm's on 10"s... and total weight being 250lbs(guesstimate). Depending on the top speed you were 'wanting'... you would gear accordingly.

EVERY setup is slightly if not significantly different... I 'know' 'my' setup's limits. Weight being the BIG killer of TAV2's... which is due to 'bad' gearing. Id have to say you should have no issues w/ a TAV2 w/ a modded clone (no more than 10-12hp), on a mini bike/scooter. :thumbsup:
 
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