heavy metal

[desertdweller]

Hi guys...first time mini builder here.....I got ahold of an old 50cc Honda knockoff...gutted it.....put a stage 2 mod predator 6.5...on it...jackshafted it...handlebars...catch can...skull...ignition cutoff switch...custom footpegs...now this porker weighs a hundred pounds easily...so before i spend MORE money,I understand the 6.1 ratio...just not sure how to get it...
Clutch..10 t
Jackshaft small...10t
Jackshaft large....14t
Rear sprocket....37
Wont move an inch.....calculator I later found says its geared for 60.768 mph..so my question is if I change the largen jackshaft sprocket to 10t...and the rear sprocket to 60t...will this give me the 25-30(plus take off power)mph I'm looking for?....or would this porker do better with a torque converter?....trying to post a pic,doesn't seem to want to let me....

 

[chancer]

Check out this jack shaft calculator. just punch in numbers till you get to 6:1 ish. I looked at your numbers it looks like if you just swap the 10 and 14 JS gears to 14 and 10you will have 5:1. Still not 6:1 but it may get you movin with the parts you already have. Also calculate the rear tire size.
https://www.affordablegokarts.com/GearCalc.php
My opinion:
Also 100lbs seems reasonable for a stage 2 212 predator your probably pushin 10hp. But I dunno.
Depending on the rear tire with the extra HP 5:1 may work

 

[desertdweller]

tire

Ya....throught about that AFTER I posted.....130-60-10.....its 15 inches across....and fat

 

[chancer]

Then I second my first post. Sounds like you know 6:1 is good all around gear ratio. My knowledge is on Karts. But 6:1 with 13" tires and 6.5 hp they say is good. Borderline with 15" tires. and 5:1 with 13" tires is borderline may work may not.
My Opinion:
But 100 lbs (if it were a kart) is light and you have more than 6.5hp. So It "may" work ok. If you swap your JS gears and go 5:1. Its worth a try. If it does not work don't keep trying or you will be buying a clutch too. Stop and buy the correct gears to get 6:1 using that calculator at AGK.

 

[OzFab]

Being a mini bike, it's much lighter than a kart so, 5:1 should be ok; the current 2.6:1 will never work...

I'm with chancer, switch the J/S gears over; if that doesn't work, switch the 14t J/S in for a 16t...

 

[desertdweller]

Thanks guys....I'm doing that right now....I'll post an update shortly....can someone tell me how to post a pic?....I'm on a tablet here,and there doesn't seem to be a place to upload.......thank again....

 

[OzFab]

How to post pics

Not that it's your fault but, I think your username may cause some future confusion; we have another member called "Desertduler"... very close

 

[desertdweller]

Heavy Metal

ok guys.finally got it,had to hook tablet to comp....this is the current status of the build...I still got some stuff to fine tune...i switched the gears as chancer suggested,but its 11:20 so,it waits till tomorrow....after Im sure the gearing works,gotta strip it down again,and move one side of the footpegs up or down 3/4" or so...repaint....soon as I get it dialed in,i'll post more photos....thanks again....

 

[landuse]

Nice bike

Just for your information, your first 2 jackshaft sprockets cancel each other out being 10T each

 

[desertdweller]

sprockets

Greetings from the desert,landuse.....ya its sinking in slowly....this gear ratio thing....I think for my next project,I'm going with a torque converter.....from what I understand,they deliver more power over a wider range.....is there a name brand (of T.V.)this group is familiar with?.....

 

[KartFab]

there aretwo main 'brands' of torque converters, Genuine Comet, and chinese knock offs of genuine comet. Just hop on ebay, bmi karts, or gopowersports.com and search for TAV2 or 30 series torque converter kit. You will see a bolt on plate with drive, driven belt, and sprocket in the kit.

Genuine comets are about $250, and knockoffs are about $135 ive used both. Also, there is the GTC brand, and i have used one of them, but wasnt a fan of their backplate - it sucks.

(PS. its not too late to just slap a torque converter on your current build)

 

[desertdweller]

Check out this jack shaft calculator. just punch in numbers till you get to 6:1 ish. I looked at your numbers it looks like if you just swap the 10 and 14 JS gears to 14 and 10you will have 5:1. Still not 6:1 but it may get you movin with the parts you already have. Also calculate the rear tire size.
https://www.affordablegokarts.com/GearCalc.php
My opinion:
Also 100lbs seems reasonable for a stage 2 212 predator your probably pushin 10hp. But I dunno.
Depending on the rear tire with the extra HP 5:1 may work

the gear swap works...well enough anyway...slow start off...but 30 ft later its grabbing higher rpm's...probably tops out in the 25-30 range,i need to swap out the 13 year old petcock(lousy fuel delivery)....and as for for this project,one last strip down,one weld(maybe 2)...paint,clear coat....then start on my next one...1970's old school chopper...twin engine....side by side....time to start scavenging parts

 

[chancer]

Please start a build thread on the twin engine chopper and document it here to share with us. That sounds really cool and Innovative.

 

[desertdweller]

twins

Totally doable......with twin engines,its not goin to be very "mini"...in fact I think I'm leaving the engines stock...to give the illusion of size....to do a '70's style " Easy Rider" chopper......even though side by side,would be easier....I don't know if its right for this model.....in tandem,they would give more to the illusion of the big V-twin......I'll know more after I start getting things together

 

[266101463]

Sprocket

Hey guys. Is an aluminum sprocket a bad idea? I can not find a steel sprocket with 48-55 teeth and 1 inch bore.
I will be going off-road, but nothing crazy.
Thanks for the help.

 

[mckutzy]

#### guy....
Start your own thread, don't hijack another's...

 

[landuse]

Hey guys. Is an aluminum sprocket a bad idea? I can not find a steel sprocket with 48-55 teeth and 1 inch bore.
I will be going off-road, but nothing crazy.
Thanks for the help.

#### guy....
Start your own thread, don't hijack another's...

Yup, please start your own thread

 

[desertdweller]

heavy metal hemi

ya know....when I built this engine,i just ordered a stage 2 mod kit(carb,air,exhaust)...when I got done,it sounded like a rat motor.....pleased but confused,i did some checking,turns out these(mod.#60363)are hemi motors...he he he ....im using super unleaded,with a 107 octane boost(in a bottle)....this thing raps out like a 2 stroke....I had no idea these motors came in hemi version....now that I do...change of plans,change of plans, change of plans....I had to special order the 16t 3/4 bore sprocket from ombwarehouse(THANX GUYS)...should be here shortly(a week?)...giving this one to my kid...already have 1 motor,and about 25ft. of 1 1/4 galvie pipe....soon as I get another motor,i can start taking measurements,and decide which way to go......

 

[mckutzy]

Higher octane gasoline is kinda a waste of money in these engines as they don't have the compression to utilize the higher rating. 89 is good enough.

 

[Desertduler]

Higher octane gasoline is kinda a waste of money in these engines as they don't have the compression to utilize the higher rating. 89 is good enough.

Exactly, and low compression engines with high octane fuel tend to go flat on the top end RPM levels. If a engine does not have the compression ratio to squeeze the high octane fuel enough there is a waste of BTU's, there is a BIG misunderstanding of octane rating of fuel and how it really relates to power output and why engines with higher compression ratios need higher octane fuel and engines with lower compression ratios do not.