Predator 212cc Worksman Adaptable motortrike

[StabbyJoe89]

Hey guys,

I'm building a Worksman Adaptable tricycle into a motorized trike using a 212cc Predator 6.5hp engine

I have a very thorough knowledge of bicycles, but pretty much haven't got a clue about engines apart from the basic mechanics of how they function. I'm getting a Predator from Harbor Freight, running it with a torque converter, and purchasing all the other gasbike.net trike kit parts from ebay/amazon. I'm gonna use this trike to commute to/from work, I'm aware it's not street legal. Planning to cruise at ~15-20mph in the bike lane with lights/reflectors and follow traffic laws to appease cops.

I'm posting here because I need some advice, I was wondering what a good sprocket size would be to pair with a 10T driver?
Tricycle weight with rider, engine, and gear will be about 330lbs. The 212cc 6.5hp engine is rated at 3800rpm, 8.1 ft-lbs@2500rpm, I'll be using a torque converter. I'd like to be able to cruise at 20-25mph and care more about less engine strain and durability rather than top speed. Choices I see with the kits seem to be 36, 40, 44, 48 mainly?

Also, I want the engine to run as quietly as possible since I'll be in traffic. I was wondering if it's safe, in terms of backpressure and stuff, for me to only install an aftermarket exhaust pipe and muffler. Down the line, I do plan to also get an air filter, springs, and re-jet kit to improve performance, but I was wondering if it's safe to wait on those and for now just run the engine as is, but with an aftermarket torque converter and exhaust & muffler to quiet things down.

Thanks so much!
Plamen

 

[chancer]

That all sounds like a good plan. Of course you can leave it all stock.
I have seen a couple goofy configurations of a Car muffler attached to a small engine.
Not that it is a goofy idea, it will definitely keep it quiet and wont hinder performance.
Just what Ihave seen were hack jobs.

Sorry I am not aware of the proper gearing for this project. But I like the idea. Best of luck.

 

[mckutzy]

What's the rear axle look like with out the box on the back..
What size is the axle...
I'm thinking the tried and true 6:1 ratio even with the TC.

With a motor of this size... Your going to need brakes... Good brakes.
Mechanical brakes for typical gokarts will do... But hydraulic are better.

 

[StabbyJoe89]

Measured the axle to be 22.2mm or 7/8". This video has a great undershot of the axle/drivetrain at the 1:00 mark https://www.youtube.com/watch?v=C4Yyt3u9kkY&t=1m Crankset seems to connect to a coaster hub, with a fixed cog on the non-drive side. Then the fixed cog on the hub connects to the fixed cog on the axle. Really have to come up with a way to attach the sprocket. The plan is to rely on the front drum and coaster brake for a while, then to upgrade to a mountain bike suspension fork and 203mm disc rotor in the front. Thanks for the quick reply!

 

[ezcome-ezgo]

Around here the Bike People will tar and feather anyone on a motorized vehicle on "their" bike path. Also that coaster hub is designed to transmit human torques in one direction. 6.5 hp will likely destroy it in just a few revolutions.

 

[mckutzy]

Get hubs and sprocket(or a sprocket bored to size) to fit the shaft, mount the motor.
For 6:1 ratio(12t clutch,72t axle)....You have cut out a bit of the deck plate or raise the axle to accommodate the sprocket size( a 72t is 8.8" OD).... although you might get away with a larger ratio, a 60t (7.3"od)......

Youll need to get better brakes than those front drums... that wont be good enough........
Like I said get the mechanical setup, itll mount to that axle size(youll need shims cause you axle is 7/8" they are 1").

 

[StabbyJoe89]

Get hubs and sprocket(or a sprocket bored to size) to fit the shaft, mount the motor.
For 6:1 ratio(12t clutch,72t axle)....You have cut out a bit of the deck plate or raise the axle to accommodate the sprocket size( a 72t is 8.8" OD).... although you might get away with a larger ratio, a 60t (7.3"od)......

Youll need to get better brakes than those front drums... that wont be good enough........
Like I said get the mechanical setup, itll mount to that axle size(youll need shims cause you axle is 7/8" they are 1").

Mckutzy thanks so much for the responses. Can you please tell me if I'm off base or if this is realistic?

I was thinking I could avoid using a massive 72t by throwing a jackshaft into the mix. Could I run the drive sprocket from the torque converter to a dual sprocket on a jackshaft, then run the dual sprocket to the axle?

So using this 36t/12t dual sprocket

and this jackshaft
http://www.bmikarts.com/thumbnail.asp?file=assets/images/03191_3.jpg&maxx=450&maxy=0

I was thinking run the 12t torque converter drive to the 36t dual (creating a 3.0), then the 12t dual to a 24t axle (so 2.0) which would create a 6:1? If that works I could even run a 12t dual to a 48t axle, that would yield a 12:1?

Are you sure I wouldn't risk blowing the torque converter with a 6:1 ratio? I'm just concerned about the weight of the whole thing. I'm 180lbs, 20lbs gear, 40lbs engine, and I'm guessing a 80-100lbs trike (but I haven't weighed it). So something like 320-350lbs, and I need it to move at a consistent 15-25mph with no concern for top speed but definitely want it to last as long as possible. By the way the rear drive wheels are 26" so that might factor into things. Thanks again!

 

[Poboy kartman]

The weight is really not an issue at 6:1.....HOWEVER!!!!! 26" rear tires ARE a HUGE issue!!!!!

Minimum 8:1.....10:1 probably more what will work to give you torque and the top speed you're looking for.

 

[mckutzy]

Ya a jackshaft can help, Weight does play into the factoring of the gearing, having a TC also helps reducing the initial torque to the drive train....But if the pedal were still installed the ratio should be fine.... You start pedal to reduce the static force, once the mass is moving itll have no problem moving it...
Here's a gear ratio calculator.
http://www.affordablegokarts.com/GearCalc.php

Take a look on my build, I use a 7:1 ratio and have a car spare tire w/24"OD... alot of mass there alone, it still gets up to speed quickly, from a stand still.....

If it were me on your ride, Id just jack up the pillowblocks a few inches to clear the sprocket, run a 72t, or even the 60t and carry on.... less to buy and fit to make it work.

Edit: Poboy posted in between...... Bike tires are skinny compared to the average tires used on karts, there is less contact with the ground........ But most of which we all talk abouts in relation of ratio's is they are taking off from a standstill.

 

[StabbyJoe89]

Your replies have been awesome, thanks guys. I used the calculator. With a 12 engine to 36 jack in / 12 jack out to 36 axle I get 9.0. With what you guys are saying that should be a safe bet? It would also allow for cruising 21mph @ 2400rpm (peak torque @ 2500) and maxing out at 33mph @ 3800. I plan to always pedal it up to 5-7mph before I use the engine, that along with the torque converter should help for the low end. Planning to get this 36t #40 7/8" bore sprocket for my axle,

replacing that with the current 20t will be the first step.

Would it be ok to run an aftermarket exhaust & muffler without messing with the internals of the engine? Thinking something like this for $50

 

[chancer]

Yes

---------- Post added at 08:37 PM ---------- Previous post was at 08:29 PM ----------

Most common clutches are 12 tooth on #35 and 10 tooth on#40.

So double check you can get all your sprockets and clutches the same. Before ordering.

They do not intermix.

 

[StabbyJoe89]

Yes

---------- Post added at 08:37 PM ---------- Previous post was at 08:29 PM ----------

Most common clutches are 12 tooth on #35 and 10 tooth on#40.

So double check you can get all your sprockets and clutches the same. Before ordering.

They do not intermix.

Gotcha, so the TC I'm getting comes with a 12t #35 and 10t #40. I'm also getting a 12t #40 5/8" bore sprocket that I want to put on the TC instead of the 10t. Then off ebay I'm getting a 36t and 12t 3/4" bore #40 for the jackshaft, and finally the 36t #40 7/8" for my trike axle. Does that sound ok?

 

[bob58o]

So 36:12 and 36:12 again?

9:1?

I like it.

I was going to suggest 10:1 too, but 9:1 should be ok (I'm guesssing)
Check out kartcalc.net on a mobile device. It will give you guidance. Pick the jackshaft option.

Engine: Just like a kart
Weight: Just like a Kart
Tire size: Twice that of a kart

I thought they were 24" Tires?

 

[StabbyJoe89]

All 3 tires are the 26 x 1.75 solid, airless tires that Worksman carries. Worksman have a 26 front, 24 rear unless you go for the airless tire or mag wheel upgrade, then all are 26. Currently it's a bumpy ride and that's only at 5-10mph. I'm cutting them off soon and switching to 26 x 2.35 tires, which I'm hoping will help a ton.

In terms of axle sprockets I'm finding it'd be $30 cheaper to run a 9.0 (36t) than a 10.0 (40t). Would 10 be significantly better for my application than 9? I can see a lot of stop and go in traffic so I could see that. Mainly I just want to get a lot of life out of my engine, if 10.0 might contribute to that that's reason enough for me to get a 40t instead.

 

[bob58o]

Kartcalc.net on your mobile device (unless the app is down).
The jumbled mess below will be less help than the app.


People like 5:1 or 6:1 (as a minimum with a Centrifugal Clutch) on a go kart with similar weight, similar engine and tires half that size.

So say 300lbs with driver, 13" tires, 6.5 HP, and 5:1 gear ratio. (FOR A KARTING EXAMPLE)

8 Ft Lb of torque at crankshaft.
8 X 5 = 40 Ft Lb Torque at axle.

40 / (6.5/12) = (40 / 0.54) = 75 Lbs Linear Force

So 300 lbs weight and 75 lbs linear force as a minimum to get moving.
75/300 =

0.25 Lbs linear force per 1 lb weight?

Relating that info to your trike....
If you have 350 lbs weight with driver... You need AT VERY LEAST....

350/4 = 87 lbs linear force
With 26" tires, you need 91 Ft lbs Torque at the axle (87 lbs x 1.08')

20% torque loss through TC system
2.7:1 gear ratio provided by TC

91 lbs x 1.2 = 109 Ft lbs

Engine has 8 Ft Lbs

Need 109/8 = 13.625:1

13.625 / 2.7 = 5:1

9:1 should be fine.
It is 80% more than the minimum TQ required to get it to move.
It will go 35 MPH at 3600 RPM.



The 40T vs the 36T will give 10% more torque and 10% less top speed.

 

[chancer]

Bob something you may have missed earlier in this thread. From Mckutzy.
Would it effect the needed gear ratio?

The tall skinny bike tires are making a very small contact patch with the ground, should cause very little resistance. Would these require less initial Torque to get moving. Compared to big Fat 20" kart/buggy tires. Therefore allowing a taller gear.

 

[mckutzy]

That's why I said that earlier, and like wise, I think also thats why my bike is fine in the ratio dept, cause of little contact patch to the ground comparatively speaking to other similar bikes...

Also, the theory is for when it is at a standstill to get it moving...

OP- The header and filter are a cheap basic upgrade, kits are out there, also you will most likely need to re jet the carb...
If any of those kits have new springs, dont bother using them unless your going to open the motor and do more than above.

 

[chancer]

And If you get a kit from GoPowerSports.com it comes with a proper jet for the new filter.
and use coupon code DIYGOKARTS for 10% off

 

[StabbyJoe89]

That's why I said that earlier, and like wise, I think also thats why my bike is fine in the ratio dept, cause of little contact patch to the ground comparatively speaking to other similar bikes...

Also, the theory is for when it is at a standstill to get it moving...

OP- The header and filter are a cheap basic upgrade, kits are out there, also you will most likely need to re jet the carb...
If any of those kits have new springs, dont bother using them unless your going to open the motor and do more than above.

Are you saying that if I install only an exhaust header and muffler (no air filter,l or springs), i would need to re-jet the carb?

 

[chancer]

Yes. The extra air that the intake allows need a little more fuel. Not to worry though it is easy!

https://www.youtube.com/watch?v=7VDqC6390s8

https://www.youtube.com/watch?v=KFNjClKkmf4