Pocket Bike Engines Tutorial



Heres a pic I found of one of my older builds. Its a little easier to see the design than the previous pics.



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Heres pics of parts needed to assemble the actual rack. These are all the parts nessecary except for gas tank brackets.

Pic 1

starting with part #1.
2 @ 16''
These are the rear verticals . I usually use 1 1/2 inch angle iron for these. The bike i'm building needed new forks as the old ones were bent. I decided to cut up the old ones and use the forks as verticals.
Because I'm building on a beach cruiser style frame , I figure the curved forks might suit the frame better than straight iron.

Parts 2, 3 . and 4 are all 1 1/2 '' angle iron. I used a rusty old bedframe some one had tossed.

Part #2
these are the 2 side rails
2 @ 15 ''

part #3
the 2 front mounting brackets
Make 2 @ 10 ''

Part #4
2 jack axle mounts
Make 2 @ 5 ''

Parts #5 and #6 , I made out of aluminum just because I had it. Most of the time I just use steel flat stock.

Part #5
Front rack plate
Make 1 @ 2'' by 9 ''

Part # 6
Rear rack plate/ motor mount
Make 1 @ 4 1/2'' by 9 ''
You'll see the one in the pic is actually 6'' by 9'' and I've cut notches for the primary chain and exhaust. This is extra work with no real benifit but maybe a little more structural integrity.
Ideally it should have a couple extra inches at a rightangle at the back to keep it from flexing under torque . see pic 4 to get a better idea of what it should look like . I've blacked out the unnessecary part.
Parts #5 and #6 should be thicker than the angle iron as theres abit of pressure on them and these should not flex under load.

I do not weld . I use 1/4 '' bolts at 3/4 '' long for the entire project.

Get 24 of these bolts, nuts, and lock washers. You'll need 2 2 1/2'' inch bolts also. these will be 1/4 '' aswell. and a 1/4 '' drill bit.

I use a cut off blade in my grinder to do all the cutting.
If you weld or can get it welded , by all means but do not weld parts #1 and #4.
Next post we'll assemble.



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Assemble the rack​

See first 3 pics and mount the side rails to the rear plate/ motor mount . Notice which way the angles are facing on the rails. this is imperative to mounting the verticals .

Also the rear bolts should not be more than 1 '' from the rear of plate or they will be in the way of the pulll starter housing . 1 '' from rear is perfect and front bolts of rear plate should be the same . see pic 2 for bolt placement
Use a square

If you look closely at the rear plate you'll see a couple blue markings. This is where the engine mounts. as you can see it is not centered but off set to the right so we get our chain aligned properly with the wheel .
When i I say left or right I will always be refering to the direction when viewed from the rear.
PIc3 will show you proper engine placement . The rear left engine bolt is the easiest one to start with and should be drilled 3 1/2 '' from the left and 1'' from the rear , this being the centre of hole. use a center punch before drilling to get excact.

It can be kinda hard to drill the holes excactly where they should be but you can easily make an imprint of the engine bolt holes with a piece of paper of cardboard. just wipe a little oil or grit on the bottom of the engine where the bolts go and set it on a piece of paper. then use the paper to transfer the bolt patern. Be sure to keep it squared to the left side rail

Next , attach the front plate as shown in pic 4 .
use 2 bolts per side on both front and back plate. Again please use a square.

pic 5 shows the proper [placement of the front rack mounts these should be centered with the rackand 1 1/4 '' inches apart. agan notice which way the angle is facing.

the vertical side rails will mount 2 '' from rear as shown in pic 6 these should be able to swing freely back and forth when loosely bolted on, Round off the top of them with a grinder if nessecary.

Next post we'll mount the rack on the bike and set up the jackshaft. I always wait till I know everything is good,THEN I dismantle and paint, otherwise I usuallly end up wrecking the paint job as I'm installing the kit so i f your going to paint , dont bother reefing the bolts super tight if your gonna take right back apart.
Cheers \


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I'm likin' this. So far, it's all stuff I could find in a couple of minutes in the junk yard. Keep it comin'. Please.


Thanks Alaska. I had to invest 7 dollars on this project. nut and bolts , everything else was junk laying around. Is it fairly understandable so far?


Mounting the jack axle and completing the primary drive

In the first pic , you'll see where the jack axle mounts go . Look at the next few pics to see the clearance from exhaust , chain, jackaxle etc.

The bolt holes in the jack axle mounts should actually be slots for chain tension/ aligning jackaxle/.

It's best to drill holes for the jack axle main bolt and sit the whole jack axle assembly in place and check clearances , lengthen, shorten pocketbike primary chain as nessesary.
then drill and bolt jackaxle mounts to
side rail. c clamps will help alot at this stage and again , take your time and make sure the jack axle is squared up with left side rail.

In pic 2 the j axle is in place with primary chain attached, a 5 inch pullly has had the center cut out so it will slide over the jack axle and is just sitting in place untill we see what we need for spacing.

Once we know that we'll make a spacer and bolt the pulley (or secondary sproket if a chain driive) to the primary driven sprocket.

Hopefully yours is looking like the one in the pics. The last pic shows the verticals folded in underneath but these should swing down when you lift the rack.

Once we mount a gastank to the rack, this will mount on virtually any bike with 3 bolts with out having to drill the bikeframe. Even a full suspension with a little mod.

Were almost finished



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I can re and re this entire kit from 1 bike to another and be riding in under 10 minutes!!!


more On Porting And Blowdown Time For The Fanatics

skip If You LIKE As Doesn't Pertain To RAck Build​

These pics all show the port timing of this engine. this is essential information a person must have to properly change the port sizes on any engine. Alot of peple think by enlargening the exhaust port, they're going to gain power but as you can see , yu can cost yourself an incredibable amount more power than you can gain.

These diagrams are of the Honda ne50 cc that I have n my trike Its a 2stroke , oil injected engine with a 6 volt charging system , points ignition system , spring starter . its pretty cool old motor actually, considering its 30 yrs old and still running like a clock.


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By making the exhause bigger only it causes more raw fuel to go straight through into the muffler equaling less power theroetaccly.