My 70cc happytime project (many pics within!)

Bogaurd

Member
Joined
May 15, 2008
Messages
44
Alrighty - I've started a project building up a bike with a 70cc happy time engine which I purchased from www.zbox.com.au.

I've been working on and off on it for around a week now, and figured I'd share some photos - apologies, the earlier photos were taken with my mobile phone, they're not of the greatest quality ;)

The bike I decided to build this up on was a 2006 Avanti Escape which I picked up from a local second hand store for $75. The bike was in terrible condition, broken chain, ruined paint, missing brakes, stuffed bearings - you name it. I decided to strip it down and rebuild it.

Here's the frame when I first stripped it down... (click to enlarge the pics)


The chipped paint (this thing was also covered in so many stickers!)


I started sanding the paint back, but gave up after 15 minutes & took it down to a nearby sandblasters - for $15 I had the frame sandblasted, and for another $5 they sprayed it with an etch primer.

Sandblasted:


Primed:


A light sand later, ready to paint:


Painting the frame (hanging on the clothes line, haha):


Soo... how'd it turn out?






So for $30 I stripped all the old paint & gave it a nice black satin paint job. Nice! :D

From there I fixed up the rest of the gear on the bike, bought a set of brakes for the rear, replaced some bearings, re-oiled & tuned everything - it was all working great.

A few days later my engine kit arrived, hurrah. I went abut getting it all setup on the bike, I replaced a lot of bolts with hardened or high tensile steel bolts, as the Chinese ones that came with the engine kit seemed to be made of something similar to chalk ;)

Engine in the frame:


As you can see, there was no way the carburettor was going to fit in the frame, there's not enough room. To get around this, I modified the intake so that the carby sits to the side of the engine. This is a temporary intake, I'll weld up a proper one soon :)

Intake:




The bolts on the rear motor mount were replaced with 60mm high tensile steel bolts, and the mount was slightly modified. There's also a bit of black cloth tape wrapped around the frame there to prevent it from getting too damaged.

High tensile steel bolts:


The bottom tube on the bike I'm using is very thick - diameter is somewhere around 50mm. I didn't feel like drilling the frame, so I took a large hose clamp, drilled through it to bolt it to the bottom engine mount, and then tightened it up around the bottom tube. There's some rubber between the clamp and frame for now too, you can see it in the photo - this is actually a very strong mount, and the load is evenly distributed on the tube rather than crushing it at a single point.

Bottom mount:




The wheelset I have on the bike has disc hubs - intended for use with disc brakes - I have a disc break on the front, but the rear stays do not have a mount for a caliper, so I'm using v-brakes there.

Given that I have a disc hub, which is designed to deal with large amounts of torque, I figured I'd mount the drive sprocket to the disc hub. This gives a much more solid point to mount to, can be mounted with more precision, but more importantly, will transfer the force of the engine to the whole wheel evenly, rather than just the spokes on one side.

Due to clearance with the rear stays, the sprocket could not be mounted directly to the disc hub. I drew up a simple design in CAD, and took it down to a local engineering firm to have an adapter plate made up to allow me to bolt the sprocket to the disc hub. The hole in the sprocket is also being enlarged to allow clearance over the disc hub.

The hub:


A diagram of the adapter plate mounted:


The pink shows where the adapter plate will sit, the green is the drive sprocket, the black lines are the mounting bolts, the white blocks are spacers.

The adapter should be ready for me to pickup tomorrow, or Monday at the latest - so I'll have the bike finished by then. I've already taken it for a few rides by hijacking the wheel from another bike I own & mounting the sprocket in the conventional fashion, hehe :D. The cost of the adapter plate is $30.

I'll post some more photos & info as the bike progresses more!
 
Last edited:


A

Alaskavan

Guest
Good work. That's going to look sharp. Let us know how the adapter plate works. Someone else posted that they had trouble using a rear disc brake mount for their sprocket. The bolts kept pulling out or breaking. There was some speculation, but no real reason why that was happening (possible alignment issue?).
 

Bogaurd

Member
Joined
May 15, 2008
Messages
44
Good work. That's going to look sharp. Let us know how the adapter plate works. Someone else posted that they had trouble using a rear disc brake mount for their sprocket. The bolts kept pulling out or breaking. There was some speculation, but no real reason why that was happening (possible alignment issue?).
Yeah, that sounds a bit odd - there should be no reason that the bolts would break or come out - after all, the hub is capable of standing up to the forces of very sudden deceleration via disc brakes, which would be much more demanding than the limited torque put out by these motors... I'll let everybody know how it goes though :)
 

kjparker

Member
Joined
May 5, 2008
Messages
163
Hey, stupid question time.

When you removed the forks in preparation for paint, did you remove the bearing races as well? if so, how? I thought they were pressed in, yet it looks like yours are out....
 
Last edited by a moderator:

Bogaurd

Member
Joined
May 15, 2008
Messages
44
Hey, stupid question time.

When you removed the forks in preparation for pain, did you remove the bearing races as well? if so, how? I thought they were pressed in, yet it looks like yours are out....
Hey there,
I did take them out, yes. Mine were sealed bearings, and they were pressed in to some degree. I got them out by inserting a screwdriver down the tube where the steerer would sit, positioning it on the rim of the bearing racer, and tapping it with a rubber mallet. They came out fairly easily. I used a rubber mallet to put them back in as well :)
 

kjparker

Member
Joined
May 5, 2008
Messages
163
can you post more information with regads to your sprocket mount? Im interested in doing the same!
 
L

Large Filipino

Guest
With that intake you can get a cool air filter with all the room.
 

redman

New Member
Joined
May 5, 2008
Messages
7
i did a disk mount adapter and it works great. one step better would be some form of rubber cushioning to take the shock out of the pulse of the motor to relieve the spokes. mine have held in there but its what i see as the weak point. make sure you attach with high tensile bolts though.
 

Attachments

redman

New Member
Joined
May 5, 2008
Messages
7
your bike is taking similar steps to mine, i like it. i never finished to the level i would like though. stick at it!
 

Bogaurd

Member
Joined
May 15, 2008
Messages
44
Hey guys, thanks for the responses.

I did some more work on the bike this afternoon - I sprayed the engine with a high temperature matte black engine paint, and I fabricated a bracket which mounts the fuel tank over the rear wheel.

I'll take some photos later this evening and upload them :)
 
Top