Cannonball Builds a Briggs and Scrap Iron

[cannonball2]

Ive had this poor little 1976 3hp B&S for many years. It was headed for the scrap heap. I rescued it when I was in the small engine business as a parts source. I thought it was cute and tucked it away. Turns out only the points need cleaning. Its a reasonably uncommon configuration with the updraft carb, which is very compact, just perfect for stuffing into a bike.

I wound up with a Schwinn Delmar trade. The frame configuration is great. With a single top tube its wide open for bigger engines. The frame is also wide for larger tires/wheels.

So this is whats going on. This is really I guess a light motorcycle as the reduction will run through the bottom bracket. Ga does not require pedals so I guess I don't either. The drive will be to a Nexus 3speed IGH driven on the right side. I have been beating a Nexus with a 49cc 2stroke and it hasn't failed yet. I think with careful handling of the Briggs I can make it last if not I will find an SA IGH.

I'm really tickled about the way I did the bottom bracket. Normally I make discs to hold 5/8 bearings and weld them to the BB. What a PITA! This was a five minute bolt on and it clamps so well I couldn't budge it hitting the shaft with my copper hammer.

Will be running 26x2.4 Cyclops tires on 50mm rims. Has a new Cruzer(don't say Whizzer!) 8qt gas tank. One of the nicest tanks I seen from China.

This is where it is now. I'm in and out of town so it will progress slowly.

 

[Tony01]

Oh man that BB.. why didn't I think of that..... so good!

which 50mm rims do you plan on running?

 

[cannonball2]

My wife gets bikes from the thrift stores in our area for me to use as donors. These were from a Huffy Regatta, complete with the Nexus hub.

 

[scratchbuilder]

Yeah!!!following...bb..its nice how some ideas just come together eh..i like those Cyclops..i got 1600 miles on mine. Like the tension set up too.

 

[cannonball2]

Thanks!

I have been running Hookworms and they are great tires. The Cyclops seem to be comparable but cost much less. I have been running Cheng Shinn tires for years on M/Cs.

Ive had good results running the hard skate wheels as idlers. You get 4 for $10 with really nice bearings. I prefer spring loaded idlers but there was no practical way to use a spring in this set up.

This Briggs had one of the blocks that had the cast in air guide in the front. A bit of work with a hacksaw and Dremel liberated the cylinder for more of an engine look will probably aid in cooling while moving. The guide was very necessary when the engine was used in a stationary mode. I also rounded the head to match.

 

[curtisfox]

WOW! got to watch this,KOOL bottom bracket mount shaft, never cease to amaze me with your ingenuity......................Curt

 

[scratchbuilder]

Oh, yeah I was wondering about the 'look' of the engine. I was looking how to remove the same on mine, ended up just drillin holes. I got one to practice on. What you did is a nice look. Skate wheels

 

[curtisfox]

CB 2 what size is the shaft 3/4" ?...................Curt

 

[cannonball2]

Curt the shaft is a 5/8. A 3/4 could be used if the bearing housings are not excessively large.
These are close flange bearings. They have the holes as close to the bearings as possible. When bolted down the bolts are against the BB tube locking the bearings positively in place.

Got the drive line finished. The largest sprocket I could fit with out frame interference was a 44t. To get the ratios I had to resort to a 9t front. Not a lot of teeth! There are 5 in the chain at all times so should be fine as long as the chain remains tight.

I like to run BMX chains they are smaller, plenty tough and fit the common CG sprockets.
better. Problem is most driving sprockets don't fit. I thinned this sprocket(it was for a #40 chain). I locked it to a piece of jackshaft and put a bearing on the shaft. By holding the bearing and evenly spinning the sprocket against the wheel on my grinder I had a custom machined sprocket in about 15min. I faced it by turning it against a 60 grit sanding disc with my drill press. Home machining at its best!

I will be running BMX rim brakes. The best fit is right behind the motor. Will make a mount that fits off the motor mount. This ones going pretty well/fast.
but the devil is in the details as usual.

 

[scratchbuilder]

Your engine looks like mine did in the beginning!! I like your creative thinking. If its layin around...its like umm if I do this, I can use that. Hey I've read some of your elec. build threads, and was wondering if you know how useful are unite motors. I clean a guys shed out was there was a 500w razor, so I thinking of using it, on my cargo bike. Dang you already got your tires! Gonna be a mover!!

 

[MEASURE TWICE]

Nice, the carburetor you have with that elbow makes it fit in the frame as is!

Same engine or very similar Briggs. I have 80202 0430 3hp. Another am not yet figured how I may use is a 3.5 Briggs. I was going to swap it into the build I already have but the cranks shaft size and length has me doing some creative thinking if it will ever happen.

The cranks opening on my bike I never bothered doing anything as nice as the way you used the pedal crank part of the frame. I just covered it over with weld metal plate to keep dry. I have a California Off Highway registration. No pedals are OK for it. Not for on the streets though, trails where allowed by Fed, State, County and Private Lands.

 

[cannonball2]

MT

The first MB I built probably 30yrs back was very similar to this. It reduced through the bottom bracket but was belt on the primary side and chain on the other. It was powered by a 3hp Tecumseh. Was a good ride. Ga dropped the pedal requirement to allow the 50cc
scooters on the road.
The cops down here are pretty cool and generally if you are behaving pretty much ignore home built two wheelers. Used to see a guy all over town right in the middle of traffic on an old mini bike.

 

[cannonball2]

Your engine looks like mine did in the beginning!! I like your creative thinking. If its layin around...its like umm if I do this, I can use that. Hey I've read some of your elec. build threads, and was wondering if you know how useful are unite motors. I clean a guys shed out was there was a 500w razor, so I thinking of using it, on my cargo bike. Dang you already got your tires! Gonna be a mover!!

I assume the motor you are referring to is a brushed chain drive unit?
Whats the voltage? If it is chain drive I see no reason it wouldn't work with the right ratios. PM me or start a thread in the Ebike section.
We could use some activity down there.

Got the rear brake worked out. I like it there. Main reason its there in that position it will allow a fender to pass thru. Wouldn't at the top. I am going to run fenders on this one to make it a "proper" little Motorbikecycle. The cable will travel nicely under the engine. Will be running the super sticky clear BMX pads. Man do those things stop! Hope they are kind to the powder coated rims. The calipers just clear the tires!

 

[Tony01]

Nice, that bracket won't snap off under heavy braking?

What is the mod you did to the engine for the airflow?

Your info and pics got me convinced to use the CST tires on my next 4c build. I want to go with wider rims though, maybe 2.5" or 3"

Briggs builds just look right... can't wait to do another.. I'm stuck with my first 2-stroke right now..

 

[cannonball2]

That's a valid concern about the bracket.

When the bike comes off the stand and is dismantled for paint I have a gusset already fabbed to weld to the bottom of the bracket and the frame. That should be overkill.

The engine originally had a flat probably 2"x3" plate cast into the front of the cylinder which directed the blower forced air across the front and around the cylinder to assure adequate cooling in a stationary situation. Before removing the plate the engine looked like it was in a box with the front of the cylinder invisible. The cylinder is now out in the open.

Not all B&S engines were like that.

I'm impressed with the tires. The sides walls seem very flexible which I believe will make for a good ride. Nice on a rigid bike. The Hookworms are excellent riders.

Very nice bike in the pic! Love the stretch. Very well thought out. Pulley is killer to!

 

[cannonball2]

Only had this am to work on the build before I have to leave town for a bit.

Got the fuel tank mounts fabbed and welded and the bike off the stand and on two wheels.

Toying with the idea of adding pedals behind the bottom bracket. There is a coaster sprocket in the chain in the right side pic, gives the idea. Might just work with an SBP freewheel adapter, a freewheel and some fabbing. More later.

 

[silverbear]

That's going to be a sweet rider. I love what you did with the bottom bracket.
SB

 

[scratchbuilder]

Lookin good, like the slight tilt of the engine.

 

[cannonball2]

Thanks Yall!

The tilt is to clear the fuel petcock/head bolt interference. Was as low as the engine could be placed. When I made the tank mounts I raised the tank a fraction and all is good now.

In order to get the engine that low had to saw the engine drain plugs off flush. Will remove, drill and tap the side cover for a drain, or possibly cross drill the lowest side cover bolt to drain when removed. Which ever is easier.

 

[Ludwig II]

What about a plug like this?