Which engine which frame should I use

[57ChevyWagonMan]

My Motorcycle Build

I am in the collecting and planing stages of my vintage motorcycle replica. I already had a 1953 Briggs and Stratton 1.5 HP engine I was originally planing to use. For a motorized bike it is just over the limit at around 53cc. I just found a 1958 Wisconsin 7 hp military spec engine with waterproof magneto ignition. Definitely well over the limit. Which engine would you use and why. I have an early 50s Schwinn but I hate to cut up a vintage bike and I have 2 mountain bikes a Giant and a Murray. No mater which frame I use it will require quite a bit of modification. I could also build a scratch frame and I would like input on these options as well. I already have a new springer front fork that I intend to use.

Thanks!

Mike

 

[cobrafreak]

there are venders here that will sell you a frame that accepts your engine. call them.

 

[Mr.B.]

The Briggs is a little small and will most likely be more like a “motor assisted’” bike with some pedaling required, but it will be easier to fit into the frame.

The Wisconsin will have low rpm’s but tons of torque = A somewhat slow bike but able to climb steep hills and never having to pedal.

It will be much harder to fit into the frame but a couple of us here have done it. It‘s also very heavy so your mounts, wheels, etc... will have to be plenty strong! Because of the width you’ll likely need a jackshaft.

And it will sound more like a actual antique motorcycle.

For performance you’ll probably want to change the carburetor on either of these as both were originally designed to be stationary engines.

Either way you’ll have to modify, buy, or make a frame...

I’m a big fan of using vintage engines, I’ll look forward to seeing what you build!

-Kirk

 

[57ChevyWagonMan]

I just did some math and that Wisconsin is 292cc. That is quite a bit. My first bike was a Kawasaki KE100 and that thing would go 50 mph. Now when you guys talk about changing the carburetor. I noticed a bunch of people mounting what appears to be a motorcycle carburetor. Is that what you guys recommend? How do you select a carburetor?

I was also thinking about shaving the head and polishing/matching the intake ports.

Mike

 

[Mr.B.]

I have 1939 Wisconsin Model AK on my build and used a 22mm Mikuni carb- It’s a common carb & readily available on Ebay, and inexpensive.

It works very well!

I’d also recommend buying a Wisconsin manual, again readily available and inexpensive on Ebay.

Attached a graph from my old manual that shows the “A” series block models and ratings. As you can see the rpm’s are slower than a modern engine but they have a much larger throw which gives you killer torque.

Since your engine is 7HP you may have to get a larger carb?

Interestingly enough, my AK also has 292cc's so perhaps you’ll be OK?

Anyway here’s a link to a helpful site where you can date your engine...

http://pwp.att.net/p/s/community.dll?ep=16&groupid=256080&ck=

Also a thread link to LouieMCman’s 1910 “Peace”, another builder who used a old Wisconsin...

http://motorbicycling.com/showthread.php?t=25753

-Kirk

 

[57ChevyWagonMan]

Thanks for the info. I asked the proprietor of the Wisconsin site for a copy of the manual. I am fairly sharp when it comes to engines. So I jumped right in. I filed, cleaned and set the points and it gave a good spark. I then took the carburetor apart and scrubbed it out good and put it all back together. It runs well! No smoke no knocks! So my $35.00 beast lives!

Mike

 

[57ChevyWagonMan]

Well I had asked before about frames. I have the ability to build my own but I have 3 bikes I could butcher into BT era frames.

Murray Mountain Bike

1950's Schwinn

Giant Mountain Bike

Also I got nice fenders with the Schwinn.

And I got this springer off e-bay

I am leaning toward scratch built especially after seeing the excelsior V Twin build

http://flashbackfab.com/pages/excel00.html

Mike

 

[Mr.B.]

If you decide to use that big motor you’ll have to stretch to center section of any of those frames...

I think the Giant would probably be the easiest conversion, although perhaps still a little “clunky” looking...

But if you have the skills & tools building your own would be the most satisfying and you would able to have total control over proportions.

-Kirk

 

[57ChevyWagonMan]

Kirk,

Thanks for the mock up drawing. Pretty cool! As I sit and look at the possibilities, building my own seems to be the most practical. Especially when you consider all I would actually use of an existing frame is the rear triangle and the head tube. I have always wanted to build a bike frame from scratch too.
I have a full machine shop here at the house, a couple of benders as well as welders, torches and I even have access to a CNC plasma table.

So I guess my next step is to sit down and nail down a design as accurately as possible in CAD. What crank would you experienced builders recommend I use? I already have purchased a brand new wide spread 1 piece crank that will likely still require further modifications and I also have the 3 piece from the Giant.

Mike

 

[Mr.B.]

With the Wisconsin you’re probably going to need something wider than a off the shelf 3 piece...

I’ve made my own by forcing Harley wheel bearings into the bottom bracket and using a 3/4” shaft cut to length and turned at the ends for the crank arms, (but that was the larger old US standard size BB like your old Schwinn has).

Member SportscarPat sells a real slick system that doubles up the pedal crank & a jackshaft pulley and has adjustable width, definitely worth considering!

http://sportsmanflyer.blogspot.com/

If you are going to build your own frame you might want to use a taller head tube than the Giant has.

-Kirk

 

[57ChevyWagonMan]

Kirk,

I had already intended to use the longer head tube. My intention was to use the longest one my springer front end could take. I think this springer looks a little like an early Triumph. Perhaps that is where Schwinn first got inspiration for their design. The drop loop tube design is quite elegant but somewhat pointless when you consider the flat bottom crank case of my Wisconsin. I am thinking step boards forward of the crank cut from diamond plate would be very cool.

Mike

 

[Huffydavidson]

It's not cool unless its a custom one of a kind.

 

[Mr.B.]

If you do use those Giant arms maybe there is some off the shelf wider axles that that will work...?

I’m afraid I'm really not that familiar with these smaller/metric BB sizes.



Does anyone have any ideas and links???



FYI: With my Wisconsin AK engine build- Shroud intact on the right and pulley/guard on the left (1.9” off the side cover) my diy pedal cranks are 12.5 inches wide on the inside of the arms...

They are fairly centered on the bike, but if I wanted I could probably lose 1.25” on the right. <Hope that helps!

-Kirk

 

[57ChevyWagonMan]

Right now I am trying to figure out what to do about the pedal crank. I had a little bit of an exchange with Mr. B about this in PM. I am now leaning toward a 3 piece arrangement. I have the aluminum one off of the Giant mountain Bike. It would not be too difficult for me to make a custom crank shaft to satisfy my bike's needs. Is the Aluminum one too chunky? If so what should I be looking for?

Thanks!

Mike

 

[57ChevyWagonMan]

Well, Not much interest in what I am doing?! I spent some time on a cad drawing to try and figure out some angles and such. The drawing needs a few more details added but overall I think it captures the flavor of what I am wanting to do.