New project idea

It has been quite cold so I haven’t been riding my latest full suspension rig a whole lot, but I am very satisfied with it and I am continuing improvements and refinement.

I have a simple but excellent 12V lighting system, with bright lights front and rear. Yesterday I completed my brake light, rigging a bright red led to a simple 12V battery pack (4 AA batteries) to a simple switch attached to my rear brake lever. I soldered a metal spring and attached it to the throttle body with a small zip tie. I soldered a small metal washer and attached it to the brake handle. Another zip tie leads the washer to the spring when I squeeze. Simple and effective.

My financial situation is expected to be much better next year and my thinking is to buy a small motorcycle. But I have one more motorized bicycle idea:

I have a 140cc 4 stroke, taken from a lawnmower. I intend to convert it for horizontal use, welding on a oil slapped and closing and opening some holes. Should be very reliable. Would have to grind the drive shaft down from 7/8” to 3/4” for a chain driving centrifugal clutch.

I just snagged a motorcycle triple tree stem for a few bucks! I have a couple of nice springs that will fit the big tubes needed for the project so I am foreseeing a kind of plunger tube within a tube. I can make that work by chopping a headtube off a derelict steel bike and welding it to a cafe racer frame of my own design.

Researching pieces, I see that motorcycle fork tubes are very expensive.

I’m thinking that I can rig all this up, add all lights and mirrors and get a motorcycle tag. Has anyone done this?

 

[Timbone]

I’ve been looking at this closely and testing the rolling chassis. I think I am good - here is why:

First these pics are deceptive. That “tiny gusset” rear of the seat post is not so tiny. It is a piece of 1/4” steel welded like a mofo. That will not give.

From the gusset to the very end of the tailpiece, length is about 14”. I have a forward seat bracket (welded), a mid support about 1” aft of the gusset, and the final bracket is about 10” aft of the gusset.

The seat is more “forward” than it may appear. My weight will probably be centered about 4” to 6” aft of the gusset. I’m not an engineer but I understand force. It would take an incredible blow to bend that piece of unistrut 8” to 10” behind that strut.

I do have some metal pieces that would work perfectly as added strength and, after I wire in my turn signals, I may add some strength.

Right now, I’m focused on starting this motor. I need to make sure my carb is not my problem. I be adding the fuel tank soon.

Thanks for your comments.

 

[Timbone]

Here ya go, adjustable jets, both high and low jets..................Curt

https://www.amazon.com/TECUMSEH-CARBURETOR-520-918-631245-631820/dp/B00KI11P96

Thanks very much for the suggestion. I cannot get my 4 stroke motor to start with my 2 stroke NT carb, even with bigger jets. This is the route I will go as the motor’s original carb is plastic junk.

This is why I like this website!

 

[curtisfox]

Probably have to make your own intake, if you use big washer with the right size holes, and handle bar tubing. Should be easy........Curt

 

[gary55]

Timbone had me wondering about the choices of materials he used on his last wild project, but I wound up eating my hat so I imagine he will do the same with this one as well. I'm just gona sit back shut up and watch it come to life.

 

[Timbone]

I had a very good day today. I was too busy to take pics. I’ll take a few tomorrow.

First, I had to repair my current bike’s rear wheel. Three brokens spokes caused by pressure of the hub adapter. Easy fix but those two bolts are not enough.

I got a great chance to inspect my wheel while replacing spokes. I am declaring my method of 14 gauge spokes soldered after lacing to Halo SAS rims to be a total success. All of the 33 unbroken spokes looked good. A very solid wheel. Anyone willing to spend $150 for one?

Ok, as for the current project I had a major breakthrough: I got the 4 stroke engine started! Pull starting was killing me so I welded a 15/16” socket to a carriage bolt and, using my electric drill, I managed to get a good start and run with no fuel line, just gas in the float bowl. I was running on premix, too, and I think there was oil in the cylinder because the exhaust was very smoky.

After replacing the premix with real gas, I was able to get a real start. Much cleaner run this time. But, no throttle response! I messed up big time, running the throttle cable to the clutch control. Geez, it’s much more complicated that I thought it would be with all kinds of plastic parts pushing against one another.

So, very quickly, I made a simple linkage from my clutch control to the throttle cable so as the clutch relaxes as the throttle opens. After this change I was unable to restart after several pulls.

My main problem is that the carb is flooding the cylinder. No control for this as best I can see. No bulb. No screws. So I am trying to start it with throttle open and clutch off. I am getting backfire thru the intake nearly every pull but no start. I’m thinking that the flooded cylinder is holding fuel thru the exhaust stroke and, since the spark fires even during the dead cycle, it’s igniting at the wrong time.

I’m thinking I need a different throttle cable attachment so that clutch and throttle are controlled individually.

I know I have a working motor now so it’s time to move on. I need to solder on a kill switch. Need to find a 35W to 40W headlight. Need to weld on two rear blinker lights. And I need to seal the ugly fuel tank - there are two or three pinholes. Will probably finish the torque converter tomorrow and be ready to roll!

Almost there...

 

[darwin]

WOW, what a project. Can't wait to see it finished. I think you should leave it w/just a lacquer finish over the bare metal, not a nice paint job. Kind of like a survival bike etc. Bug out bike.

 

[Will'smotobikes19]

I have an old 207cc lawnmower engine that’s as old as me 20. I got it for free but wonder if I can convert it to horizontal shaft. From what I’ve heard some holes have to be jb welded and a new place for an oil dipstick made. I’ve seen people lapping valves on old engines 805roadking always does that. The carburetor isn’t hard either. The mounting holes are on the cover so engine has to be mounted different on a minibike.

 

[Timbone]

I have an old 207cc lawnmower engine that’s as old as me 20. I got it for free but wonder if I can convert it to horizontal shaft. From what I’ve heard some holes have to be jb welded and a new place for an oil dipstick made. I’ve seen people lapping valves on old engines 805roadking always does that. The carburetor isn’t hard either. The mounting holes are on the cover so engine has to be mounted different on a minibike.

Converting vertical to horizontal is not difficult at all. You can make an oil flipper out of pretty much any piece of metal. Just screw it to the con rod/crankshaft. Before everything is buttoned up be SURE to align the timing marks and have the pushrods in properly.

 

[Will'smotobikes19]

Can you give me a link to that seat?