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'm a little concerned about that swingarm. I think it wants a much wider pivot and two shocks so it can't swing side to side. To me it looks like it's going to fold up. Hope I'm wrong.

Thanks for your comments. Part of the deal of posting in here is getting feedback from others.

These pics can be very deceiving. This swingarm is very strong. I learned a lot from my last full suspension build. I wrapped what was a very stout mountain bike fork in many layers of metal. I cannot imagine how much force would be needed to bend any part of it.

The swingarm axle itself is 5/8”, locked inside 1/4” angle iron pieces. I’m not going to be doing any MotoGP style corner leans so I have no fear of loads getting out of hand. The monoshock is rated at 1200 lbs.

I’ve already done some testing rolling down hills on rough ground. Sure feels solid.

One of the things I’ve learned about motorbikes is that full suspension really takes away a lot of stress from nearly every part of the frame. From lights, to CDI to engine mounts - everything really - most of that day to day road banging is eliminated and everything works better.

I have to smile a bit. Motoredbikes.com is a site where builders put 212cc Predator motors in Walmart bikes! Now that would scare me!

Tim

 

[Timbone]

looks like work in progress. sure, couple chain stays to drop down from the seat mount to help with side loading. he has some great bikes from what I've seen.. can't wait to see what tank's goin on it! already lookin long and mean

My fuel tank! Geez! I’ve welded it up and need to clean it out and seal it. I’m not quite done with it but it’s not a great mix with my frame. Hence no pictures. The view from the front will be OK but - I might as well say it - I’m not pleased with it. Hey, I can always do something else!

 

[Spare_Parts]

I have to smile a bit. Motoredbikes.com is a site where builders put 212cc Predator motors in Walmart bikes! Now that would scare me!

Tim

Nothing wrong with that. The Chinese are looking like expert welders and I know those bikes have had stress analysis done.

 

[Old Busted Hotness]

These pics can be very deceiving. This swingarm is very strong. I learned a lot from my last full suspension build. I wrapped what was a very stout mountain bike fork in many layers of metal. I cannot imagine how much force would be needed to bend any part of it.

No need to imagine, just do a little math. Let's say there's 200 pounds on the rear wheel when it's all done. If the swingarm is 24 inches (which it looks to be, give or take) then there's potentially 400 foot-pounds going thru that pivot. If it's a straight vertical load it's all good. Throw a side load in there (cornering) and 400 foot-pounds could easily twist something loose. It could be the seat tube that fails. Not sure what your frame is made of.

If you think that joint can take 400 ft-lbs, then good on ya. If not, reinforce it. You're in a better position to know than I am.

 

[Timbone]

Nothing wrong with that. The Chinese are looking like expert welders and I know those bikes have had stress analysis done.

Wrong and wrong. Walmart bikes are not designed for any kind of heavy use. The rule that 75% of bicycles never go 100 miles is in play here. Use at your own peril!

 

[JerboaJohn]

have to go over all wear points, and don't install a 212cc engine and you'll be ok lol

2 problems I had with my Adventures 700c were handlebars wouldn't stay tight, and the kickstand vibrated loose on a long trip. Pacific Cycle i think it is

 

[Spare_Parts]

Wrong and wrong. Walmart bikes are not designed for any kind of heavy use. The rule that 75% of bicycles never go 100 miles is in play here. Use at your own peril!

I'll show you some close up pictures of the welds on my Wal-Mart bike and you show some of yours. Don't feeds us the line "They are ugly but strong " either. How about that hoop under the engine.

Your 75% theory is just stupid.


Btw, what program did you use for stress analysis? Does it accept unistrut as an input?

I have nothing against building your own stuff but you need proper tools imagination and some skills. You have imagination for sure. Seem to be lacking in the other 2 areas.

This thing is a death trap.

 

[Timbone]

I'll show you some close up pictures of the welds on my Wal-Mart bike and you show some of yours. Don't feeds us the line "They are ugly but strong " either. How about that hoop under the engine.

Your 75% theory is just stupid.


Btw, what program did you use for stress analysis? Does it accept unistrut as an input?

I have nothing against building your own stuff but you need proper tools imagination and some skills. You have imagination for sure. Seem to be lacking in the other 2 areas.

This thing is a death trap.

I hurt your feels.

I’ll argue if you want. There’s a reason you get a Walmart bike for $90. They are cheaply made with cheap materials and cheap components. Those welders are ripping through those frames. These bikes will not last long as bicycles and the manufactures know it. When a tire goes flat or one of the cheap brakes fails, the owner will throw it in a shed or garage and it will rot. It is well known in the industry that the vast majority of bikes sold - and most are cheap bikes - never log 100 miles.

Walmart bikes are not made for motorization. They can hardly stand be pedaled daily. Hey, my first motor build was on a Walmart frame. The frame was very quickly pushed to its limit.

I spent a few years in metal shops, making good money. It was hard work! I’ll go slow and constantly test my creations. I’ve seen lots of bike frames fail. That’s because they are only engineered for bicycle stresses with very little room for error. The same applies to Walmart bikes.

 

[bikejock]

Intresting. Nice work. Looks like you could add some motorcycle or moped wheels with that kind of setup at least for the front depending on the type of forks you get & the width between them. Right now I just got a basic mountain bike suspension setup that I’m using hydraulic disk brakes for in the front of my bike. Used to have a triple tree fork but it wasn't disk brake conpatable & didn't have suspension which made for a rough ride. Always wanted to try using motorcycle or moped wheels because the roads are a bit rough in my area for a bicycle doing 30 mph or faster.

 

[bikejock]

I hurt your feels.

I’ll argue if you want. There’s a reason you get a Walmart bike for $90. They are cheaply made with cheap materials and cheap components. Those welders are ripping through those frames. These bikes will not last long as bicycles and the manufactures know it. When a tire goes flat or one of the cheap brakes fails, the owner will throw it in a shed or garage and it will rot. It is well known in the industry that the vast majority of bikes sold - and most are cheap bikes - never log 100 miles.

Walmart bikes are not made for motorization. They can hardly stand be pedaled daily. Hey, my first motor build was on a Walmart frame. The frame was very quickly pushed to its limit.

I spent a few years in metal shops, making good money. It was hard work! I’ll go slow and constantly test my creations. I’ve seen lots of bike frames fail. That’s because they are only engineered for bicycle stresses with very little room for error. The same applies to Walmart bikes.

Thats why try to I source good quality bikes from craigslist. I wouldn't ever trust a Wallmart bike. My latest build was a Dyno beach cruiser which uses a sturdy steel frame & really takes a beating with a 69.5 cc 2 stroke on there topping 30 to 40 mph. NEVER use an aluminum bike for a 2 stroke build. Try to go with steel if you can at least when it comes to 2 strokes. Learned that the hard way & snapped a mountain bike frame almost in two.