99cc rack mount 3 speed spoke drive MTB

[silverbear]

Welding will be another day when there is no rain, but it won't take long and doesn't need to be pretty. A photo is pictured from another build using copper pipe and a sausage shaped muffler of the same size and shape as I just ordered on ebay. 99 cents for the muffler, new but no packaging and $4.00+ to ship it. It will screw into the copper fitting at the end of the 3/4" copper pipe. Copper pipe to copper fittings will not be soldered as the solder will melt under high heat, so they will be bolted together. I think this will make a nice, clean exhaust for the MTB.

Also pictured is an internal view of the two halves of the Sturmey Archer throttle type shifter for the IGH. Next to last photo shows a small circle toward the bottom. In it is a small spring which is supposed to have a ball bearing sitting on it of a diameter that when pushed it can recede into the hole and sit there under compression as the twist grip shifts from one gear to another. Smaller than the hole and larger than the spring. Last photo shows three depressions which the bearing can click into at each gear selection. It stays in that position until a bit of wrist effort shifts the 3 speed hub into the next gear. Slick. However, I don't have that ball bearing and no luck in town finding one at either of the hardware stores or NAPA. I tried bearings from head sets, but they are too big. Bigger than a BB from a BB gun. So, I'm on the lookout and will dig through my nuts and bolts and strange bits containers for the goldilocks ball bearing which is... ah, just right.
SB

 

[Intrepid Wheelwoman]

I like that twist grip gear shifter Silverbear, it's a very neat and tidy piece of work. I haven't seen one like that before but can well understand why you would want to use it on your bike because it would be just so darn useful.

 

[silverbear]

Hi Anne.
Yes, they're nice and were in use in the same time frame as the hub I'm using. I notice that the spacing between the depressions is not equal, but must be perfectly right for the gear positions. Four or five years ago I bought several of these in different states of not all there. One is complete and I have it on the 3 speed Elgin Velocipede which has an IGH hub at the rear wheel and key parts from an SBP shift kit I purchased from CB2. I like the shifter for one, because it does not draw attention to there being gears and two, because it is in hand all the time with no need to lift the hand in search of a lever type shift control. I may take apart the remaining one to see if there is a bearing in there of the right size, but then that one will be missing two parts instead of just one. First, do a search for the missing ball bearing as I may get lucky.
SB

 

[silverbear]

Curtis Fox sent out the pulleys yesterday and they were in my mailbox today. Pretty fast shipping in state. With the pulleys on the jackshaft I can see how much needs to be cut at the top of the angle iron rail to make clearance for belt and pulley. Not shown is the pulley for the 3 speed hub. What fun it was getting that snap ring into place.

Not much time right now for bike work as the fishing opener is tomorrow and I've been helping neighbors get their docks in and boats launched, set a minnow trap for bait and have enough that I gave away minnows to neighbors. In town they sell for $7.00 a dozen. Mine cost a slice of bread for many dozen. Rainy weather has kept me inside for the most part as far as bike work.

Also pictured is the other 3 speed shifter of a completely different design. It is a Shimano for the 333 IGH. I notice that the three recesses the ball bearing slips into for each gear are equi-distant while the S.A. is not. I wonder then if it is wise to use a Shimano shifter with a S.A. hub. Don't know, but it is something to consider.
(cont.)

 

[silverbear]

I also made a wee copper gas filter for the new engine. There isn't much room so I made it extra small out of 1/2" copper water pipe and end caps. The end caps are drilled out to receive 1/4" copper tubing cut off with appropriately, a tubing cutter. I cut extra grooves in the tubing ends so that gas line can get a better grip when cinched down. The filtering medium is fine grade stainless steel wool. Solder holds the pieces together. Usually I make my gas filters bigger out of 3/4" pipe. I started making these a few years ago and find that they work well and of course I have this thing about copper.
SB

 

[Intrepid Wheelwoman]

Shiny, - it's like a little jewel

 

[fasteddy]

Silverbear,

It's looking great. Definitely a solid run around bike. Copper it is indeed the poor mans gold.

Steve.

 

[silverbear]

Hi Anne and Steve, two of my very favorite people!
This is the first for a wee gas filter. Would you believe that all of the steel wool you see in the first photo got crammed into that bit of pipe? I read somewhere some years back that very high tech filters used in nuclear plants used stainless steel wool as a filtering medium. The light bulb in me brain flickered a bit and I found some for sale on ebay (not that I needed ten yards of the stuff, but that's how it came so thankfully I won't run out soon) and made my first copper gas filter. I know you can buy a perfectly good in line gas filter for a couple of bucks, but this is copper ya know and I made it meself, so that makes it special ya see and makes it just right for a motorbike. Goes faster and smoother possibly. And it's prettier, too. And it ain't plastic, either. So...seemed like a good idea at the time.
SB

 

[dtv5403]

I apologize that I havent read the entire thread, so if the answer to this question is somewhere in here, I have not seen it. Are you using the stock carb?

 

[silverbear]

Midway in this build I switched engines. I had pulled my 99cc Predator from another build and that engine does have a different carb from stock. It runs an NT type of 'speed carb' and was a big improvement on that engine's throttle response. Along the way I decided to purchase a new 79cc Predator for this MTB and so far at least I'm running the stock carb. I don't think having enough power will be an issue with this bike as it is a light frame and the gears should help distribute a good bit of torque. I'm not looking for it to be fast, either, anticipating a top speed of perhaps 30mph. Should be fine stock.
SB

 

[dtv5403]

Was just wondering if you had the thermal insert and gaskets for the stock carb that I might be able to use, I'm going to use a 19mm carb but the stock thermal baffle and gaskets should accommodate the intake manifold Im using. If you have them, pm me and let me know what you want for them. I do agree the stock carb should make decent power. I just prefer the 19mm carbs for a couple reasons.

 

[silverbear]

I think your 19mm carb (I'm guessing it is like for a China girl... a motorcycle type) is better than the stock carburetor. With the 99cc I was trying to milk more juice out of it since it was powering a heavy bike (1950 Panther) with a canoe sidecar & dog passenger. Plus this old circus bear.

The speed carb I used required an adapter I think I purchased at BMI karts (memory has holes in it) and I retained the original thermal baffle and gasket. I wonder how one could make that thermal baffle. Perhaps a scrap of plexiglass could be shaped and drilled if you can't find a stock one. One of those plastic kitchen cutting boards would be about the right thickness. Good luck in your quest!
SB

 

[curtisfox]

You might try here and see what you can find,or nas SB said BMI...........Curt

https://www.affordablegokarts.com/

 

[silverbear]

You might try here and see what you can find,or nas SB said BMI...........Curt

https://www.affordablegokarts.com/

I think you're right, Curt. AGK, it was.
SB

 

[cannonball2]

Nice progress SB! The engine tucks in nicely. Looks like the light at the end of the tunnel is getting nearer.
I would suggest a bar welded across the hubs swing arms to tie them together. The hub will do pretty well at that task but may have a tendency to allow the arms to twist. Other wise looks like you have done an amazing job of engineering! Congrats on over coming all odds!

 

[dtv5403]

Agk has gaskets but no baffles. Bmi has nothing for the 79cc that I could see. I may go ahead and just bit the gasket from agk and go without a baffle unless I can turn one up around here somewhere.

 

[silverbear]

Agk has gaskets but no baffles. Bmi has nothing for the 79cc that I could see. I may go ahead and just bit the gasket from agk and go without a baffle unless I can turn one up around here somewhere.

I think you could make one pretty easily from a plastic vegetable cutting board. Might find one at GoodWill or Salvation Army. And it seems to me that people have made intake manifold gaskets from cereal box cardboard.
SB

 

[silverbear]

Nice progress SB! The engine tucks in nicely. Looks like the light at the end of the tunnel is getting nearer.
I would suggest a bar welded across the hubs swing arms to tie them together. The hub will do pretty well at that task but may have a tendency to allow the arms to twist. Other wise looks like you have done an amazing job of engineering! Congrats on over coming all odds!

Thank you, sir! It does look like the end is in sight. Curtis was kind enough to send me a couple of old idler pulleys and I've been pondering that swing arm, trying to picture where a spring loaded idler could go to keep tension on the final drive belt. A few rainy days is good as a pause in the process to give some thinking and staring time.
SB

 

[dtv5403]

I appreciate the suggestions, but I'm a bit leery of trying to make my own gasket without knowing if I have the proper cutting tools to make perfect holes, and are you sure cardboard is a good material? It's not waterproof. As far as the baffle goes, it's not 100% necessary, all it really was gonna do was move the manifold away from the engine because the manifold is perfectly round and won't sit flush on the intake port without some filing/grinding to make it fit. But I've seen other engines run fine without an intake baffle, I don't think it will hurt anything and it's another invention I don't have the tools for, but again I really do appreciate the suggestions. I can tell you're trying really hard to help and that's very nice of you. Thank you.

 

[dtv5403]

I did just read a neat little trick for creating the pattern for the gasket. Smear some oil on the surface where the gasket is going, then press the cardboard on the surface and the oil will make the pattern for you. From there just gotta figure out how to cut the tiny holes. Think I have an idea for that.