Speedway front fork rebuild

cfh

Active Member
#1
Over the weekend i bought a 1972 Speedway Green Horn. It was in a box, all taken apart, but mostly there. Unfortunately the bike was just worn out. I mean everything was worn. this thing got used! Came with the original HS50 motor (dated early 1972), which was also pretty worn.

I can deal with most of the wear issues. But I've never dealt with a Speedway front fork that was "loose as a goose" and just worn beyond usage. I had to come up with a way to deal with this. Unfortunately Speedway parts are pretty hard to come by, so had to do some adapting to make it work.

This information should apply to all Speedway front forks. But the measurements may be different for the 10" wheel models (I'm using a 14" wheel Green Horn for this example.)

First up you will some parts...
(1) Bronze bushing 1" ID 1.25" OD 2.5" length. Mcmastercar #6391k45
(2) Buna-N Rubber U-Cup Seal for 0.282" Groove Width, 0.955" ID x 1.545" OD x 0.25" Wide. McMastercar #9691k57
(2) old and used Rupp 1971-1975 Front fork strut bushings #17496. The more used, the better.

First need to get the old Speedway forks apart. Mine were tough birds. the original nylon bushing inside was jammed in there (and destroyed), and made taking the forks part difficult. In theory unscrew the fork cap and side the fork apart. then there's a large threaded bushing at the end that allows the parts to come off the upper strut. There should also be a spring in the lower strut.



The original Speedway nylon fork strut bushing. My that's pretty screwed.
 

cfh

Active Member
#2
Next up is to deal with the nylon fork strut bushings. I do not know a source for original Speedway versions, but we can take some old (used) Rupp 1971-1975 strut bushings and modify them to work. On this 14" speedway wheel fork, the Rupp version needs to be cut to 5.75" in length. I used a band saw to cut them.



After you have them cut to length, the ends need to be modified. The rupp version has too big of a lip on the edge. That needs to be sanded to fit inside the Speedway fork screw-on cups. I used a belt sander to do this. Also the second (lower) lip needs to be removed. Again I used a belt sander to do this.



After the used Rupp fork struts are sanded, the end should fit easily inside the Speedway fork screw-on caps.


 

cfh

Active Member
#4
Now comes the tricky part. On the Speedway screw-on caps, there's a bronze bushing inside. On my forks, this bushing was so worn, it was like a hotdog in a 55 gallon drum. The wear was also uneven. Check out the picture below. They should be 1" inside diameter, and 1.25" outside diameter. And .200" tall.

Also the rubber seal inside the screw-on cap was worn to death too. That will need to be replaced too.

 

cfh

Active Member
#5
Again these parts probably aren't available anywhere. But Mcmaster Car has some material that should work. I bought their bronze bushing 1" ID and 1.25" OD and 2.5" long. I put this on a lathe and cut it like a pepperoni to a thickness of approximately .200". I don't think this thickness is really that critical. If you don't have a lathe, you can cut them with a hacksaw (and then sand it clean on a belt sander.)

McMaster Car also sold some decent rubber seals. Not perfect replacements, but pretty good. It will work. And they are cheap, like (5) of them for about $5.



Original Bronze bushing on left:
 
#6
I used to make those for ATK rider. He also supplied me with the plastic bush. I may still have a set. Looks like you made all the parts so all the better.
 
#8
Yeah working on 45-year-old minibikes you darn near need to give yourself a Tetanus shot because they are all full of rust. I like what you did in fixing those forks. You did a great job at being able to improvise and fabricate since they no longer make replacement parts for Speedway bikes by finding some alternative parts that allowed you to reassemble the front fork. Bronze bushings are tuff and will not rust so hopefully they work well with some grease to lubricate them inside the fork. Too bad there is not a website devoted to Speedway minibikes like there is Rupps. I see you modified a stock Rupp front shock nylon bushing to work. Good idea.
Right now I have to deal with a rusty rear rim on my Rupp and I may just get a cheap can of spray chrome which will look better than rust. I will sand it smooth and spray it. I thought about getting an expensive product called "Easy Chrome" which is very expensive at $250. I don't want to dump too much money into the bike since I simply want another minibike to enjoy at my cabin, (I will have 3 minibikes once I get the Rupp running) and I have dozens of miles of low maintenance gravel roads to ride on there. I am building it to be used and that is why I am not going to make it into a museum piece as some people do to their Rupps. One for me and my wife and son to ride together on.
 

cfh

Active Member
#9
As a last step, the outside fork wipers are available on ebay. They are expensive, but i bought a set to finish up the project. I've heard of some people using heat shrink tubing for this. But I have not tried that.

 
#10
As a last step, the outside fork wipers are available on ebay. They are expensive, but i bought a set to finish up the project. I've heard of some people using heat shrink tubing for this. But I have not tried that.

These are for late 70 and 71 forks. 72-73 are different.
 

cfh

Active Member
#12
Yea dang you're right. Though they fit the moving part of the fork, they are too skinny to get over the threaded bushing. will have to come up with some other idea. Because i'm pretty sure that part is not easy to find...
 

cfh

Active Member
#13
There’s a bunch of fork caps on eBay for various makes and models bikes. Has anybody tried any of these to fit on speedway front forks?
 
#14
There’s a bunch of fork caps on eBay for various makes and models bikes. Has anybody tried any of these to fit on speedway front forks?
Depending on the popularity of the bike once in a while someone makes an aftermarket parts for them. Too bad that nobody has set up a Website for the restoration of Speedway bikes. You could try direct Googling of the needed part. Maybe you could set up a website dedicated to Speedway minibikes. I love the look of a well done restoration and I love to go to car shows and I would like to restore and old car someday. and I also restore Snowblowers too. A dedicated fan has setup a website were you can order aftermarket parts and even some New Old Stock parts for Gilson Snowblowers. Here is my 1973 Gilson made Montgomery Ward 8/26 I restored.
 

Attachments

cfh

Active Member
#18
Ole can you scan that paper sheet on Speedway forks? that looks pretty cool.
Gusto i was thinking of doing a Speedway web page. But my information is fairly limited on those bikes. I can start it, but it will be thin, and the info may not be totally accurate (best guesses on my part.)

Here's the Green Horn. No front fork dust covers, but it will work. Not really the right shade of green, but it will work.
Note I had to use "Goop" on the new front fork seals to keep them in place (because I don't have the dust covers, which would do that.)

 
#19
I will scan it, on mine if I remember correctly the seals were under the cap and there were little plastic seal spreaders and the bronze bush. The sheet shows the exploded diagram, I have to go get it as I put it back in the shed. Back in a few.
 

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