Harrison Wildcat mods

cfh

Well-Known Member
#1
Picked up a Harrison Wildcat on craigslist yesterday. Doing some of the standard mods that make it a more viable and structurally sound bike. It already had the jackshaft plates (factory installed.) But it did not have the angle iron modification. Also I always weld a kick stand mount bracket on this frame too. But the biggie that really needs done (at least for my fat butt) is a springer front end.

To do this you'll need some parts:
(4) spring cups.
(2) springs (both available from https://www.OldMiniBikes.com/nos-front-fork-springs-and-cups-kit.html )
And the biggie...
(2) 11/16" diameter 12" long solid steel rods.

Now the 11/16" diameter (.6875") rod is kind of tricky to get. It's obviously not a common size. But that's what works. You may have to do some hunting to find it. Or buy 3/4" (.75") rod and turn it on a lathe.

Note you could certainly adapt this spring concept to other makes/models of mini bikes.

The key to this modification is doing the cuts in the right places. Below the picture shows the general cut idea. This modification on the Harrision adds about 2" to the overall fork length. This makes the bike ride better! It increase the rake slightly, increases ground clearance a bit, and levels out the motor plate to the ground. Again makes for a better ride!

 

cfh

Well-Known Member
#2
First you need to cut the original Harrison fork. Measure 2" down from the top of the bottom triple tree, and make your cut. Next the left-over lower portion has to be trimmed to 7", from tip to end. (You'll cut off about 1.5")

 

cfh

Well-Known Member
#3
Now take the two 12" lengths of 11/16" rod, and hammer it into the fork ends. Keep hammering until you "bottom out". After you've done that, you can put it in the vice (as shown below) and weld on the lower spring cups.



 

cfh

Well-Known Member
#4
Note i forgot to mention that the top spring cups need to be welded to the (cut) triple tree. That can be seen (tack welded) in the first picture above.

Another tip is that the triple tree tubes do have an inside weld. You may have to run a de-burring bit inside the tube so the new lower section slides into the triple tree without binding.
 

cfh

Well-Known Member
#5
Here's the angle iron modification to the lower part of the Harrison frame....
Using two 6" lengths of 3/4" angle iron, it is welded to the bottom tube of the frame and to the motor plate. This gives the frame much needed support (especially if you're using a bigger motor like a 212 or a 10hp tecumseh.) Note this frame has the stock jack shaft mounting plates, so those did not need to be added. The added kickstand mount was welded to the frame too (opposed to using the original style bolt-on kickstand.) This is available from https://www.OldMiniBikes.com/kick-stand-and-bracket.html
cfh



 

cfh

Well-Known Member
#6
Back to the springer mod...
Here's a picture of the welded up front end parts test fit together. I can see i have a bit of work to do so the 11/16" bar fits without binding into the triple tree. This will involve some gentle grinding/deburring of that internal tube weld on the inside of the original triple tubes. cfh

 

cfh

Well-Known Member
#9
When I get the parts back from the powder coAyer I’ll show how they all fit together and how much travel they potentially could get. My guess is it’s only a few inches. But that’s OK because I’ll take anything. As I get older suspension becomes more important
 

cfh

Well-Known Member
#10
Here's the fork springers installed and you can get an idea of the amount of travel that can be had. Note the sliding rods have a thin coat of wheel grease on them to prevent rust.

Overall the project was a good one and not too expensive or time consuming. cfh



 

cfh

Well-Known Member
#11
I forgot to mention on the Harrison front end there's a bracket that holds the fender. That has to be cut off. Then you drill two 1/4" holes in the bottom triple tree. Those holes are used to attach the fender (using a 3/4" spacer.)



 

cfh

Well-Known Member
#12
Just rolling this thing around the garage i can say this... the front end is much more solid now. It's definitely heavier. The feel is very tight and solid. More so than an original Harrision. I think this is a really good mod to do to the front end.

All i need now is a seat (and some fenders) and i'm ready to put on a motor and a series 30 torque converter/jackshaft. I'm going with a 5hp Tecumseh on this bike. I have a harrison with a 10hp tecumseh and frankly, that thing is a freaking monster!

On this bike i will be using a 16 tooth jackshaft cog. On the 10hp tecumseh harrison I put a 20 tooth jackshaft cog. But with the smaller 5hp Tecumseh, i think 16t is a better choice.
 

cfh

Well-Known Member
#19
I have ordered a seat. it is the thing that is holding the project up the most.

Had to make a change to the torque converter implementation. the jackshaft is not used now, as i went with a comet/china TAV30, implementing the mounting plate. The jackshaft would be used if i went to the Tecumseh 10hp. But with the HS50, there really isn't a good way to use a jackshaft. This was a heck of a lot easier to do though. Just a bolt on thing. And it's nice as the cover fits well (with just a couple cuts to the plastic.)

One thing i did do though is change the drive gear on the TAV30 setup from 12 tooth to 16 tooth. The TAV30 kit comes with a 12 tooth #35 chain driven sprocket. The rear wheel sprocket is 72 tooth (stock harrison), and a 12 tooth drive would make the bike have too much torque (and no high speed.) With the 16 tooth driven gear it should go about 32 mph.

The only hassle is, i have to machine the 16tooth 5/8" hole front sprocket to get the TAV30 front sprocket to align with the rear sprocket. Took .200" off one side of the front 16t gear cog, and used a couple washers on the other side. This got the chain alignment where it needed to be.

Probably need to make a custom exhaust too....



 

cfh

Well-Known Member
#20
Put on the fenders and the throttle and the brake and rode it around. This is a lot better (to me) then the one i have with a 10hp Tecumseh! (that thing is a MONSTER.) Good speed to power ratio, and rides nice. Just need a seat. And then i'll make a custom exhaust for this Harrison wildcat... cfh



 
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