Help with adding Front Suspension forks!

[Hec In Omaha]

Here is the deal, I want to add front suspension to my Azuza Mini Bike. I have bought a set of Yamaha PW50 Forks from a seller on Ebay. The problem is that the seller can't read a tape measure. They are too narrow by about 3/4".



I want to even use a PW50 steering head to upgrade to bearing supported steering.

The wheels are Azuza 8" Tri-Stars with 480/4-8 tires. Is there a tire option that is narrower than this combo?





Do I modify the Yamaha triple trees to get the required fork width? I was thinking of using a hole saw to cut the trees and re weld them so that the fork holes line up with the center steering hole. This will give me the fork width I need but will be a P.I.A.!





Do I butcher the Yamaha triple trees to cannibalize the pivot tube and the two fork clamps that are tacked welded to the underneath of the lower tree. I would make new triple trees a la Mini Bike Style and graft the pivot tubes and fork clamps to the lower tree. I would allow two new holes in each tree for new handle bars that would be welded in.

Any suggestions?

BTW this project can be followed in the project section under the Side Car Build for 6HP Azuza.

Thanks again!

 

[markus]

see if someone on here can measure up an aired/mounted 3.50-8". I'm not sure if they end up skinnier than the 4.80's do. I dont think they made a 3.25 in an 8" size. There was also 2.50x8" they are really small and skinny, the wheels that they were intended for had pretty skinny bands to it may end up looking like a rubber band on the azusa wheels! I saw some of them for sale on ebay, they were for Indian/italjet "mini mini" and Broncco Fantichino's.

 

[Hec In Omaha]

Markus,

What do the tire size numbers tell me? Specifically the 4.8/4.00? I know my rims are 8" in diameter and are 3" wide. I found these on EBay.
\3 50 8 Tire w Inner Tube Scooter Mini Bike 3 50 x 8 | eBay

Vee Rubber 3 00 8 3 00 8 Tube Type Scooter Tire | eBay

Hec

 

[markus]

its supposed to be "standard inch" measurements, but if its on a wider or skinner wheel it will vary and its not always dead on from one company to the next

this is from Dennis Kirk catalog:

Standard Inch
Example: 3.25H-19
The Standard Inch systems are found on older motorcycles. Tires with these Inch markings do not include an aspect ratio designation, which is 100%. It means the cross-section tire height is 100% of the width. Inch size tires are all bias-ply construction and not belted. They are no longer being fitted on new motorcycles and are gradually being phased out of use.

In the above size, 3.25 is the width, H is the speed rating, and 19 is the rim diameter in inches. The aspect ratio is not listed, but is 100% of the tire width.

 

[TANKSAREUS]

I always found this usefull from MGF Supplies website

Tires for all kinds of Go Karts, Mini Bikes and Baja style vehicles. Slicks, studded, knobby, sawtooth and ribbed tires.

There are 2 methods used to measure tires:

1: If a "x" separates the 1st 2 sets of numbers the 1st number is the overall diameter of the tire. The 2nd number is the overall width. The last number represents the rim diameter.

2: Used for smaller and industrial tires. If a "/" separates the 1st 2 sets of numbers the 1st number is the overall width of the tire. The 2nd number identifies the section height. This is the measurement from the crown to the bead of the tire. The last number is the rim diameter. The overall diameter of the tire is D + D + C. So for a 4.10/3.50-4 tire the overall diameter is 11" (3.5 + 3.5 + 4).

Note that all measurements should be made when the tire is inflated to its recommended air pressure.

 

[Hec In Omaha]

Tank and Markus,

Thanks for the info. Now the tire markings of 480/4-8 makes sense. Didn't quite know what the 480 meant. Anyways went ahead and ordered the 3.5-8 tire with tube from EBay. Should be here in a couple of days. Keep y'all posted. I am crossing my fingers that narrower tire solves my problems:thumbsup:.

Thanks again!

Hec

 

[Hec In Omaha]

All,

Here are a couple of pics showing the Azuza 8" x 3" wide Tristar rim placed between the Yamaha PW50 forks. The overall width of the rim is 3-9/16" wide at the widest point. The forks are 3-15/16" wide. Man that's only about 3/8" clearance on each side! I hope the 3.5" x 8" tire I ordered fits. We will see I guess. Keep ya posted.




Hec

 

[Dadrider]

That chart makes sense. I was always wondering what the numbers on each side of the " / " stood for. I need to tuck that chart away somewhere for reference.

Thank you for sharing.

 

[Dennis B]

If you can remove the fork tubes from the triple tree and know your exact measurements I can get new triple trees last cut on a high Def table. I just need your measurements. Any width 1/8", 3/16", 1/4" thick plate.

 

[jeep2003]

I think Id probrobly cut the trees into 3 parts and add a piece of metal on either side to widen them. It would be easier than making them from scratch and neater then reconfiguring them to straight

 

[Dennis B]

The laser cut trees are $25-$35 a set plus shipping which is usually a flat rate heavy envelope.

 

[Stangrcr1]

I took a set of 6" TriStars and cut a 1/4" off the inside of each to make them skinnier. Just some lathe time for me, but made the clearance so they would fit in my Bird frame. Had to drill a new hole for the tube stem, but no big deal.

Dunno how much material is available on the 8" ones, but possibly an option...

 

[Hec In Omaha]

If you can remove the fork tubes from the triple tree and know your exact measurements I can get new triple trees last cut on a high Def table. I just need your measurements. Any width 1/8", 3/16", 1/4" thick plate.

Dennis,

What kind of files does your laser cutter need? I could supply drawing files in either .DXF or .DWG format. I thought of doing the exact same thing, that is making new trees and having them laser cut. I have a few designs that I would love to get laser cut. One is a seat mono shock for mini bikes. Mmmmm Laser cut.........
We'll see how the 3.5" tire goes. Heck at 3/8" clearance on each side of the wheel at least my sidewall will be self cleaning!:laugh:

Hec

 

[Dennis B]

I don't know the file type. I just draw a picture and give it to my buddy.

 

[Hec In Omaha]

Markus,

Thanks for the tip on finding some narrower tires. The 3.5" x 8" tire arrived today. I mounted it on the wheel and it fits! The new tire is a little shorter than the old one.





Because of this I will order another 3.5" x 8" tire for the rear. This way I can weld the fork steering head on the frame making sure the bike sits level. I have read that you want the front a little higher so that when you get it on the bike sits level once the forks are compressed. I still need to drill out the forks to accommodate the 5/8" axle.

Lesson's learned:
A Yamaha PW50 Front Forks and Triple tree will work with an 8" rim with a 3.5" x 8" tire mounted to it. So go find some PW50 forks and suspension to your mini bike!:thumbsup:


Thanks to all who chimed in on this!
Hec

 

[Hec In Omaha]

All,

Here is a couple of pics of the PW50 forks resting on the frame. I plan on keeping the same rake angle of the factory Azuza Steering Tube. The PW50 handle bars are a little low. I even jammed a fender in between the forks for grins!:thumbsup: I will have to notch each side of the front fender to clear the forks. No big deal.





I won a set of 2006 Honda Rancher TRX350 Handle Bar Clamps on EBay for $9 shipped. I think they will work with the PW50 Top Tree. The PW50 handle bars are welded to a bracket that is bolted through the top tree with a single bolt and therefore have no adjustment. The 2006 Honda Rancher TRX350 Handle Bar Clamps are taller than the factory PW50 ones and they give me the ability to angle the handlebars.



One step at a time! :wink:
Keep ya posted.

Hec

 

[Hec In Omaha]

All,

I forgot to add this pick on my previous post. It shows the Steering Head Tube Angle on the PW50. I imported a picture of a PW50 into AutoCAD and measured the angle of the steering head tube measured both from level ground and vertical. . Maybe I should keep this angle on the Azuza Frame. Hmmm?



Hec

 

[jdogg]

There is always these to raise the height Hec as a last resort seeing as you bought new bar clamps! Or new bars! :doah:

110cc Pit Dirt Bike Pit Bike 22mm 7 8" Handlebar Clamp Handle Bar Risers | eBay

 

[Hec In Omaha]

Jdogg,

Thanks for that, but I don't want to have to make new trees. There is no room on the top tree plate for a two bolt handle bar clamp. See 3rd pic in my first post. I would have to build something different to attach those.
As for the handle bars, I will first try to bend my own using 1/2" Sch80 seamless pipe. The pipe has an O.D. of 0.83" as compared to 7/8" tube which is 0.875". Should work in the clamps. I have a Harbor Freight pipe bender and two angle finders and lots of pipe! :thumbsup: I have never tried bending handle bars before. How hard can it be! Famous last words right? If that doesn't work I suppose I can cut the Azuza ones right at the top top tree and weld a horizontal piece to connect the two.

Hec

 

[Hec In Omaha]

Howdy All,

Got some work done on the Mini Bike this weekend. First I tried my hand on bending some handlebars out of 1/2" Sch 40 pipe. I must say that it is harder than I thought. I messed up my first two attempts. In fact, I ended up using the left half of attempt #2 and re-bent a corresponding right half. BTW Attempt #2 had two left halves! Doh:doah: I used a the shoulder of a 9/16" bolt as a plug. I plug welded the bolt shoulder and welded up the two halves in the center using my Hobart Handler 140 Mig Welder then ground the welds smooth. I am running gas with it. I just got the welder last week and I really like it. I am a newbie to welding but work for a company that does industrial pipe fitting so I have access to guys that can give me help and pointers. I am learning. The hand grip area of the handle bars are intentionally long for now. I will cut them back a couple of inches once I mock up the brakes and throttle.
I cut off the Azuza Steering Tube with a portable band saw. Went through the welds like butter. I have the Yamaha PW50 steering tube chained clamped in place for now. A co-worker, who we call Stretch cuz he is 6'-7", will tig weld the PW50 tube on for me. Stretch is a certified welder.:thumbsup: I am still debating on whether to use the Azuza 30 deg fork angle or the PW50 26 deg for angle. I don't know if there is a benefit one way or the other. Comments? I am also contemplating adding a cross bar to the handle bars. That would give the mini bike a motocross look. Hmmm.

Here is what I have so far. I just figured out I have hit my limit for Pics? So one for now.

Hec