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Seeings they are similar to a gas powered pocket dirtbike the forks could be a better upgrade seeings both have a 10mm steering stem bolt.......

The MX500/650 front forks closely emulate the Oldschool Rupp minibikes and the Kawasaki M75 minibike with subtle differences too...Finding a really good set isn't cheap though...

PW50 front forks are a good consideration too..

Good Luck
 

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Any clue where to shop for them?...ones I'm finding on Amazon are all the bigger hollow stem bolt like a traditional motorcycle
 

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Any clue where to shop for them?...ones I'm finding on Amazon are all the bigger hollow stem bolt like a traditional motorcycle
Vintage minibike classifieds and ebay..

On the ones with the hollow stem bolt you can unscrew the stem bolt and make an adapter to adapt basically any set of forks to fit any type frame...

Theres guys on the oldschool minibike forums cross breeding them with USD forks from pitbikes..........

https://www.popscreen.com/prod/MTgxMDI5OTYw/Rupp-Scrambler-Vintage-Minibike-Suspention-Forks-and-Handlebars-Old-Mini-Bike

These are from a Rupp



Kawasaki front forks....




If you go with the pocketdirtbike front forks I suggest buying an extra set of upper and lower fork clamps and doubling up the upper and lower fork clamps for extra strength for that heavier e-bike...
 

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Just modded my sons suspension...........heres what I did:

An XR50 stock rear shock lines up and bolts right on with the stock hardware after pushing out the bushings in each "eye" (end) of the shock and replacing with new 1/4 x 5/8 x 3/4 bushings from ACE hardware ($2.99 ea). This raises the rear about 2" and gives a much softer/smoother ride with more travel. I had one laying around from other builds Ive done but the stockers are cheap on ebay (or any other pitbike shock).


For the forks.......

Theres a hole in the bottom of the forks where you can put a VERY LONG allen head tool (I had to make one using a hex apex and welding to a long metal rod with a nut welded on the other end) Remove these 2 bolts and the 2 bolts on top of the forks to disassemble. The white nylon bushing that keeps the inner fork tube stable can be compressed using small screwdrivers to pry it out after you pull the fork tubes out. Replace the bolt you just removed with a longer bolt (length depends on how much longer you want it to be/how long your new springs are) I had to make my own bolt as my local stores didnt have anything long enough in the correct thread. (I simply cut a bolt in half and welded in a metal rod to make it longer) You will find a rubber tube inside the spring in the forks when you disassemble. You dont need it. I cut this (1/4" length) and put it under the head of the new bolt to keep the bolt from slamming on the rebound of the fork. (thats the banging noise you hear on your stock forks. Older dirtbikes with spring forks used a rebound spring in this place....you could do that too. Make sure to account for this added length when choosing/building a new bolt) I cleaned/greased up everything and then reassembled using a longer spring I got from ACE. I dont know what the stock spring rate is but I bought the closest thing I could find in the same diameter/spring rate & length I wanted. ($2.99 ea) Put it all back together and you end up with the forks balancing out the rear end for ride height. The new seat height is 27". (Not sure what stock was) This made the bike waaaaay more fun. Even just riding around in the grass, you dont feel any of the little bumps etc..... With the added leverage, stoppies become easy. Super cheap mod!!

I also had a KX60 rear brake lever laying around so I fabbed up a bracket and cable to add a rear foot brake for it. Welded on some metal to widen the footpegs and sharpened them up. Hit me up if you have questions.
 

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Where could one find a new white nylon bushing for the forks? Ours broke on one fork and is now jammed. Can’t find specs for a replacement.
 

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they dont sell individual fork parts for the 650 unless someone is parting them out you should try and sorce some used forks for parts or contact razor for a new pair.
 

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Just modded my sons suspension...........heres what I did:

An XR50 stock rear shock lines up and bolts right on with the stock hardware after pushing out the bushings in each "eye" (end) of the shock and replacing with new 1/4 x 5/8 x 3/4 bushings from ACE hardware ($2.99 ea). This raises the rear about 2" and gives a much softer/smoother ride with more travel. I had one laying around from other builds Ive done but the stockers are cheap on ebay (or any other pitbike shock).


For the forks.......

Theres a hole in the bottom of the forks where you can put a VERY LONG allen head tool (I had to make one using a hex apex and welding to a long metal rod with a nut welded on the other end) Remove these 2 bolts and the 2 bolts on top of the forks to disassemble. The white nylon bushing that keeps the inner fork tube stable can be compressed using small screwdrivers to pry it out after you pull the fork tubes out. Replace the bolt you just removed with a longer bolt (length depends on how much longer you want it to be/how long your new springs are) I had to make my own bolt as my local stores didnt have anything long enough in the correct thread. (I simply cut a bolt in half and welded in a metal rod to make it longer) You will find a rubber tube inside the spring in the forks when you disassemble. You dont need it. I cut this (1/4" length) and put it under the head of the new bolt to keep the bolt from slamming on the rebound of the fork. (thats the banging noise you hear on your stock forks. Older dirtbikes with spring forks used a rebound spring in this place....you could do that too. Make sure to account for this added length when choosing/building a new bolt) I cleaned/greased up everything and then reassembled using a longer spring I got from ACE. I dont know what the stock spring rate is but I bought the closest thing I could find in the same diameter/spring rate & length I wanted. ($2.99 ea) Put it all back together and you end up with the forks balancing out the rear end for ride height. The new seat height is 27". (Not sure what stock was) This made the bike waaaaay more fun. Even just riding around in the grass, you dont feel any of the little bumps etc..... With the added leverage, stoppies become easy. Super cheap mod!!

I also had a KX60 rear brake lever laying around so I fabbed up a bracket and cable to add a rear foot brake for it. Welded on some metal to widen the footpegs and sharpened them up. Hit me up if you have questions.

Could anyone please supply a link to any better spring just like how HUBBYRACING was able to obtain? Or any other better recommendations to make the MX650 perform better? Or any other better fork that directly bolts in???
 

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this very exspeisve mod where they use down hill mountain bike throw axial air forks with a mountain bike throw axial hub laced into a BMX double wall rim then you can use the mountain bike disk brakes a BMX goos neck and low profile BMX bars

you have to buy the forks new once the head tube has been cut to fit a mountain bike the head tube will be to short for a MX 650

dont even try to use a cross country fork it will snap you have to use ones rated for down hill mt bikeing

bearings cup sizes shims spacers and all of that fun stuff depends on the forks be prepared for lots of trial and error sence all mountain bike frames are difrent its trial and error on bikes as well

its not worth it IMO ($$$ to $$$$) unless you have down hill MT bike parts laying around...
 

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Thanks, but not an option for me.



Could anyone please supply a link to any better spring just like how HUBBYRACING was able to obtain? Or any other better recommendations to make the MX650 perform better? Or any other better fork that directly bolts in???
 

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I ended up 3D printing some 3 inch spacers in PLA. I printed with 100% fill so they are solid. I purchased M8-1.25 x 200mm bolts and put the spacers in. Now my forks at least are as high as the rear end. I am going to throw on the new forks this weekend and try it out. The springs may still be an issue. If so I will take them apart again and find some better springs.

I just wanted something to ride around with my 10 year old. I added a 1800 watt motor and 48v battery. It gets up to around 25 with me on it. I weigh 240.

A few photos are attached.
 

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Did you have to make a long Allen head tool like hubbyracing described to get to the springs? Or did you figure something else out?

Please let us know how this turns out!
 

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To remove the tubes, I just used an 18 inch bit extension holder from amazon. I also got a set of magnetic bits at the same time. It worked great. (Links below)

I took it out for a test spin and it made a pretty big difference. No issues at all and it seems pretty sturdy.

Instead of taking my existing fork apart, I ordered a SX500 Front Fork thinking it was an exact fit. I was wrong, but with another 3d printed spacer, it worked out perfectly and with new springs in the tube and a rubber bushing on the large bolt, I am getting a much better ride without bottoming out over bumps.

With the internal 3d printed bushing above and the 3d printed spacer, I am about 4 inches taller than stock.


https://www.amazon.com/gp/product/B00132FUP4/ref=ppx_yo_dt_b_asin_title_o08_s01?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B07G6RX35J/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1
 

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Thx for the reply and the details. Super helpful. I have a few bikes (sx500, mx500 and mx350) for the kids. The mx500 needs new batteries and is in rough shape. Think I will clean it up, new batteries, upgrade the suspension and drivetrain so I can ride it around with the kids. Then they will have a bike to grow into as well.

Ok I’m lying I am doing it for me. Lol
 

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Just finished doing this upgrade to my son's bike. Posting my results.

I started with upgrading the rear shock. It is 190mm long and looks the same as the stock one just a bit longer and is a direct swap. My son complained about it sliding him forward more that the rear is taller and so I ended up here. Thanks for the post BTW I have been wondering about upgrading the forks for some time and this is a perfect cheap solution.

Rear Shock: https://www.ebay.co.uk/i/153794616042?chn=ps

I started off at Ace and got longer similar diameter and gauge springs. $2.48 each. They were 5.5 inches long with slightly more tension. (Stock springs are 4 inches). I also grabbed some 1/2 in diameter x 1 in long springs for the bolt heads to soften the recoil "whack" $0.46/ea.
20200615_134337_1592253849551.jpg
They had no bolts that would work so I up buying some 5/16 round stock and tried to get my neighbor to weld for me to extend original bolts.
20200615_135949_1592254930042.jpg
I'm sure this would have worked fine but his wife has them all on quarantine and he can't come out to play.

So I went to Tacoma Screw and got 2 M8x1.25x200mm bolts. These are the perfect length. $4.24/ea.
*** The new bolts are 6mm hex. The stock bolts are 5mm so be prepared to make another tool to install these.

Ebay link to similar bolts: https://www.ebay.com/itm/1-M8-1-25x200-Stainless-Steel-Socket-Allen-Head-Cap-Screws-Steel-8mm-x-200mm/173473742224?hash=item2863d73d90:g:XOUAAOSwzlFbdFb9

While at Tacoma Screw I checked out their compression springs and found much heavier gauge 6" springs that are stiff as hell. I'd like to try the lighter gauge springs from Ace on my daughters bike to see which I prefer.

Tacoma Screw 1 3/16" x 6" spring #809 $15.13/ea. This is 6 times the cost of the Ace spring.
20200615_134337_1592253849551.jpg

I put it together with the 1/2" springs on the bolts first. I modified a washer by drilling a 3/8" hole in a smaller washer because a larger one won't fit inside the bottom of the forks and slid that on top of the spring. Then I cut about 5/16" off of the rubber bushings that aren't needed and stacked that on top of the washer. 20200615_105425_1592254116869.jpg
I figured this would dampen the "whack" sound the best. And it works really well.

Stock seat height 22.5 in 20200615_124316_1592254031059.jpg
New seat height 24.75 in 20200615_124147_1592253874284.jpg

For my tools to extract the bolts I got a little creative due to my being cheap and too impatient to wait for anything to come in the mail. And my lack of a welder....
I took a 16" spade bit 20200615_140108_1592254916524.jpg
and carefully filed the end down to 5mm.
20200615_135748_1592255191526.jpg
This worked well for extraction.
For the install I found an old gift my wife gave me and a t45 torx bit.
20200615_140137_1592254950367.jpg
Barely fit but I was pleased it got the job done.
20200616_074939_1592318994595.jpg 20200615_202823_1592319013415.jpg
*** Update: this tool broke 1/2 way through the second install. Had to cut the filed end of the spade bit off and use it for second bolt. It isn't quite 6mm closer to 5.5mm. This barely worked and I have since bought the extender listed below. I may try to have my neighbor weld a 6mm hex bit onto the round stock in the mean time so I can start making the progressive frankenspring.

In conclusion I wish I had a welder. Would have made this go easier and cheaper. The 5/16 round stock could be used both for the extraction tool and bolt extenders. Instead I have cut bolts and wasted a bit of the round stock. If you don't have access to a welder I would just purchase everything as a kit online. Including the bit extender and bit set mentioned in a previous reply. That set would be sweet to have anyway.

Links to bit extender and bits:

https://www.amazon.com/gp/product/B00132FUP4/ref=ppx_yo_dt_b_asin_title_o08_s01?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B07G6RX35J/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Thanks again for the original post. Made this a breeze.

UPDATE:

I installed the lighter gauge springs from Ace on my daughters bike. And some slightly longer and stiffer small springs for the bolt "whack" dampening. Here are my conclusions:

The lighter gauge springs from Ace, although they are 1.5" longer than stock, are still too soft for me to jump the bike with. (I'm 155 lbs.) They bottom out easily but do offer the height increase I was hoping for. The HD springs from Tacoma Screw are nearly perfect but don't offer the softness you would want for a leisurely drive but are great for MX type riding. So, I am thinking about cutting the HD springs in half and either welding them to the stock springs or; cutting the longer Ace springs in half as well and combining them with the cut HD springs. This would provide a progressive type of shock that would be soft at first but stiffen and hopefully not bottom out in the end.
Ace springs compressed a total of 2.5" on the test drive.
20200616_075848_1592319670700.jpg
Tacoma Screw springs compressed total of about 1.5".
20200616_080021_1592319693015.jpg

The stiffer springs I bought to help dampen the "whack" I think are better than the springs used on the first install and I think I'll buy two more of them to provide the best sound dampening. 20200615_210502_1592280317643.jpg

I'm also thinking about finding a spring that will fit in between the rear shock absorber spring and the center shaft to provide a progressive type of suspension for the rear as well. 20200615_203459_1592280446164.jpg
20200615_203653_1592280505341.jpg
I'm sure this won't be an easy thing to find but I'll update if I can find something that works.

I'll also update about the results of the progressive front suspension. I think it'll be perfect.
 

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