J-S Motocross page. Home made fork air tank system, and Winter MX ski setup and snow conversion

Welcome graphic

This is a collection of pics a few ideas I got around motocross stuff. Up to now, I only have info on:
 
Home made Air tank system and Winter MX ski setup and snow conversion

Air tank system:
This is a air tank system that was brought together with ideas from me and other people in different forums; among: http://www.ktmtalk.com/, http://www.thumpertalk.com/ and http://www.dirtrider.net/

SMC setup

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To help you with the parts needed, I tried, eeh! to draw the front triple clamp without the number plate to explain what parts to use and how top mount them. My bike is an 03 CR250, I think the installation would be pretty much the same from one brand to the other. There are different colors for the main components and I will provide links for you to see and have an idea where to buy these items.
Feel free to start from this to build your own and bring up your new ideas so we can all benefit from it!

 
Using only SMC components http://www.smcusa.com/default.asp
 
Tubing: I planned to use some polyurethane tubing. The pressure rating is plenty high. I chose 4mm od and 2.5mm id. The SMC part
# TU0425
 
Yellow:
(1x) yellow adapter is threaded in the handlebars. I tought a good wiring configuration would allow also the handlebars to be rotated front to back without hurting the plumbing too much. The 90* swivel being installed directly under the handlebars and pointing on the side allows the bars to be rotated any way you like without straining the tubes and plumbing. SMC part # KQ2L04-M5
 
Blue:
(3x) Adapters 90* elbow swivel female- /to eazy connect 4mm (outside diameter) tube fitting. SMC part # KQ2LF04-M5 . One will plug into regulator. The two others are to be used on the fork cap but will not thread directly to the fork cap. You will need the use of a threaded tube to link the female coupler to the fork cap hole.
 
Threaded M5 male/male adapter home made
To fabricate the threaded tube I used some 3/16 brake line tube and made the M5/0.8 thread using a dye. We have no choice but to use threaded tube mated to a female coupler to obtain an extra long reach male coupler. Nothing availlable on the market is long enough to reach the thread down in the pressure release hole. There is 6mm to go before the thread starts down that pressure release hole; and there is thread from 6mm to 12mm down. 
 
After you have finished cutting some thread on the tube, the threaded tube must then be cut to the right length. Thread one end of the threaded tube to the female elbow fitting until it is completely seated. Leave one end threaded and then measure 11mm of tube protruding out of the female adapter. Exactly 11mm is very important because if there is only 2mm longer, the tube will sit on the ICS (inner chamber spring) metal washer and effectively block the air passage. Use alot of teflon tape to ensure a tight fit. Thread into the fork cap. This procedure will not alter the fork cap in any permanent way. When you decide to remove the system, simply put back the stock pressure release screw and no one can tell what happened before; as opposed to most other setups...
 
Gray:
Plug-in Y with eyelet and solid tube male # KQ2U04-99
 
Black:

SMC Dual adjustment regulator. It has separate adjusters to meter in and out flow. I think this would be nice. M5 port / 4mm part # ASD230F-M5-04

 

Red:
red represent the places you will need to fasten on the number plate back side. There is a red dot center of the eyelet on the Y connector. This will need to be tied somewhere. Also I tought of using some kind of system to prevent the tubing from being caught up. This is why the two red strips. I haven't come up with anything brighter than adhesive tape.
 
Black:
There are some black plugs inside the handlebars if you look carefully. These are some cork or rubber plugs that you need to trim. They will need to make an airtight fit inside the handlebars. What is a little bit challenging is measuring the volume before gluing the plugs. A ballpark volume would be between 120cc and 75cc. Measure the volume before gluing the plugs. You can glue these plugs inside the handlebars using JB WELD type glue or 30 min+ epoxy.
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Winter MX ski setup and snow conversion:

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This project took a long time but it was definitely worth it. What took the longest was finding the right geometry for the ski to be stable yet corner well. The ski is a special design that has a carbide on each side to allow agressive cornering. With the studded sand paddle tire at the back you dont miss summer one bit. Fill your boots with spare spark plugs and go!

 
 
Front Suspension and Ski
The keel under the ski is not like the conventional "V" shaped with one center carbide touching. It is like a "n" shape under with both outer edges holding a carbide. This allows for aggressive turning and banking without the front end washing out. AD Boivin desinged a real snow bike ski:
 
AD Boivin:
The improvements on 2004 models are aimed at having a front ski able to keep grip under severe banked turns. AD Boivin found a very clever concept called the twin axis. Here is the microfiche, see pages 5 and 6: http://www.snow-hawk.com/en/service/manual/pdf/ch11_English_2004_600HO.pdf 
 The bad news is you have to order everything on page 6, except the carbides. Instead go for some Shaper Bar made by Stud Boy, part # DOO-SD156-45. These are 4.5 inch and any more than that will make for an unsteerable ski in front of your bike.
 
 
Rear traction
What works best for loose or packed snow is a sand paddle tire with snowmobile studs between the rubber paddles. More paddles are needed (8-10) because snow is not as dense as sand. Chisel studs for drag racing works best (flat sided directional). Ice screws are not a good idea for the paddle tire because they don't last long and rip easily compared to snowmobile studs. It is very important that you never use studs that are too long. If you exceed the profile of a normal tire, the studs will wreck alot of expensive parts on your bike: swingarm, airbox and mud guard.
 
Chain slider extention
It is best to use a 90* teflon extention on the swingarm to prevent the chain from catching on to studed rear tire. I will elaborate on this in the near future.
 

Questions or comments:

payantjs@hotmail.com