ExiteBike is a modernized magnum X build by river2strokes.
when purchased, the bike was barely rolling and missing most of the things it needed to even roll, let alone run.
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like many of you i was faced with the choice of stock restoration, but to me, the bike seemed like the perfect candidate for an entire rethought to the magnum X itself. what if it had a useable suspension and rippin motor to boot? if puch made a mini cross today, what would it be like?
after reviewing current mini cross bikes i noticed all of them had hydraulic front suspensions and mono shock rears, with liquid cooled 50cc motors, and that became my end goal. A hydraulic suspended liquid cooled magnum X build.
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Front Suspension:
front suspension is from a Polini X1 or X3 mini cross. they are full on polini/paoli and cost me $57.50 shipped on eBay for the tree and fork legs. pretty stellar deal considering they are 30mm hydraulic with brake caliper mount. the stock head tube/steering races don't match at all and there is no real way these will just bolt on. tried welding a streetmate steering tube on and the length was correct but the steering races and width of head tube was not. i ended up buying an X1 frame on eBay and will be swapping the steering tube over to the magnum X for '0 complication' fitment. here they are mocked up with he stock head tube
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*the polini X1/X3 wheels take a 10mm axle and need axle reducer bushings
Rear Suspension:
the rear suspension is a hybrid of an AR50/80 'uni-trak' suspension/swinger and the stock puch swinger, with the positioning of a yamaha DT50 'mono cross' design.
i was able to make the my design work without the use of any linkages. all that was needed was a hefty piece of square tube welded in the middle of the frame to serve as mount and pivot point for the shock.
Initial Mock Up
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It is very important to ensure that you have enough travel so that the swinger doesn't slap the frame. The AR mono shock offers 3" of travel and i left myself with ~1/4" of play.
+Gussets and Welded
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took extra precaution to ensure i had as close to perfect alignment as possible
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The AR mono shock has 5 positions and DOES NOT BOTTOM OUT! i am ~165lbs and tried it on the weakest position, jumping up and down on the bike. Then i had my buddy who is 200+lbs try it on the lowest setting and no bottom. Concept proved IMO. The stiffest position will more than likely be the best for off road, but i also plan to use this as my pit bike for next racing season so having the adjustable rear is actually quite nice.
Power Plant
I had intended on trying the 77 70cc reed kit and their water cooled head - i did not do my research on the head and will be going with a 47mm gila cylinder to match. In order to do that i needed to bore the case (still in progress). Picked up a flap wheel and headed to the drill press.
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I also conservatively matched the case to the cylinder, as I'm trying to avoid TIG welding the case.
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I had the entire build in a box ready for CBBG but unfortunately did not make it this year. planned on powder coating the frame swinger wheels n bits. not really sure on a color scheme yet but i do want to fit contemporary plastics, radiator and shroud, and re cover the seat with some cool looking mx grippy pattern.
this is where i am currently on the build and will update as i progress - thanks for lookin!
when purchased, the bike was barely rolling and missing most of the things it needed to even roll, let alone run.
like many of you i was faced with the choice of stock restoration, but to me, the bike seemed like the perfect candidate for an entire rethought to the magnum X itself. what if it had a useable suspension and rippin motor to boot? if puch made a mini cross today, what would it be like?
after reviewing current mini cross bikes i noticed all of them had hydraulic front suspensions and mono shock rears, with liquid cooled 50cc motors, and that became my end goal. A hydraulic suspended liquid cooled magnum X build.
Front Suspension:
front suspension is from a Polini X1 or X3 mini cross. they are full on polini/paoli and cost me $57.50 shipped on eBay for the tree and fork legs. pretty stellar deal considering they are 30mm hydraulic with brake caliper mount. the stock head tube/steering races don't match at all and there is no real way these will just bolt on. tried welding a streetmate steering tube on and the length was correct but the steering races and width of head tube was not. i ended up buying an X1 frame on eBay and will be swapping the steering tube over to the magnum X for '0 complication' fitment. here they are mocked up with he stock head tube
*the polini X1/X3 wheels take a 10mm axle and need axle reducer bushings
Rear Suspension:
the rear suspension is a hybrid of an AR50/80 'uni-trak' suspension/swinger and the stock puch swinger, with the positioning of a yamaha DT50 'mono cross' design.
i was able to make the my design work without the use of any linkages. all that was needed was a hefty piece of square tube welded in the middle of the frame to serve as mount and pivot point for the shock.
Initial Mock Up
It is very important to ensure that you have enough travel so that the swinger doesn't slap the frame. The AR mono shock offers 3" of travel and i left myself with ~1/4" of play.
+Gussets and Welded
took extra precaution to ensure i had as close to perfect alignment as possible
The AR mono shock has 5 positions and DOES NOT BOTTOM OUT! i am ~165lbs and tried it on the weakest position, jumping up and down on the bike. Then i had my buddy who is 200+lbs try it on the lowest setting and no bottom. Concept proved IMO. The stiffest position will more than likely be the best for off road, but i also plan to use this as my pit bike for next racing season so having the adjustable rear is actually quite nice.
Power Plant
I had intended on trying the 77 70cc reed kit and their water cooled head - i did not do my research on the head and will be going with a 47mm gila cylinder to match. In order to do that i needed to bore the case (still in progress). Picked up a flap wheel and headed to the drill press.
I also conservatively matched the case to the cylinder, as I'm trying to avoid TIG welding the case.
I had the entire build in a box ready for CBBG but unfortunately did not make it this year. planned on powder coating the frame swinger wheels n bits. not really sure on a color scheme yet but i do want to fit contemporary plastics, radiator and shroud, and re cover the seat with some cool looking mx grippy pattern.
this is where i am currently on the build and will update as i progress - thanks for lookin!