mongoose cx450

friedwires · Sep 18, 2011

my nine year old son just bought this bike yesterday for $40.00. we put a new throttle on it,stuffed some new lead in it and did a few adjustments and away he went.the bike runs pretty good for what it is.and he doesnt seem to mind the noise.the bike is loud as shit.so much for my quiet nightly bike rides

i think i'll put another sla or two on it and hopefully fry something on it to make way for an upgrade.i wanted to tear it apart when we got it home,but he insisted i didnt and said he just wanted to ride it. :twisted:

i have a few 600w lashout style bmc motors kicking around so i'll probable go that route.i'll need to find a drive housing and planetary for it,or build a jackshaft for reduction.

emoped · Sep 18, 2011

Kai has been riding the one I picked up for a year or so now .... the lead just gave out. I think it is a really heavy bike thou. Uncomfortable seat. But I also really LIKE the grips and that it has disc brakes. As he gets better I will sell it and build him a better faster , lighter bike :mrgreen:

friedwires · Sep 19, 2011

yeah,the bike really is a tank,it should hold up pretty well with some real power.the first thing i'm gonna do to it is replace the pos. fork with a better and lighter pos. fork. i have a used rst capa that needs a new home. it has to be 100 times better than whats on there now.i also need to find a longer rear shock to give the swingarm a bit of travel.my kid loves to jump

and the thing lands like a bag of bricks,its pitiful. today i took a look at my bmc motors and none of them have the rpm marked on them. it would be nice if i could get away with a single reduction, but i'm not counting on it. it looks like the motor will fit nicely in the swingarm though.

friedwires · Sep 24, 2011

if my calculations are correct,and if not i'm sure you guys will set me straight. i'll need about 11.8/1 gear ratio at 38v to keep the speed down around 20mph. thats assuming i get 105.6 kv out of the motor. at its rated wattage at 24v the rpm is 2535.i spent the morning scrounging parts and i'll be using a flip flop hub for a jack shaft with #25 primary,and bicycle chain secondary. the rst fork is installed and works nice.i also found a bigger mtb shock for it.its a little better but not much,so im still on the prowl for a rear shock.

friedwires · Oct 8, 2011

and it no longer lands like a bag of bricks. i found an older rock shock for the rear.its 7.5" eye to eye with a 2" stroke. it came with a 500lb spring and with my weight on the bike it would barely compress. so i cut and modified a lighter atv spring to fit. i'd say its about a 200-250lbs spring. its a little weak for my weight but for daniel its perfect. the swingarm is getting over 4" of travel now and can land a jump nicely.he rode it around a bit and jumped it a few times and had a shit eating ev grin every time he landed it :twisted:

Trackman417 · Oct 16, 2011

I am so jealous of your build! I wish i could find some actual cool stuff at garage sales around here but the stuff is either over priced or just plain boring. I love what you did to the bike man kudos to you!

friedwires · Oct 18, 2011

there's still much to do. I haven't gotten around to modding the mac yet and i'll need to design the battery pack soon. i'll be useing saft 5ah D cell nicd 36s 2p or possibly 3p if there's room. i also have a lyen 12 fet for it and the chain and sprockets are on order. i wish i could tear it down, but my kid is riding the hell out of it. i'll just have to wait till i have all my ducks in a row. been looking for a longer fork to get the front end up. if i dont find something soon,i may just lower the rear for now. i could always leave the old tabs on the swingarm in case i want to go back up with it.

Ypedal · Oct 19, 2011

not sure if you know this or not, but just in case, you should never charge Nicad/nimh cells in parallel...will add more info if you need it !

friedwires · Oct 19, 2011

thanks YP, no reversed cells as of yet! :twisted:

i use three sla chargers through relays that are switched by 50c klixon switches that i bury in the packs. works great every time.i charge the three strings in series and discharge in paralell

nonlineartom · Oct 20, 2011

I've got a build thread on here of one of these, exactly the same. I used a 1200W geared cyclone kit with LiPo batteries, think it's under "Tom's mini dirt bike build thread"

I ended up selling the bike before I got a chance to properly ride it. It looked too much like a motorbike to ride around without getting pulled over and it was a little on the compact size for what I wanted. Great bike though, and steel so you can weld it easily . Good luck with your convesion

friedwires · Oct 20, 2011

been there and read that, did the new owner finish it?

nonlineartom · Oct 21, 2011

no idea, he said he would post an update and never did, It was working when I sold it him just needed the brakes connecting up and the batteries mounting properly.

friedwires · Oct 21, 2011

i managed to dig the controller out of the motor today which was a real joy :evil:

and i also got the #25 sprockets in the mail. so the jackshaft is now put together. hopefully i'll find some time over the weekend to button up the motor. i'll be useing 10 guage for the phase wires with ring terminals and bolts to the controller.

friedwires · Oct 22, 2011

the halls tested good so i got the soldering done.

wingtip · Jan 13, 2013

Did you ever get this together? I just found one of these bikes on Craigslist for a song and need some inspiration.

Dauntless · Jan 14, 2013

wingtip said:
Did you ever get this together? I just found one of these bikes on Craigslist for a song and need some inspiration.

Dang, so YOU'RE the one. 6 weeks I'm sweating my truck in the shop, never seems to come home, then on the eve of being able to go get it, it's GONE. . . . !

friedwires · Jan 14, 2013

The bike runs great and has been steadily flogged on for over a year now. i'll have to take some pics and get them posted. although everything pretty much worked as planned. the bmx hub jackshaft couldnt handle the power very well. after It destroyed two of them i decided to cut the hub out of a curry scooter rear mag wheel and use that instead.it also destroyed several freewheels before i spent some money on a decent one. its been rock solid since.been thinking about doing some mods on it soon. I'd like to go from 36s2p nicd to 42s2p nicd. and play with the programing on the lyen 12fet.

friedwires · Jan 17, 2013

here are a few photos

View attachment 2

Denisesewa · Jan 17, 2013

I did one of these several years ago, used a brushed 1200 unite on 48 volts with an Altrax AXE controller,yamaha yz seat, downhill mtb fork and a ton of chassis mods. it turned out great.

mongoose cx450

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