52cc Stage 2 CAG CVT powered X-Games Motobike

This is the Motobike that I got a good deal on:

The nice girl that owned it won it and kept it in brand new condition!

I remember seeing one of these at Wal-Mart a few years back and thinking it would make a great freeride bike with an engine. It turns out to share brakes and rear shock with the Razor Mx500/650 which are heavy duty. The frame is nicely welded aluminum, and the fork, steel.

First thing I did was peel off the X-games decals,and feel kinda bad about it but the replacements will be cooler if I do replace the decals. The thought of blending in with this bike and keeping it low key is an appealing one. With all black fairings it looks more like a mountain bike in the dark than a dirt bike, which I know will generate some confusion even with a license plate.

Depending on the fitment of the engine I might make a mount that attaches it to the frame or the swingarm. The CVT came today and it looks to be worth the price, the engine should be here soon. The dirtbike exhaust came as well and will park the mufflers in between the number plates, which will probably require some heat shielding to not melt. I like the idea of having the mufflers shielded from burning skin and out of view. If they're not quiet enough I'll grind off the spot welds and repack them. On cars I've seen that dual mufflers tend to lower the note of the engine and make it less raspy, so thats what I ordered, and it has an expansion chamber. It's gonna get wrapped so I don't burn myself, because I ride in shorts like a dumbass.


The steel 72t sprocket is very heavy so I'll drill it like a brake rotor most likely. I bought a freewheel that has four mounting holes that match, but it's a POS so I'll try to use the ACS Crossfire I have and mount it to the Sturmey S3X that I acquired a while back hoping that I could make a hybrid hub with the SRK3 on my electric bike and use the best parts. No luck with that, so I have it left over, perfect for this bike!

The CVT will require mounting the engine backwards, as it reverses the drive direction. Hopefully there will be no issues with oiling or the orientation of the carb. I'm planning on making an engine mount that bolts on and integrates a skid plate, since there will be less clearance than a dirt bike without cutting into the frame and welding in an engine mount integrally. This bike will be more for fun and light use, and the engine will be mounted similar to a Puch moped but reversed with the plug coming off the back. The only way around this is a reversing jackshaft setup but I'd rather just keep the chainline clean by centering the output of the cvt with the swingarm pivot, and using pegs. Like my other bikes, I'm using pegs because I'd rather not trash my ankle accidentally digging in. With the trans mounted in an L shape with the engine (not sure if it's possible yet) the pegs can be mounted where the crankcase is on the swingarm by simply removing the one piece crank and using a long bolt, axle, or allthread.

The engine will look somewhat different because it will have the CNC machined head and some other upgrades. $120 off Ebay, not too shabby.

When I arrive at a good looking and reliable final engine mount design, I'd entertain the thought of making more and selling them. These bikes can be obtained off Craigslist or Ebay for cheap, and they're actually really nice for the money. I'm really excited about this because with the CVT and gears it should be able to climb at tree and still get good top speed since these little buggers rev to 11,500 supposedly.


I also ordered an adjustable three shoe clutch since people have had major issues with the springs snapping on the other ones. Of course mine arrived already broken form the manufacturing process, where they peen the cir-clips down that hold the clutch arms, and freeze the assembly and broke a clip. Totally stupid, the manufacturer doesn't understand how this clutch is intended to function, as it is now it would stick and send you through a fence! So I gotta rebuild that, and once the engine comes, replace all of the hardware.

The KTM style gas tank will require gutting the fairings or fitting some old plastics from the MX650, they're yellow, yuck.

My goal with this is to have fun with it and break in the engine, whether I keep it or sell depends on how much I like the OCC bike that I need to finish, once its done. It's really gonna be awesome, a dirtbike style moped/bicycle. If I can find cranks wider than the CVT + engine + pullstart width, then it'll go back to having pedals because I think that two sprockets on the hub might be an option, with a fixed one on the engine and a freewheel for pedals so no freewheel crank sprocket would be required. Freewheel cranks kinda scare me, it's like a buzz saw!

This bike should be ripper, and if I can get it really quiet then it will be nice for some light trails.

I'm gonna return the gas tank that I have and ordered a different one tonight that will wrap around the frame better and sit low. Had to order a vent cap too. I'd like to keep the black fairings if possible and just notch out where the tank sits and spread the halves out.

This bike will require a good digital tachometer with some sort of bars or shift lights, I'm sure Ebay has something perfect for the job.

What I'll end up using this unit that I bought off Ebay a while back for about $40.

It's a small one wire unit that will fit nicely on the tank or the handlebars. I was going to use it on the Raven bobber but I ordered a cheap analog tach that should work and fit the theme of that bike better.

The trail tech is a nice one though, I wish I could afford it but I try to keep individual component cost low since it snowballs. If the CVT works right there won't be much need for shifting except for big hills. It's better to stay in top gear on these hubs since its direct drive, so its most efficient and reliable in that gear.

I kinda want to build a spare wheel instead of relacing the one that I have so that when the hub needs rebuilding there is a wheel to use. I need to figure out a way to mount a disc to the geared hub, the OD is too big for a thread on adapter so it's gonna be tricky and might require using a brake for a pit bike or scooter with a bigger bolt pattern.

anybody know how to make a CAG run backwards?

The motor came today! Wow am I impressed with how light it is, about 10lbs. I wanted silver, but my second choice was red and that's what I got, looks really nice! I think I might paint the cover for the cvt red to match the starter.

The engine's gonna be tilted with the jug angled down toward the rear tire, not sure if that's an issue. The intake should be able to be flipped around to get the carb reasonably level. I read somewhere you want the intake side tilted up slightly.

I'm thinking a tubular steel engine cradle with a plate to bolt to, and a skid plate underneath will be the best way to mount the engine. I'd like to find more info on running the crank rotation backwards, if the engine can work as well like that as forwards, with a modified CDI. Running the engine backwards would allow for the engine to be mounted the regular way, with the drive to the left side. There are claims on pocket bike sites but I haven't seen an explanation. If you know how to make that work please let me know. I realize I'll have to use an electric starter or a drill.

Thanks lowracer, I read your thread on your rack mount, and the power and speed sound great

Power density is what I'm looking for on this build, I'm sure if I take preventative measures that it will at least last as long as an HT. Thank you for listing off the major problems!

I wonder if NT carb off my HT will work if re-jetted if I have problems with this one. I guess a Walbro clone is cheap anyways.

I bought an adjustable three shoe clutch that uses the springs in compression instead of stretching out hook springs. Of course it looks like it needs to be completely re-manufactured brand new, since it's frozen stuck. I like the two shoe clutches as they look the easiest to work on, but I don't know where to get one for a CAG, and I read somewhere that the friction material is too thin on those.

Sounds like this one isn't gonna be a quiet trail rider after all. I might make this the bike that I resell after breaking in the motor and having some fun. I need to sell one or maybe two of my bikes by next summer.

Hoping to have enough gearing advantage to be able to cruise at a low rpm and reduce the noise. We'll see.

If there isn't any problem with having the jug upside down I guess I'll set up the engine mounting so that it sits backward in its cradle. I worry that it's gonna flood the head every time I park it though, maybe that's unfounded, and at least the exhaust port is on the bottom.

This is the one I got:


It looked like a nice balance between the two extremes. One of the circlips is broken, they peen the pins after putting them on for some insane reason. It seems like I'll need to rebuild it and make sure everything moves freely so I don't get a runaway bike situation. Both my bikes with centrifugal clutches will have lanyard cutoffs for jetskis to avoid craziness.

I thought that the CAG clutches needed a woodruff key slot, so that was another reason I decided to go with this one. I really don't know, trying to move the project along has forced me to order first, ask questions later on a lot off small parts because of the lack of info.

I need to get my OCC bike finished next and then this one will be the winter project. I plan on making a cool looking engine cradle strong enough to bottom out on.

Well I tried to put it in the CVT drum and it looked like it would fit if I adjusted it a bit. Maybe filing the material will be required to get the diameter right. There are three nubs on the base that limit the contraction of the arms which will need filing down a bit. It's proabaly meant for other bikes like you say, but may still work. The watercooled bikes make more power, so I would assume that this is an upgrade in friction material.

I really don't want to have recurring centrifugal clutch problems, so I hope this works or I can find a two shoe that fits. We'll see.

Maybe McMaster or Grainger has proper springs, if you can measure the general K rate of the springs to get a reference to be softer than. I certainly do like the 2 shoe clutch a lot better since it looks a lot simpler to use than the three.

Do all the red spring two shoe clutches on Ebay work for Cags? I was under the impression there was a key on the crank, and the two shoes don't appear to use a key.

http://www.pocketbikeplanet.com/showthread.php?t=79248 Good info on here for modding the stock 3-shoe clutch to work reliably.
Looks like the two shoe fits, I just had to see a pic. From what CAM2 says, the 2 shoe would be lousy on a motorized bicycle to be used around town. The springs, and the friction material are too aggressive on the two shoe for cruising on a pocket bike.

I wish I could fit a manual clutch on here like a HT, it would take skill but it would make the bike more versatile.

I was just remembering modifying a clutch like this at my old vintage shop to fit in our pit Yamaha Zuma, I think it was something to do with repetitive clutch failures. It involved grinding those little nubs down I think. I'm a very visual thinker so I could just be having a case of deja vu, but I remember doing the clutch on that thing at one point. I used to go 60 mph downhill on that thing wearing a baseball cap, what an idiot!

Cool, thanks for the info. I'm glad that at least the two shoe are an option if this doesn't work out. Since there isn't any racing around here I'll just be using this bike for riding around town. It sounds like the two shoe is a good option for racing though, with the higher engagement rpm. I think it'll probably be easier on the bike if I have a lower engagement rpm since it'll be going through a 7:1 reduction in the cvt when it's in low then through the 21t output sprocket to a 72t rear for a reduction ratio of 3.4:1 so if I'm doing the math right it'll have a total reduction ratio of 23.8:1 so at redline of 11,500 the rear wheel will be going approximately 483 rpm. With 20" tires the max speed in low on the CVT is about 28mph, obviously it will be shifting up so the top speed should be much higher. If I choose to use the Sturmey, which I think I will, then it will have additional gear reduction for hills, since there are many around here. I'm excited about this build, it's going to be very cool when its done. I really hope that everything plays nicely with each other and I don't get into torque induced breakages like on my electric MX bike.

Plans might change. I might leave the CVT out and run the motor in standard configuration to a left side drive. Maybe I can stack a sprocket and a brake rotor on the left, crossing fingers on that. It may need to be tack welded, or maybe the ISO brake rotor adapter could serve to tighten on every braking. Hope they're out there right hand threaded, I would think so?

Leaving out the CVT will make it more reliable obviously, and weigh 15 lbs less.

The CVT would be more suitable for a cruiser since it's smooth. This shouldn't be a cruiser I realized. I'll save it for a future build, it might fit a china girl and will definitely fit a 49cc four stroke. I'd like to make a four stroke build some time for a chill bike.



Swingarm geometry will need to be figured out so it doesn't skip chain. The fork travel is limited so it shouldn't be a big deal. I'm not sure whether I want to use a drive reduction. That adds weight and is kinda unnecessary if I go with the wind-up racing clutch recommended by Lowracer and run it through the stock bell to tiny sprocket to the 72t out back with 3 gears with 177% spread. It would be cool to be able to take off strong in 2nd and go to third, saving the delicate tiny gears for 1st for hills.

On second thought, eesh, total gear ratio of 10.3:1, I don't think that's enough. It'll need a hoot box I'm thinking at least, maybe the geared trans doesn't reverse, gotta look into that. It would be nice to be able to take off from a stop easily in top gear. Definitely will need more gearing. Meh, at least hoot boxes are cheap!

I could have a massive sprocket made for the rear, but it would cost a fortune.

The engine cradle is going to be awesome, a tubular steel geometric structure! The aluminum skid is on the way.

My goal with this bike is to keep it simple and light, the aluminum frame is begging for a light engine, and the CVT kills that benefit by making the engine combo about 35 lbs. If I can make this build top out around 50-60lbs I'll be psyched, because then the simplicity will work to push less mass, instead of a complex heavy bike.

I think I'm going to candy apple the fork and swingarm for giggles. The anodized red aluminum look will be the theme.

I've been on a diet too, not sure how much I've lost. I hope I'm losing weight, I drink too much cola! It'll be kinda like a mini supermoto when it's done. I wanna go fast on this girl!

Because they make one for the Cag already and it only costs $50 vs mucho spendo on that Qmatic thing. They're used on the 49cc super pocket bikes with big frames and wheels and are reliable. I have one here, I just want to get rid of all the complication and the weight.

Turns out the chain reduction boxes are crap unless you mod them and the gear reduction boxes reverse drive direction like the CVT. It's making the choice simple on this one, no reduction box and the racing clutch that engages very high rpm through a geared hub is the way.

I can make it work without any gear reduction box if I shift up through the gears every takeoff. 1st would be about 18:1 through 20" tires, I think that's fine. 3rd would be about 10.3:1. This bike won't have pedals initially because of packaging and might never so it better have some nuts because its meant for hills and city.

I gotta stop thinking about this and finish my simple OCC build.

I'm having trouble deciding which transmission choice to take:

The first two options will have more ground clearance, weigh about 15lbs less:

Centrufugal clutch & single speed geared really low for climbing (necessary around here) 30mph top <--- most reliable setup

Centrifugal clutch and Sturmy S3X 3 speed fixie hub running backwards through left drive locknut arrangement. 45mph top

The CVT improves top speed potential and acceleration across the board. Is it worth the 15lbs and extra complication?

Centifugal clutch + CVT and single speed wheel 45mph top

Centrifugal clutch + CVT + geared S3X hub 50+mph top <-- Most inherently unreliable setup

The engine and tranny determine the design of the engine cradle, so I need to decide first.

I can also use the swing arm pivot point as a mounting place for a jackshaft with a longer axle bolt and some sprockets. I don't think it'll be necessary since the fork doesn't move a whole lot.

Anybody experienced with these types of transmission combinations want to offer any advice? Obviously, eliminating as many components make it more reliable, but also slower if the weight reduction doesn't make up for the lack of gearing. I don't ave any experience with the new hub, I know that the Cag engine would kill a regular freewheel hub with pawls, so its uncertain whether this hub can hold around 4 hp that will hit strong when the clutch engages. I've decided the best lube isn't grease or light oil for the geared hubs, but 75-90 gear oil like you'd use in a car's diff. The grease kept all the crap around the planetary gears, and the hubs run too loud and crunchy on light oil.

Can I use synthetic grease on the wheel bearings and get away with not having to get sealed bearing wheel hubs?

Here's a video of the CVT in action on somebody's four stroke. Mine is the newer model with cooling fins on the variator pulley and a thin aluminum cover.

http://youtu.be/mBgZMOvqbX4

It looks to go from 7:1 to whatever final drive ratio is in there, I think it's 3:1.

I also found out that the rear hub has pressed on disc adapters, so putting on a geared hub in will require buying spokes. Not a biggie.

I'll be selling this bike after I break it in and have some fun with it, so I'm wondering how fast and feature packed I should make it.

Here's another thought:

If I use the Sturmey fixie hub, they're traditionally put together with a right hand threaded right hand ball race cover thing. It normally tightens with use on right drive. Would it naturally loosen to the point of causing the bearings to be too tight if used left drive? If you really wail on a fixie and do a lot of skid stops its the same thing right?

The idea for left drive to use an iso adapter for the locknut should work in theory. It's going to have to be a good quality aircraft aluminum or steel one for it to hold up. Of course, like any jam nutted assembly, if it's not tight enough the brake and freewheel could just spin right off under power. If I found a steel adapter it could be tack welded to the hub center, kind of a pain.

Other than those issues, it should be okay I think. The hub is symmetrical inside with regards to rotation, just a bunch of planetary gears and a selector clutch.

I dunno, the CVT might be worth putting on to keep the engine from shock loading the hub too much. The hammering of a claimed 4 hp has the possibility of causing problems. I'm thinking about making some sort of internal shock bumpers for the drive center in the hub, because at least on the freewheel versions, I know a big shock load can cause it to crack. The fixie one is mad beefy, but still, the cush will benefit the planetaries. Dirt bikes have dampers in their hubs for this reason. The CVT belt will cause some give in the system and make for a smooth takeoff.

I was going to save the CVT for use on a Huasheng 4 stroke for a cruiser but I cannot get over how ugly they are, and since it's air cooled you can't cover it up with a bunch of fairings. It's a great engine, just needs a more attractive starter. Modifying the CVT to work at lower revs might be difficult, or easy I haven't looked into how much the spring pressure can be changed. It would certainly be easier to follow my original plan to put the high rev 2 stroke motor with CVT on. It's gonna have lousy ground clearance, so hopping a curb will probably be the most it can do, but realistically this will be a motorcycle in its speed capability with this motor, so might as well treat it like a street bike and embrace the low CG.

It sucks to have the cylinder going backwards. The cooling must be compromised a bit. I got a The mountain bike fender to use as a rear fender spat to keep the tire from shooting crap at the shock and motor. It seems logical to have the head pointed forward though. I guess part of the doubt is how important the engine angle is to lubrication. The intake can be mounted in a way to tilt the jug down for more clearance, is that bad? Radial engine had their cylinders painting downward, so why not this? It would help with the cooling as well because the fins would be exposed to oncoming air.

I already have some ideas for more Cagllari builds, since the engine is so compact it's ideal for bikes that haven't worked for traditional MB engine kits. It's just kinda awkward, since the mounts are on the bottom except for two on top. The width and combined weight of the CVT and engine combo kinda sucks, making low mounting get in the way of pedals on a suspension bike.

My plan with this build is bang for the buck. I tend to fall in love with the bikes I am working on, and don't want to see them go. I was going to sell this bike after finishing it, but there is the fact that I'll never find another brand new Motobike. There are a lot out there in great used condition though, it's such a beefily constructed BMX, meant for jumping without crushing your nards.

I think I'll keep the bike to enjoy and sell engine mounts if people want them, since I'll have a jig to do so. I can't decide on a drivetrain, they're all a compromise in one way or another. Spinning the motor backwards would save some, but I'd have to rely on a drill or the "crappy" electric starter flipped backwards. I worry about the balance of the electric motor at high revs. If it's not a complete POS it would be neat to use the starter motors overvolted as a hybrid electric Cag drivetrain! I'm pipe dreaming.