52cc Stage 2 CAG CVT powered X-Games Motobike

[16v4nrbrgr]

Thanks for the compliments,

It makes good HP but not the best torque, the CVT helps a lot though and some lighter rollers in the variator will help to keep it in the powerband longer, something I'd like to try this year since they are cheap and standard sized stuff.

The piston ported pocket bike engines like on my BMX actually have a better torque profile for everyday use and are built a bit stronger since they are used for power tools as well, but make less peak hp for top speed unless you mod them out. The pocketbike gurus over at Pocketbike Planet forum have built some really wild ones!

 

[16v4nrbrgr]

I'm gonna try some higher octane, a gallon of 96 from the racetrack with the same 40:1 mix of Lucas. I think this motor would run smoother on it, figure why not since this bike is good on gas mileage.

 

[Flattie42]

Hey buddy, glad to see your still around riding and working on the bikes.! I was just looking through my email and saw you posted updates on your threads..... I haven't been posting much lately myself since I've been busy practicing machining work on the lathe trying to make some precision parts for my bikes and be able to show you guys... I wanted to make a set of bronze bushings for my Motobike to replace the plastic swingarm pivot bushings that are currently installed... There's just a tiny bit of slop in the rear end that you can feel when riding so I thought I'd attempt to re-create the plastic bushings from a high grade bearing bronze, maybe come up with a more solid design for the bolt that holds the swingarm together.....

If you haven't already, you should check out the last couple pages on my Motobike re-design thread on the pocket bike forum. http://www.pocketbikeplanet.com/showthread.php?t=81182&page=20 I finally got her all finished up and painted then took a few test runs after assembly and it seems to be working out just as I had hoped for.

I got some footage of me taking if for a spin, I'll see if I can PM it to you. I remember you asking where did the Motobike go,? Lol it's still there, mainly in concept haha, the seat fairings and swingarm pivot assembly that I chopped off and re-welded are the only two actual parts that remain.

Cheers brother on making that awesome bike, it was definitely a fun experience seeing each others progress on the builds.

 

[maniac57]

Pretty cool build there Flattie42! Strangely compelling....I can't seem to look away!

 

[Flattie42]

Thanks man, if only I wasn't so critical of my work,, or if I didn't keep on screwing up (lol) I would have finished the bike a lot sooner.. Even though I probably wouldn't have been as satisfied with the end result if I had kept the bike 'as is' once I got it running.... I'ts more of a shelf queen right now sitting parked in the garage since I don't wan't to abuse it much and it's also a nice conversation piece lol. Maybe one day if I build something cooler I'll try jumping it on the ramps back in the woods LOL.

I was kinda surprised that me and 16v had almost the same original idea of putting the reed inducted 'Cag' engine on the X-Games Motobike without even knowing we were doing the same thing...

While I was redesigning my bike (hacking apart the frame) for like the 7th time, I decided to use a piston ported engine which I was more familiar with working on and it seems to produce more power. They really do get good gas mileage, especially with more than one speed.

 

[16v4nrbrgr]

Wow, Flattie your bike is looking great now that it's all finished up! I would be up for purchasing a set of those bushings from you for the swingarm if they take up the slack. At 42 mph the bike has a tendency to get a into tank slapper which I think is due to the minor swingarm sideplay.

I kinda wish I went with a piston ported motor for this bike, they are great motors and make better midrange torque. The cags are kinda soft midrange but the top end scream is really nice, but they have a kinda weak crankcase for the amount of power they make with the eBay "staged" mods. So you gotta put those nuts on the head bolts or studs, next one I might weld more material into it around the holes and use studs so I can retorque the head.

I played around with the idea of a water-cooled engine for this bike, which would work if I figure out the mounting, but it would add another 20 lbs of water cooling stuff. I as well haven't ridden mine in a long time, but I'm going to pick up some 96 octane tomorrow. I think it will run cooler on 96 and I might not have to rejet it, which is an option though. I really should spring the $20 and get some lighter weight variator rollers to spread the powerband more, need to get a scale and weigh what I've got. There's 3 out of 6 stock rollers in it which works well, but could use upshifting later.

 

[Flattie42]

Thanks for the compliments 16v.! I really do appreciate it man.!! I'd be more than happy to make you a set of bushings for your Motobike. I just need to measure the bushings on my bike and put in an order online for some 954 bearing bronze... I'd only ask ya to cover the cost of material and shipping and they're all your's. I know how much machine shops charge for something like this and I couldn't charge ya for that.. This is only just fun for me. The process should be fairly straightforward. I'll make sure to take some pics of the process and keep you updated.!! Cheers.!!!!

 

[Rudz]

Wow, that's a beautiful bike, I wish I could find one of those bikes and try and fit a China girl in there

 

[16v4nrbrgr]

Thanks Rudz! You can still find them on craigslist sometimes, thats how I found mine from a nice girl who had won a raffle when she was at the x-games and never rode it since it's a novelty bike. Hyper brought the bike back in mild electric form, there's a lot of potential for a sweet higher powered electric build with one!
http://www.walmart.com/ip/Hyper-Motobike-Boys-36-Volt-Electric-Bike/23149110
I don't think a China Girl engine would fit one of these bikes, certainly not in-frame, but a bunch of other motors can work if you make some brackets for them. I was thinking about making a different mount for a water-cooled engine but I don't even ride much these days so I haven't changed it. I figure it's worth a try building another Cag engine or two for it before getting drastic, especially when this motor is doing quite well still. I gotta ride this weekend, its been a long time and its all prepped to go.

 

[16v4nrbrgr]

New stuff on the way to improve the bike:

Lighter CVT rollers, hopefully higher than 3rd gear on the rear cassette will be useful with this.

A long single muffler to quiet the bike down, its too loud with the dual "mufflers" on the current pipe.

A steering damper to eliminate the shakes at high speed, especially with the new rollers which should stretch it out to a higher top speed.

The rear is too softly sprung, so I ordered a shock with a 1500lb spring. I'm also considering adding preload to the front fork springs, and putting some grease fittings on the ends so I can add some cheapo "squirch" damping. The new rear might be constructed so I can open it up and grease it as well. It would be nice to get fancy adjustable hydraulics front and rear but they weigh a lot and would be more than I'm willing to spend on this build, which rides very comfortably at sane speeds as-is.

 

[16v4nrbrgr]

Here's the new muffler. The split clamp sleeve fit the pocketbike pipe well so I just used a hose clamp and then another two holding the canister to the underside of the seat. I had to make a couple brackets out of aluminum angle and used some old delrin bushings I had as heat isolators for the 6mm bolts holding the mounts to the seat.

 

[16v4nrbrgr]

I opened up the CVT case to replace the roller weights with the light Malossi 2.3 gram kit, and found the belt totally shagged from the cvt pressure of heavy weights at high speed. It left a bunch of goo all over the inside of the case that I had to clean out, there was gummy rubber dust buldup behind the varaiator plate as well. After everything was cleaned out I installed the Malossi rollers and plate guides which fit perfectly. Fortunately I had a spare CVT belt to put on so I was able to put it all back together. THe new rollers should make the belt last longer and the gearing work better with the derailleur.

 

[16v4nrbrgr]

Today I made mounts for the steering damper. It took a while to design and fabricate some nice strong lightweight mounts from aluminum and attach them to the fork. The damper works great, and the adjuster will be accessable under the fairing. I still need to make a couple spacers for the fairing to clear the damper. I'll space out the left side too to make it easier to access the petcock lever under the fairing.

 

[16v4nrbrgr]

I had to space the fairing out with pieces of brass tubing as standoffs for the bolts. When looking at these pics I just noticed that my kill switch wires are chafing and the plastic covering split, fixed that up too.

 

[16v4nrbrgr]

I went for a couple rides around the neighborhood today and tested everything out. Overall its much improved, no more headshake with the damper and the exhaust is much quieter now. The increased backpressure from the muffler and the use of 96 octane gas limited my revs to about 9000 rpm when I could pull 10K with 91 octane, so it needs jetting to be a racer on 96 and attempt another top speed run. I can indeed use a couple more gears on the derailleur which is nice because it has enough power to climb hills in 1st, yet I can quiet the engine down a lot to cruise in upper gears. The 1500 lb rear shock makes it way more stable at high speed too, although its a bit bumpier than before over rough stuff, to be expected. With some carb tuning it should easily go faster if I decide to keep running 96 octane, which is pricey but runs smoother under high load. Once the motor can pull max revs another set of CVT rollers for final tuning might be in the cards, but for now I'm really happy with this setup because it has way more torque and gear reduction for real life use. One of my goals with this bike was to tame it down a bit so its a lot lot like a quiet street bike when around people. That has come in handy so far because I saw less frowny faces today and even a couple smiles on my rides.

 

[LandSpeedRecord]

I absolutely love this build. I had plans on putting 2 of those motors in a Skyhawk GT2 frame but that is being put off to build a sensible 4 stroke. Anyway I just wanted to compliment all the aspects of your work. Great bike, style, engineering, and creativity.

 

[16v4nrbrgr]

It has been a couple of years since I last rode this bike and I really miss the fun. I'm going to be cleaning her up and getting ready to ride again. I'm pretty excited about some upgrades I'll be doing to further fulfill the potential it has.

The upgrade I've planned first is to widen the range of the cassette to 50t since these are available now, the top gears are 50-46-40-36-28 whereas my existing cassette has 41-36-32-28-24-21. I think it will have enough torque to wheelie and get a better run through all the top gears for a higher top speed. A medium cage derailleur and a couple of different extensions are going to hopefully make it work.

I would like to find some really sticky, possibly gum BMX or moped racing tires to be able to lean at really low angles. The odyssey tires have been awesome but I think that there is more grip to be had. It's possible I could use a chemical tire treatment or tire warmers if I was nuts. I really didn't get much wear with the tires on it, so I think a softer tire would be worth the increased wear rate.

Then there is possibly tuning potential with the CVT variation weights, clutch and flywheel lightening, porting, maybe a bigger carburetor, etc. The motor mods may come later or not, hopping up one of these too much might make it too unreliable. It's a 7 lb tiny engine with thin cases, so there are limitations. That being said, I think one of these with enough gear to really zing can be a reliable motorized bicycle engine ideal for shift kits because the torque impulses are low.

Making it too hot or too peaky would take away from the fun. I could probably do a watercooled cylinder but it's going to be expensive with all the complications it adds. A really powerful water cooled pocket bike racing engine could probably take this bike to 70 mph. I'm quite satisfied with 43, the gears should add a couple more mph.

A new rear shock with adjustable preload damping is in the works, I like the spring rate it's got now but some rebound damping will reduce the springback. It might be possible to put zerk grease fittings on the front friction fork to get some cheap damping there as well. All this will add up to more smoothness and stability at speed.

Maybe a small airbox would quiet down the intake, they definitely work on my auger bmx. A small plastic bottle of some sort with a 7/8" inlet will work. It would be cool to upgrade to a bigger scooter x-pipe later.

 

[16v4nrbrgr]

All of the parts have arrived, I'm hoping to find the time to get it all together very soon. I found a hydraulically damped adjustable shock that's a direct fit for this frame called the Chaser. It's a nice little shock for the money, has the right spring rate on it already too. I'll post pics of it when it's installed.

I don't have a suitable shop right now, so I have been looking into getting some space to really get back into motorbikes. In the meanwhile, it's always fun to think about new bike ideas.

It would be cool to have twin brake rotors in the front, it looks awesome on fast superbikes. I was thinking it might not be too expensive to do on this bike by using pocket bike calipers. That's basically what it has on it now, and they sell mirrored sets for front and rear.

You can get really cool looking floating brake rotors with color anodized center hubs now too. On top of looking killer, they might get rid of squeaking when hot since they can grow in the floating pin mounts.

There's really nothing wrong with the braking force right now, but this mod might be totally worth it. It would require making a second caliper tab for the right fork and welding it on. Then there's attaching the rotor to the other side of the wheel, probably with a clamp adapter.

I'm still on the lookout for an airbox, a shaped OEM one for a racing 50-80cc bike motor that is small enough to fit under the swimgarm. An old plastic pill bottle might work for that. I liked how the muffler worked, so now quieting the intake will make the bike more chill with people. Ram-air actually works on these bikes but you need to be careful not to lean out. I messed with the airbox on the BMX and it actually worked best at a neutral air pressure. I'm sure you could jet for this on some carbs.

Im posting here to motivate myself to do this stuff, progress will be way faster when I have a place to tinker.

 

[indian22]

This is an excellent bike & I'm glad you've pulled it back into your life and are making some nice upgrades....thanks for sharing!

Rick C.

 

[16v4nrbrgr]

Thanks Rick, it's been a lot of fun, I can't wait to get back riding!

I finally bit the bullet and ordered the brake parts, I know I still haven't gotten to starting it up and doing the derailleur and cassette...

It's gonna look sick though, twin red brake calipers and some floating rotors with gold hubs!

Instead of using a twin pull brake lever I'm going to try adapting a BMX detangler splitter as a cable to both calipers.

It's going to require basically mirroring the caliper bracket on the left fork to the right and welding it on. I'll probably do the same thing I did on the back wheel to mount the second rotor, by using a split shaft collar drilled and tapped for the rotor bolts. It may be possible to thread the hub for a cheap disc adapter if I can find a die that big.

I'm hoping that the serrated rotors don't make the brakes judder, I think I remember getting rid of the original front rotor for a round edged one a long time ago to get rid of that feeling. If it's bad I guess I could just get another one piece rotor. With the braking split between the two brakes it might not be an issue.

Still searching for a plastic airbox to quiet the intake down. The goal is to make the bike neighborhood friendly.

Im also still looking for a place to set up shop, but I might start taking on some of this stuff during lunch break at work or something. The weather is getting nice around here so it's time to get prepared for some fun rides!