52cc Predator Auger Powered X-Games FS20 BMX

[16v4nrbrgr]

Naw, I just put it up as an example for those who would want to try something similar because the FS20 was discontinued for a while after I built this thing. I guess it's back now, although with reading the recent news about how Walmart treats their employees like dirt, it's up to you whether you think it's a good buy. The bike itself has been great, all the stock components are strong enough to put up with my flat-tracking abuse, lol. Hyper and Kent make good department store bikes in my opinion, build to withstand a 300 lb American 12 year old going off dirt jumps.

 

[d_gizzle]

My wife is an overnight stocker at walmart so I know a lil about that. And I been eyeballin the Hyper 36v e-motobike I seen at wally world. It looks like a decent first electric bike. Never had one but would like to try one out. Any suggestions?

 

[16v4nrbrgr]

It does look to be a pretty decent electric assisted bike, I can't find the exact wattage of the motor but some say it's 500W, might be able to up it to 750W or 1HP by simply adding another 12v battery in series with the 36v pack to overvolt it. I don't think burning out the hub would be much of a concern if you always pedal off from a stop, and once it's moving the back-EMF from the motor should prevent too much current through the windings that would otherwise melt the winding lacquer insulation and cause a burnout.

I really like how the frame rides, my Cag powered motobike rides pretty well even up to 37mph so far, it could use a hydraulic mountain bike rear shock and maybe some sticky grease in the front fork sliding parts to add a bit of high speed damping, I had the fork bottom on some hard bumps and the grease mod with some rubber bellows to contain it helped my Razor electric dirtbike to have much nicer fork damping.

 

[d_gizzle]

"I don't think burning out the hub would be much of a concern if you always pedal off from a stop, and once it's moving the back-EMF from the motor should prevent too much current through the windings that would otherwise melt the winding lacquer insulation and cause a burnout."



Way too much too soon. But I think I get it a little. The hub is wrapped with copperwire and if you strain it by taking off from a dead stop it will stop the rear hub from working? But if its already spinning,and with gentle throttle acceleration,it should be fine? And all I need to do this is a 12v battery wired positive-negative on both sides?

 

[16v4nrbrgr]

Well to make it simple, if you up the voltage, mor current will flow through the motor, the maximum current flowing at zero rpm through individual sets of windings for longer period of time than if spun up to speed where the heated time per winding will be less, along with the effect that electric motors have of creating an increasing reactance with increasing motor speed, which is kinda like dynamic electrical resistance which limits the current flow and therefore the heat, also the maximum rpms a motor will spin.

Basically you would want to find out what type of batteries are used in the pack, and order another one, I suspect they are 7Ah AGM batteries in the box under the seat, and then open the loop and add another one in series to make the 3x12v batts into 4x12v batts for 48v, which raises the current achievable through the motor at full throttle (if the controller can handle it), and therefore the raising maximum torque and rpm. I suggest doing some basic introductory reading on electric motors and bikes, and picking up an electrical circuits textbook, which will have more than enough info for hot rodding an electric. You have to be careful when you exceed the manufacturer's specs on battery voltage, you can toast controllers and motors with the increase in current through every bottleneck in the system's wiring, which can cause heat, and if the motor is brushed, wear those out quicker because they tend to spark.

If you'd like, check out the Razor MX650 mods thread over at Pocketbikeplanet forum, I documented my trials and tribulations overvolting, and then completely reconfiguring my electric motard so it makes torque and not noxious smoke and parts reciepts, lol.

 

[16v4nrbrgr]

Well I'm putting it up for sale, because I realize it may take a while to find a new owner right now. There's a thread in the FS section with the price and details.

 

[jjvsb]

looks like its going to be a really cool little bike! Ill be keeping an eye out for the fished product.
I think the bmx type motorized bikes are tight. I don't see enough of them.
my first several builds were 20'' (custom frames)

 

[paul]

that is one cool looking motorized bicycle. i uploaded to the forum. welcome jjvsb, great to have you with us

 

[16v4nrbrgr]

looks like its going to be a really cool little bike! Ill be keeping an eye out for the fished product.
I think the bmx type motorized bikes are tight. I don't see enough of them.
my first several builds were 20'' (custom frames)

That's a rad little BMX you've made jjvsb. Mine's been a finished product for almost a year now, and I've been riding it a lot. If you read through the thread you will see how it has progressed. It's got about 15 hours on the engine and I've got too many motorized bicycles so I'm selling it on craigslist. I really love it though because it's got so much torque it peels out the rear tire about three revolutions every time I take off, and any hill can be tackled without any pedals required. As such, I'm tossing all lowball offers in the junk bin of my email account and having a good chuckle doing so, she's the brother bike to my X-games motobike, the BMX has lots of torque and would rip offroad with some knobbies (does it on slicks anyways ), and the Motobike with the reed valved 360 crank pocket bike engine has quite a bit of horsepower.

Brother and sister, they won't be separated without an offer I can't refuse.

 

[16v4nrbrgr]

Changed out the 75W-90 gearbox oil for a fresh 250cc of oil yesterday and went for a ride. I have to say that I am really happy with the Predator auger engine and it has been a wonderful motorized bicycle engine with its supplied 90 degree gearbox. I think I'd like to someday weld another set of spring retaining rings on the bottom of the exhaust bend union at the jug, if the safety wire fatigues then the exhaust can pop off since the springs are only on the top side, it could really use a strong spring on each side of the flange and the end of the pipe like a dirtbike. I had it pop off halfway up the hill yesterday so I gravity biked it home and used a piece of welding rod as some improvised safety wire until I get another roll of stainless from the store. LOL

 

[16v4nrbrgr]

I haven't updated this thread in a while because there hasn't been much to report, this bike has been great and she's always there for me.

Might switch to some BMX knobbies I have, the tread is worn off both the front and the rear checkerboard tires the bike came with, I rotated them a while back because the rear gets worn out from peeling out, lol!

I've decided to finally change the muffler setup since my extended pocketbike muffler looks kinda crappy and I think I can make it a bit quieter without reducing the flow by using a Briggs 6.5 muffler from the auto parts store.

It will hook up to the exhaust with a 1" pipe threaded conduit coupler and a piece of 1" threaded conduit as the reducer from 1" down to the 3/4" pipe. With this setup, I can replace the muffler if it gets gunked up or ugly with a new one from the store for $6. I was thinking it might be wise to put safety wire loops on the muffler and the coupler, to keep it from unscrewing from vibration.

I'm thinking it might be fun to put a big bore top end on the bike and gear it a bit taller to stretch out the torque, or possibly do a red-head conversion with separate jug and high comp head, or maybe even the watercooled cylinder, but for now, I'm really happy with the way the bike works as it is and highly recommend using this type engine if you want a reliable two stroke bike engine with great torque.

 

[Flattie42]

Hey 16v, how are the projects? It's funny I actually have a couple of those Briggs bullet mufflers and tried them on the piston ported engines. Great minds think alike I suppose... My grandfather owned a hardware store and worked on lawn mowers back in the day, he cleaned out his shed and handed me a box full of some 30 year old parts, lol. Some were still even in the original packaging. I welded one of those mufflers to a straightpipe exhaust just to see how well it would work out. It does a pretty good job muffling the exhaust noise, but kinda restricts the flow a bit. I was going for a ride and turned onto one of the main roads by to my house... I hit the throttle and all the sudden the engine opened up as the muffler vibrated loose and got lost somewhere behind me, lol. I was able to keep up with traffic no problem in the shoulder. My ears were ringing afterwards though.

 

[16v4nrbrgr]

Hey Flattie, thank you for the experience with the briggs muffler. Glad to see you're still improving your motobike build too! I think maybe the muffler could be drilled out in the center to free it up a bit. I was thinking about putting it after the main existing canister, but might just mount it after the chamber.

I haven't done much with the bike lately, put a headlight on it, I'll put up a pic soon. I should prolly weld the muffler adapter on. It's gotta be safety wired to keep the threads tight if the pipe is supporting the muffler, so some washers will be tacked on.

Have the dilemma between a skid plate or a kickstand, maybe the kickstand can be turned into a rear skidplate bracket too.

Might use this as my pit bike since its a simple bike and has been fun. Then I could run shop errands with it and actually use it more.

 

[16v4nrbrgr]

LED headlamp attached to the front fender

New Briggs muffler with the center hole drilled out 1/2", end of expansion chamber opened up to 3/4", it's loud, lol!

Managed to make the kickstand fit.

 

[Flattie42]

Lookin good! How's the performance over the stock muffler?

Did you see the pipe I built for my Motobike? For the stinger tip I used the top from a chopped off bicycle seatpost, lol. I had my doubts when building the shape and length of the pipe, but I have to say it works out pretty well and sounds sick! I looked at pics of as many 2-stroke exhausts as I could to get an idea of the shape needed to increase performance for these engines. The main goal was to build something that looks cool like a dirtbike exhaust while still being able to function. Can't wait to polish er up after fixing the couple small leaks... Oops. lol.

I've been working on the Motobike moreso than my motorized bmx... I bought a couple bottom bracket upgrade kits from eBay which converts the one piece crank to a square tapered crank... This way the crankset spins more concentrically so the jacksaft doesn't variate causing the bike to jolt back and forth at high rpms. I just need to relocate the engine plate on the bmx... I was thinking of using a Cag engine as the powerplant since the bike is smaller like a cag and it's only a single speed... Cheers!

 

[16v4nrbrgr]

It definitely has more pickup now, most of the power will be from opening up the outlet of the x pipe, it had a smaller outlet tube which I took out and made it 3/4" through. I still gotta ride it a bit and adjust the carb for it and I have a couple different heat ranges of plug to try.

If you have over a 30:1 overall ratio a cag would work well with the nuts on the head bolts inside. The piston ported motor is hard to beat though, it makes great torque and still revs really high, and its easier to start and tune.

Glad to see you're having fun with the bikes, I'm going to mess around with mine tomorrow and get the tuning set up. I'd like to make it quieter somehow without plugging it up, maybe another baffle or something will help.

 

[Flattie42]

At the moment I've collected about 8 piston ported engines and 3 Cag engines, lol. I definitely favor the piston ports overall... I was hoping to sell the bmx with a cag engine to free up some space in the garage... If I don't get too attached to it, that is. Lol.

I was thinking of making a stealth bike with an engine soo muffled it wouldn't be any louder than a 4 stroke... Then hide the gas tank and engine inside the frame with some sheet metal or a wicker basket, lolol...

My Motobike is geared at 20:1 and shifts up 5 speeds making the final gearing ratio 10:1. If a jackshaft or gear reduction box is used, then the ratios get multiplied together... I'm using a 5:1 cateye gear reduction box with a 12tth engine sprocket, then to a 48tth crank down to a 28tth, the 1st gear rear freewheel sprocket is 28tth and goes down to 14tth. I also figured out that the j-shaft doesn't increase or decrease the ratio, but helps add more torque or leverage to the drivetrain. It's the same concept as using a larger/smaller rear drive wheel.

 

[16v4nrbrgr]

It's been a while since I've ridden this bike, I took it to the racetrack to use as a pit bike for a while, but brought it home since I feared it would be abused at my shop.

It needs a new air filter, since I broke the Folger's coffee airbox loading the bike in the back seat of my car, lol. I'm gonna just use a X1 pocket bike velocity stack with cone air filter off Ebay.

I could really care less whether I tick people in my neighborhood off from intake noise, they all rev their noisy Hondas and jacked up trucks driving past my house everyday, so effem, lol!

I might put some knobbies on her and do some hillclimb trials stuff in the hills at the Sears Point racetrack, since it's private property I might be able to get away with doing some trail riding. The trails around here are off limits to motor vehicles, which unfortunately includes mopeds and motorized bikes.

 

[16v4nrbrgr]

I installed the new air filter, leaving off the choke plate which is unnecessary on my motor. I also welded a safety wire loop on a new Briggs muffler (without the baffle drilled out) and installed it to hopefully lower the noise. Most of the noise comes from the intake area so it would be worthwhile to install another coffee can airbox over the filter to muffle the noise. The bike runs great as ever and I zipped all around town this afternoon, but its too loud at full throttle and my ears are still ringing lol!

 

[16v4nrbrgr]

Bought some more coffee to make another airbox to quiet the intake down, it really needs it!