14T rear, 16t drive front, it does 25 flat out this way or flop the front sprockets and it'll do 35 but not hills well and its not a goped at that speed, so its a torque monster.
52cc Predator Auger Powered X-Games FS20 BMX
- Thread starter 16v4nrbrgr
- Start date
I'm gonna swap out the clutch today and find out how much material needs to be taken out for a reasonable stall speed that climbs hills well. The pocket bike clutches I bought off Ebay may have a different slip characteristic so I'm gonna be careful to not drill too much material out. I managed to pull over 11k rpms yesterday with the cat pipe on, but the clutch was slipping a whole lot when hot so its time to change it at approximately 8 hours total on the motor. For a $5 clutch, 8 hours is reasonable I think, considering the thrills it provides. 
Wow!
At 25mph on the flats, it's geared well for low end and hills.
At 35mph but not for hills, it's geared well for flat ground.
Is there some way you can create a 2-speed shift kit?
If so, you'll be able to make better use of your bike.
Good job so far!
A jackshaft setup would allow right sided shifting, maybe a Sturmey fixie hub could be used backwards on LHD but its a stretch, I think it would eventually come apart. I like it the way it is, if I had gears I'd get going faster than the stability of the bike is safe for as a BMX. Downhill going 30+ is pretty crazy with a solid fork I think. I have a hydraulic fork which I may use later on this bike, hafta see. I like it a lot the way it is, but a suspension fork and front disc brake would be nice also, although heavier. On dirt and gravel roads the bike really comes into its own and feels lively, and it will climb anything I could throw at it. Part of not wanting multiple gears is to keep the number of complicated assemblies on the bike low, so I can just go ride, there a lot of maintenance with motorbikes, and less is better. It also has to meet some legal definition, which gearing it like a goped for a max of 25 makes it legal as a huge goped, I can point to the sticker and say, "see, it sez here, GO HUGE" lol.
The reason why I like this bike so much and probably will keep it indefinitely is that is tends toward the practical side. So far, other than the skid cracking, it has been very trouble free.
The reason why I like this bike so much and probably will keep it indefinitely is that is tends toward the practical side. So far, other than the skid cracking, it has been very trouble free.
Last edited:
Turns out the clutch is fine, just needed some oil mist buildup cleaned out with alcohol and a scotch brite and the spring stretched with my thumb. I think it will go another 10x what its done if I can make the spring compensate for wear well enough to keep the engagement rpms pretty consistent.
http://www.target.com/p/huffy-boy-s-revolt-20-bmx-bike-black-blue/-/A-13899431#prodSlot=medium_1_39
Here's another bike that would work for a drivetrain like this, I can make something similar for this frame if the demand is there.
Here's the other one which would be sweet for motorizing:
http://www.target.com/p/polaris-kid...-blue-white/-/A-12035119#prodSlot=medium_1_46
Here's another bike that would work for a drivetrain like this, I can make something similar for this frame if the demand is there.
Here's the other one which would be sweet for motorizing:
http://www.target.com/p/polaris-kid...-blue-white/-/A-12035119#prodSlot=medium_1_46
I put the bike up on CL, since I want to see if the local economy is completely shot. The experiment is to start throwing stuff at the wall and see what sticks.
I haven't had any bites on CL so I keep riding the bike and having fun. The other day the trans drive freewheel blew apart so I bought another Crossfire freewheel locally and its alive again. I think maybe next time I would like to try the GT 120 point ratcheting freewheel since you need to take care not to apply power too hard initally and make the pawls bounce. The 120 will probably avoid this, although I'm not sure about its power handling. This is kind of a mental note for myself and a record that the ACS crossfire holds up to 11 hours of 4 hp BMX riding, not bad! I think all the dirt and gravel riding with on-off throttle and wheel hop killed my last one, a problem I had with the Sturmey 3 speed on my electric dirtbike before. For pavement a freewheel is great though, and really improves the eficiency, and overall it prevents strain on the clutch and motor so its worth changing one once in a while.
Last edited:
My strat has been to use a smaller diameter rear rim, reducing the load on the free-wheel, raised RPM as a result, and then add a trike-tranny as a 3-speed jack-shaft to regain the top-speed.
12.5 inch rear rim, 20-tooth California-excess bmx freewheel, shimano nexus 3-speed jackshaft, and using a pocketbike 5-to-1 reducer tranny on the 52cc 2-banger. The pocket bike tranny has a 10-tooth bmx sprocket, the shimano has a 21-tooth input and a 20 tooth output, and again, the rear has a 20 tooth bmx freewheel. Engine is flipped so the output is on the right-leg side. Pedals removed( not required in my jurisdiction ).
I got 43 mph out of those 52cc's in that config without pedals.
Pedals are great and all for exorcize, but so is pushing with your foot, as in motor assisted foot scooter. I advocate the motorized kick bike because they are legal where most motorized bikes are legal.
These are where I start
12.5 inch rear rim, 20-tooth California-excess bmx freewheel, shimano nexus 3-speed jackshaft, and using a pocketbike 5-to-1 reducer tranny on the 52cc 2-banger. The pocket bike tranny has a 10-tooth bmx sprocket, the shimano has a 21-tooth input and a 20 tooth output, and again, the rear has a 20 tooth bmx freewheel. Engine is flipped so the output is on the right-leg side. Pedals removed( not required in my jurisdiction ).
I got 43 mph out of those 52cc's in that config without pedals.
Pedals are great and all for exorcize, but so is pushing with your foot, as in motor assisted foot scooter. I advocate the motorized kick bike because they are legal where most motorized bikes are legal.
These are where I start
Those are pretty neat. My BMX is basically an stand up scooter legally, but its a dirtbike in practicality. I like to climb steep hills and shed dirt and gravel with it. I have it geared to climb all hills without any assist, so it maxes out about 25-30, these engines on X1 and X2 pocket bikes are capable of 60 mph on flat ground. I really like the engine and recommend it, revs freely.
I wouldn't be caught dead on a kick scooter though, lol but that's just me. Don't advertise your goofy looking scooters in my thread.
I wouldn't be caught dead on a kick scooter though, lol but that's just me. Don't advertise your goofy looking scooters in my thread.
Last edited:
I think I'm keeping it for a while, really don't even want to sell at 500, no offers that even high yet. Its okay, it rides really well and I enjoy it so whatever.
Last edited:
So I had a new problem with my ACS sprocket skipping pawls, so I shot it with PB blaster to actually wash out some of the grease in it, since its relatively new, and also retensioned the chain that looks to have stretched somewhat. Now it works again, lol YAYY, guess the ACS Crossfire needs good chain tension or it wobbles a bit too much and skips. Good to know, otherwise it works great and handles about 4 HP my auger makes with the pipe.
The grease used in freewheels matters a lot too.
I used to take my bmx freewheels apart and rinse out all the factory grease and used light lithium grease instead. Worked much better in cold Ill winters...might help your issue to switch to something thinner.
I used to take my bmx freewheels apart and rinse out all the factory grease and used light lithium grease instead. Worked much better in cold Ill winters...might help your issue to switch to something thinner.
I think it'll blow up before the grease wears out in it lol, the last one did. It felt fine today and engages well now, I think most of it was due to the chain tension, since its the $20 Crossfire and not the $60 Crossfire Pro that has better bearings that run true at all times. I was reading that a freewheel can skip if it wobbles, the new expensive ones have very nice bearings to prevent this, but since I think every freewheel has a finite life on a bike like this I'm gonna stick with $20 ones, lol.
I heard that.
Cleaning out the thick grease is still a good idea anyway to prolong life.
I've even used gear oil but it's messy.
Cleaning out the thick grease is still a good idea anyway to prolong life.
I've even used gear oil but it's messy.
Yeah that's what I already did, with PB Blaster. The real issue is the alignment of the inside to the outside, and having enough chain tension on it so the first pawl will pick up and then the other two follow. If it has something better like tri-flow or something more slippery I think it will misfire again.
Thanks Otero, I'm too poor to give up, maybe more desperation than persistence, lol!
I was poking around looking for engine stuff and found a WATER COOLED 52cc 2 stroke!
The neat thing about this is that it would be a direct replacement for the air cooled one on there now.
I'm not sure if there really are any advantages to running this since it needs a pump and battery or a belt driven pump, along with hoses and a radiator. On RC boats it gets a constant supply of cold water passively. I think maybe it would allow the use of higher compression ratios per grade of gas since it *should* cool the combustion chamber better than an air cooled.
I also found a 71cc cylinder kit for these which is used on high powered augers. I can't find any sources from the US though. The 71cc augers cost more, so I think that market is protected by not importing cylinder kits, lol.
The Predator engine has been excellent, and I'm sure it has many hours left on it, gets better with every ride!
I was poking around looking for engine stuff and found a WATER COOLED 52cc 2 stroke!
The neat thing about this is that it would be a direct replacement for the air cooled one on there now.
I'm not sure if there really are any advantages to running this since it needs a pump and battery or a belt driven pump, along with hoses and a radiator. On RC boats it gets a constant supply of cold water passively. I think maybe it would allow the use of higher compression ratios per grade of gas since it *should* cool the combustion chamber better than an air cooled.
I also found a 71cc cylinder kit for these which is used on high powered augers. I can't find any sources from the US though. The 71cc augers cost more, so I think that market is protected by not importing cylinder kits, lol.
The Predator engine has been excellent, and I'm sure it has many hours left on it, gets better with every ride!
Last edited:
You still looking for that polaris bike? Fingerhut
http://m.fingerhut.com/thumbnail/Sp...Mpos=31&Mpper=15&pageSize=15&Mfsort=Relevance
http://m.fingerhut.com/thumbnail/Sp...Mpos=31&Mpper=15&pageSize=15&Mfsort=Relevance
