Necro's 4 speed 125cc Lifan Build Thread

ultralight01 said:
It's likely related to chain sizes or sprockets being too small or anywhere near off/incorrect size. If you used 420 on a 41 sprocket, etc.
Jerking could be the engine not getting enough fuel. You could try a pump. Plus you've just got a lot of chains and complexity everywhere...
Clutch may also need adjustment... but out of the box? Hopefully not... but it's a Chinese engine correct?

Edit: After some more research it's very likely you need more fuel delivery to the carb. Gravity feed isn't enough for even small motorcycle engines.
http://www.autoanything.com/fuel-sy...ITwb9FkAPsYdUOZfY2Jmhncnu1PdYCS48AaAmp78P8HAQ
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I'm sure it has nothing to do with the engine itself. It's something to do with the chains and gears that I added to connect the engine to the rear wheel. Maybe my freewheel is defective or something, but the engine has plenty of power and doesn't seem bogged down at all.
 
It was chain size. Switched a chain and now it runs fine! Took it for a test ride, works great. Got it up to about 45 mph with no problem. Didn't take it any faster cause I was freezing my ass off, it's like 35 degrees today. Still tons of fun...
 
Jerking could be chains too loose. More pictures would help.

420 chain is perfect for 41 sprockets. gravity feed is just fine. What chains and sprockets you running?

If you are driving a freewheel from the engine you might have these issues. Ie no engine braking?
 
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I am using a freewheel, but changing the chain fixed the jerking. Now I just have to see if the new chain breaks, and if it doesn't, problem solved.
 
Today I attempted to take a video for you guys, but I didn't have an assistant, so I just attached the camera to the bike handlebars, and the video was so shaky and terrible that it wasn't worth uploading. Anyone got any ideas on how I could get some footage of myself actually riding the thing?

On a side note, the bike can do 0-50 mph in less than a quarter mile. It's incredible.
 
Put your phone on the road and fly past it? Make a strap and tie it to your chest? Buy a GoPro 3 for 100 and make fantastic videos?
 
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Nice!! I've had good luck with duct taping one of my old iPhones to the chin cage of my helmet. The only thing is use gorilla tape and not duct tape as the duct tape will leave a residue that is difficult to clean off the soft material inside. Also takes a couple tries to get the right angle of road and sky. I think a go pro mounted on the helmet or some video sunglasses would be the best though.
 
I'll post a video as soon as I figure out how to make one that isn't ****. And yes, I am really using it. I rode it to work today, took it up to about 55 mph. Still not close to the top speed. I also added fenders, which haven't fallen off yet, so that's a plus.
 
I'm thinking of building a 670cc V-twin predator mini chopper. I've seen that thing in action on a rinkydink go kart with thinner tubing than a bicycle, it's pretty bad ass and with custom headers installed, it spits flame and sounds like a beast! Anyone interested in this death machine? May be a few months until I have the funds to pull this kinda thing off. The engine itself is 700, the bike could run me anywhere from 80 to 400, and then there's the torque-a-verter, running me around 250(?), the chain, the jackshaft (this is the reason for the disclaimer below), and finally, the throttle handle, shifters, grips, a comfortable seat, and a good ice cold bottle of virgils root beer sitting on the side of the tank. BTW, I also have an aosom cargo trailer rated to 180 pounds, so if anyone could give me any pointers as to how I could turn it into a soundbox with a cooler, it'd be much appreciated.

(Disclaimer: do not attempt this at home until I have verified that the engine and vehicle is safe[ish])


BACK TO YOU, NECRO!
 
The 670 V-twin is really overkill. If you want to go fast, 212cc predator or 125cc lifan have more than enough power without nearly as high a price tag.
 
TheNecromancer13 said:
The 670 V-twin is really overkill. If you want to go fast, 212cc predator or 125cc lifan have more than enough power without nearly as high a price tag.
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Yeah, well I live for the power of big engines on lightweight two wheeled vehicles, and I also love the speed, so I figure bicycle+670 V-twin+jackshaft=badass bike that can outrun cops? Not that I would, but you know. I have also seen how giant this engine is, and that's why I'm getting a chopper bike. Oh, forgot about the mounting plate: I'm likely going to have one fabricated so I can move the oil cooler to the front of the bike. That'll run me anywhere from possibly 80 to 350, depending on the thickness of the mount, how it will be placed on the frame, and how much support my jackshaft is going to need. Likely going to make myself a mount for that, tapping into the side of the mount for the lower seat post clamps.
 
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Look up 600cc motorcycle frames on google images, then compare that to a bicycle frame. You're trying to build a motorcycle. Just buy one, it'll be much much cheaper in the long run.
 
Yeah, I am building a motorcycle, but note that I stated lightweight, and again, I saw this thing on a God damn kart with tubing HALF the size and thickness of a bicycle frame! I'm going a (slightly) safer route in choosing a mini chopper frame.

What I want is a bike barely anyone has dared build. The main application to this predator is power washers, lawn mowers, go karts, mini bikes, that sorta thing. I'm not a stupid dickbag who will try to go from zero to sixty in point five seconds. I know this engine is three times larger than a 212, and I also know that when experienced guys warn me against going with something so large, you are probably right and there are likely huge safety problems.

But im doing it anyways, and it's not out of idiocy. A 20hp engine is definitely not something to mess around with, as one mistake can be fatal. But I see it as a challenge, from every one of you who say I should just get a motorcycle, to build this safely and amaze you all. I'm planning on this engine being able to go at least 140 tops with a jackshaft. I might just replace the existing shaft with a longer one and support it from the seat tube to lower mounting costs. Oh, and all materials will be 2ga steel at the least (besides the frame).

P.S: I didn't mean to jack your thread necromancer. Have you been able to make any more progress?
 
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Yea, the bike's almost done, but the other day I knocked it over and the wheel got wedged against something and bent, so now I need a new front wheel. I have taken it on a 20 mile test ride, however, and it didn't fall apart, as well as doing a speed test, current top speed is 68 mph, and it could go a lot faster if I changed the gearing.
 
TheNecromancer13 said:
Yea, the bike's almost done, but the other day I knocked it over and the wheel got wedged against something and bent, so now I need a new front wheel. I have taken it on a 20 mile test ride, however, and it didn't fall apart, as well as doing a speed test, current top speed is 68 mph, and it could go a lot faster if I changed the gearing.
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Although you only have four gears. May I suggest building a rear wheel with a standard 7 speed freewheel cassette? Or, if that's too much, you could go as low as 3. Or perhaps an internal gear hub. I've heard of them going all the way to 14 gears inside those things!
 
xXNightRiderXx said:
Although you only have four gears. May I suggest building a rear wheel with a standard 7 speed freewheel cassette? Or, if that's too much, you could go as low as 3. Or perhaps an internal gear hub. I've heard of them going all the way to 14 gears inside those things!
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Actually, with the current gearing, 1st and 2nd gears are pretty much useless, topping out at about 5 mph and 12 mph. That's why I said I could go much faster if I wanted. I'd just switch out my 40t for a 20t and I'd double my top speed. Also, there's no way a standard bicycle chain would withstand the torque that the engine puts out, so shifting through the rear hub is out.
 
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