speed
- Thread starter 2stroke
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you won't see 35/40mph with the 48cc china-girl engine.
In fact without modifications you are seeing some nice speed on the 48cc
the best modification out of the box is the "tuned exhaust" you can get from Sick Bike parts
Sick Bike Parts
you can also get a 36tooth rear sprocket, however this will severely hinder your "up hill" climbing ability.. so if you get the 36t sprocket be prepared to help"pedal" on the up hill sections of your rides.
In fact without modifications you are seeing some nice speed on the 48cc
the best modification out of the box is the "tuned exhaust" you can get from Sick Bike parts
Sick Bike Parts
you can also get a 36tooth rear sprocket, however this will severely hinder your "up hill" climbing ability.. so if you get the 36t sprocket be prepared to help"pedal" on the up hill sections of your rides.
1st thing to upgrade are your brakes...
make sure you have good disc brakes....
DO NOT port the engine. especially if you are new to this. Just enjoy the bike for what it is.
make sure you have good disc brakes....
DO NOT port the engine. especially if you are new to this. Just enjoy the bike for what it is.
Not sure of your motor, but all the cranks Ive seen only stroke 39mm
a 45mm piston would give you an effective 62cc engine.
my 50cc grubee is a 40mm piston. Measured 49cc actual.
"porting" is very different from "bluprinting" & a very miss used term all over the motored bike forums.
By all means clean up the junctions of the intake & exaust ports & make sure the gaskets are not resricting any flow.
I have rolled my box stock 50cc motor to 32mph with simple tuning details (with the stock choker exaust) the motor was really shaking at those rpms...NOT recomended...it climbs like a winded dwarf with the stock gearing. So gearing for more speed would make it worse.
A real expansion chamber really helps the motor breath, but you need to know basic carb tuning to fully realise the potential. (all the info is posted on the board)
good Luck.
a 45mm piston would give you an effective 62cc engine.
my 50cc grubee is a 40mm piston. Measured 49cc actual.
"porting" is very different from "bluprinting" & a very miss used term all over the motored bike forums.
By all means clean up the junctions of the intake & exaust ports & make sure the gaskets are not resricting any flow.
I have rolled my box stock 50cc motor to 32mph with simple tuning details (with the stock choker exaust) the motor was really shaking at those rpms...NOT recomended...it climbs like a winded dwarf with the stock gearing. So gearing for more speed would make it worse.
A real expansion chamber really helps the motor breath, but you need to know basic carb tuning to fully realise the potential. (all the info is posted on the board)
good Luck.
Get a better air filter. Even a homemade filter is better than the stock one. And if you're using the NT carb, punch some extra holes in the filter cover for more air flow. I did notice a bit of a difference after doing that. And don't forget to do port matching!
Something you might think of is your body position. If you can cut a couple of inches off the ends of your handle bars and lower them a bit you will go faster.At fifteen MPH most of the energy is spent by moving the air out of the way.There's a lot of modern mountain bike frames that have the handlebars much too high in relation to the seat if you want to go faster. On my road bike there is a drop of about 6 inches from the top of the saddle to the middle of the handlebars. On my motorized bicycle it's more like four. I personally don't think that your handlebars should be above your saddle if you want to go faster.
I would also check your tires. I went with a 26 by 1.5 semi slick and pumped them up to eighty pounds so they would roll easier.
I also made sure my wheels were true and my bearings are greased and adjusted correctly. I would also check my brakes and see if they're not rubbing. Every little bit helps. I also upgraded my chain to a KMC 415 BMX chain so that it runs with as little drag a possible. (its also silver and looks cool).
I did some coast down tests even before I took the engine out of the box, just to se how much speed I could get out of my bike before I even bolted the engine on.
mike
I would also check your tires. I went with a 26 by 1.5 semi slick and pumped them up to eighty pounds so they would roll easier.
I also made sure my wheels were true and my bearings are greased and adjusted correctly. I would also check my brakes and see if they're not rubbing. Every little bit helps. I also upgraded my chain to a KMC 415 BMX chain so that it runs with as little drag a possible. (its also silver and looks cool).
I did some coast down tests even before I took the engine out of the box, just to se how much speed I could get out of my bike before I even bolted the engine on.
mike
Raised seat
If you only raise your seat then You might increase your frontal area. I would think about getting some lower, shorter handle bars and maybe a longer stem. Something that makes your back flatter. If you look at Time trial bikes the body position is fairly narrow and stretched out and those guys get to go at pretty good clip.
If you stay with the standard mountain bike handle bars and body position you mite as well drag around a parachute. The handle bars on my motor bicycle are about two and a half feet wide and they work much better for me than the stock bars that I had started with. I consistently beat my neighbor going downhill on his mountain bike even though we had similar riots and similar tires. The main difference was that my body position was lower and more narrow and farther out than to his. Were pretty close on weight.
mike
If you only raise your seat then You might increase your frontal area. I would think about getting some lower, shorter handle bars and maybe a longer stem. Something that makes your back flatter. If you look at Time trial bikes the body position is fairly narrow and stretched out and those guys get to go at pretty good clip.
If you stay with the standard mountain bike handle bars and body position you mite as well drag around a parachute. The handle bars on my motor bicycle are about two and a half feet wide and they work much better for me than the stock bars that I had started with. I consistently beat my neighbor going downhill on his mountain bike even though we had similar riots and similar tires. The main difference was that my body position was lower and more narrow and farther out than to his. Were pretty close on weight.
mike
My bike goes around 30ish, 66cc stock engine 44t, still on its first tank of gas with a 20:1 ratio, all i did was port my intake and make a 9 degree bend in it so the carb clears.
Don't listen to them cut your piston skirt and make your exhaust port bigger it made all the difference on my bike
Only mods I have are: cut piston,kx 65 exhaust, shaved head and its makin 35mph!!! And now has a powerband!
Only mods I have are: cut piston,kx 65 exhaust, shaved head and its makin 35mph!!! And now has a powerband!
Congrats on bumping a thread from 2011 started by a member who hasn't logged into the site since 2011.
You must be new. lol
You can easily get 35-40 out of a 48cc with some simple bolt ons. I suggest puch 50cc hi hi head and real dellorto 16.16 carb from treatland. Also mate the billet manic mechanic intake manifold and good expansion chamber exhaust. I also suggest the shift kit from SBP to get the most out of your engine, or gear down from the 44 tooth.
Here is my 48cc bike with only those modifications done to the external of the engine, fully stock internals.
http://motorbicycling.com/showthread.php?t=56583
Here is my 48cc bike with only those modifications done to the external of the engine, fully stock internals.
http://motorbicycling.com/showthread.php?t=56583
Ohh very sorry Sir!, no I did not look at the date because I saw it at the top of the threads I considered it new, bad bad mistake on my part! I must be new! Lol
