48cc vs 66cc power comparison

Discussion in '2-Stroke Engines' started by 210061741, Nov 12, 2009.

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  1. 210061741

    210061741 Guest

    Ok this may seem like stupid.
    but i'm looking for some good opinions here.
    Especially if you have ridded 48cc and 66 cc bikes.

    Now legally the 48cc is good to go.

    I have one now and it rocks.
    Lots of mods.
    But im thinking about dumping some Rock Solid High Performance parts into it which are alot of $$.

    My question is how much more power will i really feel from the 66.
    Should i buy a new 66 and get the High Performance Parts for it?
    Or should i keep going with my 48cc.

    Obviously the 66 could get me in trouble but fortunatly where i live they leave the MB'ers alone.
    Unless you break traffic laws.

    They haven't ever stopped me and i have seen many police in my travels.
    My mb looks like a dirtbike and i don't hold it back at all.
    The police arrested someone here once and lost the case.
    The MB'er won, so now the police will not bother us.

    I could get away with the 66er.

    But how much faster will it really be?
    I run high revs with a 36T and my 48cc will hit 40 / 45 mph now.

    I might appreciate the bottom end a little more but it seems that the 66er's don't like the high RPM as well.

    So i was thinking Rock Solid billet head / Ceramic coated piston / 50cc jug / and maybe the performance CDI.
    Does there CDI change the timing?
    If not it ain't worth the money in my opinion.

    Now obviously thoose parts for the 48 cost more than what i can get a new 66er for complete.

    What do you guys think ????

    Remember legality isn't the issue speed is.

  2. Fabian

    Fabian Well-Known Member

    The 66cc will give you greater torque spread with more bottom and midrange torque.

    Top end rpm is irrelevant as the 66cc motor vibrates something shocking above 4000 rpm.
    The best way to take advantage and also build bottom end torque on these engines is to use the standard exhaust pipe - no modifications.

    Speed isn't what you should be talking about as it's best to fly under the radar and not stand out by zooming along at a pace that's unrealistic for someone on a bicycle to be travelling at, also not having an engine that's screaming it's head off, attracting unwated attention.

    What you should be talking about is maintaining a consistant 20 mile an hour "average speed".
    To do that, you'll need an engine with lots of bottom and midrange torque, pushing you steadily uphills at reasonable speed without having to rev it's guts out.

    There's a public perception that someone riding a screamer engine, must be going faster than someone with a quiet slow revving engine, even if both are travelling at the same speed.

    For this reason i want a 100cc engine with port timing suited to low rpm and high torque and a very quiet exhaust system.

    The best way to fly under the radar.

    Last edited: Nov 13, 2009
  3. AussieSteve

    AussieSteve Active Member

    At 45 mph with a 26" wheel your engine would be doing about 8000 RPM. That's screaming for one of these things.

    More (low-end) torque is the way to go, I reckon. Then you can gear a little higher and achieve the speed without revving the guts out of the engine. The 66cc is better in that regard. (That's what I have.)

    I, too, am ordering a billet head from Rock Solid Engines. The high compression ratio will improve bottom-end as well as increase HP at higher RPM.

    ... Steve
  4. motorpsycho

    motorpsycho Active Member

    the way i look at it is, if you do get stopped...how can they prove that you have a 66 c.c. over a 48 c.c.? there is no real way to tell unless they took the jug off and measured the piston and stroke.

    My 50 c.c. is as fast (maybe even a little faster) than my friends 80 c.c. (66 c.c). His has more bottom end torque and it has better take off, but i can catch him once we're moving and i can pass him. we both weigh about the same and our bikes are set up very similar, except he's using a 24" frame with 20" wheels, and i'm using a 20" frame with 20" wheels. I have added an expansion chamber and a high flow air filter since we last ran together. Last time we ran them together, both of our bikes were box stock (stock exhaust, stock air filters). By adding the pipe and air filter, i have increased my top speed from 24 mph, to 32 mph.
  5. AussieSteve

    AussieSteve Active Member

    You guys in the states are luckier than most of us in Australia. Here, even a 50cc is technically illegal, so we have to be ultra-careful. According to the law, our engine output must not exceed 200W!
    We only get away with it because they tend to turn a blind eye, but we can't afford to attract too much attention.
  6. 210061741

    210061741 Guest

    As far as legality where i live in pa particullarly i'm lucky.
    My motor isn't that loud even with the expansion chamber and the men in blue leave us alone.
    The slower i go the better chance of being run over.
  7. 210061741

    210061741 Guest

    Yes i'm sure i push 8000 rpm prolly higher.
    My 48 runs sommther at higher rpm.

    Now iv'e got to make a descision.

    66cc or 48cc

    I wish i knew if i could get the 66 to really rev up.
    Obviously i could run a 30T or something and be ok.

    But i like the revs and the smoothness.

    I just don't know what to do.
    I want to get a new motor today.
  8. Bobbyoutback

    Bobbyoutback Member

    If your in Australia the cops now have a mandate to bust any bikes with a power plant over 200 Watts , they can hit you with some big fines , plus confiscate your bike .
    You could then challenge them in court to prove your bike is only 200 watts .
    How ? :devilish:

    Guess some riders could have a hidden throttle slide switch that will limit revs to just under the 200 Watt mark they can hit if busted !

    Have Fun
  9. 210061741

    210061741 Guest

    Well i guess i'm gonna try a PK.
    I heard Grubee shipped out the new Q4 GT-5 dated 8-30-2009

    No speed carb / No wide 40mm Mounts ??????

    Gonna go with

    Model : PK80J-SILVER
    Engine type :
    Single cylinder, air-cooled, 2-stroke
    Power * Rotary Speed
    Rated Power :
    2.0Kw / 5000r / min
    Max Power :
    3.5Kw / 6000r / min
    Ignition Mode : CDI
    Fuel type : Octane 89 and above
    Lubrication Oil : 2 Stroke Synthetic Motorcycle Oil
    Mixing Ration for Fuel and Oil : 16:1 for new sets (20:1 after running approx 500Km)
    Spark Plug : Z4C 14MM
    Fuel Consumption : 2.5L / 100Km
    Clutch Type : Friction Plate / Dry
    Speed Limitation : 38-53km/hour

    Looks like getting the RPM up to 6000 which should be a piece of cake will output som serious power.

    Guess i'll find out.

    I will be dissassembling / Porting Crankcase Tranfers / and hopefully changing out the 6202's for some sealed 6202's if there not in there before i mount it.

    Not looking forward to the Break in though, it's getting colder latly and long rides take a little more stamina.

    I will be sure to post pics and findings.
  10. motorpsycho

    motorpsycho Active Member

    well i'm pretty lucky then i guess. I live in the county and we never see cops around. If someone does call the cops, it can take them over an hour to show up.
    But where i live, people ride 4 wheelers, dirt bikes, golf carts, go karts & mini bikes on the roads. No one ever bothers them unless they do something stupid.
    My friend lives in town, and we have both ridden our mb's past police and they just smile and wave.
  11. 210061741

    210061741 Guest

    I believe as long as you aren't acting out of control and you look safe they don't bother too much.

    When i ride my MB I wear a full faced Dirt Bike Helmett and Racing Gloves.
    Kinda hard to miss the guy all geared up like that riding a bicycle.

    Especially when most motorcycle riders don't wear a helmet around here.

    I got a helmett to keep my head warm and because soo many things break all the time.

    The Chain coming off scares me every time.

    I have had the back wheel get locked up 3 or 4 times luckily at lower speeds under 15 mph.

    Most of the time i travel at least 30 to 40 mph.

    I'd hate to throw the chain and smash my brain at the same time.
    Then i couldn't fix the darn thing.
  12. Al.Fisherman

    Al.Fisherman Active Member

    I feel for you fellow MB'ers else ware. Here in Alabama the law is... anything 150cc and under, no registration, no insurance, no license/permit at 16 and above, (some restrictions under 16) no lights unless ridden at night, then lights capable of being seen 500'. My son has been stopped a few times... the LEO's are intrigued with it and want a better/closer look.
  13. 210061741

    210061741 Guest

    You are lucky AL.

    I want to move to Alabama.

    Any good CNC / Engineering / Programming / Drafting jobs around there.

    Hook me up.
  14. Learner4life

    Learner4life New Member

    "at 45!!" lmaoooo. I really hope we all figure out what it really takes to build these to go 45 without list of 100 things popping off or giving out when starting with a normal bike, before a tradegy will force us to. I love building bikes, I might love nothing more. But for some reason, i have bad feeling not everyone going 55, 45, etc on bikes that started as pedal power are goign to make it to xmas this year. Stock muffler agree 100%, even the stock carb, believe it or not. my best compression is just leaving it alone and daily.. checking everything, especially oiling chain while warm. I want to post some pics of my new build, but forcing my self not to until the new brake set up is on it, its so hard to wait!! TY all for being here as a community to find, this my first post, im offially the biggest nab here, woot! lol
  15. Michael

    Michael Guest

    Hi, I was asking myself the same questions. I just got a 48cc grubee skyhawk gta2. I also have a grubee skyhawk gta5 66cc(ovbiously I put a 49cc head on it to avoid police) anyway, I keep my bike's in very good condition, they both have high performance carbs, and poo poo exhaust systems. I was on my 66cc, my buddy was riding my 48cc. We went on the highway, our other friend was in his truck clocking our speed. I expected the 66cc to perform better, surprizingly. the 66cc clocked at 105km/hr. the 48cc clocked at an amazingly 125km/hr! I was baffled, they both have the same aftermarket parts. My buddy know a lot about these bike's. he told me the 48cc has more "Back Pressure" and Revs higher, combine those with a poo poo Exhaust (Puts more Back pressure, more power) you'll wish that you've had a 48 - 49cc earlier. I know I do. I sold my 66cc and now all I'll ever use is a 47, 48, 49cc motors. the 66cc has much lower RPM's than the 48cc. The 48cc has higher rpm's + back pressure + high performance parts = more power and speed. Basically the higher the RPM, the faster you go, you just need to capture the back pressure. I suggest a High performance Carb, A poopoo Exhaust. those parts greatly Improved both my bike's power, speed and efficency
  16. Fabian

    Fabian Well-Known Member

    For crying out loud, you should not be riding any faster that 30 mph on a motorised bicycle without large disk brakes, and even then, you should not be riding faster than 30 mph.
    It's completely foolish to push things any faster.

    You should be using the extra torque of the 66cc engine to haul serious payload at 3 mph: http://motoredbikes.com/threads/australian-heavy-haul-may-2016.47426/

  17. Steve Best

    Steve Best Well-Known Member

    the 48/49cc head will not fit on the 66cc because they are different bolt patterns?
    I found the Poopoo exhaust slowed the GT5A motor down 5-10kph.
    Any and all mods on my Grubee GT5A with 40t sprocket still have it limited to under 70kph, which is over 10,000rpm.