How fast can your 80cc really go?

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markeatmark

markeatmark

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Jun 17, 2009
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xlite said:
I do think it's possible to do 38mph w/44t (downhill). But it's like that fellow here says about skydiving w/o a chute. You can't do it a second time.

Many guys who placed in the Deathrace noted that engines were not the same afterwards and would not race again. I noticed the same result when I over-revved my second bike.
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I've gone 38 with a 44 tooth and down hill and many times I've held it wide open for several miles. I have more than 1000 miles and the motor runs just fine..wee.
http://c2.ac-images.myspacecdn.com/images02/109/m_1379f6574879471d88b168ccb15c70fd.jpg
 
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BarelyAWake

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/facepalm

One day maybe ppl will figure out that we all share almost identical machines (for all intents and purposes lol) and as such there simply isn't that much variance in believable speed claims.

Having said that, up to 40mph is still somewhat believable - even tho I only clock a sustained 33mph via GPS with my lardbut 200lbs & less-than-efficient knobby-tired mountain bike, I bet my lightly modded motor could do close to 40mph even on flat, smooth ground IF it were on a skinny tire roadbike with a very light & small 11yo riding it (for less wind drag, the BIG prob here) & with the proper sprocket ofc. But it would defo suffer for the experience, it seems close to redline @ 33mph ;) (that'd be the 44t)

So yeah - 38MPH going downhill as markeatmark claims is totally believable - heck my GPS has registered 35.6mph as a top speed, it's just really bad for the poor lil motor and is ofc "cheating" as it's downhill lol A fascinating example of the problem w/drag is I've never been able to break the 35mph barrier no matter how steep a downhill... I've also stopped trying as it's sketchy as all get-out on my bike and I'm simply not interested.

Once ppl start claiming past 38mph or so on stock HTs with ratty ol' mountain bikes on the flat & level... well then it's time to break out the waders lol
 
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BarelyAWake

BarelyAWake

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OMG!!1! I jus figured it out!

I've neglected to wear SPANDEX w/sponsor logos all o'er it and a lil pointy helmet ffs - that's gotta be good fer another 10mph at least lol

or so the lil voices tell me o.o


Gdamn this Tshirt & jeans, I'm shavin' my legs and ridin' nekkid WHOOHOO!!! :D
 
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C

chrisme

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I mounted a hood scoop and a big wing on my bike, it increased to 10hp, now I can go 80mph with my 44t sprocket no problem!
 
Bikeguy Joe

Bikeguy Joe

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The fastest I have ever had one of my bikes going was in 7th grade when the bully kids threw my Roadmaster 24" girls bike with "banana bike" handlebars off the 60' cliff at Thompson Ledges Park.

I think it got up to about 60 mph before it hit the ground from the looks of it afterward.
 
Bikeguy Joe

Bikeguy Joe

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I have claimed 45 mph at one time on a chinabuilt bike, but in retrospect, I think it was a combination of the optimistic guy beside me in the car, and hearing the song of the sausage creature playing in my head as I rode helmetless, in between the gravel berm and a total stranger on a crappy back road @ 38 mph.
 
mechanickid

mechanickid

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my top speed has stayed around 35 on flat with 38 tooth after i got a new cylinder and rings a month ago, but now i dont see the same power as when i first got them, should i just get new rings again?
 
I

impression

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xlite said:
Yeah!

I got even better idea! Put the 44t on the engine and little 10t on the back wheel! And find biggest hill in town (to go down of course). THEN come back and post in this forum.
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impression said:
sigh, that's just stupid as the engine won't have the torque.

changing the 10T to 11T gives a 10% decrease in engine rpm for the same speed ;) therefore also giving a 10% higher top speed in the condition that the engine produces enough power
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xlite said:
LOL! :) :) :)
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Err, i was speaking about the SBP's Shift kit and refering to the output side of the transfer shaft, it's normally 10t, but moving to 11t would give a 10% decrease in engine rpm for the same speed therefore also giving a theoretical 10% higher top speed on the condition that the engine produces enough power to reach it.
 
X

xlite

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impression said:
moving to 11t would give a 10% decrease in engine rpm for the same speed therefore also giving a theoretical 10% higher top speed on the condition that the engine produces enough power to reach it.
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True. Key word is "theoretical".

Unlike many here you seem to realize the SBP kit has NO advantage in terms of top speed compared to a properly matched non-jackshaft setup. Ratios are of no use w/o torque.
 
BrettMavriK

BrettMavriK

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I disagree.
One advantage is the fact that I can set top gear for far longer legs for top speed than a single speed set up and not lose the fast power acceleration to get there. Single speed set ups are always trying to find the balance between acceleration and top speed. It sucks being stuck in one gear all the time.
What I am trying to convey is the fact that single speeders would never try to put on a gear that would bring their bikes to their true top speed potential, as they would have absolutely no acceleration off the line. Multi-speeders can have it all; find the max top speed and still get there quick.
I'm hitting just under 45mph with my latest ride with a stock motor and carb with nothing more than a expansion chamber. Soon I will have an HT motor built that will bring me to the 50+ mph mark,
and I will have a video to prove it. I have a friend who is a State Trooper with a legal radar gun.
 
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xlite

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BrettMavriK said:
What I am trying to convey is the fact that single speeders would never try to put on a gear that would bring their bikes to their true top speed potential, as they would have absolutely no acceleration off the line.
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Never is a strong word... specially since that is EXACTLY what most single speeders want to do.
My comment related to top speed and top speed only. Not how fast to get there or ability to burn rubber.

"Lisa... In this house we OBEY the laws of thermodynamics!" -Homer Simpson :)
 
FileStyle

FileStyle

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try doing 50 mph without the "transmission".with only single speed (oh, it can be done) and I will, my goal is to have a 60 mph bonneville bike. technichaly your considered a motorcycle with a jack shaft. its a form of transmission!
 
BrettMavriK

BrettMavriK

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Yeah and Technically,
over 30 mph (20 mph in some states), over 50cc, over 2hp, you're a motorcycle as well.
This thread didn't ask how fast can your perfectly street legal motorized bicycle go...
and if you go over your state's legal speed limit, you're a motorcycle, so wouldn't it make this thread moot if you want to be Technical???
 
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