power band

rickdiculous

New Member
Aug 27, 2008
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am i running my 80cc engine in its power band? it runs good out of the blocks but then starts to "four stroke". if i have a really long stretch to run to get the revs up it seems to power through it, but it really has to get rippin. i'm running a 36 tooth rear sprocket. should i put on the 44? is there a 40t?
 

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jf30cp

New Member
Jun 23, 2008
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as far as i know these engines dont have any reeds so it cant really have a power band. But you will get better throttle responce at highr end speeds.
 

Andyinchville1

Manufacturer/Dealer
Dec 26, 2007
502
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Scottsville, VA
Hi Rickdilous,

As far as sprocket size you can get anything from 18T to 76+T (NOTE: Below 27 T requires disc hub mount only)....Check out the links below.

Hope this helps you.

Andrew
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
These engines (and indeed all engines) have a "powerband".

The four cycling is due to (partly anyhow) the extremely crude carburation.
 

tylerlough

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May 28, 2008
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Mishawaka, IN
I believe my carb is the limiting factor on my 80cc because it will rev up to 7000 rpms for a few seconds then just bog down. I haven't tried to move the clip down to richen the mixture, that may help.

It'll keep gaining horsepower up to a certain rpm, then start dropping off. If the carb can't keep up then power will really drop off.

My bike isn't together right now so my help is limited.
 

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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Duvall, WA PNW
www.sickbikeparts.com
am i running my 80cc engine in its power band? it runs good out of the blocks but then starts to "four stroke". if i have a really long stretch to run to get the revs up it seems to power through it, but it really has to get rippin. i'm running a 36 tooth rear sprocket. should i put on the 44? is there a 40t?
You know when you are in the power band, because you feeling the engine torque accelerating faster than the current speed. Power band in motion = butt feel.

I hear this "four stroke" thing all the time - I actually think it has more to do with exhaust than the carb. If you don't have an expansion chamber, then you won't really put the engine power to the ground. Nor will you be able to shift the power band. I think the stock carb actually works OK, and going richer with the needle won't change the top end. I also have news, the engine needs to be a tad leaner at WFO, and you can get there with a smaller jet. Stock is .70mm, I run a .65mm, Ghost0 runs a .60mm.
 

misteright1_99

New Member
Mar 21, 2008
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Treasure Coast, Florida
I believe my carb is the limiting factor on my 80cc because it will rev up to 7000 rpms for a few seconds then just bog down. I haven't tried to move the clip down to richen the mixture, that may help.

It'll keep gaining horsepower up to a certain rpm, then start dropping off. If the carb can't keep up then power will really drop off.

My bike isn't together right now so my help is limited.
Your engine is only going to flow as much as your carb and exhaust allow. The stock carb is quite small and if you have cleaned up your intake and exhaust ports and gaskets the engine will allow more airflow, especially with a chamber. Running the stock 14mm carb you are limited to the airflow, so you are limited to fuel so max of .65 or .70 jet size. I run a 18mm carb with a chamber and flow much more air and therefore I use a .85mm jet in a 48cc engine, and could probably go up one more size. My engine now pulls throughout the entire rpm range and does not flatten out a max rpm's...