49cc vs. 80cc

[John-Forrest]

Hello,

This past spring I took out my 49cc engine and put a 80cc on. I am wondering if there is any real difference in power/speed. I did initially note a bit more climbing power, but later that just died down and engine started conking out on very steep inclines.

I was hoping I'd get 30+ mph, but if I go beyond 20mph, engine rattles like crazy and nuts/bolts start falling out. So I can't really go faster.

Someone told me that 49 cc works better, he actually put my old 49cc on his bike and said it works great! He suggested I go back to 49cc.

What are other people's experience with this?

John-Forrest

 

[arceeguy]

With a 44T rear sprocket (stock with the kit), I have found no real difference in top speed - but the larger 80cc (66cc actual) engines do pull hills better. The 50cc engines seem to run smoother at higher speeds, but this could vary from manufacturer to manufacturer. All these engines look the same on the outside, but some have better internals than others.

I weigh about 175 lbs, and I can go 32mph on a flat surface and 35 mph down a slight grade. Up a 5% grade, the 50cc slows to about 25 but the 80cc will maintain 28.

FWIW, I usually putt around town at 20 mph. Great fuel economy, low noise, less surprises from motorists that aren't expecting a bicycle to be doing 30+. I'll open it up on roads with plenty of visibility and light traffic.

 

[motorpsycho]

i have the 49 c.c. slant head 2 stroke engine on a 20" frame with 20" wheels and a 44 tooth sprocket. My friend has the 80 c.c. 2 stroke engine on a 24" frame, with 20" wheels and a 44 tooth sprocket. His motor is broken in, and mine isn't fully broken in yet.
his gets going from a dead stop better than mine does (more c.c. = more bottom end torque) but i can catch him once we get going and stay side by side with him at 25-28 mph.
he does weigh more than i do (i am 155 lbs) but even if i ride his 80 c.c. bike, i still get about 25-28 mph top speed out of it.
i think the 20" wheels takes away from some of the top speed because most bikes with 24" or 26" wheels seem to get a little more top speed than what we're getting with the 20" wheels.

 

[Cornell]

I got 26 wheels 80cc mine's do 50 to 55 top speed

 

[darwin]

More CC's = more love!

 

[JerboaJohn]

it's a whole debate, but me too favor the 48/49cc. mechanically more cc's is more torque at any rpm. it's a bigger fist punching, but there's a lot to be said abt a lighter piston and how high it can rev all else being equal.
I'm also fighting thru making the 1st of many hand-made heads for the little HT's. I kind of had to at first bcs I have 1 of only a few dozen mfgr spec error piston/cyl that were sold in Sep. with a bore of 42.6mm and the stock 40mm head chamber is too small for a good seal.

can't remem who said he had his 48cc's running 10k rpm and he said they were smooth as butter before he blew them up redlining it downhill again and again

 

[rover528]

it's a whole debate, but me too favor the 48/49cc. mechanically more cc's is more torque at any rpm. it's a bigger fist punching, but there's a lot to be said abt a lighter piston and how high it can rev all else being equal.
I'm also fighting thru making the 1st of many hand-made heads for the little HT's. I kind of had to at first bcs I have 1 of only a few dozen mfgr spec error piston/cyl that were sold in Sep. with a bore of 42.6mm and the stock 40mm head chamber is too small for a good seal.

can't remem who said he had his 48cc's running 10k rpm and he said they were smooth as butter before he blew them up redlining it downhill again and again

Where are you getting a 48/49/50cc motors build kits from. I'm on my first project so I need everything. I live in Calgary, Alberta, Canada.

 

[Street Ryderz]

Where are you getting a 48/49/50cc motors build kits from. I'm on my first project so I need everything. I live in Calgary, Alberta, Canada.

Motorized Bicycle Canada. Home of the Grubee Skyhawk Bicycle Engine ki

Motorized Bicycle Canada is the largest Motorized Bicycle engine kit website in Canada. We have the high quality Sky Hawk engine kits at the lowest prices.

www.motorizedbicycle.ca

 

[rover528]

Motorized Bicycle Canada. Home of the Grubee Skyhawk Bicycle Engine ki

Motorized Bicycle Canada is the largest Motorized Bicycle engine kit website in Canada. We have the high quality Sky Hawk engine kits at the lowest prices.

www.motorizedbicycle.ca

For a little advice. If I want to do my first build and decide on the motor kit I want to use should I just order it then look for a bike that will be good for the motor kit. I seem to be having trouble finding a bike without paying a lot for a used bike.

 

[Sidewinder Jerry]

i have the 49 c.c. slant head 2 stroke engine on a 20" frame with 20" wheels and a 44 tooth sprocket. My friend has the 80 c.c. 2 stroke engine on a 24" frame, with 20" wheels and a 44 tooth sprocket. His motor is broken in, and mine isn't fully broken in yet.
his gets going from a dead stop better than mine does (more c.c. = more bottom end torque) but i can catch him once we get going and stay side by side with him at 25-28 mph.
he does weigh more than i do (i am 155 lbs) but even if i ride his 80 c.c. bike, i still get about 25-28 mph top speed out of it.
i think the 20" wheels takes away from some of the top speed because most bikes with 24" or 26" wheels seem to get a little more top speed than what we're getting with the 20" wheels.

Seems you put very small wheels on very large frames. The way most bicycle frame sizes are measured is by the seat post length. However frame geometry can still be very different depending on model and manufacturur for the same size seat post tube. Still generally speaking a 24" inch frame would be for someone around 6'4"+.

Here's a frame proportions calculator that can let you know the general area you need in a bicycle frame size for your particular body build.

Bike Size Guide

New Bike Size Guide Launching 11/17/23

www.competitivecyclist.com

One would have a very difficult time keeping the crank from hitting the ground with a frame that large and wheels that small. Even with a 20" seat post tube would be for a person close to 6' tall. Probably still too large of a frame for 20" wheels and without having crank drag.

Now if you made a very common mistake of thinking wheel size is the same thing as frame size (these frames that use 20" & 24" wheels are generally a lot smaller); one could possibly put 20" wheels on a bike that had 24" wheels.

My desire here is simply to educate so that we're describing things with the correct technical terms.