Getting a 49cc engine to pull a big guy up hills?

[markjs]

Got me a 49cc to play with. I was thinking, the 66cc just cruises up a hill decently on a 41 tooth sprocket, at about 12-15mph.

Well I was thinking even it, would be nice if it had more oomph up hills. So I was thinking about using the 44 tooth I have on my 66cc and going with a 48 tooth for the 49cc motor. Do you guys think that will provide enough torque for hills? If it tops out at 25, I'm fine with that. it's the speed limit all over town anyway.

Also wondering how tight do I keep the head bolts (yeah the guy before me replaced the studs with bolts)? I'm just worried because they're small 6mm bolts and not the 8mm ones I'm used to.

 

[Sidewinder Jerry]

Got me a 49cc to play with. I was thinking, the 66cc just cruises up a hill decently on a 41 tooth sprocket, at about 12-15mph.

Well I was thinking even it, would be nice if it had more oomph up hills. So I was thinking about using the 44 tooth I have on my 66cc and going with a 48 tooth for the 49cc motor. Do you guys think that will provide enough torque for hills? If it tops out at 25, I'm fine with that. it's the speed limit all over town anyway.

Also wondering how tight do I keep the head bolts (yeah the guy before me replaced the studs with bolts)? I'm just worried because they're small 6mm bolts and not the 8mm ones I'm used to.

On 26" wheels at full throttle (6800 rpm) on level ground using a 5\1reduction transmission with a 48t in the rear will give you a top speed of 22 mph. That's only a 24\1 reduction. Depending on how big you are and how steep the grade of the hill is you may need as much as a 53.69\1 reduction to climb the hill. Meaning large people, steep hills, and small engines need multiple engine driven gears.

 

[Gordy]

Get a 50 t lol

 

[markjs]

Got me a 49cc to play with. I was thinking, the 66cc just cruises up a hill decently on a 41 tooth sprocket, at about 12-15mph.

Well I was thinking even it, would be nice if it had more oomph up hills. So I was thinking about using the 44 tooth I have on my 66cc and going with a 48 tooth for the 49cc motor. Do you guys think that will provide enough torque for hills? If it tops out at 25, I'm fine with that. it's the speed limit all over town anyway.

Also wondering how tight do I keep the head bolts (yeah the guy before me replaced the studs with bolts)? I'm just worried because they're small 6mm bolts and not the 8mm ones I'm used to.

But it should pull hills like mad right?

 

[markjs]

On 26" wheels at full throttle (6800 rpm) on level ground using a 5\1reduction transmission with a 48t in the rear will give you a top speed of 22 mph. That's only a 24\1 reduction. Depending on how big you are and how steep the grade of the hill is you may need as much as a 40\1 reduction to climb the hill. Meaning large people, steep hills, and small engines need gears.

But it should pull hills like mad right? That's my #1 priority with this project, something that can tackle all the hills around here...

 

[Sidewinder Jerry]

But it should pull hills like mad right?

Maybe or maybe not. Like I said it depends of how big you are and how steep the grade of hills is. On my shifter bike the reduction range is 66.79\1 to 16.25\1.

Your engine has 1.6 hp at 6800 rpm and 2 NM of torque at 4500 rpm. So what that means if you and your bike weighs around 350+ lbs and you're trying to go up a 30% grade hill; you'll need a reduction of 53.69\1 to climb it at full hp. Which would be around 10 mph on 26" wheels. The steepest paved streets in the world are around a 37% grade.

 

[markjs]

Well I decided, despite all the trouble, I am moving my PK80 to my new Granite Peak Roadmaster, and putting the 50cc on my current machine, a Peugeot rigid frame "mountain/road" bike. I know even if the 50cc works well enough for me, I will prefer the performance of my PK80 66cc,, and the new bike has crappy front suspension, a better seat, and a rack that can serve as a rear fender. It will be the more comfortable ride, cuz even crappy shocks make for a nicer ride on our local, crappy, bumpy, "chip seal" roads...