# Water cooled motobike

I'm going to assume this is what you're using and that you have a 10t on your engine; along with 26" tires. DNP 7 speed freewheel (32,24,21,18,15,13,11). Always take off in 1st gear.

(4.1×(21÷10)×(40÷9)×(32÷32))=38.27:1

(4.1×(21÷10)×(40÷9)×(13÷32))=15.55:1

(7,000×26×π)÷(1,056×4.1×(21
÷10)×(40÷9)×(13÷32))=34.8 mph.

If you changed the 40t to a 48t and started using the 11t for the high gear, you should be able to climb any paved hill without losing your top-end speed.

(4.1×(21÷10)×(48÷9)×(32÷32))=45.92:1

(4.1×(21÷10)×(48÷9)×(11÷32))=15.79:1

I know you like to off-road with this bike. You may want to consider Fabian's double chainring SBP shift kit. You would shift like this 1(1-4), 2(4-7) for 8 sequential non-redundant ratios. It'll also help lower the lateral stress on the bicycle chain.

I like to include in that math a range between engine and crankset that matches close enough 60rpm cadence to mid-motor RPM.

I enjoy boosting speed. My test up the most challenging street hill so far was the only hill I HAVE to help. Even then, I'd boost it above mid rpm, rest a bit while it slowly sagged, do it again, and it did well, I did too.

Its alwayz good to keep Plan B in shape. Case you run out of battery, or gas, done both recently, yeah I was dumb. But tough too.

I like to include in that math a range between engine and crankset that matches close enough 60rpm cadence to mid-motor RPM.

I enjoy boosting speed. My test up the most challenging street hill so far was the only hill I HAVE to help. Even then, I'd boost it above mid rpm, rest a bit while it slowly sagged, do it again, and it did well, I did too.

Its alwayz good to keep Plan B in shape. Case you run out of battery, or gas, done both recently, yeah I was dumb. But tough too.
For hill steep climbing (20%+ grade) on pedal-only bikes I use a 22:34 crank to cog ratio with a triple chainring set. At a 60 cadence that's around a 3 mph speed on 26" wheels which is turning the rear wheel close to 40 rpm. The 32:32 would be turning it at 60 exactly. Changing from the 40t to a 48t wouldn't change anything in pedal-only mode it'd just give the engine a lower ratio to transfer power at.

My advice is to lower weight by removing the battery pack since it wouldn't be required via vacuum pump.
Depends on what that battery pack weighs, with 4.7 hp you have a lot of power to work with.

3.5hp if I am reading correctly, also, your stranded if that batt dies or is left with out charge.

Just making a suggestion and dont actually know if it can give enough flow.

There may be larger options aswell for vacuum pumps.

I packed a 12ah battery for a while for my lights, not saying it's an issue.

3.5hp if I am reading correctly, also, your stranded if that batt dies or is left with out charge.

Just making a suggestion and dont actually know if it can give enough flow.

There may be larger options aswell for vacuum pumps.

I packed a 12ah battery for a while for my lights, not saying it's an issue.
It has 3.5 kw. Which is about 4.7 hp.

I stand corrected!

I stand corrected!
I have those days when just being able to "stand" is an accomplishment in itself...lol.

My advice is to lower weight by removing the battery pack since it wouldn't be required via vacuum pump.
Actually, it's only a 3lbs battery and the pump is quite small. I have a 20amp fuse, a switch and a weatherproof box for it all and it works quite well. Bike cools down real quick. Nice to be able to run it with the bike off. Gonna upgrade to a temp sensor to save battery power, but at .3 amps it uses very little power

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