first four stroke build - advice needed

[Flight Risk]

All I’d like now is for someone to look over the gear ratio and confirm that 2.5 horsepower with a cvt will be enough power to be practical and fun

I'm just curious Toby, in the UK do they not allow 2-strokes, since you mentioned no Grubees. Are you able to get Predator engines as I think they may be more tunable and reliable than a Lifan (though Lifan in general is very popular).
If your mother loathes motorbikes, I'm surprised that she would like a motor-bicycle any better. Is it a stigma thing or a safety thing? I would think she would rather have you riding something a bit more reliable, with proven brakes, lights, and able to move with traffic. They are even bringing back the Cushman scooters and Whizzers. BTW- whatever happened to legit mopeds?
I think you are on the right track with gearing. You can always change a gear after you have ridden for awhile and you may even be able to add a bit of leg power for steeper hills.

 

[Toby woodman]

I think the consensus is that if I can build it I can ride it, just because she probably doesn't think that someone could build a motorbike

 

[darwin]

How do those sprocket's turn the wheel?

 

[Toby woodman]

the chain coming from the clutch goes to the large sprocket, the hub is mounted on a plate to just in front of or just behind the seat tube. the chain to the back sprocket goes from the small sprocket. its just a jackshaft with both sprockets on the same side, in my new version of the jackshaft the sprocket and big sprocket are on the same side. here is a picture.

 

[Toby woodman]

Here it is on the bike

 

[DAMIEN1307]

bike

YEP, It does look like a bike to me Toby...lol.

 

[COGHandyman]

I will stick with my 2 stroke Phantom 85 all day long over a four stroke...More than enough torque for hills and plenty of power for flat out higher speed riding...Considering all the adaptations needed on the four strokes, as well as the expense of it after you got everything said and done, the P-85 is the best of all worlds...Power and speed.

I can hit mountain foot hill roads at an easy 40 MPH going uphil using around half throttle and cruise the flats at my normal cruising speed of 30 to 35 MPH at a quarter throttle...The highest I have had it is 51 MPH before I chickened out...I have no need to use all that power, but it's nice to know it's there, I can even start from a dead stop with no pedaling required without straining the motor whatsoever...It is all stock, no modifications to the motor.

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That's also how I felt about my two-stroke. If I fix the vibration and reliability issues (front motor mount) it would be good.

I'm also going to try some four strokes just because I'm curious and want to learn I have both smaller and 79cc four strokes.

 

[COGHandyman]

All I’d like now is for someone to look over the gear ratio and confirm that 2.5 horsepower with a cvt will be enough power to be practical and fun

I know this is a very old post now.

I just wanted to answer since no one else quite did yet. I think two and a half to three horsepower from a lifan type engine should run a cvt torque converter.

My Chinese scooter has a 3 horsepower 50cc four-stroke engine and it runs through a CVT. It gives speed from 35 up to 40 miles an hour, excellent brakes and decent lights and a horn.