Phatmoto Pro 125cc 4-speed?

[Motorbike Mike]

Ugh ok.

 

[FNTPuck]

The lifan is way too big to fit in that frame.

Its a great motor for reliability but it is very heavy(heavier than a 212!), not the best power(~8hp), limited aftermarket compared to a 212, and physically huge with the integrated transmission.

Don't get me wrong, it would make a sick bike with the 4sp and smooth ride, but would need a custom frame setup and a lot of work when you can do a 212 to make a lighter, more powerful bike for much cheaper.

 

[Vikingimike01]

I mean, the thrust to weight ratio is higher than on the 66cc right? I am pretty sure both are about 20 kilos. Or is the 66cc 16kg? Can't remember.

 

[Motorbike Mike]

The built in jackshaft isn't limited to running power to the left side of the bike. You can easily hit up sbp and/or staton to get a new shaft, better bearings and sealed bearing bottom bracket with the chainring freewheel to make use of a multi-speed rear wheel with motor power. That lifan 79cc lifan should have plenty of torque to accelerate quickly in 1st gear and go at least 40 without engine mods. Only reason it's not geared to go that fast single speed is it would accelerate like a dog, and they need to comply with MaB speed limit laws.

I like the chainring freewheel idea. Thanks.

40? I hope so but I’ll find out when my phatmoto bike gets here from gas bike.net. I’ll gear it up to the highest point that little 79 can handle with a 200# rider and see. Governor bypassed.

 

[Frogslayer]

I mean, the thrust to weight ratio is higher than on the 66cc right? I am pretty sure both are about 20 kilos. Or is the 66cc 16kg? Can't remember.

I think the China girls weigh in around 9 kilos...

 

[CrazyDan]

2 strokes will always outperform same-sized 4 strokes if both are properly tuned on thrust to weight ratio.

 

[Vikingimike01]

The biggest reason on why I would like a 125 lifan, is less maintenance, not a POS, and come on, it's a 125 4 stroke.

 

[motorhedfred]

You're making a big deal about the extra weight of the 125 but it also has nearly twice the displacement of the 2-stroke 66cc, probably more than twice the torque AND it has gears. You could argue that it will affect handling...definitely if you try to cram it in there with the cylinder pointing toward the head tube. However, if you install with the cylinder pointed foward the way it's designed to run, the impact on handling would be minimal. The reason is the drivetrain weight will be at or below the axle centerline.

 

[Frogslayer]

The weight sucks yeah but the deal breaker is it physically not fitting inside that frame. @Vikingimike01 lay out your 2 stroke maintenance schedule vs your 4 stroke maintenance schedule please humor me cause once either jetted correctly or the carb mixing needles are set 2 strokes are nearly zero maintenance.

 

[motorhedfred]

The weight sucks yeah but the deal breaker is it physically not fitting inside that frame. @Vikingimike01 lay out your 2 stroke maintenance schedule vs your 4 stroke maintenance schedule please humor me cause once either jetted correctly or the carb mixing needles are set 2 strokes are nearly zero maintenance.

Agreed, but I figured that was a given since the image from the OP is admittedly doctored and the engine is not to scale with the bike.