Z50a With a Lifan 125

[jaxpc]

Hi;
I'm new to Mini Trails. (I usually build and restore 82-84 KTM 495's)
I've had a 69 z50 frame for years, and I think it's time to build a nice
z50 with some non stock modifications, like the engine.
What are my main concerns with putting a 125cc Lifan into my bike?
It will be a semi-auto, with a 22mm carb. (the usual complete Lifan
125 engine kit from Ebay) Thanks.

 

[Mini K1]

My mostly-stock Z50A feels squirrely at 35 mph. Your planned 125 build should be a hoot... Have fun!

 

[kirrbby]

The new motor will be a bit heavier, longer, and wider. The supplied carb/intake might not fit in under the frame/tank.
You will have to make a bunch of stuff work, as you're unlikely to find stuff that's made for the job. Lights and wiring will have to be adapted to work with 12v and CDI ignition. 12v battery/box.
All you have is a frame, so you can search out parts that will work, or can be made to work. Foot pegs/kickstand. Carb cable. Exhaust... Stock parts that touch the engine, probably won't work without some modification.
But this job has definitely been done before. You should be able to find some info.

 

[kirrbby]

If your frame is 1969...K1 frame...it won't have provisions for a foot brake. Just 2 hand brake levers on the bars. So that means 2 things...you won't be able to get a manual clutch engine...and with 125cc you might want to consider installing a disc brake, at least one.

 

[jaxpc]

I have been looking at some of the special parts I will need for the bigger engine. Like the slanted air cleaner.
Also, the foot pegs bracket is available for the 125. I won't be using any lights, so it will be an easier to install the electrics.
I mainly want to see what the 125 will feel like. (Or do I?) It's good to know that the engine will fit without hitting the front
tire or fender. (I'm sure it will be close) I will use the hand brake on the bars, as the Lifan is a semi auto. Thanks for all the tips.

 

[cjpayne]

You will definitely need some suspension upgrades. Those pogo's will be spooky with alot of added power/speed.

 

[Robert thran]

I build this k-2 about 7 years ago with just a 30 over 70cc, custom made intake, sl70 carb, and 2 brothers pipe and advancing flywheel and 4 speed trans… it was about as fast as I wanted to go on an 8 inch wheel hard tail..

 

[jaxpc]

I'm only doing this build because I have a frame. (Rolling frame, as of yesterday) And it sounds like a fun/different
project. If I want fast, I have several 82-84 KTM 495's for that. 60 MPH on a bike this small does sound "exhilarating".
I'm still going to do it anyway. LOL.

 

[Old Guy Too Many Bikes]

Exhilarating will be an understatement. Consider moving up to 10 inch wheels.

 

[kirrbby]

I've been to 50mph on a hardtail, and it's no sweat really. 60 will be a whole different deal tho.
But with no lights, it don't sound like you're planning to spend much time at 60 anyway. You're just mostly after some zippy fun. Nothing wrong with that. Biggest fear might be keeping the front tire on the ground. On a hardtail, it only takes a second, and your butt can be bouncin on the sidewalk...and your ego could be damaged a bit if that happens

 

[Robert thran]

One other thing I would check closely for is hair line cracks in the rear section of the frame. It’s not uncommon,, you sure don’t want to be going 60 with a cracked frame And hit a dip or pothole in the road..

 

[jaxpc]

I got my Lifan 125cc semi engine. Very quick shipping.
Another question. This engine will use a 22mm carb. Can I run the stock 1969 z50 throttle setup, or should
I go with a standard dirt bike type throttle? I hear there may not be enough throttle travel using the stock throttle.

 

[Old Guy Too Many Bikes]

I'd definitely switch to the more modern standard throttle cable twist grip.

 

[MountainMini]

These are a nice option. Aluminum and you have different adjustment slots too pic from Nibbi on Amazon.

 

[Robert thran]

With the stock sl70 carb I was able to use the stock setup. Not sure about the carb you plan on using?

 

[jaxpc]

Nibbi throttles look great, and I may get one. They also make slanted air filters. Thanks for the tip.