Poor Man's Shifter Kart: Engine Choice?

[Blackdog]

My "next year" project swirling around in my head.
Probably find an old rolling chassis and go from there.
I know there's a world of high-end racing engines/transmission out there...but the "poor man" part is going to eliminate those.

Choices: Air cooled dirt bike motor...maybe 250cc with included transmission.

or, something like:

Lifan 250cc? The little 125?

https://www.ebay.com/itm/Lifan-125c...-70-ATC-Z50-CT70-CL70-SL-XL-SDG-/361501714644

Tranny is "three up", right? Should be fine...I don't need six up.
Can someone pint me to more info on these?
Water cooled, right? Is there a water pump on the engine out-of-the-box?
You need to clutch after you get into first?
Also...what sort of RPMs and horsepower are those making stock?

 

[Joe-405]

All of your answers are here..............

http://www.pccmotor.com/lifan-125cc-motor-eng.html

 

[Blackdog]

Thanks. I don't see answers on that page...maybe I'm missing something.

That Lifan 125...roughly what sort of horsepower is that making stock? I don't really understand KW @ RMSs ratings.
Does shifting actually require full use of the clutch or can it be "slam shifted" once running?
Why are most racing engines water cooled? Are there water-cooled Lifan or once you get into water cooled single cylinders...that's racing $$ category?
Thanks

PS: Is a Semi-auto engine, like this, appropriate for speed shifting (without use of manual clutch?)
http://www.kronikracing.com/125cc-Lifan-Semi-Auto-Pitbike-Engine_p_345.html

 

[ezcome-ezgo]

Part of your answer:

 

[Blackdog]

So 6.5 KW @ 7500 RMP only makes 8.7 HP?
Is the 125 Lifan on a light frame fast?
What kind of HP are the pro racing motors making?

 

[Kartorbust]

So 6.5 KW @ 7500 RMP only makes 8.7 HP?
Is the 125 Lifan on a light frame fast?
What kind of HP are the pro racing motors making?

Older karts were using the 2 stroke Honda CR125. Some use the 4 stroke CR125F. Others are in the 250cc class. 8 and 3/4 hp is plenty to move you around no problem. I mean some karts are using a centrifugal clutch of one kind or another with the Gx160 (4.8hp), GX200 (5hp) and the Predator 212 (~6.5hp) and they all to fine stock and modified. This Lifan 125 is probably for cheaper starter pit bikes and are enough to move a teen or adult (within reason) just fine.

My thing is, the engine is kick start, which might be fine or a complete pain. I wouldn't worry about the power too much, should be more than enough.

https://www.youtube.com/watch?v=MlTIuVfFx5s

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[Blackdog]

Thanks...I'm doing a kart now with a 212 Predator, but thinking ahead to a shifter kart.
Do these 125 or 150 Lifan transmissions do OK long-term (non-racing)? Can you slam-shift them without clutching?

 

[ezcome-ezgo]

I'll be Frank...

Frank: "Don't slam shift. Ever."

 

[Blackdog]

Wrong word maybe? What I really dont understand is:
On the pro racing machines...are they actually clutching when shifting? because I cant' see it if they are. those transmissionsare designed to be direct-shifted?

And on a Lifan with a 4-up like this (the semi automatic) , are you clutching between gears?

 

[Aircomet]

I would highly recommend the Lifan 125cc engine. My buddy repowered an old Honda CT70 minibike with one this year. The engine runs excellent and when we race it up against my minibike with a predator 212 and torque converter it wins. As soon as he hits around 3rd gear and is able to really wind it up it just pulls away. So yeah, plenty power for a kart.

As far as shifting goes it depends on the model you purchase. A semi auto model doesn't have a clutch to use. You simply let off the gas and shift. It has a built in centrifugal clutch to take off and a clutch basket with plates that is automatically actuated by the shifting lever between gears.

If you get a manual clutch model you will have to clutch the engine between each gear. Not a big deal and is really quick with practice. But definitely no bang shifting.

They are air cooled as the listing says. Most small displacement atv, dirtbike, and even motor cycle engines are aircooled. Simpler system and saves weight. You have to get into the very high performance, high $$$$ stuff to see water cooled. As long as you don't let it sit idling for more than a few minutes at a time you will be fine. It just needs to have some airflow traveling over the fins.

All around, the 125cc Lifans are very strong engines. More hp with much wider and higher rpm band than a regular industrial engine like a predator. The semi automatic is a bit more expensive but I feel worth it. Also you may want to watch the description to see what the shift pattern is. Some of them are like 1 down then Neutral then 3 up (1N234). That makes 1st kinda a pain to use. Definitely look into 4 up (N1234).

Hope this helps.

 

[Blackdog]

Thanks man...that was really exactly what I was looking for. Understand a lot better.

 

[Blackdog]

What would be good dirt bike engines to consider?
Four stroke/air cooled?

 

[Kartorbust]

That's a loaded question and one that'll get many different answers. I've never been in motocross, so I'm not going to be helpful on what to get as far as a good engine for this. However if look at used bikes in the 125cc-150cc range from the major players, long as parts can be had easily, you should be fine. Kawasaki, Honda, Suzuki, KTM (still make 2 strokes new iirc), Yamaha, etc. I'd bum around Craigs list, eBay, and bookface (Facebook) market place for used bikes. Just be mindful and bring a friend if you buy one in person, try to get the seller to meet you at a Police or Sheriff's department, just so the sale doesn't go south and turn ugly.

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[anderkart]

What would be good dirt bike engines to consider?
Four stroke/air cooled?

A 4-stroke might be a better choice for an older air cooled engine from the 70's-80's.

It's fairly easy to do a top-end on a 2-cycle, but you'd need to split the (lower-end) cases to replace the crankshaft seals that tend to harden/wear out on older engines. 2-cycles wont run when these crank seals fail, but 4-cycles will; they just leak a little oil...

I own a pair of (early-80's era) Honda XR-200 dirt bikes I bought used 25 years ago, they both still run very strong and have been amazingly reliable.

The older Honda 200X 3-wheelers had a similar engine and might be easier to find a deal on, lots of guys used to remove the (perfectly running) original engine from their 200X to instal larger engines. If you don't find any listed for sale; posting your own Wanted ad in the motorcycle section of your local craigslist would be something to try ...

 

[Blackdog]

Is a 150-200cc 4-stroke dirt bike motor and transmission going to move a 200 pound rider on an older racing frame....like 70-80 mph top end?

Whats the top end of a Lifan 125 on an older racing frame? roughly....

thanks

 

[Kartorbust]

This may help. https://www.youtube.com/watch?v=ONtAuOsQ1nA

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[Blackdog]

This may help. https://www.youtube.com/watch?v=ONtAuOsQ1nA

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Hmmm...I'm not sure what that means. The title says "4 stroke vs. 2 stroke"...but the clip doesn't explain anything about the difference or explain what the guy is running on that kart.

 

[Blackdog]

I'll be Frank...

Frank: "Don't slam shift. Ever."

This world of shifters is pretty confusing for the neophyte. So here's a guy with a decent racing shifter, a 125cc two-stroke, and his kart appears well set-up. Apparently this is a 125 from a Honda CR125 dirt bike.

https://www.youtube.com/watch?v=hsgQoLMMEoY&t=96s


As he describes it, you only clutch to get into first...after that, sequential shifting does not employ the clutch. You simply blip the throttle and shift. So it would be good to understand that on a dirt bike transmission like this...is this an accepted means of shifting? Does it put some additional wear and tear on the tranny which this guy, or others, just accept as the cost of doing business this way?

 

[Kartorbust]

If your worried about clutching, Rekluse has a conversion kit that changes the manual clutch for an automatic clutch. At $499 It's not a cheap endeavor, however it is an option. https://rekluse.com

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[Nosandwich]

wrong

Wrong word maybe? What I
really dont understand is:
On the pro racing machines...are they actually clutching when shifting? because I eant' see it if they are. those transmissionsare designed to be direct-shifted?

And on a Lifan with a 4-up li shirke this (the semi automatic) , are you clutching between gears?

You are probably looking in the wrong place, ( maybe...they have paddle shifters ...but ..automatics?) THAT'S just stupid... no way!