Kp-Mini Self-Destruction [Build]

[deadwood83]

Alright, following the death of my hellcat project, I needed to heal my heart.


My younger brother has a KP mini, and we tricked it out with BRT parts. 36/31mm ported head, hardened valves, stiffer springs, upgraded cam, 70mm piston and matched cylinder, PWK32. It is one dangerous machine.



I... really like the counterbalanced engines. After coming from the vibrations and inevitable transmission failures in the ZS190, I was ready for a change.


Enter, 2021 KP Mini! In white, of course.




Anyway, the 223cc is awesome. No question. That bike has about 20-21hp and gobs of torque. But... is it really enough? No, no it is not. While mini shopping, I found the Tianda TDR300. It's a little small displacement affordable race bike. That, of course, lead me to researching the engine. Apparently it's a Zongshen 300 with 6 forward gears pushing 25-28hp.



Six gears... 20% power increase... mini bike? More than double the stock power? What? And it (in theory) fits? Whaaaat?



I sat, and I stared, and I soul-searched for a good 28 hours. Then I ordered the engine. What is impulse control? Idk, still trying to figure that out.


But there are some complications.

1. This engine is water cooled. Where do you even put suitably sized radiators on a KP mini? I started by looking at CBR rads and KTM CX-W rads. Fitting those in the front fairings seemed... complicated.
2. The intake points the 'wrong' way. This ended up being a non-issue. The stock airbox had to come out for the 223cc big bore, I have no illusions of it being adequate for this engine.
3. Temperature control. Typically, this would go on an EFI install which has a fan controller. I do not have the patience nor dyno to properly tune, and the tank does not really accommodate a pump.
4. I cannot weld. I do not have the tools, nor have I ever welded (unless you count plumbing and electronics soldering. However, I can bend sheet steel with a 20-ton press and I can make molds up to 12"x12"x12" with my 3D printers.
5. Sprocket offset? ALso a non-issue. The cover bolts are your bog-standard 8mm hex heads. By using photogrammetry, I was able to approximate the sprocket distance from mount. It should be identical to the pre-installed 157FMJ engine.
6. Footpegs. The KP mini mounts the footpegs and kick stand on the bottom of the engine. Luckily, this engine case has those mounts present (or so it looks from the pictures).
7. Height? This engine is actually shorter.
8. Front engine mount. I will have to fab at least a new lower half. THis shouldn't be too bad. I have a friend who can weld the top and bottom together, and I can bend/press from a 3d printed mold I design in SolidWorks.
9. Can the rear hub take that power? Ehhhhhhhhhhh. Probably not. if it breaks, I will look into the solid Grom CBR conversion hubs. That said, I do not go hard off the line. I prefer clutches to last, so I go hard after the line. Probably only marginally better.

Okay, so now to the solutions.

• I found a build where a gentleman cools a 1000CC bike with an under-seat radiator. This seems nifty, but it is also where the battery lives.
• But where would this fit on a KP? I recalled a shot from Small ENgine Velocity's youtube channel.
• Look at all that space! It's occupied by a single wire (and an airbox which will no longer be in the bike). Bracketry and radiator will be where the plastic currently sits. SPAL push fan (5.2") will provide the airflow when not in motion, and a cheap temperature controlled relay will handle the fan and provide an output to a small gauge/datalogger.

• I have looked at SO MANY radiators in the past 24 hours. Think full page of google images. Multiply by 18, then search for dimensions. I have settled on a Gen1 KLR650 radiator. The fill port should be under the seat, but I will have to bend the ports to point the opposite direction from where they are. The original rad is known for letting the bike overheat... on a 650cc engine. If it runs too hot, I can look back into dual rads under the fairings, or just get a Gen2 rad which is thiccer.

Riding season just ended here, so I will not be rushing this project. I cannot find any evidence of anybody swapping this engine into a KP Mini (or any bike, from cursory searches). This is unknown territory. I have only my wits, the mechanical skills of a drunk simian, and my smooth, smooth brain.





So far I have ordered:
- Engine
- Bike (thanks to Pete @ Kronik, who it would appear threw in free rearsets)
- MT-15 rear shock. It is a bit short, but thanks to a gentleman on facebook, it can easily be raised by altering the wishbone geometry in the suspension linkage. Drill 2 new holes, attach T-piece there instead of lower original hole, gain 2 inches and preload reduction.



I need to get the bike into the kitchen (where it's warm and good things are made) as opposed to a 3rd party garage where it currently resides ("Hey fam, can I use up about 2 foot by 5 foot in your garage?").


Engine comes with a PWK34. Will have to see what the quality looks like, might spring for a Nibbi or faux-Sudco.


Gearing is similar to the stock KP. One exception is first. The 300CC has a 2.56 ratio as opposed to the 3.077 in the lifan. Primary reduction is also reduced on the 300cc at 3.09 compared to the Lifan's 3.35. Final drive is .938 Lifan and .857 on the Zong. Shouldn't be gearing limited at all.



It looks like many of the top end parts are related to the NC250. This makes me wonder if some of the performance parts from one of the guys around here would work. I am trying to find specifically a worked head or high comp piston (though at 10.5-10.7 it is already a tad elevated). My goal is to break the 30hp barrier in a Lifan KP Mini. Is it smart? No. Can I recommend it? Not yet.


But it should be a fun challenge.