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.

[PhildoScaggins]

We are watching you with great interest...

[franque]

Yeah, what he said... Is that motor basically a liquid-cooled CB bottom end with an NC250 top end? If so, that's really cool!

[deadwood83]

Originally Posted by franque

Yeah, what he said... Is that motor basically a liquid-cooled CB bottom end with an NC250 top end? If so, that's really cool!

I would love for this to be totally top-end compatible (NC250 with a different cam grind) but the Tianda diagram 'Chinese Name' column shows CBS300 in the name for the head and cylinder. Their parts diagrams tend to be really good about calling out NC250 parts by having NC250 in the Chinese name.

In my dreams, an 82mm or 84mm big bore kit from an NC250 would fit; making a 343/360CC total displacement engine. Why? Because stupid. The one BIG issue I can foresee which would break compatibility is increased stroke. The NC260 is about 56mm while this has a 65mm stroke. If the kits that nzbrakelathes sells can easily accommodate the extra stroke though?.... Maybe I should figure out where to put an auxiliary fuel tank.



Also, I will not post a link to the seller on Ali until I get the engine in my hands, but so far they have been insanely helpful and have had excellent communication. Their engine listing apparently includes a bunch of goodies. They mention the carb being part of the package, but I got a message asking if I would like to wait 4-6 days or get a partial refund because they were out of wiring harnesses. I was not expecting a bike wiring harness to come with it.

[franque]

Sounds great! Yeah, I didn't think about the stroke differences, you're right about that. Where are you looking at parts diagrams? I would guess that they are quite different, even though the cylinder head looks very similar. My guess is that the case mouth is quite a bit smaller than an NC250.

Also, just out of curiosity, did the 167FMM drop right in? If so, very interesting! Do you have details for the build of your brother's bike?

[deadwood83]

Maintenance manual: https://tiandaracing.com/wp-content/...ice-Manual.pdf


Did you say, "Parts?": https://tiandaracing.com/wp-content/...-Catalogue.pdf


Unfortunately, I was just the idea man, part-financier, and free labor (80% of it) on my brother's build. I did not document it well.



Parts were sourced from Plug N Play Performance in Indonesia. Short list:
BRT 70mm forged piston w/ rings and wrist pin

BRT ceramic coated Super head (36/31mm) with BRT valves, springs, OE Honda CRF150F wipers(the head is GORGEOUS)
OE Honda 2006 CRF150F cam carrier
OE Honda CRF150F valve cover
Ceramic coated BRT 70mm cylinder
EBC CR85 clutch fibers
MasterCam (Indonesian brand, not the software) Stage [unsure] racing cam
Nibbi PWK34 carburetor
Misc mods (intake plenum, throttle cable, couple bolts)
Harbor Freight "catch Can"


Initially, the exhaust valve seized within 3 miles. Very (the gentleman in Indonesia) reached out to BRT and did some digging. Found the guide was under-honed, sent a new guide, spring set, seat, retainer, wipers, and 5mm flex hone via DHL free of charge. The man is a legend.

Supposedly BRT is developing a 4v head for the motor, with an ETA of Feb-March (barring any delays). With the big head (2v) the bike already RIPS. If you dump the clutch with any sort of frequency, it will break the cush drive within 1 season. I am a huge fan of the guy and want to support him, but one of my passions is troubleshooting combined with ample stupidity/silliness. I wanted to do something new, novel, and push the limits of Lifan's mini.

PnP/Very/BRT do offer a 300CC kit with the big valve head, but case boring is required. If I am going to drop a brand new engine from a bike, I do not really want to risk not having it. Plus by the time you pay for all the bits, plus machinist time, the new engine is cheaper? (It's not once you factor in time spent researching, radiators, etc).

I cannot say for sure if the new engine drops in, as it is leaving China today. I can say with absolute certainty that the front motor mount bottom half will not line up. The rest of the measurements seem to line up with the Lifan casings. I could not find exact drawings of the 157FMJ, but the 162FMM, 162FMJ, and 157FMI all shared the same lower castings so I felt confident using those drawings as a basis. By trhese drawings, the front lower engine mount from the KP mini will have to be remade. It should not be very difficult since the top hole (on the motor) seems to line up with the top hole (on the mount).

The 174M-3 (CBS300 engine) comes standard with a 520 sprocket, but my searching on TaoBao seems to indicate a 20mm output shaft commonality across the listings. This is the same shaft dimension on the KP Mini from factory (Zs190 is 17mm) and even if my memory is failing me, sprockets are cheap and plentiful.


Limited pics of the other build:





And the seller provided images of the exact items I will receive. As expected, 4-pin DC CDI, 2-pin trigger, bog-standard Honda-style rectifier, and the wire colors even look similar. All connectors appear to be identical style and shape. At worst, the pinouts will need to be redone.




Comes with a PWK34 clone. No idea what jets are inside, but they will likely need to be changed due to living 4500+' asl.

In my searching, I discovered the Kayo EFI setup that comes on the PitsterPro LS250. Since one of my favorite rides involves climbing 6000'+ elevation in 40 minutes, I would be lying if I claimed it was not intriguing. I couldn't find concrete evidence that CHondaChondaChonda ever got the tuning process to 'take.' I'll see how it runs with the PWK before going totally crazy, but my brother said he is very interested in EFI for his Lifan.

You'd think I would be the one clamoring for EFI after bringing a 40-year-old Yamaha Xj back to life but here I am telling him "carb is fine." For being called unreliable, picky headaches those old Hitachi CV carbs sure do seem to work incredibly well after you: ultrasonic every single individual part, match the TB flaps to bores, put in new diaphragms, throttle valve seals, springs, mixture needles, mixture o-rings, fuel delivery o-rings, reassemble, synch, colortune, synch, colortune, synch, colortune, synch, colortune, and then finally adjust idle.

Obligatory XJ pic:
(nvm, forum fails to upload every version of my XJ photo)

Even after riding his souped-up KP Mini; when he played the "pursuit vehicle" on my Xj his feedback was, "you should have warned me the throttle is so sensitive." Man I love old bikes.

[Bruces]

just wondering how the border will handle that engine ,is it epa approved ?

[deadwood83]

Originally Posted by Bruces

just wondering how the border will handle that engine ,is it epa approved ?

WOW. That question got me digging HARD.



Okay, near as I can tell, yes, it is EPA certified. Engine debuted in 2018, and from the EPA's 2018 publication, here is a Sanyang 278cc (Marketed as a 300) listing.

Oh, I'm dumb. The Tianda is sold in the USA. Tianda is where I got the idea for this engine from. So yes, it is most certainly EPA approved.

Heck, the Tianda is sold in California. So it;s probably CARB approved too I would guess?

[Falkon45]

Man... this has me wanting to do a 300 build on my KPM. Hmm.... I wonder if they make parts for the NBf2.

[deadwood83]

Okay, a couple more hurdles discovered.

1. The new engine comes with a 3-phase magneto. Luckily, this is likely an 18 or 21 coil unit, so it should have no problem running the LED lights and the fan. UNluckily, Lifan uses a 2-phase rectifier in the mini. To counter that, the new engine comes with CDI and recumfrier. I will have to run at least one wire.
2. Wiring diagrams for these engines are literally impossible to find. Tianda throws an 8-pole stator in and uses a 5-wire setup since they run carb and 0 lights. Their only concern is running the gauge, and keeping the lipo topped-up. They also do not provide a wiring diagram, just photos. Cross-referencing Russian MX bikes with the engine (Zuum CX300 NC and BSE Z7 and Racer SR-X2) they do not offer any manuals with wiring diagrams. This might get interesting because the lifan 2021 wiring diagram shows two 12V outputs. The second output drives horn, headlights, running lights.

On point two:
Attachment 23267
Interestingly, the gear indicator shows 1-6. Turns out this engine DOES come in 5 and 6 speed varieties. No idea which one I will receive. Honestly, both are fine. Final drive should be similar either way. 5 speed will be easier to wire. 6 speed will be neater.



The Zong rectifier is 6 wire.

Yellow X3 - AC in
Red - 12 V Out
Green - Ground
Purple - ? Hopefully switched 12v out. This seems to be the most likely scenario since vsense id really ancient. Engine can run on battery while I measure. Alternately, I just hook it up and if I get no running lights then I know it is vsense. Many 6-wire rectifiers available, so that's just a time thing.

I got a final measure on the planned radiator loc. It is 7.25 wide inside to inside. Both KLR gen rads will fit horizontally, but the gen 1 is about 1" shorter so I ordered that.

My MCO.MSO was not in the box, and I have been having trouble reaching Pete @ Kronik. This is odd, since he has always been incredibly responsive in the past. I believe things are probably happening and it's just a matter of poor timing with USPS load.

NC250 cylinders are def not interchangeable. Gaskets are totally different, coolant outlet/inlet is totally different. The head really does look like an NC250 though, and it uses NC250 valves.

[deadwood83]

Okay, the engine is here.
The MCO is here.
Vin inspection done.
DMV appointment set.
Still making room in my living room / kitchen to perform the surgery.
SV Racing stopped responding to me once I disclosed I was not shopping for parts to replace broken pieces on a Tianda. I guess they are either too busy, or don’t care about projects.
The engines available to order are 5 speed versions. I cannot find any gear ratios for them. The geartrain bears the same casting numbers as CB250 (ZS170MM-2) transmissions. I am having incredible difficulty finding a 6-speed star. Drum, forks, pawl, countershaft/main shaft are all available on Taobao.

The 6 speed is probably not at all necessary. Realistically, it just splits 3rd/4th gear and removes a tenth or two from final drive. However, in my quest to make a minibike viable for both city and highway without spending $7000 on a Grom + CBR swap, this is my punishment.
If anybody has a hook-up on a Hawk 6 speed shift star…. Hit me up. The fourth image on this post looks like EXACTLY what I need. http://www.chinariders.net/showpost....&postcount=196
Maybe a CRF230F shift star would work? The gearset will not, as the primary reduction is wrong. I also need 6th to be an overdrive.

Meanwhile I have a theory. I found another bike this is used in. It is used in the United Motors Commander/Sport/Classic line of bikes. Indian reviews of the bike indicate it gets a bit flat feeling above 70. This is probably due to gearing combined with Zongshen’s choice of cam grind.
Let’s look at the venerable NC250, and SOHC cam geometry. It has a 77mm bore from factory. Examining the heads, we see that the combustion chamber itself is wider.
We know from the Tianda parts fiche that the CBS300 uses the same rocker arms as the NC250, same exhaust gaskets, and the same intake manifold. Cross-examination of scaled photos shows that the NC250 and CBS300 use the same rocker<->cam locations relative to the centerline of the cam, and they use the same valves. Therefore, the only way to bring the valve heads physically closer is to pivot them about the stem head locations. Even pivoted, the valve lift relative to the face of the combustion chamber would remain unchanged if both engines had a similar cam grind.
That said, the cam grinds must be rather different due to Zongshen’s own output charts showing such contrasting curve shapes. So, I am doing an experiment.
Hypothesis: The CBS300, having identical valve are as the NC250 can flow a hypothetical equal amount of air through the engine. The CBS has a torque curve which declines at a more rapid pace at the higher RPM ranges after peaking around 8200 RPM. The primary differences between the two engines base configurations are cams (potentially) and bore x stroke. The CBS, having a longer stroke, exhibits a “block outrunning the head” scenario where piston velocity exceeds airflow capability.
Process:
1.) I have ordered an NC250 cam. I plan to remove the rear bearing, measure the solid rear lobe on the CBS cam, and press a new bearing onto the NC250 camshaft at the rear (left) location to both:
a.) remove frictional losses of a steel bearing round against the head
b.) try out the NC250 camshaft.
By using an extra camshaft, the option of returning to CBS300 is maintained. Furthermore, the cam end on the CBS300 can be examined for bearing swap at the same time. Likely bearing candidates are sealed units with one side removed to maintain oiling system efficacy.
2.) Porting. This is a minibike, not a cruiser. Power should be upper midrange for maximum stupidity. TO this effect, I will work on valve guide humps on the exhaust and intake, without touching the guides themselves, and widen/flatten the floor a little. That’s it. I don’t want to go to 10k, just lift and shift the curve a little to the right.

Fueling: I am torn. FCR35? PWK34? Lectron (SSR 300 flavor b/c similarity)? Kayo/Rojo EFI? I am strongly leaning Lectron after taking a slide-valve carburetor up the canyon. I thought my Yam was bad, but it has CV carbs which masked the problem more than I realized. If I go Lectron or EFI, I will be sacrificing some max power… but climbing 7000 feet in elevation within 35 minutes or less is also something I do every two weeks. FCR35 would hands-down win on the street but has a track record of being a touch picky about large elevation swings. PWK I just listed because the engine came with one, and they’re dead-nuts simple to jet. They get really awful for rapid altitude changes though.

I get plates on Tuesday, and that’s when the bike will move into my kitchen for surgery. It’s really tempting to just rush to cram everything in, but I am trying to take my time and think everything through beforehand. It’s a lot easier to have a plan and wind up scrapping 50% of it than it is to formulate 3-4 plans one after another.

[deadwood83]

I wish I could re-title this thread because I just thought of a zinger.


Cooking With Gas: A Culinary Cycle Story


NOTE: Engine supplier is yitonmoto on AliBaba. Awesome folks to work with, highly recommended, small selection but they spent DAYS with me in chat before I bought a single item, and then continued to deliver impeccable service. I would go drinking with these guys. They're awesome.


The bike is titled, plated, in my home; and I have begun disassembly and analysis.

The radiator... is going to be tight.I used Amazon boxes to protect my hardwood and tiles floor. Yes I use a kegerator, yes I homebrew, and yes, one of the brews got really high in alc content.




I Don;t know why Lifan got rid of the color on the side. It looks really nice. I also have some ideas for somewhat inappropriate stickers. With a new engine, it is a new model of bike, and that gives me opportunity to name it.

Paint quality has declined in the 2021 model year. Sadly it is weak, and eager to rub off. I may vinyl the whole thing (with the current scheme plus some extras)


I ordered an FCR28 as found on the Honda CRF250. I am researching if the 2009 CRF450 upgraded water pump (Boyesen) will fit. I also found the original supplier of the speedo. This one is useless. When going 35 it shows 43-44mph. Seems dangerous.


Oh.... and the six-speed transmission is on the way. Cost $57 + $74 shipping to USA for main and countershaft (loaded with cogs) + drum + forks + retainer + retainer spring.


Still going forward with my NC250 cam swap. Zongshen marketed the CBS300 as a budget alternative to the NC250. In marketing, it is bad when your "budget" engine outperforms your "flagship" thumper. I am more convinced than ever that they detuned this .


There is a local shop who offered to do milk headwork but no flow bench. The internal routing of the head and layout just SCREAMS, "I'm a TRX300EX derivative!" so I will be using proven TRX porting as reference.


I THINK properly tuned FCR, Cam, and Headwork will get me crazy close to 30BHP. Tianda measures 27.5 with a free flowing exhaust and Nibbi PWK34 (compared to the 25.4 Zongshen publishes) so these other bits should get me there.


In stock form, this new engine has more power than I know what to do with. The real challenges will be gearing and carb tuning. FCR guys say that going PWK or CV -> FCR gives about an extra 10% in the top end which at 25hp would be 2.5. Add half that to the 27.5 Tianda got and we're already at 28.25. Hoping that porting with FCR adds that missing 1.5 to hit my goal.



Otherwise this will be my only vehicle with less than 100bhp/L. (2003 M3, 1982 Yamaha 650, 2019 Hyundai Veloster Turbo). At least the Yam and BMW do it honestly (no blower).


More to come as I progress.

[Falkon45]

That model name... baaahahahahahaha!!!!

Also, KP-MOTO club has an exhaust for the KP-mini. So, you can factor that in also, unless you plan on building your own.

[culcune]

I am guessing paint quality was down due to reopening after COVID shutdown. I wouldn't be surprised at other quality control issues you might run into.

[deadwood83]

Originally Posted by Falkon45

That model name... baaahahahahahaha!!!!

Also, KP-MOTO club has an exhaust for the KP-mini. So, you can factor that in also, unless you plan on building your own.

ROger that, but sold out nationwide with next expected delivery sometime around January. I neither weld, nor plan to learn welding in my kitchen so the KP-Moto CLub exhaust is what I am looking at. There are other possible alternatives (Kymco Spade MMNTHBX exhaust, Yamaha YZF-R15 exhaust, Kymco A.I.R.150 Exhaust) which all look like they would work but only the Kymco/Lifan offerings are of an appropriate diameter (at least 33MM I.D at the head) and the MNNTHBX and Taiwanese offerings are really expensive.

Originally Posted by culcune

I am guessing paint quality was down due to reopening after COVID shutdown. I wouldn't be surprised at other quality control issues you might run into.

Hoping the paint is all I encounter. So far, other aspects look OK. It;s a shame about the paint because on closer inspection it is actually a pearl white, but you can't see the pearl because of the micro scratching all over the clear which came with the bike.

Maybe 3m Ghost Pearl, but the gloss instead of satin. Satin is a pain to take care of. I wish Lifan sold the decals so I could just redo it.




Ugh. Just realized I forgot to drain the carb before bringing it in.