Kp-Mini Self-Destruction [Build]

[Falkon45]

Well, the problem with the 390s are there were trying to cut weight. They also said bad machine work, so the heads were uneven, and would vote head gaskets.

But, how the kp radiators are mounted, there's one on each side. That gives you some space, if you have somewhere to put them. The fluid does green the lowest point up to the first radiator, across, and down through the second radiator into the head. Same principal, just split in two. Combined, they should have approximately the same surface area as your radiator. The side closest to the head has the fan mounted. It's also the fill and radiator cap. I haven't looked for the high pressure caps that can fit, but this just have me the idea to look for them.

[deadwood83]

Originally Posted by Falkon45

I mentioned the KP radiators, because it's actually two radiators. With the twin radiator confuguration, you could set them up like the VFR 800 rads were. Small, yes, but I believe those would be sufficient, unless you're running very high compression, and fueling on the lean side. My fan very rarely runs on the KPM. My KTM, on the other hand, was always at, or just below the "hot" line. They ran hot from the factory. The radiator is a decent size. I have mine off the bike. I can try and take some measurements for you. The fan is still attached also, so those will be close enough for you. I never did the FAL upgrade. I just used engine ice to keep overheating at bay.

Innnnnteresting. The shroud makes it look like one big unit. My CB rad is scheduled for delivery on Saturday. We'll see how close that size is and I'll see if Lifan is willing to sell rads to me should it prove to be another dead end. I do worry about exhaust clearance. It is already going to be tight, and setting the rads inboard of the frame's leading edge may prove to make it too tight. We'll see!

Originally Posted by grumpyunk

The PC cooling is not a real comparison in that the fluid boils inside as you note, while the coolant in a bike cooling system should not get to the vapor state.
Model T cooling used no pump. It was all done by convection(perhaps the wrong word) where hotter coolant was less dense, colder more dense, so a thermal circulation of liquid coolant occurred.
If you heat the coolant in a radiator the hot coolant will attempt to migrate to the top, the colder coolant to the bottom. That is the effect that would reduce the load on the coolant pump and be a more natural effect. Free circulation...
A cross flow radiator back about 1967 was a big deal, and allowed lower hoods on cars. There was less convective circulation, so there was concern about overheating in lower speed traffic. I cannot verify, but think larger pumps were installed 'just to be sure'. I don't know if I was clear, but I was suggesting mounting the radiator in a 'vertical' orientation, with the tubes going up and down. There is a post about mounting an oil cooler, actually more than one, in a vertical mode on site. I was thinking off-center mounting, FWIW, but I do not have a machine to futz around with attempting of different spots.
tom

Okay, I think I follow. Unfortunately the KP is just a wee little thing. Lifan left more or less 0 room behind the cowling so my original thought of vertically oriented KTM XC-W rads went out the window. I don't think it can host a radiator large enough to work without a fan in traffic. I may be underestimating the engine's heat tolerance (My XJ650 seems to do Okay without a rad and all 4 of its cylinders) but I also don't have a ton of radiators laying around. This is my only liquid cooled bike so supply is slim.

Originally Posted by wheelbender6

What is the HP rating on that NC250?

Should be about 25 hp atock at the crank. There's an RX3 dyno floating around here showing 22.2something wheel.




Speaking of exhausts, I have had a hell of a time looking for one. The KP exhaust 100% will not fit. Not even close. THis engine has more of the ole up-n-down and when I tried to see how close the stock exhaust was.. well it just wasn't.


So I browsed Ali. Lots of photos, and sellers frequently include measurements.



Using SOlidWorks' sketch trace feature and the technical drawing from Zongshen, I got the exhaust port to be 108* off upward centerline. Sadly no top-down drawings so not super sure on the angle out, but would wager 30-45* off the front face. THis lead me to several candidates, with some being rules out quite quickly. All had the "looking up" exhaust port, with some showing the desired bend towards the centerline of the bike at the head to interface with the diagonal-facing exhaust port.



Top down is Yamaha MT-15, CBR150R (2010-2016), and Benelli Leoncino 250.


So here's what's wrong with all of them:
- Yamaha: Too Small. 28mm inner diameter. May as well cut off one of the rocker legs and only run on one exhaust valve.

- Honda CBR: Angles are too shallow, and at minimum would need to be cut and re-welded to turn the header towards the exhaust port.

- Benelli: That bend in the head pipe causes it to cross the centerline of the Benelli motor. I can;t have that because that's where one of my engine mounts lives. Benelli uses a front mount, but the exhaust goes forward of it. That's where the radiator will live.



But then, like a beam of light from the heavens... CFMoto 250NK exhaust. From photos, it looked PERFECT. SO, I went to the fleabay and found a seller. Fleabay sellers are WAY better about responding to messages, even if its the same seller as on Ali.




So I messaged:
"Hello friend, I am but one sad man building a happy motorcycle. Can you please share A and B sizes?"


With my heart soaring, thinking I had discovered the key, the perfect factory made system that would bolt on with only minor cutting and grinding; I awaited the reply with baited breath. I fought, and distracted myself by watching Long Way Up, hardly able to resist impulse-slamming that big blue "Buy it now" button. Then, not one hour ago...





I want Gina to be wrong. No, I NEED Gina to be wrong. Gina... why? </3


I felt let down. I felt hopeless. I felt helpless.
But then I recalled that I have a very powerful set of tools: several 3d printers and SolidWorks. I could prototype a tool, made to alarming accuracy, to sand down the exhaust flange. So sketching just happened. Something I can mount on a drill, with sandpaper on the inside, which can evenly reduce an outer diameter....



I forgot I can make my own tools. Eureka! I ordered an NK250 exhaust.


Oh, and my crimpers were too small for 16ga wiring. Some slightly larger ones showed up today. Now I can complete the wiring.

[deadwood83]

CAD is done. Just need to print my new tool and get an 8mm bolt and nut.

[JerryHawk250]

Originally Posted by wheelbender6

What is the HP rating on that NC250?

GPX Moto's site say 32hp but specs. say 19kw which is just over 25hp

[grumpyunk]

Assuming you want to reduce the diameter A down to 42mm give or take... What difference (within reason) to you need to worry about being circular? IOW, the exhaust seals on the edge of the pipe, not the diameter. There can be irregularity in the diameter that will have no effect as long as the retainer can clamp tightly to hold the pipe against the sealing ring.
I do not know how trying to fit a 42mm ID tool onto a 45mm diameter pipe is going to work even if said tool is spinning at 1500 rpm. It will just bump into the 'end' of the 45mm pipe. I think I would have tried using a belt sander, vertical, with a table, such that I could hold the pipe against the moving belt, rotating as evenly as I could, to shear off some of the excess diameter. If you get a small table, you can work in 'arcs' of sanding, doing one arc, shifting the pipe, and then another 'arc'. Resting the pipe on the table and rotating should allow good control of the contact area without having the pipe moving around too much. You could get 'pretty close' and then use a flap disk or cutting wheel to shave off the resulting 'bump' areas. I think. Again, dunno how 42 is going to fit over 45 without some prodding???
tom

[deadwood83]

Originally Posted by grumpyunk

Assuming you want to reduce the diameter A down to 42mm give or take... What difference (within reason) to you need to worry about being circular? IOW, the exhaust seals on the edge of the pipe, not the diameter. There can be irregularity in the diameter that will have no effect as long as the retainer can clamp tightly to hold the pipe against the sealing ring.
I do not know how trying to fit a 42mm ID tool onto a 45mm diameter pipe is going to work even if said tool is spinning at 1500 rpm. It will just bump into the 'end' of the 45mm pipe. I think I would have tried using a belt sander, vertical, with a table, such that I could hold the pipe against the moving belt, rotating as evenly as I could, to shear off some of the excess diameter. If you get a small table, you can work in 'arcs' of sanding, doing one arc, shifting the pipe, and then another 'arc'. Resting the pipe on the table and rotating should allow good control of the contact area without having the pipe moving around too much. You could get 'pretty close' and then use a flap disk or cutting wheel to shave off the resulting 'bump' areas. I think. Again, dunno how 42 is going to fit over 45 without some prodding???
tom

This is the beauty of 3d printing material selection. I am going to print in PET-G, and the 'leaves' of the tool will have some flex. For reference, it;s the same base material as 1gal bottles of water, just thicker and with an internal geometry to aid in rigidity (but no too much!

I also designed a tapered bell crown into it. This section view might help explain more. The sandpaper is looped inside then extends back out between the leaves so that it is held in place but can still be removed/replaced easily. Yes, the pipe does seal against the face via gasket, but I am going to try and make it seal on a stepped face which is shown here in a rough approximation of the port using real dimensions.



Electrical harness is more or less complete. Just deciding where I actually want to tap ignition voltage and return to VSense, and then I really need some sort of documentation to see if the display supports showing a 6 in the gear indicator field. Sadly, the manufacturer has not been very responsive. I am hesitant to re-wrap the loom until I know if I need to run another wire for the gear position sensor (would need to know the pin on the header)

[grumpyunk]

Is the engine used OEM in bikes that are available in US? That might be a source of a wiring diagram that would show the switch encoding. Unless it is a plain rotary, which it could be, needing that many conductors, it would be encoded such that in a specific gear, multiple conductors would be grounded(I think it is ground...), which would make the display show the proper gear.
I guess I'm not sure if it is the display on the cluster or the need for X number of conductors that is the exact question. But that's ok as you can look at it so given the display is NOT showing a gear position, you must be in 6th... no?
tom

[deadwood83]

Originally Posted by grumpyunk

Is the engine used OEM in bikes that are available in US? That might be a source of a wiring diagram that would show the switch encoding. Unless it is a plain rotary, which it could be, needing that many conductors, it would be encoded such that in a specific gear, multiple conductors would be grounded(I think it is ground...), which would make the display show the proper gear.
I guess I'm not sure if it is the display on the cluster or the need for X number of conductors that is the exact question. But that's ok as you can look at it so given the display is NOT showing a gear position, you must be in 6th... no?
tom

Probably going to wind up with a GPS from a Suzuki Dr250. IT should be center ground and then the same sequential connection found in the Lifan box. THe freedom of doing my own wiring is that if it doesn't match, then I can just swap pins at the connector. With the alternator finished re-terminating I still need to throw that back in the crank cover. I'll worry about the position sensor when I am at the taking engine apart stage.


Speaking of taking the engine apart, I have NO IDEA how thick the castings are at any point in the head. A Spare head was $51 USD so I threw that in my alibaba agent order. The transmission is sitting here in DHL packaging waiting for when I am at the engine dismantling part. Trying to stage this out in a semi logical fashion.

• Radiator, frame, prelim exhaust while the new engine is loosely placed in the frame (to check clearances) then remove engine again.
• Rear suspension after removing engine so I can use my scissor jack at the frame point and minimize load while maximizing working space. Re-install rear suspension with new bits.
• Front suspension where scissor jack can support at lower frame tube, and drilling for single rivnut at lowest point of radiator mount while front suspension is off and no engine present to minimize stress on front frame member.
• Radiator bracketry after first (lower rad mount) rivnut installed while bike is on rear stand with nothing else mounted (except front wheel b/c hitting your knee on the jack is really painful. Re-cut petcock tube and re-thread at the same time.
• Engine work
• Re-mount engine
• Plumb cooling and intake.
• Fabricate/alter throttle cable and figure out clutch cable replacement model / new bracket.
• Mount exhaust
• Wait until it's bearable to ride (>45F)

And speaking of radiators, dare I say that the CB250 radiator is almost a perfect fit? It is within 1/4" of the lower width of the fairings, and has a tab (meant for the fan) which can get an enlarged hole dead center at the bottom for a grommet.


Ho-ly smokes. It's almost like obsessive measurements and everything paid off. But now I get to figure out how I want to make the upper bracketry. It is tempting to just do two L-brackets, but I would prefer to avoid excessive drilling/riveting on the front frame tube.



Frame in blue mounts in red. The T section looks and feels like the frame tubes aren't properly notched to each other and they just used a box reinforcement with tons of weld to glue it all together. Might be strong, but sure seems like it might also be a pain to drill/tap/rivnut there.

[deadwood83]

Alright, back at it.


I basically took the month of December more or less off because i just didn't feel like working on it. I hit a wall on top rad mount I would be happy with and I let it get under my skin and stall everything else.


The 2nd head came in, so I have a practice/final. The motor mount also came in so I can cut the Lifan and the Zong mounts and get them welded together.



SanSan also delivered the non-proprietary dash cluster. Glad I didn't put the wiring harness back on because it uses a completely different connector set.. and yes, it supports displaying 6 gears!


TO get myself off dead center on rad mounts, I created a rough cad so I can mentally visualize while considering options.

I also started porting the head because it seemed more straightforward than sitting and beating myself up over the rad mount. The ports on the CBS head aren't tragically bad or anything, but it becomes evident why the power peaks at 9k looking at shape and overall size. Doubly so when your overall size is significantly reduced by the super nasty seat protrusion.



I'm keeping the porting really simple and minimal. Just flattening the floor a skoosh, removing casting flaws, port-matching, and matching seats to the port chambers.
In this photo, one side is about 50-60% done and the other is untouched (intake).


There's not a ton of material on the walls in contact with the water jacket so material removal is rather limited outside of the center divider, which is solid. Valve guides really don't intrude much, so I'll be leaving those alone.



Once I tear down the engine for trans swap i'll finish valve work by lapping them to the head. Looking at the brand new sealing surfaces on the NIB head, I'm not sure if I trust them to be amazing. Probably just a bit of edge softening to fight knock as well.



Also, Gary @ Pitster/GPX said he's just waiting on some wiring harnesses and then I'll have an NC250 EFI setup. Since this engine shares a whoooole lot of similarities where the fuel meats the air and spark, I think it will work rather well.


Last image, just an assortment of the tools I have designed so far to help with bushing thickness reducing, diameter reducing with a hand drill, locating tools for drilling rivnut holes on tubing, etc. I like these because it lets me use design abilities to compensate for lack of experience and training in precisely locating holes, etc by hand.

[deadwood83]

Porting and polishing is more or less done. Some small details to clean up manually, but I'm done with the power tools.


The chamber was a bit rough for my liking, and had some sharp ridges that just screamed pre-detonation, so it got polished. Too much porosity to fully eliminate, and it was crazy difficult to preserve the contours while polishing, but bristle disks and carefully cut soft sanding discs worked out okayish. I also did minor deshrouding on hard machined edges by the valve seats. From the Tianda engine manual, you can see from a used engine the air/fuel mix enters from a very narrow area (it removes carbon deposits to an extent)

I focused mostly on the sides from centerline to the cleaner parts.


To compensate for the polishing, I will have the head decked by ~6-10 thousandths. Since the piston is PVD coated I don't want to have to adjust the valve reliefs; hence the conservative number.



Exhaust bowls and runners got a polish after rough matching to valve seats. The shorter side is ever so slightly widened compared to the long side so that velocities will be more equalized.




Intake was port matched. The included manifold has the same ID as the EFI manifold. I used a round-nose conical burr and gently ground until it witnessed on the manifold, then blended. I may go in with some 120 taped to my pinky just to clean things up. Intake was left alone after carbide, no sanding.



Spark plug hole was deburred with a straight wire brush. It was dead slow, but worked well enough.



I feel my work is far from professional, but I am fairly satisfied with the outcome considering it;s the first time I've ported anything and my dremel has seen far better days. It 100% needs a new armature and new brushes.


Oh, and the valve seats are specced at 1.5mm in the manual, but they all measure 1.2mm. Neway pilot ant 45* cutter en route to fix those.

[grumpyunk]

Given how close the intake valve seats are to the edge of the chamber, cutting material off the head to bump the CR may run into problems. There is very little material left at the edge of the intake valve, and the seat may get cut by the milling machine.
If you look at the Tianda example there is some distance from the edge of the valve seats to the flat of the cylinder head where the head gasket(fire ring?) will be compressed. I just would be very careful as there is a lot less margin than in the image you showed as your example/guide.
I am NOT any sort of expert. But, I would take a look at the edge formed on the head where the bore for the valve seat was made. That slight corner, actually an arc of it, could be rounded, right where the Tianda picture seems to show intake flow cleaning off any carbon deposit. If the flow is from the center of the intake towards the exhaust valve, there is a lip that could have the corner take off with just a slight bit of work. I await some more expert comment... Were I doing the grinding, I'd run something along there to take off the corner, even just a portion of the diameter.
tom

[deadwood83]

Originally Posted by grumpyunk

Given how close the intake valve seats are to the edge of the chamber, cutting material off the head to bump the CR may run into problems. There is very little material left at the edge of the intake valve, and the seat may get cut by the milling machine.
If you look at the Tianda example there is some distance from the edge of the valve seats to the flat of the cylinder head where the head gasket(fire ring?) will be compressed. I just would be very careful as there is a lot less margin than in the image you showed as your example/guide.
I am NOT any sort of expert. But, I would take a look at the edge formed on the head where the bore for the valve seat was made. That slight corner, actually an arc of it, could be rounded, right where the Tianda picture seems to show intake flow cleaning off any carbon deposit. If the flow is from the center of the intake towards the exhaust valve, there is a lip that could have the corner take off with just a slight bit of work. I await some more expert comment... Were I doing the grinding, I'd run something along there to take off the corner, even just a portion of the diameter.
tom

Good observation! A sheet of Norton wet/dry automotive 1000 grit sandpaper is about 8.5 thou thick. The edge of the seat (not the edge of the sealing surface, which is deeper) is about 50 thou from the head face.



I'm not too worried because the piston is generously cut



ANd it's hard to see, but there is actually a vertical of about 8 thou off of Zongshen's relief cuts.




Also, look at how terrible their valve surfaces are. Some of it is dirt (I have only cleaned the head with a vacuum) but their cutters are... ehhhhhhhhh.


I do not have a mill or anything of the sort, so any decking would be done my an engine shop. I will of course ask them their professional opinion at the time.



Also, I ordered this head specifically so I still have the head the engine same with in case I messed anything up too bad hahahah.


By the edges that could maybe be taken down a tad, were you talking about these guys?

They got softened a bit during the polish while I tried to keep it more defined between the valves. My thinking is that the Tianda manual

(same engine BTW, so margins are the same, just the carbon ring shows what the actual bore/piston area is compared to this clean head)

shows where the flow is going as stock. The geometry (as stock) is biasing it towards the center meaning there is greater resistance to flow moving away from center. I softened the edges to each side of where the Tianda image shows the flow with the intended goal of promoting charge to enter across a greater section of the valve. (this is just my seat of the pants thinking though, and I could be completely backwards!. ... which I think is part of the fun.)



More than that though, I think the greatest benefit will be from matching the seats to the bowls. The fit from factory was.... uninspiring.




And if I messed it all up.. I still have another head.... Though I should probably fix my dremel before attacking that one.

[grumpyunk]

The circled (in red) areas are exactly what I was considering. The 'clean' area is a bit more towards the center of the chamber, but... removing a bit of that ridge would increase the flow along a wider swath, I think. Even just taking the sharp edge off a bit more would allow better flow. I do not think you want turbulence there, inside, a tumble, yes, but more flow is a goal in that area. I think. Again, not a 'port person' by any stretch. Though, am considering getting a second head for a CG250 for 'experimental purposes'. Right now, too many other things taking up my time...
I agree that cleaning up the fit of the pressed in valve seats should make things flow better. That alone might be the best investment of time/material. Were I doing a cleanup, I would tackle that first as it to me is 'best bang for the buck', and I would be a lot less worried about cutting away too much material and weakening 'things' in that area. It should stand a good grind with no problems, and give good results. I have watched a vid about work on some 302 heads.. and I think the guy spent a lot of time on some stuff, cutting away around the valve seat, sort of near the cylinder wall when the head would be installed, and to my mind, little gain. Best work was port matching and cleaning up the seat 'fit' to the port wall. (removing the 'ring' right behind the seat)
The second pic in post #40, intakes on the right, you could round off the 'ridge' on both intake & exhaust. Not remove much, just make the ridge be a 'not ridge'. Actually, it is not a ridge, just a more sharply defined corner.
Again with the youtube, there's a guy name Paul who 'fixes' messed up heads. He does machining. Went .. and looked. Paul X

See here:


see how he cleans the chamber and around the valves. I again repeat, I know NOTHING, but what I saw demonstrated. He seems to know his 'stuff'. If you watch his other work, about cams and cam bearings, I go WOW, he's a true artist. IMO
Another is myvintageiron7512, the guy who did the head cutting to relieve around the valves and allow more area to flow.
Here's the 1st of a 5-part:


I watched them all. Made me want to 'do' a 302 with some of those heads.
tom

[deadwood83]

Neway cutter came in.

WOW.


Try to guess which seat found a Neway.



I also found a bunch of rear suspension and frame issues that lifan willfully ignored or tried to cheap around. I don't feel like documenting those today, I'll stick with my seats.

[deadwood83]

Impeccable. (top left is a piece of swarf from cutting I hadn't blown away yet).


Now just deck and swap heads while I rebuild the trans. Oh, and camshaft. But I can't compare angles and lift until I have both in hand.