There’s a big bore kit producer in Thailand Keng Engines. There’s a you tube vid of it puttting out 38 hp 38 ft/lbs tq which is a lot more than the usual. I did a search for it here, kinda surprised it’s not being discussed KLX402

 

So... where's the link?

 

They're on freakbook(I don't do freakbook), and also youtube in Tia. Looks cool, but I can't tell how they make a 402 live, lot's of material removed to make room for the piston. Plus, the 250/300 head is not going to flow enough to take full advantage. In addition to cubes, looks they bump the compression quite a bit. The power would be nice, but I would probably upgrade since we have options here that are not as affordable in Thailand. Looks cool though. I got a KLX230 for my kid when I picked up my 300, so they also offer a 269cc kit for the 230. Maybe something to think about. They showed an EJK with one of there kits, not slamming EJK, but I would not be inclined to go that route. Would do a power commander or go after the API ecu(which is also Thai) for a big bore. They have cool stuff over there for the KLXs, and it makes sense since bigger bikes and euro bikes are BIG dollars.

 

Seen it on Fb. The klx402 has some nice additions. Worth the time to take a gander, 38 hp 38 ft/lbs tq is well above the bill blue big bore fcr35 2 bros M7 equipped klx sitting in the garage. Modifying the water jacket flow through the cylinder and head is intriguing.

 

Hit up you tube search Keng Engine klx402 38 hp and tq will make a regular klx into a 230. Its worth looking at. Made the klx350 big bore in the garage hide with its tail tucked hmmfff 🤯

 

Not to nitpick, but it is 38 n-m so roughly 28 ft-lbs. Impressive number, nonetheless. I think it is a little more involved than a cylinder, piston and a tune though. High compression may not work well with pump gas, and I wonder how the rest of the engine will hold up, what has been done to make sure it can handle the upgrade. Since I don't speak Thai, I can only go on what can be seen.

 

The 402 kit picture on Fb contains some not so usual components. Larger injector & coil spark plug cap, reground cams along with the usual mod parts pipe & header, piggy back fuel controller, big bore cyl piston, etc. I don’t speak Thai either so it’s a mystery to me, that’s why I asked about it here maybe someone does. And possibly the tuning specialist guys here would share their thoughts. Or maybe not.

 

Ordinarily, with the KLX, we think if a BB kit as piston and cylinder R&R ... It appears the above is more like creating a custom "one-off" engine that happens to use the KLX bottom end... Not sure this changes our landscape..

 

The cylinder certainly doesn’t have that casting appearance but does have a pressed in iron liner. So your probably right about being it being a one off. Their countries additional tax on bigger cc bikes promotes big bore conversions so its reasonable to see engine builders like Keng.
I inquired about their cams since that’s the one thing not done on the klx in the garage. The price was certainly worth looking further into. Considerably less than the ones available here.