Luxon 150SX - Weight, First Ride

Well, you pretty much nailed it in your post: "A 2023 GasGas is cheaper, lighter, easier to maintain and has a better platform for all tuning needs motorwise."

EFI is awesome if it works correctly. Removing the need to jet a carb makes life a lot easier. But it comes with added sensors, complexity, and weight, which is no good. And if it doesn't work well on top of that, then the carb bike is a lot better in the end. I'm sure KTM will sort out the issues eventually, but you're still left with a heavier bike. For me, a big part of riding a 125/150 is how light the bike is. A big chunk of that goes away when you add EFI.

I've made a lot of progress, just have to catch up posting it now. Here's a video from last week of the first start since putting the motor back together. Felt good to hear (and smell) it running again!

I like to run a 14 tooth front sprocket on my bikes. It's more efficient as the chain doesn't have to make quite as sharp of a radius around the countershaft, plus I like the ratio it offers (going 14/49 for now). Problem is that the stock chain guard doesn't work with a 14 tooth sprocket, but a Dremel tool makes short work of that. A bit disconcerting that there's less protection now, but I have never had a chain break in all my years of riding, so I wouldn't expect it to be an issue.

Some miscellaneous items:

Rear brakes - I like running the Fasst Co return spring setup. It's small, light, elegant, inexpensive, and works really well. It's on all my bikes:

Stock rear caliper, but with our carrier to save a bunch of unsprung weight (101 g lighter). Motostuff rear rotor:

I'm running the matching Motostuff 280 mm front rotor as well. But the caliper bracket came a grey color, which just wouldn't work. So I did what any rational person would do; stripped the finish, buffed off the logo, re-anodized blue to match our color scheme, then laser etched the Motostuff logo back on the bracket:

A couple shots of the left and right showing the various coatings, parts, etc. 

The kickstart lever (and rear brake arm and shift lever) is hard anodized black. That should hold up quite well, but as expected some marks appear after a few kicks and it hits the peg. I might grind away a clean aluminum spot so it looks more intentional. Note the Powervalve adjuster body and kickstart lever "base" that I forgot to Cerakote. Might get after that soon too. There are also a few steel bolts that I just didn't have titanium versions of, but those are on their way.

Big fan of the Acerbis frame guards, primarily for the added grip on my boots. These are on all my bikes as well.

I'm still running our Gen "2.5" clamps as discussed in a previous post. Those have an integrated HPSD mount, which is nice if you're running one like we are here. The Gen 3 clamps don't include this, but are compatible with the bolt-on brackets since we found the HPSD isn't used by too many people. 

We've introduced out 4-post bar mount system and those are available to fit most stock clamps in addition to our triple clamps. So I've added those to the build. These in particular fit the Renthal FB36 bars, but we have them for 1 1/8" bars as well. Nice and light weight, compact, and adjustable feel with different bushings. These mounts stop the twisting issues from tip overs, but are not connected left to right like our previous mounts so they're lighter, allow for more accessories to mount to the bars, and have a bit more flex for comfort.

Not many people making 7/8 bar mounts these days or even 7/8 bars. They're just not strong enough. A good 1 1/8 bar is plenty flexible and far stronger than a 7/8. You can buy adapters to use 7/8 in a 1 1/8 mount and can still find some 7/8 bars if you really want to, but I'd rather have something that holds up in a crash.

I don't really like the look of the 2019-2022 KTM shrouds, they point downwards and it just looks funny to me. We've worked with Spencer Luczak on a couple builds and he just finished up a 350 build of that generation about 6 months ago (https://www.youtube.com/watch?v=zi7SN96tVHw). He used GasGas shrouds on his KTM and they look a lot better! So I stole that idea and did it here too. It requires a GasGas tank, which is annoying as it's somewhat pricey. But not much relative to the rest of this build, so why not?

KTM Shrouds:

GasGas Shrouds:

The kickstart lever on this bike is held on by a heavy bolt and steel washer. There's no reason for that, so I whipped up an aluminum version of the washer on the manual lathe (new on the left) that's about 1/3 the weight and swapped the steel bolt for a titanium version. A bunch more Ti bolts showed up too, so I swapped those out creating another pile of steel bolts will go unused. Some more titanium on the way too!

The controls all sorted now. I really like the feel of ASV levers, so went I with those again on this bike. Some bling pieces, Cerakoted throttle housing, and various Ti bolts to make it look nice. Phoenix grips glued on to a Motion Pro throttle tube, then safety wired (Phoenix includes fancy gold safety wire with their grips). I've routed the throttle cable behind the number plate for a more traditional look. Plenty of length on the stock cable routed like this.

More titanium for the seat bolt and the seat and shroud retainers. These things are big and solid steel, which is a lot of weight. Nice to drop half of that with the Ti.  

And our new seat arrived today. I went with Guts complete seat: phantom (lightweight) seat foam with an all black gripper cover using the Velcro system. I run this same system on my 350 and love it, plus it drops some weight from the stock stuff while adding more grip. The cover itself is about 150 g heavier than stock (stock is just thin rubber), but the overall seat weight is 50 g lighter than stock thanks to the lightweight foam. 

I have both a Mikuni and a Kehin carb that I can run, so that will take some tuning to sort out what to go with. But my good buddy Bruce has a lot of experience with this bike, and he sent down his Mikuni carb that has had the slide cut and been jetted to work well. Rather than mess around with my carbs, I just bolted that on to see how well it goes and I’ll make the changes to mine accordingly. 

I also ditched the tubliss system and put in the Stark Varg ultralight tubes. I know there’s been some issues with them, and it seems that overall opinion is 50/50 split whether they’re amazing or junk. I already had them, so why not try? The front is only 132 g and the rear is 154 g, so superlight. But they’re expensive at $45 each! I had no trouble installing them, but was pretty worried about pinching a $45 tube…

With that, the bike is ready to ride and nearly complete. Time for a weigh in! Just like I did long ago on page 1 of this thread, I weighted the bike, tilted it up, and down, repeating the weigh in each time. And knowing the tilt angle, I calculated the center of gravity location both horizontally and vertically. 

As it sits, the bike is 91.3 kg (201.2 lb), which is lighter than stock by 1.08 kg (2.4 lbs)! I feel that’s pretty impressive for adding heavy duty wheels, a steering damper, glide plate, and a spring fork. I could probably go with some lighter weight rims, hubs, and spokes to drop below 200 lbs, and might still do that just to have done it. All these weights are with all fluids and a full tank of gas too, so no cheating there.

The CG moved forward 15 mm and up 9 mm vs stock, so not a dramatic change. Most of this is likely due to the spring forks vs the air forks. The F/R weight distribution changed to 1% closer to 50/50 than stock and is now 49.3/50.7 which is nice and balanced.

First break in ride was Friday at Pala! I had both the 350 and 150 there, breaking in new suspension on the 350 as well as the breaking in the 150. There was a big mini-bike race Saturday and they split practices up, which wasn't ideal for testing, but we made the most of it. 

I'm definitely going to make some changes and get it back on track for more testing and tuning before we call this done. Most notably the bars need a lower bend with less sweep. They were just too different from what I'm used to. And the engine is very on-off lightswitchy power-wise. I played with the power valve adjuster and made it a little better, but it needs more work. It's been quite a whole since I've ridden a 150 and I've gotten really used to the 350, so I need a little work myself too in order to get back up to speed on a small bore two stroke...

Regardless, it was a good day at the track and I have some more things to work on!

No a ton of progress on this, unfortunately, things have been busy! I did get it out to the track a couple more times for some more break in and tuning. 

Made a bar swap to a different bend, which helped a lot on the ergonomics side of things. We're on a Renthal 932 FB36 now. 

And I also swapped the carb out to a Kehin, which required a different (Domino) throttle. That made a big difference in rideability and smoothed out that on-off power I didn't like before. Still need to tune that in some, but it's really close. This is the same setup I ran on my 2016 model, so I've got a bunch of jets for it already, which is nice.

Graphics are a work in progress, but hoping to get that sorted and on order soon. Just have to find time to do it! And finally, I'm thinking about another set of wheels to get the weight down under 200 lbs fully fueled. It's close now, and just seems like a good number to shoot for!

No, just with a full tank. It's a 1.98 gallon tank, so full of fuel should add 12.4 lbs. (1.98 * 8.34 lbs/gal water * 0.751 specific gravity of VP T2). That puts it at 188.8 lbs without gas now.