Luxon MX KTM 150SX Build - Minor updates

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8/30/2018 12:59 PM
Edited Date/Time: 8/30/2018 1:05 PM

Well we just picked up a 2019 KTM 150SX and figured I may as well create a build thread! I love the 150 as it is the ultimate play bike (well in my opinion), so why not go all out with it? And we have A LOT planned for this bike. I’ll be posting up all the various aftermarket parts we add, modifications we make, details of the design/manufacturing processes of our own parts we use, as well as miscellaneous details and reasoning for why we’re doing what we’re doing. There’s a lot to do, and we’re busy as-is, so there may be some delay between posts and it this will take a few months, but the end result should be awesome!

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Initial Plans:
Nearly everything on this bike will be replaced and/or modified in some way. We’ll be starting with a complete strip down, welding tabs on the chassis for a steering damper and glide plate, powder coating, transmission work, Cerakote throughout, complete rework of the suspension, etc. Having done a lot of work and riding on the previous generation 150SX (you can see it in the picture below), I learned a lot about these bikes so I have a pretty good idea of what I want to do with this one!

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

8/30/2018 1:02 PM

Weight!

The first thing I wanted to do was get a baseline weight for the stock bike. We used two shipping scales with reasonable accuracy and precision to get a “ready to ride” weight – all fluids and a full tank of gas. The stock bike is pretty bare-bones, so we’ll definitely be adding weight along the way with a glide plate, steering damper, spring forks, and other changes, but I want to document each change/addition to understand how much weight was added and to where.

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And the nice thing about weighing the bike using two scales is that we can also measure where the center of gravity, or CG location is (sometimes referred to as the center of mass). With two scales and a level bike we know the lateral (front to back) CG location. Then raising up one end of the bike and weighing it again you can calculate the CG height knowing the angle change, the weight difference, the wheelbase, and some basic math. I’m ignoring the lateral (side to side) CG location here as the bike is mostly symmetric and is should be more or less in the middle laterally. There’s certainly some error in the CG location calculations – the scale accuracy/precision, accuracy of angular and distance measurements, compression of the suspension/tyres, etc., but it should give us a good idea of where the CG is within a few millimeters. I calculated the CG height with both the front wheel raised and the rear wheel raised, and the results were within a couple mm of each other. I took the average of the two.

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The CG is important as it is the point where the bike can be represented as a simplified point mass in analysis. For example, if you’re jumping through the air, the bike will rotate about its CG location (slightly more complex when you account for the rider and their CG location as well). How easily it rotates is a whole separate issue and is dependent on the overall moment of inertia of the bike (how the mass is distributed relative to the CG location) as well as the rotational inertia of the wheels and engine. Measuring the moment of inertia of the bike is considerable effort and to do it correctly would require a lot of time and money in building a fixture, so we’re skipping that one! Another measure of interest is the unsprung weight, and we’ll touch on that when we’re changing out suspension and wheels.
There’s a lot of talk about weight and how a bike “feels”. A few people even state that a bike doesn’t “feel” heavy, so it doesn’t matter what the scale says. But the problem with that statement is the “feel” doesn’t change physics! They are likely feeling that the bike is light because it has a well centralized CG location and a relatively low moment of inertia which will make it easier to throw around. But the scale weight makes a big difference when accelerating the bike, getting on the brakes, or changing direction. In those cases, “feel” is trumped by weight. This is obvious if you ride an Alta. The bike is really heavy, but that weight is well centralized since there is no intake, exhaust, etc. It feels light in the air and you can flick it around, but come into a corner hot and you’ll see the effects of scale weight when you try to slow down. I raced REM a couple months back; first moto on the 150 and second moto on the Alta. It was an enormous difference!

Here’s a screenshot of the spreadsheet I’m using to track everything. If you look close at the image you can see the CG location represented by a blue/white dot just above the clutch cover, which is about where you might expect it. The location is pretty neutral – near the center of the bike. And you can see we’ve already saved 3 grams by removing the warning stickers. laughing

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

8/30/2018 1:37 PM

This build is gonna be awesome, can't waitw00t

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8/30/2018 2:06 PM

Can't wait to see how this turns out!!

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2017 RMZ450
2005 YZ250-sold :,(
1998 YZ250
2005 KX250F

80% of the time it works every time
IG @hamdaddyof2 & @2HRacing
Thanks to : Factory Effex, N2Dirt, Acerbis, DT1, Fasthouse, Matix, FMF, ASV, 100% & Mika Metals

8/30/2018 2:07 PM
Edited Date/Time: 8/30/2018 2:07 PM

What sort of transmission work? Already has a Pankl made set up... super finish and cryo maybe? I will be paying attention to this thread as most of it will transfer to my 19 TC and I like to build too.

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vomiting equals disqualification.

8/30/2018 10:46 PM

I will be following this one smile

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8/31/2018 1:31 PM

Subscribed smile

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9/13/2018 5:58 PM

Well, not a lot of progress the last couple weeks. I took a quick vacation in Mexico and was rewarded with some pretty bad food poisoning. And also came back to a ton of work piled up that took priority. But we're getting back on this now.

Today I started tearing everything down. First priority is welding on the HPSD mount and glide plate mounts, then getting the frame stripped and re-coated.

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

9/13/2018 11:19 PM

Luxon MX wrote:

Well, not a lot of progress the last couple weeks. I took a quick vacation in Mexico and was rewarded with some pretty bad food poisoning. And also came back to a ton of work piled up that took priority. But we're getting back on this now.

Today I started tearing everything down. First priority is welding on the HPSD mount and glide plate mounts, then getting the frame stripped and re-coated.

Photo

This is going to be good smile

What color on the frame?

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9/14/2018 9:07 AM

blackdiamond wrote:

This is going to be good smile

What color on the frame?

I'm not sure yet, but something neutral. At this point I'm leaning towards stripping the stock powdercoat(?) and cerakoting the frame, so that gives a lot of color options. I've heard that powdercoat adds a fairly substantial amount of weight, so I certainly don't want that! And cerakote being a fairly thin coating shouldn't add much weight.

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

9/14/2018 2:00 PM

very thorough and very cool!! Any chance you guys will be making a ignition cover soon for the 18-19' 250sx?? The one on your 150 looks great!

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9/14/2018 3:21 PM

Luxon MX wrote:

I'm not sure yet, but something neutral. At this point I'm leaning towards stripping the stock powdercoat(?) and cerakoting the frame, so that gives a lot of color options. I've heard that powdercoat adds a fairly substantial amount of weight, so I certainly don't want that! And cerakote being a fairly thin coating shouldn't add much weight.

I think powder coat adds about 2 lbs?

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9/14/2018 4:20 PM

BR8ES wrote:

What sort of transmission work? Already has a Pankl made set up... super finish and cryo maybe? I will be paying attention to this thread as most of it will transfer to my 19 TC and I like to build too.

have a 2019 sx150 my self will follow !!

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[Moto D Racing

9/15/2018 11:07 AM

Luxon MX wrote:

Well, not a lot of progress the last couple weeks. I took a quick vacation in Mexico and was rewarded with some pretty bad food poisoning. And also came back to a ton of work piled up that took priority. But we're getting back on this now.

Today I started tearing everything down. First priority is welding on the HPSD mount and glide plate mounts, then getting the frame stripped and re-coated.

Photo

blackdiamond wrote:

This is going to be good smile

What color on the frame?

Luxon MX wrote:

I'm not sure yet, but something neutral. At this point I'm leaning towards stripping the stock powdercoat(?) and cerakoting the frame, so that gives a lot of color options. I've heard that powdercoat adds a fairly substantial amount of weight, so I certainly don't want that! And cerakote being a fairly thin coating shouldn't add much weight.

I've always wanted to do a bare steel frame - hit with a torch for color - then clear coated

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9/15/2018 11:50 AM

Derek Harris wrote:

I've always wanted to do a bare steel frame - hit with a torch for color - then clear coated

Yeah, considering that as well. I'm going to strip it and see how things look, then make a decision.

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

9/15/2018 11:51 AM

lukemoto wrote:

very thorough and very cool!! Any chance you guys will be making a ignition cover soon for the 18-19' 250sx?? The one on your 150 looks great!

Thanks! If we do an ignition cover for the 250, it will be a ways out unfortunately. I've got a lot on the to-do list at the moment!

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

9/15/2018 12:47 PM

Luxon MX wrote:

I'm not sure yet, but something neutral. At this point I'm leaning towards stripping the stock powdercoat(?) and cerakoting the frame, so that gives a lot of color options. I've heard that powdercoat adds a fairly substantial amount of weight, so I certainly don't want that! And cerakote being a fairly thin coating shouldn't add much weight.

Derek Harris wrote:

I've always wanted to do a bare steel frame - hit with a torch for color - then clear coated

Luxon MX wrote:

Yeah, considering that as well. I'm going to strip it and see how things look, then make a decision.

Rockstar Suzuki did that on the bikes Mike Brown raced back in the day. It's hard to see in this pic but I saw them up close and they looked badass!

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9/15/2018 2:37 PM

lukemoto wrote:

very thorough and very cool!! Any chance you guys will be making a ignition cover soon for the 18-19' 250sx?? The one on your 150 looks great!

Luxon MX wrote:

Thanks! If we do an ignition cover for the 250, it will be a ways out unfortunately. I've got a lot on the to-do list at the moment!

would like one if you every make one sx150 2019 thanks

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[Moto D Racing

9/15/2018 2:46 PM

honda70 wrote:

would like one if you every make one sx150 2019 thanks

We will definitely have one for the 125/150. Stay tuned to this thread, I'll post up as we're making them and when they're available. Probably within a month or so.

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

9/17/2018 6:55 AM

blackdiamond wrote:

This is going to be good smile

What color on the frame?

Luxon MX wrote:

I'm not sure yet, but something neutral. At this point I'm leaning towards stripping the stock powdercoat(?) and cerakoting the frame, so that gives a lot of color options. I've heard that powdercoat adds a fairly substantial amount of weight, so I certainly don't want that! And cerakote being a fairly thin coating shouldn't add much weight.

Derek Harris wrote:

I've always wanted to do a bare steel frame - hit with a torch for color - then clear coated

I used furniture paint stripper on my YZ frame and it had the awesome looking welds and I thought about clear coating it.

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9/17/2018 4:09 PM

Sub'd, the last build you guys did was spectacular.

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9/17/2018 4:37 PM

This will be good!!

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9/18/2018 3:38 PM

Luxon MX wrote:

I'm not sure yet, but something neutral. At this point I'm leaning towards stripping the stock powdercoat(?) and cerakoting the frame, so that gives a lot of color options. I've heard that powdercoat adds a fairly substantial amount of weight, so I certainly don't want that! And cerakote being a fairly thin coating shouldn't add much weight.

Derek Harris wrote:

I've always wanted to do a bare steel frame - hit with a torch for color - then clear coated

Luxon MX wrote:

Yeah, considering that as well. I'm going to strip it and see how things look, then make a decision.

I’ve wanted to do the bare frame look also. I’d love to see it!
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9/18/2018 4:00 PM

Bare chrome moly looks great but how about a carbon fiber with titanium frame... be the first! Photo

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9/18/2018 4:03 PM

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9/18/2018 4:14 PM

lukemoto wrote:

Bare chrome moly looks great but how about a carbon fiber with titanium frame... be the first! Photo

Nvm guess it's been done... Photo

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9/27/2018 7:30 PM

Finally got some free time this afternoon to make some more progress. The frame was nearly stripped of all components, but still had the annoying T-piece for the coolant lines installed. On previous years you could take this out with a 1/2" Allen wrench, but it seems they've changed it which is annoying. It's nowhere near a standard tool, so I whipped up a custom tool on my lathe and mill to take the thing out:

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It comes out just the same as the old ones once you have to tool sorted out. I used a screwdriver up top to get some leverage as it's in there pretty tight. Once you get it loose it comes right out. We're probably going to go with a MotoHose replacement piece and they include the tool with their T-piece so that's one less thing to worry about, I just wanted to get this thing out now so we can move on with the rest of the chassis mods.

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Next I wanted to test out the paint stripper I bought. I'm installing a HPSD bracket, so I just tested a couple spots: one at the head-tube where the bracket will weld on and another spot on the down-tube. I'd read that the stripper works best if the finish has been roughed up, so I tried that on the head-tube. I also tried stripper on the other spot without roughing it up for comparison.

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As you can see, the area that was roughed up came off really easily. The other spot that wasn't roughed up didn't come off nearly as easy, but wasn't that bad:

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That's it for now, hope to make some more progress this weekend!

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

9/27/2018 7:35 PM

Oh, and the stock chassis is definitely powder-coated, which is nice. But that means they had to sand blast the chassis beforehand, so it's a rough finish once it's stripped. Probably not going to look very nice with a clear coat; we will likely be going with Cerakote instead. I did take weight measurements before any stripping, so we'll get a real answer to "how much weight does the powder coat add?" pretty soon as well!

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components

9/27/2018 9:02 PM

Nice! I haven't really been checking the build section as of late, but now I will be

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@fiendz.cc

9/28/2018 11:09 AM

FiendzCC wrote:

Nice! I haven't really been checking the build section as of late, but now I will be

Good, and expect a call from me fairly soon about some Cerakote!

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Precision Engineered Motocross Components