Luxon 150SX Build - First start, various assembly details

JMX82
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4/21/2024 9:19pm
Luxon MX wrote:
Here are some engine reassembly photos. Not a ton to discuss here, just putting together things that have been discussed in the previous pages. Lots of...

Here are some engine reassembly photos. Not a ton to discuss here, just putting together things that have been discussed in the previous pages. Lots of titanium bolts, coated/anodized parts, etc. We're using V-Force reeds as I've had good luck with them in the past and the stock setup is pretty bad.

And I'm trying out the F1 Moto powervalve arms. The groove is a little smoother than stock, but I suspect the kink in the stock arms is intentional. The F1 arms are pretty crappy looking compared to stock overall. The stock arms are nicely polished. Regardless, if they don't work well, it's an easy switch to put it back to stock.

Speaking of that, the powervalve design seems pretty terrible and very tight. I suspect it loosens up a bunch at operating temperatures, but on the bench it feels terrible and is VERY hard to turn, even after polishing all the edges and checking to make sure there's no interference anywhere. It's just a poor design. Not much we can do about that, unfortunately. 

141-engine-assembly-1142-engine-assembly-2143-engine-assembly-3144-engine-assembly-4145-engine-assembly-5146-engine-assembly-6

I think the previous generation KTM 125/150's had an excellent power valve design which seldom had any failures. I think the 2016-2022 power valve design was made in intention to cut production costs by using less parts. Although it produces really good power it's not as reliable as the previous design. And what comes to current EFI/electric power valve engine design I think they tried to cut production costs even more compared to previous generations and I think that has had an negative effect how the bikes perform     

2
PTshox
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4/23/2024 8:37pm
Luxon MX wrote:
Here are some engine reassembly photos. Not a ton to discuss here, just putting together things that have been discussed in the previous pages. Lots of...

Here are some engine reassembly photos. Not a ton to discuss here, just putting together things that have been discussed in the previous pages. Lots of titanium bolts, coated/anodized parts, etc. We're using V-Force reeds as I've had good luck with them in the past and the stock setup is pretty bad.

And I'm trying out the F1 Moto powervalve arms. The groove is a little smoother than stock, but I suspect the kink in the stock arms is intentional. The F1 arms are pretty crappy looking compared to stock overall. The stock arms are nicely polished. Regardless, if they don't work well, it's an easy switch to put it back to stock.

Speaking of that, the powervalve design seems pretty terrible and very tight. I suspect it loosens up a bunch at operating temperatures, but on the bench it feels terrible and is VERY hard to turn, even after polishing all the edges and checking to make sure there's no interference anywhere. It's just a poor design. Not much we can do about that, unfortunately. 

141-engine-assembly-1142-engine-assembly-2143-engine-assembly-3144-engine-assembly-4145-engine-assembly-5146-engine-assembly-6

JMX82 wrote:
I think the previous generation KTM 125/150's had an excellent power valve design which seldom had any failures. I think the 2016-2022 power valve design was...

I think the previous generation KTM 125/150's had an excellent power valve design which seldom had any failures. I think the 2016-2022 power valve design was made in intention to cut production costs by using less parts. Although it produces really good power it's not as reliable as the previous design. And what comes to current EFI/electric power valve engine design I think they tried to cut production costs even more compared to previous generations and I think that has had an negative effect how the bikes perform     

Excellent point that is often over looked by folks; mfg's make changes to cut costs all the time. A new guy comes in to the design group and says "if we reduce this from 15 parts to 8 we save x in part costs and y in labor". He's a hero in the product development meeting. But he/she just "new coked" that design.  This type of decision is often made in a fish bowl and they ignore the "WHY" of the design they are replacing. 

Short sided... dumb. Happens all the time.

Reminds me of this "leaf" mid valve design on the KYB Yamaha forks since... 2011 ish. Less parts... simpler to mfg. No spring... etc Less labor. Doesn't give the fork as much range for damping changes. But dildo's (aka "suspension experts") will come on here and crow about this that and the other related to this change. Yet they don't understand product design meetings and basic physics. How this sort of nonsense happens. 

Oh well..... we're not going to fix this problem here on this board. (

 

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JMX82
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4/23/2024 10:19pm
PTshox wrote:
Excellent point that is often over looked by folks; mfg's make changes to cut costs all the time. A new guy comes in to the design...

Excellent point that is often over looked by folks; mfg's make changes to cut costs all the time. A new guy comes in to the design group and says "if we reduce this from 15 parts to 8 we save x in part costs and y in labor". He's a hero in the product development meeting. But he/she just "new coked" that design.  This type of decision is often made in a fish bowl and they ignore the "WHY" of the design they are replacing. 

Short sided... dumb. Happens all the time.

Reminds me of this "leaf" mid valve design on the KYB Yamaha forks since... 2011 ish. Less parts... simpler to mfg. No spring... etc Less labor. Doesn't give the fork as much range for damping changes. But dildo's (aka "suspension experts") will come on here and crow about this that and the other related to this change. Yet they don't understand product design meetings and basic physics. How this sort of nonsense happens. 

Oh well..... we're not going to fix this problem here on this board. (

 

Yeah exactly. I work as an engineer for a company which makes tractor cabins. I'm very familiar with management wanting more and more cost saving every year and they aren't interested in about usability/reliability that much because the only thing that matters for them is the EBITDA for the next quarter. It can be quite frustrating for the engineers because you want stand proud behind your own designs and that's not always possible. 

1
JackLHyde
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Nice Oak DE
4/24/2024 2:17am

Hey guys,

can you give me a short rundown on the shortcomings of the TBI 125s?

My old man (about to turn 75...) wants to get another Husqvarna, as my brother got one last year. Out with a knee injury our dad started to ride it regularly and is convinced it is the best thing since sliced bread.I try to talk him out of it. A 2023 GasGas is cheaper, lighter, easier to maintain and has a better platform for all tuning needs motorwise.

All I have seen and read the TBI is a step backwards. I was at a ADAC race last weekend and lots of carburated 125s were used, also by EMX125 racers. Somehow a good amount of TBI bikes are on the used market with low hours aswell.

The Shop

Luxon MX
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4/24/2024 7:51am
JackLHyde wrote:
Hey guys, can you give me a short rundown on the shortcomings of the TBI 125s? My old man (about to turn 75...) wants to get...

Hey guys,

can you give me a short rundown on the shortcomings of the TBI 125s?

My old man (about to turn 75...) wants to get another Husqvarna, as my brother got one last year. Out with a knee injury our dad started to ride it regularly and is convinced it is the best thing since sliced bread.I try to talk him out of it. A 2023 GasGas is cheaper, lighter, easier to maintain and has a better platform for all tuning needs motorwise.

All I have seen and read the TBI is a step backwards. I was at a ADAC race last weekend and lots of carburated 125s were used, also by EMX125 racers. Somehow a good amount of TBI bikes are on the used market with low hours aswell.

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.

6
cdoggy81
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St. Petersburg, FL US
4/24/2024 5:34pm
PTshox wrote:
Excellent point that is often over looked by folks; mfg's make changes to cut costs all the time. A new guy comes in to the design...

Excellent point that is often over looked by folks; mfg's make changes to cut costs all the time. A new guy comes in to the design group and says "if we reduce this from 15 parts to 8 we save x in part costs and y in labor". He's a hero in the product development meeting. But he/she just "new coked" that design.  This type of decision is often made in a fish bowl and they ignore the "WHY" of the design they are replacing. 

Short sided... dumb. Happens all the time.

Reminds me of this "leaf" mid valve design on the KYB Yamaha forks since... 2011 ish. Less parts... simpler to mfg. No spring... etc Less labor. Doesn't give the fork as much range for damping changes. But dildo's (aka "suspension experts") will come on here and crow about this that and the other related to this change. Yet they don't understand product design meetings and basic physics. How this sort of nonsense happens. 

Oh well..... we're not going to fix this problem here on this board. (

 

PTshox - interesting perspective on the KYB mid valve leaf updates. So far I have heard a lot of positive things post the 2018 ish update. Don't get me wrong, with time & the right shim stack you can get the older stuff (say 06 to 17) 100% dialed in but I think it just takes a little more out of the gate to get it closer to that point than what the newer stuff does. I don't want to muck up Billy's thread here so I'll take it offline & shoot you a PM. We have an interesting one going on it over on TT & I would like to hear your thoughts & ideas if you have time. Thanks! 

Rickyisms
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4/24/2024 7:20pm

My 150 powervalve has always been a PITA by hand, 125 is smooth as butter. 

1
b_kowalsk
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Thomaston, CT US
4/24/2024 8:38pm
JackLHyde wrote:
Hey guys, can you give me a short rundown on the shortcomings of the TBI 125s? My old man (about to turn 75...) wants to get...

Hey guys,

can you give me a short rundown on the shortcomings of the TBI 125s?

My old man (about to turn 75...) wants to get another Husqvarna, as my brother got one last year. Out with a knee injury our dad started to ride it regularly and is convinced it is the best thing since sliced bread.I try to talk him out of it. A 2023 GasGas is cheaper, lighter, easier to maintain and has a better platform for all tuning needs motorwise.

All I have seen and read the TBI is a step backwards. I was at a ADAC race last weekend and lots of carburated 125s were used, also by EMX125 racers. Somehow a good amount of TBI bikes are on the used market with low hours aswell.

At 75 years old I think he will be just fine with a TBI bike. Electric start being one bonus, as well as no need to jet. I've heard the tbi bikes don't run as hard on the top end but have better pick up off the bottom. 

For a racer the lighter easier to tune carbureted model may be better but if your father has already ridden the efi model and likes it I see no reason why he shouldn't go that route. 

2
JackLHyde
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Nice Oak DE
4/24/2024 10:54pm
b_kowalsk wrote:
At 75 years old I think he will be just fine with a TBI bike. Electric start being one bonus, as well as no need to...

At 75 years old I think he will be just fine with a TBI bike. Electric start being one bonus, as well as no need to jet. I've heard the tbi bikes don't run as hard on the top end but have better pick up off the bottom. 

For a racer the lighter easier to tune carbureted model may be better but if your father has already ridden the efi model and likes it I see no reason why he shouldn't go that route. 

Definitely right on that. It's his decision after all.

Luxon MX
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4/26/2024 6:05pm Edited Date/Time 4/26/2024 6:06pm

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!

 

 

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Luxon MX
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4/26/2024 6:22pm

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.

155-14t-sprocket156-14T-Sprocket-Guard157-14t-sprocket-guard-trimmed158-14t-sprocket-installed

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Luxon MX
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4/26/2024 6:35pm

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:

 image-20240426182954-1

 

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

image-20240426183207-2

 

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:

 

 

image-20240426183548-3

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Luxon MX
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4/26/2024 6:52pm Edited Date/Time 4/26/2024 7:01pm

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.

image-20240426184934-1

 

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

162-right-side163-left-side

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Luxon MX
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4/26/2024 6:58pm

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. 

image-20240426185442-1

 

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.

165-fb36-4-post-bm166-fb36-4-post-bm

4
JackLHyde
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4/29/2024 11:01pm

Some things on your recent posts:

The more teeth grab the chain, the better I guess.

What about white cable ties for the frame guards?

The best feeling I ever had was on a 2018 CRF450 with stock clamps and stock bars. It just felt right. Great bend for me and comfortable flex. I wish 7/8" bars were still common. I can't even find bar mounts to try it. Have you ever tried a setup with 7/8"?

 

Luxon MX
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5/1/2024 12:39pm
JackLHyde wrote:
Some things on your recent posts: The more teeth grab the chain, the better I guess. What about white cable ties for the frame guards? The...

Some things on your recent posts:

The more teeth grab the chain, the better I guess.

What about white cable ties for the frame guards?

The best feeling I ever had was on a 2018 CRF450 with stock clamps and stock bars. It just felt right. Great bend for me and comfortable flex. I wish 7/8" bars were still common. I can't even find bar mounts to try it. Have you ever tried a setup with 7/8"?

 

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.

1
Luxon MX
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5/1/2024 3:56pm

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:

image-20240501155551-1

 

GasGas Shrouds:

image-20240501155606-2

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Luxon MX
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1 day ago

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!

171-kickstart-washer172-kickstart-bolt173-bolts

3
Rickyisms
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1 day ago

I’d probably buy two or three of those kickstart bolt washers as long as it made sense $ wise! So annoying having to replace them every few months after they rust.  

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