For several weeks now, the RC 390 has looked like this. Untouched. Hanging on stands as
we wait for parts to arrive. Despite how in dissaray it make look, we are actually pretty
close. Today we have a lot of fun stuff to do. And before we get into this, I really want to
thank our oldest sponsor; Moto Station. They have been invaluable with this video in particular.
They helped us with the installation of the cartridges. It's not an incredibly complicated
job, but it's a job that requires a lot of special tools. Special tools that are just not
worth me buying for something I'm going to do once every three or four years. Moto Station.
Thank you! Check them out, and we'll move forward. The 390 came with a set of Andreani Cartridges for
the forks. Those are going in. You basically have to completely dissassemble the forks.
Remove the all the old internals, which are pretty rudimentary and simple, and install the new parts.
Lets take a closer look at the old internals. This is the old spring. It's a progressively wound
spring. You can tell because the coils that are closer together are going to create a softer feel.
Coils that are further apart, a siffer feel. The idea behind a progressively wound spring is
the initial bump absorption is really soft and gentle. And then as you get deeping
into the travel it gets stiffer as you go. Fine for street riding. I tend not to care
for it. But the valve in this thing is really crazy-simple. These are the ports that the oil
flows through, and as the oil flows through it pushes the spring down and opens the valve.
So that's your compression damping and your rebound damping. As the oil flows through
the spring controls the rate the oil can move through the valve. Compression damping. Rebound
damping. Fascinating. Simple little thing. However, it is not at all adjustable. So there
is no way to tune this for your style riding or if a track is bumpy or a track is smooth, you can't
make any adjustment to this. It is what it is. Each of these cartridges in the Andreani's;
one leg becomes compression damping, the other leg becomes rebound damping.
Typically, the right side is rebound damping. R. Rebound. Right. That's usually how they do it.
I suddenly loathe the idea of working on the ground.
We need to make sure that both caps are at the exact same height. The more precise you can be
here, the better your life is. Now, on a track bike you tend to adjust and tweak these things to
get the geometry that you want. You can slide the forks up and down, raise the rear shock, to alter
the bikes geometry. Change the trail number. But, whatever that adjustment is, we want to make sure:
identical. They need to be exactly the same. Oh my gosh! Now, they say these wheels are heavy,
but good-gosh they're heavy. We're going to change the tire so we're going to weigh them
and see just how heavy the stupid front wheel is. And because we recently changed the wheels on the
848 we'll be able to compare this front wheel with the 848 wheel. See which one is lighter.
This one's heavy. It's really, really rediculously heavy. Like, unbelievably, irritatingly heavy.
Oh my gosh! The rotors heavy! Alright, lets see what it comes in at.
And the number to beat is 4.4 kilograms. 5.4 kilograms.
That is stupidly heavy. Thats rediculous.
Alright, lets see how heavy the OEM rotor is. 1.8 kilograms.
Lets see what the KTM performance super-light rotor weighs.
1.26 kilograms. So half a kilogram lighter. I guess that's going to be worth it. Maybe? I hope.
Now I tend not to really be a big fan of frame sliders in most situations.
Over the years I've seen them do far more harm than good. But, I do believe in sliders on the
bottoms of the forks because if a bike falls down, invariably, these things get all beat up and
that's an expensive part. These things are only a couple of bucks. So these are the KTM official
axel sliders for the front axel. It basically replaces the nut,
the main axel nut, so it's no longer a 13mm. It is a hex head, er, a torx.
Alright now is a really exciting moment. The rear shock! And for those of you who don't know,
K-tech is probably the best kept secret in motorcycle suspension,
and for those of you who do know, you understand that K-tech is probably the
best kept secret in motorcycle suspension. We're going to open the box for the first time here.
It's so little! It looks like a mountain bike shock. Let me show you this thing.
Like, look how little it is! It's so cute! I think the shock on the Zuma is bigger.
So I think we're going to have to do is pull this little hugger out of the way. Lift the bike up
so that the wheel is basically hanging free. And then remove the shock and put the new one
in. I think Ican do this without removing the rear wheel even though removing the rear wheel
isn't that big of a deal because it needs a tire.
Rear shock out! This one is physically so much bigger than the other one.
Now the internet tells me, the fine folks over at RC390 Forum say to raise the rear 13mm. So we're
going to measure this then make the other one 13mm longer. Look. It says USA on the bottom. USA. USA.
305mm. 303mm. So, we will lengthen.
I'm always just completely amazed at how easy it is to replace a shock and then immediately
see incredible gains in performance. Two bolts. Four bolts. Tweaking this thing to get it to line
up and we have a rear shock with 13mm of ride height. Pretty easy. The chain is super loose.
I'm already on the table. I'm going to pull the rear wheel. Change the tire
and adjust the chain. Since I'm here. While its apart!
Alright, it is now one week later and I'm super excited. I just got a call that the paint is
finished. And this is my absolute favorite part of the whole thing. Putting the bike back together!
Alright, I think thats it. I think the only thing left to do now is we really need to look at it.
This is the almost final version of the KTM 390. Inspired by
Moto3 bikes and KTM's brilliant RC 8C. I've jokingly named it the RC 3C.
Over the course of the build 20 kilograms, almost 45 lbs, of weight have come off the bike.
If we do some back of the napkin math that means this bike probably weighs around 135 kilograms.
For now, we're ready for the first track day just one week away!
Look, when it comes to building a track bike I really believe the energy should be focused on,
first, making sure the bike is mechanically sound. And we did that with the valve
adjustment and going through everything. Next is bodywork. If not only for financial
reasons, but to have a catch basin in case something goes wrong. We're on
the track with other people. We don't want something to cause somebody else to fall.
And third is suspension. And that's where we focused our energy. Now, knowing me,
I will probably end up putting a full exhaust system and doing a bunch of dyno tuning and
I'll probably end up doing it this summer. Now, something I haven't told you guys,
is this bike isn't even for me. I've been building this for Mrs CanyonChaser,
who refuses to be on camera. She's incredibly shy. Even though she's riding with me since 1995,
almost 30 years, all over half of the world and back, she's never really shown much interest in
track riding until this year. This is for her. And hopefully she has fun with it. And if she
dosn't have fun with it, then I probably will. Now, I really want to thank a lot of you guys
who've been incredibly helpful along the way with advice. Especially Andy. Andy has given
me a ton of great advice, and quite honestly it's Andy's fault that we started down this road
last fall when he kept decimating me lap after lap after lap on his KTM 390.
Guys, thanks so much for watching. We'll see ya' on the track. Ride on and ride well.