'17 '18 250SX JM Racing Performance build

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11/17/2018 4:12 PM

I'm Michael Keating, suspension tech at JM Racing, and Ex-Pro Racer from the 90s. These days I race mostly the Vet A classes and still get around the track pretty good! Last year I went to Loretta Lynn for the first time on my '03 Full Blown JM Racing YZ125. An extremely fast and great handling 125, but still a True 125!! I had a little bad luck and came away with 1 moto podium (3rd) and a 6th OA in the 50+ and nothing to show for in the 45+.

This year I wanted to try a 250 and have a few more ponies!! It took me longer than expected to find one I liked, but when it came along, I got it. The problem was I only had a couple weeks to get it ready for Loretta's!

The ad said '17 250SX with about 25hrs (broken hr meter), stock engine and suspension, fresh chain and r. sprocket, fresh top end. A little risky buying a used bike, but this one looked good!

This is an ongoing build geared for performance and not bling bling! I plan on catching you guys up to where I am so you guys can see what works for me and hopefully help you get more out of our 250SX. I'll keep going and posting as I improve this bike's performance more and more!

My lump of clay to be molded into my Working Man's Works Machine: Photo

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'19 RM-Z250
'03 YZ125
'79 RM100

11/17/2018 4:36 PM

Sick story

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11/17/2018 4:54 PM

First order of business was to see where I was on the bike, how the bike handled, and what I thought it was gonna need immediately.

Time to get to work!!

I mixed up some Maxima 927 at 60:1 with some 93 octane pump gas. That was a ratio I'd never done, so I cleared it with some friends at Maxima to make sure it'd work; it would and does. Then I set off to 3 Palms, a local track, to get in some laps!

After fuelling it up with my crazy new ratio mix, I checked the tire pressure (12 in rear, 12.5 in front) then set the fork pressure at 140# and the clickers at 12 & 12 for a starting point. Shock sag was at 102 (my go-to spot for Smokers) with the clickers at 15, 15, & 1.5 turns out.

PhotoJust some easy laps to get the feel and this baby made my blazing fast YZ 125 feel fairly slow in comparison, despite the horrible blubbering on top! Headed to the van, checked my trusty fork leg zip tie to find I was a few inches from the bottom. Lowered the fork pressure 2#, got a drink, went back out, and repeated a couple more times. Got down in the low 130#s before I was using up most of the fork travel. Then went to the clickers to take some of the harshness out. Came out to 15-15 to get by til I could get into the internals and make some needed changes for a more progressive stroke to follow the ground better and handle the really hard hits that my speed needs!

The blubbering on top had been going on the whole time and I kept telling myself not to get into it today, but couldn't take it any longer. How could the jetting be this bad?? So I loosened the clamps, spun that baby sideways and pulled off the float bowl only to find the main jet lying in the bottom. Yes, it had completely fallen out! Not sure how this happened from my test ride in the bar ditch before purchasing (it was running fairly good) to my getting it on the track...???? I installed the 460 main jet, left the 30 pilot and the JD needle and hit the track again. Way, Way better! The power was hard to handle!! Something I was gonna have to adjust for and learn to handle before I lined up with fastest Vets in the country!

All was pretty good, a little lean off the bottom and a re-valve was in order for the suspenders!!!

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'19 RM-Z250
'03 YZ125
'79 RM100

11/17/2018 4:55 PM

Kx125rider wrote:

Sick story

Thanks man!!

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'19 RM-Z250
'03 YZ125
'79 RM100

11/18/2018 12:35 PM

I have a build thread on here for my ‘18 that might help you with the crappy jetting and some handling with the bike. If you’re ever in the Austin area you’re welcome to ride my bike back to back to compare.

Build link

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2018 KTM 250sx
Instagram CamaroAJ

11/18/2018 1:26 PM
Edited Date/Time: 11/18/2018 1:31 PM

AJ565 wrote:

I have a build thread on here for my ‘18 that might help you with the crappy jetting and some handling with the bike. If you’re ever in the Austin area you’re welcome to ride my bike back to back to compare.

Build link

Thanks!!! Most of that stuff is done, I just decided to post this stuff.... I'll have my build caught up to date in a week or so....
I've read a bunch of your jetting work on the jetting post that's like 12 pages long!! You guys have had a booger of a time getting that sorted out!!!

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'19 RM-Z250
'03 YZ125
'79 RM100

11/18/2018 7:57 PM

Subscribed smile

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11/19/2018 2:25 PM
Edited Date/Time: 11/19/2018 2:27 PM

Time to tear into this Bad Boy!!

Photo

I'm always surprised by guys, or girls, that will pay $600 to $1000 for a re-valve and not make sure their linkage is greased to will allow the suspension to work as it should!!

Here's how to do it...!!!
Okay guys, this is pretty intimidating for many folks...Tearing into the linkage for cleaning and greasing!! I've done this to EVERY single bike I've ever owned since 1983. Even if your bike is brand new, it probably hasn't been greased very well, if at all!! All you need to do is take your time and pay attention to which bolt went where and which way the "Wishbone" and "Knuckle" pieces go. Taking a photo can help you get it back together like it was. Okay, once the parts are off you're gonna slide the collar out of whichever pivot point you're working on over a rag or towel and be careful not to loose any needles out of the needle bearings!! Some bikes have loose needles and some are held in place by a "cage." The caged bearings stay in place, but are a little more difficult to clean out the old grease (if there is any...). To clean it out, I place a paper towel over my finger and wipe out the bearing while turning the bearing a half(ish) turn while wiping. Do this several times, like 20, til the paper towel is staying pretty much clean. For loose needles, you can easily pull out the needles with a magnet and not drop them....!!! Make sure not to loose any of these!! Clean 'em up and you're ready to put back together after you've wiped of the seals very well also. A scribe or tooth pick can get in the seal's grooves and clean out any dirt!
Time for fresh grease! The caged bearings you'll need to use your finger and "pack" the grease down in-between the needles and the cage. This also takes several times to get it good. Keep packing until you've got a smooth, well lubricated turn of the bearing when turning with your finger. The loose bearings can be a little tricky to get in place. First, you need a good bead of grease in the bearing casing, then place the needles in the case and the grease will hold them in their spot.... Take it one piece at a time. You can use a zip tie to keep collars in place that seem to keep slipping out... Make sure you get all the pivots in the linkage, swing arm, and shock!

Tightening Trick:
Next, put all the linkage parts and r. wheel back on the bike just finger tight. Once you've got them all on I suggest taking the bike off the stand to tighten the bolts so the bike is under the load of its own weight when you tighten them. This will take any play that might be in the pivot points out. Make sure you tighten all linkage pivots, shock pivots, and the Swing arm pivot!! If still seems too much for you, take it by a place like JM Racing and have a professional do the dirty work for you.

Photo

Time to do the steering head, once you've got the back end greased!! Pull the f. wheel, forks, and bars; the bars can come off with everything attached and just set them on the tank area while you pull the steering head. So, pull off the top triple clamp and then the bottom one. ON these KTMs, it's all held together by the one top bolt. Once that guy is out, it ALL comes apart! The bottom bearing is pressed on, so leave it on unless it's rusted up and needs replacing (you'll need a press for that) and the top bearing will lift right out of the race in top of the frame. I also leave the f. fender on too. These bearings are caged and I use the paper towel trick (from up above on the linkage bearings) or you can use a parts washer for better cleaning if available (I'd remove the fender for that). Then, pack that grease in there and make it good! Throw the parts back in place and just go finger tight again. Side the forks in and snug up [b[bottom triple clamps only]/b], mount front wheel and snug up the triple clamp steering head bolt or nut(other models).

Here's my trick for how tight to get the steering head:
I like to snug up the bolt so that the front end will turn all the way to the stops when I barely get it started, BUT it doesn't bounce off the stops.... If it doesn't make it to the stops, I loosen a bit and if it bounces off the stops a little, tighten it a bit more....!! This is how I like it, some folks like to run it a bit tighter for a "dampner" type effect. For me, if it's tighter than how explained, I feel like I'm fighting the steering to get it to turn and I'm half a step behind if things get a little out of shape elsewhere on the track... When you've got that right, set your fork height and tork your pinch bolts to 14ft/lbs on bottom and 17 on top.

Make sure tighten everything up on the bike and then double check it again!!

Now your suspension can work like it's suppose to...!!!

Keep your nuts tight!! A simple mark with a sharpie will let you know if your bolts or nuts are loosening up....
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Live as if you'll die tomorrow, Take care of your body as if you'll live forever!

'19 RM-Z250
'03 YZ125
'79 RM100

11/19/2018 2:48 PM

Great write up on how to properly grease. My '18 250sx came from the dealer looking like it was nicely greased. luckily I still dug into it and found that the grease was just wiped on the sides of the pivot points and the swingarm pivot bolt was bone dry... ?

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11/19/2018 6:19 PM

My ratio rite is almost worn out Michael!!

-Hope your healing up-

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Current rides-
1988 RM250
2019 KX450

11/19/2018 8:23 PM

lukemoto wrote:

Great write up on how to properly grease. My '18 250sx came from the dealer looking like it was nicely greased. luckily I still dug into it and found that the grease was just wiped on the sides of the pivot points and the swingarm pivot bolt was bone dry... ?

I know it!! You'd think grease was Crazy expensive....

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'19 RM-Z250
'03 YZ125
'79 RM100

11/19/2018 8:25 PM

Superdave19 wrote:

My ratio rite is almost worn out Michael!!

-Hope your healing up-

Haha
Thanks Bro!! I'm feeling quite a bit better!!

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'19 RM-Z250
'03 YZ125
'79 RM100

11/21/2018 9:34 PM

So, while I had the shock and back end off, I took advantage of the easy access and started on the carburetor!

First, a little jetting theory:
As I mentioned in an earlier post, my bike came with a JD kit which has a 30 pilot for the 250SX. So, here are my thoughts on making things "Lean." Lean jetting gives the sensation of "Woah, this baby really Barks!!" But in actuality, you get great sound with No Go. Sounding great while sitting on the stand doesn't win races. The pilot circuit feeds the engine with a continuous flow of fuel no matter where you are with throttle position... so basically it affects everything! If you go low with your pilot jet, your bike is gonna get really thirsty when you ask it to do something with some intensity! Also, off the bottom, it's gonna want to run away with itself. No bueno!

Now, my bike:
Back to the track for testing. Fairly dry, so I wouldn't have much trouble keeping dirt out of things while making changes!
Obviously, I wasn't real happy with the JD kit and I didn't want to buy a Keihin or Lectron carb so let's see if I can work out these jetting woes that everybody is having with their bike. So, what I want out of my bike is a strong pull off the bottom, a really strong hit with a quick fan of the clutch and handful of throttle, along with a clean run out on top! Stock jetting wasn't horrible, but was lacking what I want.
*So, to the brass I went!
*I live/ride at about only 150'-200'
*I started where everybody else does and dropped the pilot to a 40
*I lost some pull on top so I went to a 450 main
*Not much better so I went to a 37.5
*Started running away a little coming into the corners
*Tried a 460. I just wasn't getting the results I was searching for...
*Remembered my jetting theory and figured I was going about it wrong and the pilot wasn't the issue
*Went back to the 42.5 and 440 and dropped the needle
*Bingo, I was really pleased
*Tweeked the air screw a little and loved it!
It had enough fuel to allow that strong hit and had a clean tractor like pull all way til it signed off!! With a little tweek on the air screw depending on elevation, temperature, and humidity, things are really good. It sounds rich on the stand, but put the engine under a load and she sounds great!

I've read many, many post on 250SX/TC jetting and would like to try some different slides and maybe some different needles to get it really spot on! Right now and with Loretta right around the corner (at the time), it was really good!!

If you're running very lean jetting, be careful, too lean is really hard on engines...!!

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'19 RM-Z250
'03 YZ125
'79 RM100

11/22/2018 11:52 AM
Edited Date/Time: 11/22/2018 12:35 PM

I also checked the reeds with my easy access...

This was very surprising.....
Photo

The intake manifold has an offset hole and the last top end was obviously not done very well.... The gasket is backwards and blocking part if the opening! Not helping my performance!! The guy I bought this bike from had someone he knew do the job. Always take your bike to a reputable mechanic!!!
I also checked the reeds and they were pretty good. You want to look for a good seal of the reed itself up against the cage and also look for frayed edges or chips. They usually develope at the corners first so check those very close and replace if they're damaged. If the edges are good and just not sealing well, you can try flipping the reed over and that usually will fix it. If that doesn't work, your block may be warpped and needs lapping in. If you don't know what that means, find yourself someone like JM Racing that can do such things!!! I had to flip one of my reeds and the block was in good shape!
Check them regularly and stay on top of this as reed issues will decrease performance, especially off the bottom, drastically!!

It's the little details that separate most bikes and give you that extra edge and helps you get on the podium!!

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'19 RM-Z250
'03 YZ125
'79 RM100

11/25/2018 12:38 AM

You've put back the stock needle or kept le JD in ?

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11/26/2018 12:43 AM

nice build so far

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11/28/2018 12:02 PM

Time for some Suspender Work...!!!

Photo

There are more suspension tuners out there than one can count.... And just as many folks saying that their guy does amazing work!! Well, my guy is John Mitchell at JM Racing!! I haven't tried them all, but I've tried several of the big names and JM is the best!! If you're looking for someone that does good work, go to an Amateur National and check the folks on the podium... You're gonna here JM Racing many, many times! It's about personalized set ups and getting it done right!

So, while the bike was all apart, the suspenders came off, got torn down, and laid out for the Junk Man to work his magic!! Like I referred to in my testing post, we needed to plush it up on the small stuff and chop, and it needed a more progressive feel to hold up in the corners but still follow the ground, and handle the big hits!!
Photo
For somebody as picky as me, it usually takes a time or two to get perfect, but JM nailed it first try! Was I glad, because Loretta's was right around the corner!

We also went with the Ride Engineering Inc. performance link!! It lowers the back end 6mm and settles it down in the rough stuff and track through the ruts better! Big improvement!!
Photo
All in all, this JM package works and you'll feel the difference on the track!!

Most MXers are familiar with the stories if not the personal experience of Loretta Lynn's ridiculous rough track and horrendous ruts!! My JM suspension handled all this with ease including an accidental "flat ground" landing off the biggest jump on the track! A really rough track is a true test of your bike's ability to handle Real Motocross!!

If you're serious about excellent suspension, call JM and talk to John about a Suspension Set-up with some possible Personal Testing at a local track for extra tweeking! You''ll love it and see what I'm talking about!
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'19 RM-Z250
'03 YZ125
'79 RM100

11/28/2018 1:22 PM

That's the exact conclusion I came to with my RE link. Its amazing that changing the hole spacing 1.3mm can have that drastic of improvement on a bike. So much more confidence to charge into corners harder knowing the back end will track straight and rail a rut.

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2018 KTM 250sx
Instagram CamaroAJ

11/28/2018 3:31 PM

AJ565 wrote:

That's the exact conclusion I came to with my RE link. Its amazing that changing the hole spacing 1.3mm can have that drastic of improvement on a bike. So much more confidence to charge into corners harder knowing the back end will track straight and rail a rut.

Yes, pretty amazing how much better the bike handles!!

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'19 RM-Z250
'03 YZ125
'79 RM100

11/28/2018 4:25 PM
Edited Date/Time: 11/28/2018 5:15 PM

Well, I got a couple more things from Ride Engineering when I was placing my Performance Link order. I wanted to try their trick axle blocks that free up the axle pivoting and allows the rear wheel to follow the ground a little better!

Photo

Unfortunately I added this at the same time as the Performance Link and Suspension re-valve, so I didn't have time to test separately. I can feel the bike following the ground down into the whoops and tracking/pulling strong down and through with a really strong drive! So, we'll just call it a JM Racing/Ride Engineering combo well working package! I'm really happy with the Performance!

I also got the Rim lock washers to fit against the rim flush.
Photo

I couldn't resist the clean look of the their oil fill plug, so I splurged for some small bling!
Photo

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'19 RM-Z250
'03 YZ125
'79 RM100

11/28/2018 4:38 PM

That was pretty much all the time I had to get ready for Loretta's!
I needed some graphics, unfortunately I didn't get any of my requested numbers, but the graphics turned out great!! MX Gurl did an Amazing job! I told her to surprise me and this is what she came up with!!
Photo
Photo
Photo

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Pin it to Win it!!
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'19 RM-Z250
'03 YZ125
'79 RM100

11/30/2018 11:43 AM

Best of luck, thanks for the details!

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KTM250SX YZ125 YZ85 PW80 ZX6 FZX700

11/30/2018 12:41 PM

I'm confused about the Loretta"s right around the corner? Looks like winter time to me....?

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11/30/2018 2:03 PM

The Loretta Lynn race was back in August. I'm writing what I did to my bike before the race for a time line and am working up to the present.... Thanks guys!!

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Pin it to Win it!!
Live as if you'll die tomorrow, Take care of your body as if you'll live forever!

'19 RM-Z250
'03 YZ125
'79 RM100

12/1/2018 10:05 AM

Well Loretta's was going good! I started off with a 3rd in the 50+ and a 4th on the 45+ after a couple lack luster starts after we drew 36 and 38th gate pics! Crappy luck of the draw!! Anyway I wasn't planning on working on my build at the race, but had to do it!!
In the middle of the week, I noticed a drip of somethings on my pipe and was wondering where it came from til I had a closer look. It was from a crack in my pipe!!

Photo

It was just a hair line crack, but I still needed a new pipe!! So we headed over to the FMF camp and picked up a Factory Fatty & PowerCore silencer! All the talk for the SX/TC pipe is the Pro Circuit, but MXA tested them both and said the FMF Fatty offered the same benefits as the PC....
I found the FMF Factory Fatty to be Awesome!!! I definitely felt the power increase at the end of the curve with no loss off the bottom.
The un-plated finish is more challenging to keep clean and nice, but it runs cooler and performs better!

Photo

I love the look and performance of this pipe. However, I will be doing some testing with different pipes and silencers in the near future and we'll see how they stack up against each other on the track with back to back trials...!! But for now, the FMF is working great!!

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Live as if you'll die tomorrow, Take care of your body as if you'll live forever!

'19 RM-Z250
'03 YZ125
'79 RM100

12/1/2018 2:26 PM
Edited Date/Time: 12/1/2018 3:08 PM

Dexter wrote:

You've put back the stock needle or kept le JD in ?

Sorry, I didn't see your question. I went back with the stock needle. 43-73 and ended up in the 2nd clip position (down from the top).
I'm not sure what the JD needle is, since there aren't any markings other than the red or blue coloring....

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'19 RM-Z250
'03 YZ125
'79 RM100

12/4/2018 3:03 PM

So levers seem to be something everybody is changing these days....
I don't really understand most of the "unbreakable" ones out there.... As most of you have probably seen, they bend back around to the front??? It must help a little, but I want a lever that will bend is the direction that goes away from the impact!!

One of the down sides to the KTM's amazing clutch feel and workability, is a crash could cost you a Master cylinder and not just a clutch perch, just like the front brake side. One of those tabs gets broken off, and you're buying a whole new Master cylinder... That's why I went with the Rental levers, they bend in multiple directions giving me a much greater chance of not tearing up these expensive KTM Brake & Clutch Master cylinders!! The Rental levers have a Great Feel on my fingers and some very nice adjustability to them!! They also come with a nice rubber protector. A nice added touch. I highly recommend a set! I think you'll be very pleased with them.

You can kinda see the small gouge in my clutch side in this pic. A little bit of a nasty crash, but the lever and the Master cylinder and lever are fine!!
Photo

This adjusts how far the lever is away from the bar to fit shorter or longer fingers!
Photo

You can see these bend up, down, out in front and snap right back in place..... Very handy!!
Photo

Photo
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Pin it to Win it!!
Live as if you'll die tomorrow, Take care of your body as if you'll live forever!

'19 RM-Z250
'03 YZ125
'79 RM100

12/4/2018 4:35 PM

Keating wrote:

Well Loretta's was going good! I started off with a 3rd in the 50+ and a 4th on the 45+ after a couple lack luster starts after we drew 36 and 38th gate pics! Crappy luck of the draw!! Anyway I wasn't planning on working on my build at the race, but had to do it!!
In the middle of the week, I noticed a drip of somethings on my pipe and was wondering where it came from til I had a closer look. It was from a crack in my pipe!!

Photo

It was just a hair line crack, but I still needed a new pipe!! So we headed over to the FMF camp and picked up a Factory Fatty & PowerCore silencer! All the talk for the SX/TC pipe is the Pro Circuit, but MXA tested them both and said the FMF Fatty offered the same benefits as the PC....
I found the FMF Factory Fatty to be Awesome!!! I definitely felt the power increase at the end of the curve with no loss off the bottom.
The un-plated finish is more challenging to keep clean and nice, but it runs cooler and performs better!

Photo

I love the look and performance of this pipe. However, I will be doing some testing with different pipes and silencers in the near future and we'll see how they stack up against each other on the track with back to back trials...!! But for now, the FMF is working great!!

I bought a brand new 07 Ktm 300,same thing,cracked pipe.not impressed

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12/4/2018 8:11 PM

Stock pipes work well, but are not the most durable that is for sure. With regards tolovers, I like what you have done. I used to be a lever junkie, but these days I run OEM. I go the old skool way regardless of lever and put teflon tape underneath the perches, tighten more or less as usual and they just spin down in a crash. No broken levers. Fun thread.

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vomiting equals disqualification.

12/4/2018 8:21 PM
Edited Date/Time: 12/4/2018 8:24 PM

Yes, I've seen a couple folks saying the stock pipes are weak and like to break!! Is your bike an 07 or a 17??

I agree, I keep everything loose so it can move under the impact of a crash... I ran the OEM levers at Loretta's and had a coupIe falls with no problems and now I carry the OEMs for a spare.... I haven't ever tried the teflon tape trick, I'm gonna give it a try!! Thanks for the tip!!

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Pin it to Win it!!
Live as if you'll die tomorrow, Take care of your body as if you'll live forever!

'19 RM-Z250
'03 YZ125
'79 RM100