2003-1990 KX-DX Hybrid Build

Discussion for swapping a KDX motor in a MX frame...
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dfeckel
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Post by dfeckel »

So the final thing to go on before I could take it for a test ride was the chain, and I managed to screw it up!!! I got it all measured up and started grinding on the wrong pin. :roll: I knew I ordered those extra master links for some reason. Why have one master link when you can have two for just $1.79 more? Hopefully the two "master" links establish a pecking order quickly--don't want it to go like the "co-managers" at Dunder Mifflin...I'm a nerd AND an idiot...

I'll finish the heat cycles today and take it for a rip around the back point forty.

I haven't wired up the headlight, yet, but the taillight is wired and not working, so it looks like I have a bit of lighting/wiring/coil troubleshooting to do, too. Ahh, 20-year-old motors and wiring harnesses :neutral:
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Post by Julien D »

That turned out incredible. I wasn't sure about the color when you had the frame painted, but seeing it all put together I'm very impressed. Gorgeous!
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Post by dfeckel »

I figured out the lights issue today--poor previous splice in the KDX harness. In my reading about the KDX lighting coil, it seems as though it's only putting out 40-45 watts? My dual halogen headlight would draw 70 watts if I wired up both lights, so I just wired up one. Good enough for enduro tech inspection.

I also rigged up a swivelling licence plate bracket. The enduros I ride sometimes require the plate to be mounted horizontally. The problem with that is that it hangs up on trees and brush, and the tag inevitably gets bent/torn up/broken. A swivelling bracket makes it easy to switch the plate to the vertical protected position after passing inspection in the horizontal position.
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I cut out a double layer of plastic backing from an empty kitty litter bucket. (I KNEW I was keeping that thing for some reason!)
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I lined up the plate on the fender hanger to determine the best place to drill a single hole that would allow it to rotate without bumping into anything--turns out it was not the middle of the plate, but offset to one end somewhat. I mounted the reinforcment backing to the hanger with a 5/16" carriage bolt, large washers, a locking washer, and a wingnut.
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Then the plate mounts to the backing plastic, over the carriage bolt.
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Now I can simply loosen the wingnut and rotate the plate either horizontally or vertically in seconds.
Last edited by dfeckel on 03:10 pm May 01 2018, edited 1 time in total.
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Post by dfeckel »

I've had the chance to rip around the back yard serveral times, and I have to say I am thrilled with the bike. It's so light, so flickable, so responsive. I have not yet really opened it up, but the low end is snappy, strong and crisp, but very tractable as well. My little loop around the house is usually taken in second gear with drops to 1st through tight hairpin turns on my 125. I can ride the loop exactly the same on the hybrid with controllable explosions out of the corners, or I can just leave it in second all the way around, the motor cleanly lugging to almost nothing and accelerating out of the turns much quicker than my 125. The only carb adjustment I've performed up to this point is adjustment of the idle speed. Ron Black's carb and head mod came perfectly adjusted for my elevation and bike mods. I've enjoyed super-easy starting and rock-stable idle, combined with clean, snappy running in the low to mid. I still have to take it on an official test ride to try out the top end.

I was a little nervous about the clutch pull being overly stiff, probably as a result of the ancient cable I'm reusing, but the tractability of the motor allows me to clutch far less frequently than on any bike I've ever ridden without auto clutch.

The Tubliss and D 803 trials tire combo seems to work great so far in my wooded back yard. Lots of predictable traction and a smooth ride.

I still have to set my sag on the WER revalved suspension, but it's plush as can be on my little loop. Of course, I haven't hit the S. Jersey sand whoops or slick root balls yet, but if my WER experience on my Husky is any indication, I'll really like the setup.

Any disappointments? Well, the shifter is hard to remove due to its proximity to the KX frame. The bolt to tighten it hangs up on the frame when you try to remove it to take the shifter off. I can just finagle out, but only just.

The kick lever rests on the pipe when folded in. I knew this before final assembly and I hoped that it wouldn't make too much noise when the engine was running. It doesn't. No problem.

In addition to being the world's worst motorcycle tire changer, I'm also the world's worst motorcycle graphics applier. Damned things are peeling off already.

The fit of the Acerbis replacement plastic isn't all that good. Getting the seat/side panel bolts started is a miserable experience. I also had to tweak the Devol radiator guards a bit to get the shrouds to line up.

My Moose handguard mount interferes with the front brake line as it comes out of the reservoir. I need to get the mounts for the contour guards, which cost too much for what they are, in my opinion.

The clutch pull is stiffer than I like, and it grabs too close to the bar. Hopefully a Revloc Dyna Ring makes this a moot point.

Poor plug access with the IMS tank. The RB carb will likely make fouled plugs infrequent, but I'm a little spoiled by the super-easy plug access on my Huskies. Even the 4-stroke. With the 125 I can kick a soccer ball between the tank and head!!

So far, I'm just tickled. It's all I hoped it would be. Now, if I can finally beat my buddy on the 200 XCW at some of the enduros this year, I'll be ecstatic.
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Post by dfeckel »

I haven't updated in a while, so I thought I would let you all in on my travails.

I seized the engine five miles into my first real ride. It was running well on a few miles of single track, and once it opened up onto a sand road, it just seized. D'oh. It happened in top gear at steady throttle, perhaps 35-40 mph. I was sort of stuck in disbelief mode for a few minutes, and then I started checking things out. No compression. Well, at least the bottom end was still free. Carb looks a little askew in its manifold. A little push on it, and it rotated freely.

Immediate impression was that I forgot to tighten the carb manifold and airbox boot on final assembly, and the dusty conditions lead to this:

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Note the cracks in the exhaust port bridges.

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Now, those cracks may simply be join lines in the casting, but there is now a defect/crack in the plating right over those lines.

And here's a definite crack where the main power valve goes.

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Head looks fine

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Plug looks great.

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I also thought there might have been a sizing problem with the Powerseal cylinder and the new Wiseco forged piston, but I sent the piston and rings to Powerseal for them to size up, so I don't think that's the problem.

Maybe an excessively lean running condition? Even though the intake manifold wasn't clamped tight, it was still a pretty good fit. Plus, the motor seemed to be running great. The plug looks chocolate brown, so I kind of doubt the lean condition. I can't rule it out, however.

What makes me think dust was the problem was that the loose airbox boot from the KX leaves a significant gap if it's not tightened on the smaller diameter KDX carb. I'm thinking that dust was readily sucked through this gap, leading to the seizure.

Armchair mechanics, chime in here.

So, what to do? I took this as an omen from the hybrid gods that I should do a total bottom end rebuild in addition to fixing the top end. I was originally torn over whether to rebuild the bottom end, and I took the easy road. Could old main seals have contributed to the seizure? Maybe. Could those main seals be the original 20-year-old items? Could be. Did the helicoil drilling in the trans case put a bunch of metal shavings in the tranny that I couldn't flush out? Yes. Should I rebuild the bottom end so I know for sure that everything is fresh? Yeah, I think it's time.
Last edited by dfeckel on 03:11 pm May 01 2018, edited 1 time in total.
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Post by Colorado Mike »

Looks like a four corner seizure to me, but can't see the whole piston. Many times that's from too little cylinder to piston clearance, but the cooling system and air leaks are big suspects.
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Post by dfeckel »

Cooling system--I can't think of a possible problem there. No signs of overheating, no boil over, the rads were getting plenty warm during heat cycles, so no water pump issue. But that was a good suggestion.

I also thought it was a four-corners seizure, or it at least looked a lot like one. Looking down on the piston, the seizure was at 10 and 2 o'clock, right along where the exhaust port bridges are, and at 7 o'clock with very light damage at 5 o'clock.

Anyhoo, I thought this was a perfect opportunity for me to learn how to split cases and start from scratch. So out came the motor, off came the top end with the cylinder back to Powerseal for welding and replating, and up opened the laptop to start buying parts and tools.

I can now proudly state that I am the owner of a case-splitting tool, a 5-ton bench press, a crank holding tool, a three-jaw pilot bearing puller, and a multi-piece blind bearing puller set. Sigh. I think I spent more on tools than I did on engine parts and labor. The only way to know for sure is to add up the receipts, and I ain't doin' that. I learned my lesson already.

I was hoping to reuse the crank after replacing the seals, since it looked awfully good prior to splitting the cases. Too bad I turned off my brain and threaded the case splitter into the wrong case half and put a huge side load on the crank before figuring it out. Did I screw up the crank alignment? Who knows? So off to RB Designs for a crank rebuild just to be safe. I wouldn't want to go through all this trouble just to have trashed main bearings in ten hours from a misaligned crank.

I also found this little tidbit after splitting up the cases.

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It looks like a previous bottom-end blowup cracked the right case half. It communicated only with dead space, but why take a chance on it getting worse? Off to my welder guy.

Post-weld:

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I got some extra practice splitting and joining the cases because I couldn't find the pin that goes on the end of the shift drum after assembling everything the first time. I couldn't find it anywhere in the garage, so apart came the cases to make sure it wasn't in the tranny. It wasn't. Peace of mind and a little more expertise. I always say, anything worth doing right is worth doing over a couple times until it actually IS right.

The cylinder came back from Powerseal at no charge, which was nice. However, the welds protruded into the powervalve spaces too much and I had to do a bunch of grinding and polishing to get the PVs to move freely.

I put the top end back together with an OEM piston and rings.

The bike started briefly on the second kick and then wouldn't start after a dozen more. That's when I realized I had the damn muffler plug in it.

The first heat cycle yielded a leaky head gasket, so off came the head and I sprayed a bit of coppercoat on the new gasket (it was a new Athena metallic gasket). No problems, now.

So I've done a couple more heat cycles and blipped around the cul-de-sac a few times and everything seems good. I raised my needle one position to richen up the low-to-mid a bit.

So, we'll see. Needless to say, my hybrid enthusiasm is not quite a great as it was originally, but the proof will be in the pudding. I'm racing this weekend and I'll report back.
Last edited by dfeckel on 03:11 pm May 01 2018, edited 1 time in total.
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Post by Indawoods »

Well.... I wouldn't be discouraged. It is like allot of second hand things... they aren't what they appear to be. You got it taken care of....
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The Long-Awaited Race Report

Post by dfeckel »

It's time to provide some closure to my hybrid build thread with a race report from its debut at the 2010 Speedsville Enduro, put on by the Ithaca Dirt Riders in NY.

A little background--I rode this enduro last year, and it was a Death March. They had torrential rain the day before, which resulted in 80+ miles of peanut butter on ice. You know, the conditions that yield an 8-inch rut you can barely stay in with long skid marks on either side from riders' feet trying desperately to keep the bike upright. When you weren't struggling to maintain forward motion in greased ruts, you were flailing to keep the bike from shooting out from under you over the zillions of slick roots, every one of which was positioned perfectly to throw your front wheel into the next county. Wet, rocky streambeds were welcome respite because you could actually find a little predictable traction. Utter misery. I rode my '07 TE 250 Husky and made it to within 10 miles of the finish before houring out. To date, it's the only enduro I've never finished. So I had some unfinished business in Speedsville.

As you've read in this thread, I've had a few teething problems with the hybrid, and I really didn't have much opportunity to do any significant shakedown rides. I did 15 miles several weeks ago in some S. Jersey sand, but it was too hot to do more. So it was with trepidation that I loaded up the KX-DX for the five-hour drive to run the only enduro that's gotten the best of me.

Conditions leading up to Sunday were dry. They hadn't any real rain for a couple weeks, so things looked promising. However, Sunday morning was when the rain began. It was very light at first, just enough to fog your goggles. Which was annoying, because it was still dusty. My contact lenses were loving me once I ditched the goggles.

So how did the bike work? Before the first fuel stop, I was less than stoked. The front end was dancing all over the place, deflecting a lot more than I would have liked. The back end was blowing through its travel in the few whoops they ran us through, even bottoming out a couple times. I had asked for a rocks valving from WER, and it didn't seem to be working. Plus, the power was overwhelming at times. The bottom end was just too abrupt, lifting the front end out of slow corners when I wasn't anticipating it, throwing me off line. Plus, the clutch pull was too stiff. After the first 25 miles, I was certain that I wouldn't last to the end, if only because my left hand was going to give out.

At the first gas, I decided to change a couple things. First was my tire pressure. I'm always nervous about pinch flats, so I had 12 PSI front and rear for this "rock run." Even though I have Tubliss in the rear trials tire, I was nervous about running too low a pressure and maybe cutting the sidewall, which just happened to my buddy a few weeks ago. So I dropped the front to 10 and rear to 8. Second, I decided to just stop using the clutch lever unless I was coming to a stop or the motor was in danger of stalling.

Well, what do you know! I suddenly had a predictable front end. I was now able to use the KX's incredible turning ability to seriously rail some berms in the dryer sections. Plus, I think the fork broke in a bit, giving me a lot more compliance over roots and small rocks that earlier were sending me off line. The course got more technical, and the back end's softness started to work as well, giving me great traction and staying planted under power through rocks and uneven roots. And the trials tire--oh, the trials tire!!--it was magic. Traction, traction, traction!!!!

What about the motor? I commented to my buddy at the first gas that I would probably take off the RB head because the power was too abrupt. The problem was that I was still downshifting for corners like I was on my 125, and I was clutching coming out. When I decided to minimize my clutching to preserve my hand strength, I discovered what all you RB disciples were talking about--it is nearly impossible to stall this motor. You can lug it to what feels like 250 rpm and it just chugs right back up. I left it a gear high for turns, skipped the whole clutch thing, and I saw the light. THIS BIKE IS AWESOME!!

Not long after this epiphany, the steady rain converted the enduro into another Death March. I had about 40 miles of greased rut, root and rock (the unholy trinity) to trudge through, and the KX-DX shined. I stalled a few times trying to find the absolute lowest motor speed through tight rocky singletrack (it's about 12 rpm), but it always restarted on the first kick. There were a couple technical hill climbs that I KNOW I wouldn't have made on my 125 on the first try unless I was super lucky, and the hybrid motored right up. This motor, coupled with the trials tire was just unstoppable. On my 125, I can either lug up a hill or rip up on the pipe. I can't transition from lug to rip on the hill because the abrupt hit will just make for a spinning tire. The KX-DX, however, gives me freedom. Start up the hill on the pipe, slow or even stop for a stalled rider, lug a while, twist the throttle and off you go--up the hill as fast or as slow as you want.

An added perk? Good gas milage. My buddy was on his KTM 250 XC with a 3.4 gallon tank, and he ran out of fuel five miles from the end of the LONG second loop (58 miles). I still had about half a gallon left in my 3.2 IMS at the finish.

Overall, I'm super happy with the bike. After the teething problems it had, I was wondering how long I would own the bike. But now I know it's a keeper. I'm going to try the MSR Raptor Pro clutch lever to try to ease the clutch pull, and if I still think it's too much, I will probably call Garry at EFM to do his thing.

Thanks again to everyone who pioneered the nitty gritty of the hybrid build, allowing a ham-fisted amature like me to crank out a KTM EATING MACHINE!

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Last edited by dfeckel on 03:02 pm May 01 2018, edited 1 time in total.
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Post by Indawoods »

Nice write up Dave! :supz:
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Post by Jupiter2 »

i love happy endings! :lol:
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Post by bulabula09 »

NICE! i especially like the caked with mud look...im sure it adds some extra horse power haha...nice bike!
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Post by Varmint »

Nice job! I have friends (B races) that rode this one. Sounded pretty tough. :supz:
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Post by dfeckel »

Definitely a tough one. I'm a new B rider this year, and I'm just tickled to have finished it as strongly as I did.

I can't wait to try out my Pro Raptor lever from MSR. It just arrived over lunch. Thanks, Bikebandit!
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Post by Varmint »

One question... you raved about the trials tire. One of my buddies tried it at the race and promptly pulled it off. He said he doesn't suffer from wheel spin and found the performance not that great. He also noticed that his valve stem was torn; so the tire spinning on the rim probably made the rear-end even worse. He mentioned he might try it again with two bead locks. Do you have two on?
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Post by barncat »

Defeckel,
If the silencer isn't spoken for, i am interested. I have been searching, Hi and low for one..

If interested let me know.
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Post by Coop »

Great write up.

As a side note on my first ride on my '03 200 by the time we got back to the trucks, my left hand HURT and my forearm was so pumped I couldn't pull the clutch in at stops and was stalling. I think it's a combo of two things. 1) I am coming off a KX125 and I think I was doing what you were doing and using the clutch too much; & 2) I do think this bike has a hard pull for a small bore bike. My '03 BMW F650 with a standard clutch has an easier clutch pull LOL.
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Post by dfeckel »

The Moose Pro Raptor lever works very well, but it took a bit of modification to get it to work with the cable. No big deal. Also, on the easy-pull setting, it takes more lever motion to fully disengage the clutch. As a result, you have to pull it to the bar to fully disengage it, and it still drags enough to make finding neutral an iffy proposition. On the whole, however, a worthwhile mod. I still might go to an auto clutch, though.

Barncat,
REgarding the KDX silencer, e-mail me at dfeckel@yahoo.com and we'll work something out.

Varmint,
I'm running the Tubliss system. As long as it's pumped up, it ain't going to allow the tire to spin on the rim. IN addition, I rode the Ridge Riders Enduro in Hancock this weekend. 4+ inches of rain with that Nor'easter made for slimey conditions. I figured a knobby would work better in the mud than the trials tire, so I spooned on a new MX51 Dunlop and aired it to 8psi with the Tubliss. Well, it wasn't long before I was wishing for my trials tire again! The knob provided NO traction on wet roots, making for some hairy moments. Plus, starting on a hill after a bobble was tricky, too, because of all the wheelspin. Maybe the knob was better in deeper mud ruts, but there was enough of a hard bottom to the mud that I bet the trials tire would have found traction there, too. I'll be putting the trials tire back on ASAP. I'll reserve the knob for sand.
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Post by Julien D »

Awesome write up man, thanks!

Make sure you try that trails tire in the sand too, and compare. According to dirt rider mag, the trials tire really shines in the sand. I don't have enough sand out here to say, one way or another...
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2003-1990 KX-DX Hybrid Build

Post by dfeckel »

Build thread bump, as requested.
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