Repowering a KTM 640 Adventure

Discussion in 'Some Assembly Required' started by Z50R, Oct 19, 2017.

  1. Z50R

    Z50R Not lost yet

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    The bike is awesome. The handling is intuitive, it feels like factory geometry, not like a prototype where handling idiosyncrasies must be accounted for.

    The carburetor still is not right. I purchased the bike with a big bore kit and I modified the air box significantly. I am not a carburetor expert (and neither was the previous owner who put the bore kit on) so it is a learning process for me. The big bore kit throws off everyone elses input on how to setup a DRZ400e carb and what I did find is no longer applicable due to the airbox not flowing as well. The local KTM shop is excellent and they are amused by this project but a 2001 carb is so out of date that they can’t really help much. When I started it would not idle at all. It would start and run but stopsigns and traffic lights were annoying with all the throttle blipping. Additionally, the bike took 30 minutes of riding before warming up and once warm, it wouldn’t run for shit. The idle jet was way too rich and after moving to a 38(?) and adding a remote mixture screw, I have the bottom end power where I want it. The bike now behaves well everywhere except 3/4 throttle in a steady state. If I am accelerating through, no problem. If I hold at 3/4, the engine missfires sporadically. This is worse when it is warm out leading me to believe I need a needle with a fatter straight diameter. I don’t know for sure and I’ll address the issue next spring. I think the bike has a bit more power to offer and my best fuel milage so far has been 45mpg but with the current tune it is hovering at 39mpg so there is work to do yet.

    The headlight is pointed about 5 degrees to the right. In retrospect I know when in the fabrication process I fucked up (welding the tabs on the ring) but I didn’t know I was being sloppy at the time. I can’t simply make new tabs because the top adjustable slot’s geometry is driven by the inaccuracies in the side tabs. I’ll cut the triple tree mounts and re-weld them this winter to correct it.

    The seat is still the shitty/malfitting KTM part I started with. I thought I’d need to fiberglass a new pan but more thinking leads me to believe I can get away with modifying this one. Either way I need new foam because this foam is completely dead. It was bad new, it was worn out two years ago, now I am just white-trashing along on a garbage seat. I will have to pull the bike off the road for a few weeks to fix it so that is a “this winter” thing too.

    The speedometer cable shit the bed again. The way I was attaching it was causing the copper conductor to split without cutting the insulation. I spliced it back together and will need to buy a new one eventually.

    No other issues come to mind. The bike sits about an inch higher than the KTM, I have to really try to get both feet flat on flat ground. The giant loop bag was way better than panniers on the trail. Even in the incompletely tuned state it currently lives in, it is a much more responsive bike than what I had.

    I doubt it’d be a dealbreaker for me but I’d probably pick a stock bore over the 440 if I were given a choice and everything else were equal, I am in uncharted territory tuning wise and I can’t see land from where I am. I have learned a ton but this is like a self taught college course rather than one with a professor.

    If I were to build another bike (and you know I will) I would NOT use weatherpak connectors. I was happy with the Furukawa connectors from Eastern Beaver and would base the bulk of my connectors on that system.
  2. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

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    What, specifically, did you not like about the weatherpaks? I work for a vehicle lighting manufacturer and we use them almost exclusively as our "high end" option.
  3. loganlexow

    loganlexow Adventurer

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    Thanks for the updates! It sure sounds rich at 3/4, especially if its losing power instead of surging when you say "misfiring" at 3/4 throttle. I do have to say that I'm curious about the shaking you and others use to describe the LC4. I ride mine daily, and travel and my hands have never gone numb. My ass on the other hand.....ouch, this seat is not a comfortable ride. I'm really curious how you plan to go about curing the seat woes.
  4. Z50R

    Z50R Not lost yet

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    Lets start this list of complaints with the disclaimer that weatherpak connectors are a well established, field proven design and despite what I say below, they are reliable for this application. I am spoiled to have worked with better components and this list reflects that experience.

    1. The pins and sockets are rolled sheet metal. I thought round pins would be better than any other choice since wire crimp orientation would not matter and there would be less stress where the wire entered the plug. I think the method that weatherpak connectors use to keep mechanical & electrical contact between pin and socket is poor. I think my original logic is sound but it is based on using forged brass pins. There are much better methods of keeping tension between sheet metal pins than allowing the socket seam to split by design.

    2. The pins have a lot of play after they are pushed home. The wiggle room is doubled when you take into account both the plug and the socket move, it works out to be about 1/8” of engagement. I don’t have much confidence that the pins are fully engaged and am constantly pushing them that extra 1/8” after connecting while troubleshooting.

    3. The size is way too large for motorcycle applications. Weatherpak connectors are compatible with wire between 22 and 10gage. Since the same plug has to be able to acomodate such a wide range, it is overkill large for everything on a motorcycle that isn’t bolted together (the starter circuit). If weatherpak connectors tried to stick to a narrower range, they’d be better for this application but then they’d loose some of their universal appeal.

    I picked these connectors because I thought they’d be available 30 years from now, they are universally available now, and they are waterproof. In retrospect, metripack connectors check all those boxes in a more compact package and I would trade futureproofing for an even more compact connector than metripak.
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  5. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

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    I misspoke. We use Tyco/AMP Superseal 1.5 connectors. I was confusing the two styles.
  6. Dino de Laurentiis

    Dino de Laurentiis Working on it

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    For motorcycle use, I’m personally very fond of the ATM/DTM (from amphenol and deutsch respectively) series mini connector. Smaller than the standard size AT/DT connector and very solid. Waterproof too. Up to 7.5 amps per pin.
    FR700 and Z50R like this.
  7. Z50R

    Z50R Not lost yet

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    So it has been a year. My bike is everything I wanted in a moto. People who know KTMs are confused by it. My friends tell me to shut up about it and my co-workers want to know why the seat looks like shit.

    The bike gave me so few problems last year that, surprisingly, I didn’t even disassemble it this winter. There are a few nagging problems though and the seat tops the list.

    The tank is tipped about 5 degrees forward of the OEM position relative to the sub frame. This meant that there has been a gap between the seat and the tank. This gap stressed the seat cover and it ended up splitting. The rain got in and I looked like I pissed myself every time I rode. Duct tape patches looked like shit too. Additionally, the seat cover was old/used enough that the fabric was torn at the bottom edges too, this functioned as a drain for the rain water but really made it look bad.

    Step 1: separate the parts.

    8ABF74AD-B546-45B1-8FEF-66CF40368CEC.jpeg

    If the foam were good and the seat otherwise comfortable, I’d fix the seat pan and reassemble with a new cover; there is enough give in the foam for a 5 degree alteration. The foam is old enough to be going through puberty though so it has lost a lot of its strength. It is also quite waterlogged and I am not sure how I’d get it dry enough to trust it not to mold. Time for new foam.

    I had been anticipating this problem for about three years. Before the 640 shit the bed the seat was growing less and less comfortable and riding two up was becoming more and more taxing. I have made a few moto seats before and hadn’t yet come up with results I was happy with foam wise. Lots of reading suggested the foam sold for outfitting kayaks was a good idea. This foam is closed cell which means that water does not pass through nor soak in. It is obviously field tested for this feature in kayaking so there is no doubt in my mind that it will be waterproof even without a seat cover. The foam is designed to be glued to polypropylene as that is what many kayaks are made of. This is relevant because I have a seat pan made of the same plastic and this means I can use the same techniques everyone in the kayak world have already refined. The foam is also ultra dense. This means it is able to retain its shape after being carved so that comfort can be had through sculpting it to match my ass rather than simply assembling an overstuffed chair and dreaming of success. I purchased two slabs three inches thick by 12 inches wide and 36 inches long from NRS:

    https://www.nrs.com/product/2076/minicell-foam

    Glue is done by Dap Weldwood contact cement. Everyone says stick to the original formula/red label. This stuff has some incredibally dire warnings on the can about fumes blowing up your house. This made for an outdoor project.

    Step 2 was heating the center of the seat pan at the bend with a mapp gas torch and forcing an additional 5 degrees into the bend. With the bend corrected, the front seat mount catches again but not too well. The screw will be modified later to correct this problem. I marked it with a paint pen for orientation.

    ABC74B90-60D8-4FB2-9295-572A50F6C57C.jpeg

    My goal is to make a seat much more touring like and much less dirt bike. I am not a fan of butt-floss seats and want something closer to a tractor seat. My favorite OEM seat is the one that came on my first moto, a 1982 Honda 450 Nighthawk. I want to be positioned close to the tank but do not want the seat shoving my nuts into it. I also want a substantial back that my butt can push against for support and to help push the bike around. Finally, I want a passenger seat that keeps the passenger from pushing my nuts into the tank... I really don't like the nuts-in-the-tank thing, can you tell? To make all of that happen, I need wider and taller foam than OEM. I kept the full 12” width of the slab, it can be strategically trimmed later but I need some parts quite wide.

    I cut one slab at the angle of the seat then I marked and carved the bottom to match the old foam. Lots of test fits and trim sessions. It is way easier to cut more off than add some back so don’t botch the job. Carving was done with a utility blade and a kitchen knife. A belt sander was used where it could fit and a palm sander took down some high spots too.

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    The same was repeated for the front foam piece.

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  8. Z50R

    Z50R Not lost yet

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    Two layers of contact cement were added to the foam and one to the seat pan. Squish-em together after they tack up and I have a seat that a lego man might enjoy.

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    Remember how I don’t want gravity pushing me into the tank? I tipped the moto upright and measured the difference between what I want and what I have with a level and a protractor.

    DE330FE8-3A27-498E-91C2-4F00E5B1A7B4.jpeg

    More foam was cut, more contact cement, and now I have to wait for foam glue to dry. A good place to stop for the day.

    4F032761-A259-4513-97BC-32C96C3143AC.jpeg
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  9. Z50R

    Z50R Not lost yet

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    Let the foam fly.

    I started by forming the front of the seat using a bench mounted belt sander. This part of the seat is entirely convex and needs to be as low profile as reasonably possible. Where the front of the seat interacts with the pilot’s butt pad also dictates the maximum height of the seat.

    C1946FC9-4F98-46F0-88C1-F7AD5E8556FC.jpeg

    I found the belt sander adiquet for the bulk of the work but a bit confining and difficult to work around the complex curves. A co-worker suggested a flap disk on an angle grinder. I used a well worn one to make the cuts as unagressive as possible and tested in a spot that would be difficult without the ability to attack concave curves.

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    Success! I continue from where I left off on the front.

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    I took several pauses to test the fit by sitting it on the bike then sitting on it. After getting the front pretty much where I wanted it, I cut the passenger seat in.

    465A6D76-226A-49CC-9CB8-C54ED16430B8.jpeg

    I need to make the front tank attachment point still but I intend to ride the seat as such a few times to decide if I need to carve any small nuissance spots. The kayak foam is by far the best product I have tried for this application and the contact cement worked stupendously well. It cuts easly and precisely, holds its shape when sat on without being hard, and is quite light weight.
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  10. tntmo

    tntmo Oops, I did it again.

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    Is this a 70’s chopper style king/queen seat?
  11. Smokesletsgo

    Smokesletsgo n00b

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    All it needs now is a radio and an intercom system
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  12. Z50R

    Z50R Not lost yet

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    Yes
    And a sissy bar, highway pegs, and a rediculous windshield.

    The rear seat is jacked up so high to allow it to extend rearward beyond the seat pan. It is not done and will be reduced in ridiculousness later.
  13. tntmo

    tntmo Oops, I did it again.

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    Darn, I was hoping for a tall sissy bar with a Maltese cross and some chrome fishtail pipes.
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  14. Z50R

    Z50R Not lost yet

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    Ok so I lied... my wife sat on the queen seat and loves it. The daughter wants her name on it. I did some more shaping and then finished up the front attachment point. A small piece of 1/8” plate welded to the screw alligned with the orientation mark. Ground to a wedge with the lip turned up a bit.

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    Test fit then coated in clear nailpolish to forstall rust.

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    A drop of blue loctite and we are back in business. I took a test ride and need to do a bit more work around the sit bone pressure points.
    3C5F4539-055C-498E-9ED3-FB54D1959295.jpeg
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  15. Z50R

    Z50R Not lost yet

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    After finishing the hold down point for the front of the seat I took the bike out for a half hour ride with a passenger. The seat was a god send as far as having a space for me and a separate space for the passenger therefore no one feels crowded out of their spot and everyone stays comfy. On that ride I got the idea that no matter how well sculpted the seat is, it is hard and needs a softer upper layer.

    On Friday I took the bike for a commute run so I got two one hour rides in. On the morning ride I noted two other problems. First, the front did not flow well into the tank, it sat proud kind of like the difference between a drop of water on a flat surface as opposed to a drop of alcohol. Because of this, there were two pressure points on the inside of each thigh. Second, I was trying too hard for a bowl like ass pan so there were two pressure points where my butt transitioned into my thigh. On the ride home both of the above were confirmed and I noted that a bit more cut out where my legs go down at a stop light could be helpful. Standing on the pegs was not an issue so success there.

    I bought a memory foam seat cover for a bicycle to address the hardness in the spots where my sit bones hit. I carved away where all the pressure points were then test fit the seat cover after removing everything not necessary for padding.

    7E2CF2BA-ADFA-4E5E-A5E1-85E64C293FA1.jpeg

    I cut a recess..

    C3D81248-05E1-4671-9892-7169E6E97F6C.jpeg

    And glued it in place. My wife walked by at this point and was jealous. Another trip to the store to buy another seat cover confirmed that this thing is really comfortable!

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    Repeat the process and the passenger has ass padding too.

    30A0BE40-73D6-4B69-AF4D-3F9D7E5D164B.jpeg

    I’ll take it for another commute run to confirm but I think it is time to start sewing.
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  16. CRW

    CRW I dont want a pickle

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    Looks great! I always have wanted to build my own seat. You could wrap most of the seat with a thin memory foam to add a bit of comfort and smooth everything out.
  17. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

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    Incorporating the gel bicycle saddle covers is genius!
  18. Z50R

    Z50R Not lost yet

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    I went to cut the marine grade vinyl that I purchased for this project last year but couldn’t bring my self to go with vinyl. About 12 years ago I made a leather seat cover, vinyl feels so cheap in comparison. About 10 years ago I bought a hyde of black suede and attempted a project that didn’t work out. I dug up the leftovers and remnants of that project and decided there were enough large pieces left to do a suede cover. This is not ideal as suede absorbs/retains water but it might work for a while and I can re-evaluate at the end of the year or sooner as necessary. I didn’t get to sewing yet but I did get the suede cut.

    First I marked the seat where I want seams to sit being careful to keep the seams where people are not.

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    Then it is a relatively simple task of cutting leather to fit the pieces. I am planning a stitch job similar to a baseball for most of the seams. I do not want the leather sitting proud of the surface. The seam behind the pilot’s ass is going to be a traditional folded seam as I intend to drill holes on either end of the foam recess to pull the leather down through the seat and want this seam reinforced to take the load. What all of this means is that no overlap allowances were needed except this seam and where the suede is stapled to the pan.

    The suede was marked on the center line to make each side a mirror of the other.

    C6E476EF-6A05-43E5-AFC3-BC268B5F9267.jpeg
  19. more koolaid

    more koolaid Been here awhile

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    :rayof:katYou're ready for Iron Butt challenge :thumb
  20. Z50R

    Z50R Not lost yet

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    Did you pay attention in home economics? Did they even teach that when you went through? I learned to sew watching my mother cross stitch then trying to make stuffed snimals when I was in fourth grade. Sewing is an odd tallant for a guy to have and, at times, a troubling skill to have to explain. I have reconciled by telling myself that making things requires skills and there is no reason to limit my ability to make things because it is masculine to work in metal but feminine to work with fabrics. I never wanted and still do not want to ask others to help me on my projects. I’d rather spend an extra year learning a skill or saving for a tool than request favors to finish a job. I also think it is more pathetic when a man plays stupid, pretends sewing is beneath him, or that it is some esoteric art that he cannot learn because he has a penis rather than do the sewing that needs to be done.

    I have sewn a hand full of projects made in leather. Most of what applies to fabric also applies in leather. The difference is that unless you have a serious industrial machine, the holes where thread passes through must be pre-punched. I do not have any sewing machine, let alone a serious one. There are two ways to punch holes by hand that I know of: one uses a plier like tool that hurts the 250th time you squeeze it and the other is to use a hollow punch and a hammer.

    Leather is expensive. I think I paid around $100 for a side of suede and around $150 for top grain, this was about 10 years ago. This works out to be about 10 times as expensive as vinyl. Mistakes suck in leather.

    When you are sewing, your aim is consistancy. You want your stitches to be the same length and the same distance from the edge of the fabric and if possible, the same number on each side if the center line. A machine does a good job of spacing individual stitches but hand punching allows even more control if you take the time. For this project I counted holes to ensure symetry and used a ruler to lay out spacing. There really aren’t that many nor too long a seam so it isn’t too much of a burden to go through the motions.

    871B3229-F019-4FB9-BF95-81113B44966E.jpeg

    I use the smallest punch Tandy Leather sold, it takes about a 1/16” hole from the suede. I chose a 1/8” spacing. I punch on the side grain of a hardwood block held in the bench vise. When the surface is too shitted up to get accurate punches, I take the top layer off with a plane and keep on punching. This also makes a handy place to jot down hole counts to keep things symetric.

    Holes can be punched through multiple layers and I have done finishing stitches through up to 8 layers at a whack but the project will come out better if each hole is carefully punched in each layer one at a time. This is a simple project and well worth the effort to do it right.

    E2FA957E-4421-4B23-B92B-88A5738C2131.jpeg

    This is about 160 holes and time to plane the wood.

    I started with the seam behind the driver’s bum. This is the only traditional seam on this seat cover as it does not need to sit flat. It also needs to be the strongest as it will have two tabs where I will pull strings down through the seat foam to hold the cover against the double concave cut in the seat. I cut the tabs out of some scraps of leather:

    EA770A62-B3A6-4123-AE54-2A95FF5006BA.jpeg

    Sewing started at one end of the seam with needles on both ends of a waxed nylon thread. Waxed cotton works better but I don’t like waxing the thread myself and I cannot find waxed cotton in reasonable quantities. The wax helps make the seams waterproof and strengthens the seam by making it harder to over tension the thread; the wax makes tensioning the thread more gradual than an unwaxed string.

    Two needles are used because each stitch must be pulled tight, then the seam straightened, then the holes realigned before proceeding to the next stitch. If one were to use one needle and sew one half of the stitches to one end then return for the other half, the leather will not sit flat.

    36140C20-6978-47B0-9E2B-5622F1B2A298.jpeg

    It is hard to see but the lower needle has already been sent through the set of holes that the upper one is being passed through.
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