CX500 Scrambler/Desert Sled Build

Discussion in 'Some Assembly Required' started by gearheadE30, Jun 27, 2019.

  1. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    I have always been intrigued by the CX500. Unusual engine layout, some engineering quirks that were a bit ahead of its time, and what seems like a pretty good supply of parts and knowledge available online. When some friends got together and started planning a "cheap bike challenge", I knew I had my excuse to buy another old bike.

    Initial build parameters are - total budget $1000 not including tires, must be appropriately titled and registered for the street, and must be off road capable due to the route the ride would take. Once this challenge is over, I do plan to continue the build and actually make the bike "right", but for now cheap fabrication and used parts are the name of the game.

    After some searching, I settled on a 1980 CX500 Deluxe that was about an hour and a half away from me. The seller had bought it to turn into a "cafe racer" in the cheapest sense of the word, but had lost motivation and interest. Original purchase price was supposed to be $725, and I was all set to pay that...until the title came out. Uh oh. Don't you know you can't use white out on a title!? The owner had never transferred the title to his name when he bought the bike 5 years back, but he had filled it in. Unfortunately, he had now turned his titled bike into a parts bike in my eyes, since there isn't enough time in the schedule to deal with a court ordered title process, nor are all the court fees worth it for a cheap bike. However, the bike had a lot of positives, so I still brought it home, for $400.

    [​IMG]

    I got the bike home, and quickly got it running - the carbs had been fiddled with at some point and were all kinds of out of adjustment. They still aren't synced at all, but at least I know the engine runs now. After working on the bike, I discovered Progressive 412 shocks, an Ingnitech ignition, and an electric fan conversion, and the seller professed to having replaced the timing chain and guides. Apparently no leaks from the water pump, either. I have since discovered it also seems to have Progressive fork springs, along with a missing rear fender, big old cheap non-DOT headlight, chintzy plastic mini blinkers, and clubman bars. All the usual cafe-racer 101 stuff, fortunately without any sawzall or angle grinder action.

    Now I needed a title. Conveniently, there was a second CX500D on craigslist, also a bit over an hour from home. This one had a title, but had failed the engine due to a water pump seal failure and subsequent engine overheat. Both big end bearings spun, and both pistons were galled beyond use....but the rest of the bike was fine. And the price was right - another $400. Check out that sweet stereo on the bars!

    [​IMG]

    By the time I got that bike home, CX #1 was basically a bare frame. It has since been completely disassembled, and many of the parts have been listed for sale on Ebay to help offset the build budget. If you need something, let me know - I might have it.

    [​IMG]

    The plan now is to make one running bike out of the two parts bikes, using all the stock CX hardware. I can then get a few miles on the engine before working out what to do with wiring, the Ingitech unit, etc. For now I'm going to put it together with the CDI and make sure everything actually works. From there, the plan depends some on what parts I can sell off, and how much budget I can recoup.

    Already in the plan:
    -GL1100 17" rear wheel swap. I'm about halfway through this already.
    -Added rear suspension travel. I found some used Fox IFP shocks, which are supposed to show up today. This should roughly double my rear wheel travel, though I have some careful measuring to do on the U joint angles. As far as I can tell, no one has come up with a CV joint conversion yet. If the shocks are too long, they are rebuildable. I will pull them apart and internally limit their extended length.
    -Skid plate. Gotta get the engine in before I do this.
    -Fix the electric fan install - bigger fan, better switch mounting.
    -Make the stock forks work...acceptably. Thicker fork oil, preload, etc. With only 5" of travel and basic damping rods, they need all the help they can get. If I have time, I may modify the orifices to give it more bottoming resistance but keeping it plush in the center of the stroke. I have other fork plans once the budget part of the build is over.
    -Lower, dirt bend bars
    -Foot pegs without the silly rubber covers. I may have some extras from a KTM I can use.
    -Custom exhaust. the stock setup is heavy and bulky. I have an order of 1.5" and 1.75" stainless mandrel bends in the mail, along with a 2 to 1 Y pipe. I also found a vintage aluminum supertrapp muffler to cap it all off.

    So that's the basic plan. Remove a bunch of weight from a CX and make it somewhat dirt-worthy, and just generally have fun with it.
    #1
  2. MacNoob

    MacNoob piney fresh

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    Came here fearing a hack after seeing the title, staying because this looks like a cool project.
    #2
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  3. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    There will be some things done on the cheap because of the budget, but I am trying to avoid being too hacky. Build progress is a bit further along than what I've posted online, so I'll just leave this here so you can see where this is going. Yes, that's how much rear suspension travel it has now - the rear tire is about a half inch from the fender at full compression. I know the fender looks like it's too far back, but it is just because of the swing arm and picture angle. Wheel actually ends up dead center in the fender when compressed.

    [​IMG]
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  4. VX Rider

    VX Rider Long timer

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    Did you have that Ichiban Moto guy work on your gas tank?
    #4
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  5. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    I'm not sure who that is? I have 3 tanks - the two that were installed on the bikes and the one red one with the horrible paint. Selling the nice ones for budget reasons and keeping the nasty one, which will eventually be either painted or wrapped. It's not original paint and has some dents and dings, which is good because it will probably get more dents in it riding off road.

    As some of you may know, CX500s came with either a 16" rear or an 18" rear. I built my own with a Goldwing rim and spokes and CX500 hub. If someone else is looking to do this, you need a 1980-1981ish GL1100 rear reverse comstar. The hubs and drive flanges are different, but another option is apparently to swap the whole Goldwing swing arm. I guess there are challenges with this, and it gets you an even shorter final drive on the already short-ratio CX500. The wheels are not supposed to be disassembled, but it can be done. You will need to source M7 hardware to replace the 7mm rivets in the rim, but the center bolts on the back wheel are just M8 bolts, 65ish mm long.

    I thought about the 18 inch rear, but from a purely aesthetic perspective, I like a bit more rubber on the back and I like the stagger in the wheel sizes. the front is a 19. From a functional perspective, I also want all the suspension and traction help I can get from that sidewall. My only disappointment now is that I can't run a rim lock with a comstar.

    A picture of the wheel collection that came with these bikes:
    [​IMG]
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  6. VX Rider

    VX Rider Long timer

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    #6
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  7. bkowal

    bkowal Been here awhile

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    I had a CX650E, put on over 50,000kms on it, great bike. However, while you have the engine out, replace the stator. It will fail. They get no oil up there for cooling and they cook. If it isn't cooked already, it will be. I replaced mine twice. Its not a simple job on these engines, the big back engine cover has to come off. A good idea to replace the stock regulator with a more modern one while you are at it. Both parts are readily available.
    #7
  8. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    lol...watched a couple and if you really had no idea what you were doing....you might think the guy was serious haha. Love the subtle way of making fun of the fashion of the moment.

    Yeah, I know the stators are iffy... I don't think the one I am using is original and I'm going to run it because of the budget build part of this whole deal, and because I have a spare, but assuming I like the bike enough to keep it, that would probably be in the cards. If I can find a cheap Shindengen 847 I will put that on to protect the stator, but that may also be a post-Challenge modification. I'm definitely a fan of peace of mind modifications like that though. Thanks for the tips!


    Some of this happened a while ago, so will point out the rear shocks are Fox IFP shocks from the front of a snowmobile. They were the right combination of cheap, rebuildable, and revalvable if the damping ends up being too far off. They are about 15.5" center to center, which is too long for the stock mounts. With the stock frame, you are looking at about 14.5" max length before the driveshaft angle becomes an issue (single cardan shaft), and travel is limited by the very vertical shock orientation. I've got around 6 inches of travel in the rear, up from 3.3 inches stock, largely due to laying the shocks down. I strongly dislike the aesthetics of the rear frame section on these anyway, so the long shocks were a good opportunity to adjust. Swing arm mounts are stock, and the frame mounts are Chevy Caprice Classic brake caliper guide pins I had lying around which are hardened, the perfect length, and the perfect diameter. I drilled a hole all the way through the frame tube and welded both the inner and outer interface so it is supported by the frame tube and not just my welds.

    [​IMG]

    Front forks from one of the bikes appear to already have Progressive springs, but they are still too soft. The soft upper section of the spring will be removed and replaced with a spacer, and will add an additional ~1" of preload on top of that. Based on my math, that still leaves me with an additional 1" or so of margin before hitting coil bind, but I'm going to go through my math again before cutting just to be sure. Yeah, I know cutting springs isn't ideal and that end won't be perfectly square and such, but it works and isn't really a big deal as long as the non-squared end is at the top of the fork where it is stationary. 20 weight fork oil will be going in as well. The goal is for it to be very stiff - bottoming the suspension leads to bent rims, and that's no bueno. Precise handling is too much to ask for out of 33mm forks, but that's what I'm stuck with for the moment. Eventually, DRZ400 RSD forks are the plan, but are not in the budget unless I can sell a bunch of stuff quickly.

    Modified fork springs. The spacer is a cut down section of 7/8" aluminum handlebar that I had bent up off road some time ago.

    [​IMG]
    #8
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  9. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    Made an electric fan bracket, using a fan from a Ninja ZX636 and shortening it to fit. One of my CXs actually came with an electric fan already, but it was zip tied through the radiator core which is a big no-no. Stock CX500s came with an engine driven fan coming off of one end of the camshaft (the other end of the cam drives the water pump). My cam was already cut, but I'm fairly sure that this fan would clear it mounted this way.

    [​IMG]

    I also finally got my 17" rear wheel built. I can't believe that the thing was basically perfectly true with no fiddling. Mounting the tire was more of a pain than building the wheel. Hub bolts are M8 by 65 or 70mm long flange head cap screws, and the hub hardware is M7 stuff that I had from another project. Red loctite on everything, and I will be keeping a close eye on it as I ride.

    [​IMG]

    I also checked fender clearance, and it looks like all the planning paid off! Full compression gives me around an inch or a hair more between the tire and the fender, which is plenty to allow for bump stop compression on big hits. Now I can work on fender mounting tabs and such. Total wheel travel with these shocks is a hair over 6" not including bump stop compression.

    [​IMG]
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  10. rally roo

    rally roo Total poser

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    Your pictures aren't showing up; could be a google photos permissions thing.
    #10
  11. JimVonBaden

    JimVonBaden "Cool" Aid! Supporter

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    I can see them.
    #11
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  12. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    Hmm, thanks for letting me know. I updated the share info and re-linked the pictures; hopefully that worked. EDIT - well hopefully I didn't break them when I did that. seems like maybe they were fine. :doh
    #12
  13. rally roo

    rally roo Total poser

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    Fixed now. Looks awesome!
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  14. Salsa

    Salsa Long timer

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    It's nice to see a well used garage, not a hospital site!!!!!!!!!!!!!!!

    Don
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  15. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    No great pictures to report; spent time over the weekend finessing the rear shock fitment and making sure they had enough room to pivot. Added threads to the upper mounts to retain them properly, made a new bushing sleeve for the left lower mount, that sort of thing. Shocks are now done, and I've finished the filler and gusset plates and welding on the rear frame. I am leaving the stubs around the swing arm for the moment because I don't know how I am doing my muffler mount yet.

    Rear fender is cut, trimmed, and mounted to the bike now. I also added an extension made from the stock inner fender to keep mud from building up in the frame gap. The last real frame fabrication will be building mounts for all the electronic bits and making a mount for the seat. Otherwise it's just making little tabs and gussets and such. I bought a GL500 seat pan for cheap on Ebay and will see if I can make something work with that.

    Seems like I should have gotten more done over the weekend, but it is amazing how long getting all the little pieces of metal cut down and welded in takes! No pics with the fender installed yet.

    [​IMG]
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  16. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    A rather iffy picture of the rear fender all mounted up and ready to go. Yep, it's up there pretty high and looks like it hangs off the back, but at full compression it is almost perfectly aligned with the wheel and clears the tire by about a half inch at the closest point. Yes, that's really how much suspension travel it has in the back. I ride in the rain (and will be riding in the dirt and mud as well) and hate having my back constantly sprayed with water and mud, so aesthetics come second on this one. The fender is surprisingly sturdy; I was expecting to have to build much more substantial mounts than the hidden ones I was able to get away with.

    [​IMG]
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  17. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    I'm not great at taking lots of pictures, but there has been progress. Bung has been welded into the water transfer tube for the fan switch, side stand has had all the goofy tabs cut off and the hinge modified to tuck it up closer to the swing arm, KLR650 footpegs and clevises have been welded to the stock peg mount plates, stock bent shifter was cut up and modified with a folding tip made out of a seat latch, and I've finished fabricating a seat pan out of a GL500 front section. I also picked up a delightfully beefy set of the best conventional forks made for off road use: 1997 RM250 49mm twin chamber Showas. Got them at a fire sale price along with a pile of RM parts I can try to sell to offset my budget, though the forks may prove to be a post-Challenge addition.

    [​IMG]
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  18. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    Got the muffler location worked out so figured it was time for a picture or two with it mocked up. The pipe will be a bit closer to my heel than I would like, but the body of the muffler is out of the way. Tried to match the angle to the rear frame tubes for aesthetics. Pipe routing is limited by the rear brake linkage; it's as far out of the way as I can realistically make it. With the muffler in place, I now have both ends of the system fixed and can work on the piping in between.

    [​IMG]
    [​IMG]
    #18
  19. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    The bike is built and done....I need to go back through and finish pulling this thread together, but figured I would post an introduction to the trip we are about to head out on this Thursday. Should be entertaining. :beer

    #19
  20. JagLite

    JagLite Long timer Supporter

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    Fun, fun, fun :ricky
    #20