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Discussion Starter #1 (Edited)
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 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.



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. 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.
 

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Discussion Starter #2 (Edited)
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!



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.



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. It's a little different than my normal ride, but so far it's a lot of fun and a great chance to play with some fabrication and design ideas I've been kicking around. While I'm not going to go this crazy with it, this is what I do with my other big bike.

 

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Discussion Starter #4
Thanks for the heads up. I changed a few settings that should fix it; I've run into this hosting with google photos before if I forget to make the album public, though I also haven't been on a vbulletin forum in a while and it's slightly different. I can upload directly when I'm back on my other computer if they still don't work.
 

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They seem to be working OK for now. But since the PhotoBucket debacle we always recommend hosting pics directly on the forum. Hosting them on the forum also guarantees that they will still be there in the future if you decide to move on and remove them from wherever you had them hosted because you are no longer interested in these bikes (there are a lot of threads that people put time & effort into that are useless these days because of that).
 

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Looks like a fun project.

Already in the plan:
-GL1100 17" rear wheel swap. I'm about halfway through this already.
The Goldwing has a disc rear brake. Are you planning on that conversion, as well? If not, you could mate the rim and Comstar spokes from a GW to your stock hub. Or mount an 18" Comstar wheel from a '78 CX, though it would be a step down in width.

As far as I can tell, no one has come up with a CV joint conversion yet.
I've been toying with that idea for a number of years. There's a member in Italy who installed a CV joint, but hasn't shared too many details. To my understanding, it is unbooted inside the stock swing arm boot, which gives me concerns about long-term lubrication.


R
 

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Discussion Starter #8
Looks like a fun project.
The Goldwing has a disc rear brake. Are you planning on that conversion, as well? If not, you could mate the rim and Comstar spokes from a GW to your stock hub. Or mount an 18" Comstar wheel from a '78 CX, though it would be a step down in width.

I've been toying with that idea for a number of years. There's a member in Italy who installed a CV joint, but hasn't shared too many details. To my understanding, it is unbooted inside the stock swing arm boot, which gives me concerns about long-term lubrication.
R
Goldwing rim and spokes, CX500 hub. Looks like it will work based on my measurements and disassembled wheels so far, and I conveniently have some high quality 7mm hardware lying around. I know and understand the safety aspects of this, before anyone jumps on me for disassembling a comstar and rebuilding it. That part of the project is already decided, and trust me, I will be assembling and monitoring it with extreme care.

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. 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. Tire plans are probably Kenda K760s front and rear. Not my favorite dirt tire, but functional enough for this boondoggle and the price is right.

An un-booted CV is asking for failure. They require lubrication for the balls, where a U joint uses sealed roller packs. A CV is a long-term consideration at this point, but there are likely some in the ATV world that would fit the bill. I just don't know how they would survive any real shock loading and abuse, i.e. off road hillclimbs putting down a lot of power, or shock loading from getting the front wheel up over stuff. U joints definitely have the size advantage.
 

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Discussion Starter #9
They seem to be working OK for now. But since the PhotoBucket debacle we always recommend hosting pics directly on the forum. Hosting them on the forum also guarantees that they will still be there in the future if you decide to move on and remove them from wherever you had them hosted because you are no longer interested in these bikes (there are a lot of threads that people put time & effort into that are useless these days because of that).
Good call. Hopefully some of what I end up doing will be useful, haha. I will host them through the site when I get a chance.

Speaking of hosting things, I forgot to post a picture of my Comstar collection. This is getting a little out of hand.

DSC_0865.JPG
 

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You haven't seen my wheel rack.


R
 

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Discussion Starter #12
Looks almost as bad as mine :rolleyes:

You might enjoy this:
Yeah, that stuff is fascinating; the design ethos does make a lot of sense considering the maintenance required by spoked wheels. The benefits from a manufacturing perspective are huge, too. I forgot the first-generation Comstars were steel spokes. The reverse Comstars are heavy enough as it is; I can't imagine what those must weigh. Now that I've got one apart, it actually feels like most of the weight is in the rim itself. Hopefully that means it's actually a fairly strong rim and not just a heavy design. I'm going to keep at least one extra front rim lying around just in case I manage to bend one... I may run tubes in them just to be safe.

You haven't seen my wheel rack.

R
It is kind of amazing how parts pile up.


Stainless tubing showed up yesterday, and as soon as I get the collector in, I can start working on the exhaust routing. I will probably run both exhaust pipes over to the left side of the engine and then under the pegs and up the back. Left side seems the best at the moment because the curvature of the crossover under the radiator will make more room for the water out connection on the rad, and it keeps the exhaust heat away from the driveshaft boot where it runs past the swingarm pivot and may give me more routing options.

New (to me) Fox rear shocks also showed up. They are....somewhat longer than expected. About 15.5" center to center. Pics to come. I strongly dislike the rear frame section on these bikes, so I guess it is an excuse to move some things around so my driveshaft angle isn't crazy. I may need to add some bump stops or something to keep the tire out of the rear fender. We'll see.

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.
 

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I'm sure you could. At least you rotate inventory. I just accumulate projects I might never get to.


R
 

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Discussion Starter #16
Some discussion going on for exhaust fabrication and routing here: https://cx500forum.com/forum/technical-help-forum/108463-cx500-firing-interval-crank-rotation.html

Not sure exactly what I will do with it yet. But my goals are probably different than 99% of the builds here, since ground clearance and packaging are priority number 1, followed by tunability and finally outright performance.

Remember that this build is really for a cheap bike challenge with a $1000 budget, so it may or may not be up to the standards of some on here. But it is definitely an interesting exercise in what can be done on a budget.

Frame modification got a little out of hand when I started sorting out suspension travel and driveshaft angle. I'm in a good place now, but the rear tire uses almost all of the space between it and the frame hoop at full compression + 50% bump stop compression. Stiffness and damping actually feel fantastic though. This went through a lot of iterations, but in the spirit of cheap bike builds, I cut the ungainly looking rear tubes off the frame, flipped them around, and cut them down to size to meet the rear upper shock mounts. The upper shock mounts are 1989 Chevy Caprice brake caliper slide pins. I drilled a hole through the upper frame tubes and welded both the inner and outer so the tube is actually supporting it rather than just a weld. Gusset plates will be added as well for good measure. The frame hoop itself is actually the center stand with the feet and the pivot cut off. I think it came out pretty well. I have an old MX-style rear fender that will be added, and I will make a custom seat with an electronics box under it to keep everything out of harm's way. Still have to clean up the area around the swing arm support and box it in.

DSC_0965.JPG

Forks are also done. 20wt fork oil, cut springs, and spacers + 1" of preload got the stiffness roughly balanced front to rear. I know kinematic oil viscosity is not the same across different brands of fork oil, and the one I had on the shelf is pretty thick...I may end up draining and going lighter. The math leaves me with another inch and a half or so of fork spring travel before coil bind. I can always cut down the preload spacer as well. Fun fact, the spacers are the cut off ends of a bent set of aluminum bars.

DSC_0945.JPG

In other news, the tires showed up (not included in the total $1000 build budget because it's a safety thing and good tires aren't cheap). I will assemble my 17" wheel tomorrow with a D606 tire, and have a Motoz Tractionator HT to go on the front. Should still be able to attack twisty dry pavement while offering good performance off road as well.
 

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Do you have experience with the D606? How is the on-pavement performance? I've read that it's noisy.


R
 

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Discussion Starter #18 (Edited)
Do you have experience with the D606? How is the on-pavement performance? I've read that it's noisy.


R
I do have experience with it, but I might be the wrong person to ask. My normal dual sport tires on the 950 are a pirelli scorpion rally front and motoz tractionator HT rear. There aren't many tires louder than the Tractionator, but I have gotten used to it because it's cheap at $150, performs really well in most situations, and lasts me at least 1000 miles. I have yet to find another tire that can do that, and I've basically tried all of them that fit a 18x3.5 rear rim. The D606 is not loud to my ears and performs pretty well. It is a much more modern and versatile tire than its main competition, the Pirelli MT21. That being said, I've also only had it on a KTM 450 before. I'll let you know how it does on the CX once I get her rolling.

EDIT: for anyone curious, the rear is a 130/90-17 and it clears the swing arm and final drive with no problem.

More progress today. 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. My cam was already cut, but I'm fairly sure that this fan would clear it mounted this way.
DSC_1013.JPG

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.
DSC_1014.JPG

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.
DSC_1020.JPG
 

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Discussion Starter #19
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.

65301981_10162262283745151_4723811577118064640_n.jpg
 

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Discussion Starter #20
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.

DSC_1024.JPG
 
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