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Discussion Starter · #1 ·
Hey everyone, new member here. I'm a motorcycle road racer and have built quite a few race bikes but have been interested in building an older cafe racer to rip around on, in town and on the twisties nearby. Enter a poorly loved 1980 CX500 custom that had been sitting outside for over 5 years with 22k miles on it. To be honest not my first choice for a donor (was actually looking for a big bore CB) but I do like what some builders have done with the bike. I figured what the hell and took it home for $460.

Got it running today after a decent amount of work. I couldn't check compression because I don't have an adapter that narrow but it seemed to run marginally ok on the bench. Rear cover seal is leaking pretty bad, I blocked off (what I think was) the breather tube and oil started shooting out of the seal. Carbs are leaking, I did clean them but it appears the float valves are not sealing well, sometimes they leak out the float bowl vent sometimes not. Tires are shot, forks feel like they don't have oil, the rear axle hub is leaking, front shaft boot looks to leak also. Needs battery (I was running off of car battery), and the tank cleaned very well before the thing can get down the driveway. I was running bike using my son's TTR110 tank haha, the stock tank restoration would be another project in itself.

So I could probably buy a battery and clean the tank, then sell the bike with shot tires for a few hundred profit, but the carbs leak and I'd need to do the float valves and the rear seal is leaking pretty good, so I feel like I might be committed already. If I do a cafe build I will remove the engine for paint and at a minimum replace the rear seal. But if I already have it out I might as well rebuild the motor. Looked up parts and don't know where to even get piston rings, my OEM suppliers don't seem to carry a lot of these old parts. I'd have to rebuild forks of course, aftermarket shocks, throttle and clutch cables, head bearings, carb boots are torn, would end up probably doing the Murray's carbs, tires, lithium battery and new R&R to protect it, and a whole bunch of other parts not including welding a new subframe and figuring out a seat and all that. I don't like the custom's tank so I would be looking at buying a new tank too (probably some cheap universal tank).

I guess the question is whether the bike is worth it, and how far the build would go if I went ahead with it. Like I said it's not my favorite platform but do think I could make it into something cool. Are there any things that really MUST be done? I have been reading on here and looks like a lot of people change the ignition system. I have read about some other things too and wonder if I like the bike enough to go ahead with the build, because if I do I will basically end up going all out. That's how I build my race bikes, that's the only way I know how to do it. Or can I find some middle ground, like replace the bad seal and do the triple bypass but don't rebuild the motor, leave the ignition, and get by with what looks to be a ridiculously underpowered front brake system for a heavy bike? Thinking out loud here, I know I am the only one who can answer these questions of how much work/money I'm willing to put into a bike that in stock form is not interesting to me at all. But I value some other opinions if you have read this far! What would you do?

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That's easy.
If you are ready to dive in and go over the whole thing for the satisfaction of it, keep it, if not, get rid of it.
First thing first, though, is make sure the engine is okay.
Study the resources on this site for anything you need to know, and ask questions along the way as you get into it.
The people here like to help.
 

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If you go to the General Discussion section of this forum and look at the Quick Reference post you'll get a better understanding of what to do first. Lot's of very helpful information there. Welcome.
 

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'84 CX650E that is evolving into a GL500
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Welcome to the forum. Please add your location and your bike's model and model year to your profile so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your CX is about 4 decades old and the Previous Owners obviously haven't done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I'm sure you already know to look on all rubber parts with suspicion because rubber does not age gracefully. The tires are over 5 years old and you know they need replacing. The original rubber brake line really should have been replaced every 2 or 3 fluid changes (= 5 or 6 years) so you'll want to change to a stainless braided one (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).

Your experience building race bikes will help but the best advice anyone can give you about customizing any vehicle for on road use is to get it safe & reliable in more or less original condition and use it for a while so it can tell you what changes it needs to make it do what you want/need better before you start making any changes. That approach almost always results in something you actually want to keep and use but making changes based on style or on what someone else (who may or may not really understand how the changes affect the way it works) has done often results in a piece of expensive yard art that you can't stand sitting on for more than a few minutes and might even be dangerous.
 

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Kudos to you for choosing a "hurting" CX to modify, even if the decision was purely economical. To chop up a pristine example is painful for some of us to watch, even though it is their bike, not ours. Also, IMO, starting from a rough bike the finished machine is much more personal and the journey more satisfying. (y)
 

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+1 on "richinct" comment. Here is a good resource to look at also.
The Honda CX and GL 500 and 650 family of motorcycles (motofaction.org)

Verify the engine is solid. From what i understand overbore pistons/rings are not available and bottom end parts are very hard to source, most other things are available, rebuildable or upgradable.

BTW, the 500 engine is no race engine and its easier to drop a 650 in it than trying to wring out impressive HP.
 

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If you've built race bikes before, dropping the engine to replace the rear engine gasket isn't that hard and should be done if you're going to make it roadworthy regardless of your final intention (keep or sell). I wouldn't sell a bike with that leaking unless your plan is to do zero work on the bike and sell as a project to someone with wrenching skills.

IMO, the stock 500 engine is a good size to tool around town or back country roads. Certainly not the fastest thing, but plenty of fun if you're riding in the 5k-7k range. You can swap bars to get rid of the stock position.
 

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+1 on "richinct" comment. Here is a good resource to look at also.
The Honda CX and GL 500 and 650 family of motorcycles (motofaction.org)

Verify the engine is solid. From what i understand overbore pistons/rings are not available and bottom end parts are very hard to source, most other things are available, rebuildable or upgradable.

BTW, the 500 engine is no race engine and its easier to drop a 650 in it than trying to wring out impressive HP.
I would line the thingy up against any stock 650. Mind you ... the same mods could be made to any 650.

Raising HP aside - put it on a diet.
 

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Most people who do the cafe and who go all out replace the whole front forks with something like a CBR 600 or any number of front forks. So rebuilding the front forks would be crossed off the list.

I would recommend or suggest redoing the carbs and seeing how well you can get the engine itself running then take it out on the road and see how you like the sound and the idea of the sideways v-twin. Then go from there.
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I would line the thingy up against any stock 650. Mind you ... the same mods could be made to any 650.
I'll stick to what i know, was just parroting what I've heard on this site before... :whistle:
 
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Discussion Starter · #12 ·
Thanks everyone for your input! I have read the articles you've sent and done some other reading as well. I am busy with the start of the race season but should be able to at least check compression early next week. If we are looking alright on that I can assume it not running great is carb related as I suspect anyway (both leak intermittently out of the drain hoses so I'm pretty sure the float valves are not sealing well, also seems to burn pretty rich). So we'll see what we see but I am leaning towards keeping the bike and making it work!

If I test out the electrical system and all seems to be working properly, is there any reason a lithium ion battery shouldn't be used? Currently running bike off a car battery so I need to buy a small one for the bike before I ride the thing!
 
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