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Discussion Starter #1 (Edited)
New member here, and have never rode a motorcycle before in my life. I love working on my cars, and I thought a bike would be a easier/cheaper project to keep me busy. So I went out and spent $200 on a 1978 Honda CX500 that's been sitting for the past 11 years.

Here she is in all of her current glory.
IMG_20160901_165538.jpg

Using some fogging oil for initial lubrication, I got her to turn over using the crank bolt and a ratchet. Luckily, my roommate just purchased almost the same bike ('79 CX500 Deluxe...and I bought its (complete) parts bike) that's in great running condition, so I borrowed his battery to try it for real. She turns over great and has spark but the previous owner had removed the carbs before selling so I want to clean them up before putting them back on.

So naturally, I turned to starter fluid. And thank god it actually fired :). Now I'm a lot more enthusiastic about fixing her up and getting on the road. And I thought there's no better place than a forum to share this experience with and hopefully get a lot of great tips throughout the process.
Here's the short list of what I think needs to happen.

1) Carb Cleaning/Rebuild
2) Front brake caliper rebuild
3) Radiator recore? (This one's up in the air until I get a closer look)
4) Clutch? (Cable has a lot of slack so I need to investigate this too)
5) New tires/brakes+fluid/oil/coolant/battery
6) New front left turn signal...the current one is broke off (probably got dropped)

I did get a bin of extra CX500 parts a from the owner as well, so pretty soon I'll go through and inventory it. Also, where do you guys go to buy parts?

I'm hoping to have her back in good form by the end of the month, and I'd love to hear what you guys have to think of the project, your input on what I'm forgetting, and your suggestions for upgrades (although I want to get the bike running before upgrades). I have no clue how this projects going to go, but I'm super excited to start wrenching and bring this bike back to life.
 

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Discussion Starter #4
Welcome aboard.
To start see this: http://cx500forum.com/forum/general-discussion/31323-forum-settings-everyone-should-make.html
Download a FSM link in my signature. start with the high mileage service items
There are two good carb books in my sig line as well.
Check the date code on tires if over 5 years replace em regardless of tread. make it safe first then think about changes. make sure the temp gauge is in working order. good luck!
Thanks for the heads up. The previous owner gave me Larry's book and a Clymer manual, but I always love a good FSM. Tire's are definitely getting replaced after she starts running. And I didn't even think about the temp guage so that's a great point.
 

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Discussion Starter #5
Time for an update:

This weekend I took the MSF course and now I'm really looking forward to getting this bike running. I put the carbs back together (per Larry's book) and I have a couple issues:

1) The right float bowl gasket is not sealing. I was going to just get a new gasket but I decided to spend a little money on a rebuild kit (and because I lost that tiny o-ring for the ACV).

2) When I turn the throttle lever on the carbs to WOT it will get stuck there and not come back until I partially disassemble the carbs to free them up. For lack of a technical term the sliding piston thing (Piston Set,vacuum Cx500 1978 Usa 16022415003) will rise up at full throttle and then the throttle plate will get jammed on the wrong side of it and can't return. I didn't notice this behavior before I disassembled them, but I wasn't looking for it then. Is this normal? Or any suggestions on fixing it?

So hopefully the carb kit comes in after the weekend and sometime next week she'll be up and running (fingers crossed).
 

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Discussion Starter #7
Are you sure that you put the plates on the correct side of the rod?
I'm pretty sure...I never removed the plates (not that that doesn't mean they could have already been wrong), but also after checking it seems to be right. I think I didn't have the slide jet thing seated properly so the vacuum slide sat a little high and would allow for excess travel of the throttle plate.

Many hours later....everything has been taking apart and cleaned and reassembled (this time I followed Larry's book to a tee...last time, not so much haha) and the throttle plates don't get stuck anymore. After work tomorrow, I'll throw them on the bike with my fingers crossed!

I'm going in blind to reassembling the carbs on the bike, they were already off the bike when I bought it. I haven't seen any threads yet that show what I'm looking for so if anybody already knows where a helpful one is (specifically for reattaching the throttle and choke cables) that would be huge.
 

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The factory service manual (FSM) shows the cable routing.
 

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Brandon,

If you get the rebuild kits and decide to pull the carbs to rebuild, you could be the person to do a topic w/pics on a carb rebuild.

Bob
 

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Discussion Starter #11
I took a little hiatus from working on the bike, mostly due to cold weather and fixing some oil leaks on my Civic. I also wanted to say thanks for all the help so far! This project wouldn't be where it is without help from this forum (and larry's book).

Now I'm back at it, and I have a runaway RPM issue. I've done some research and below I mention a few theories, I'm just hoping you guys can help me narrow down to the most likely suspects. The bike seems to idle fine, maybe a little rough. But the second I give it a little throttle the rev's just take off. At first I thought the butterfly valve on the carbs wasn't closing and I found one of my throttle cables (return/push cable) had a kink in it so I threw two new cables on the bike. The throttle tube now actuates like it should and snaps back nicely when the butterfly valve closes. All that done and it hasn't fixed my issue. I know the butterfly is closing how it should but I still have the runaway throttle. Any suggestions? I've been reading that it could be a vacuum leak causing a lean condition, but I would think that would cause issues at idle.

There's always a chance I messed something up with the carb rebuild....I don't mind pulling them back off but what should I look for if I do? Also somebody on some post (sorry for an awful source) mentioned the vacuum slides could be a culprit...could this be the case and are they even adjustable?

Lastly, the kill switch doesn't work and turning the key to off doesn't kill the bike either so when the RPMs runaway I have been resorting to pulling the spark plug wires out. I read that going WOT will kill the bike when you have a runaway, is this true? Also what should I check to diagnose the kill switch issue? Grounds? Other connections?

Thanks!
 

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Verify that the slides inside the carb are moving freely.
If even one is stuck it can cause this to happen.
Sometimes on reinstall, the needle can get out of position and keep the slide from closing at all.
 

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Discussion Starter #13
Verify that the slides inside the carb are moving freely.
If even one is stuck it can cause this to happen.
Sometimes on reinstall, the needle can get out of position and keep the slide from closing at all.
Ok, I will look into that. I'm probably due for some research into how those slides actually work. Can I use some sort of lubricant to improve sliding? Silicone, fogging oil, motor oil, bike chain oil, etc. (I'm just listing all the lubricants in my garage now lol).
 

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Are u even sure they are sticky? clean with carb cleaner and or ultrasonic if needed. make sure they are installed correctly as OCR pointed out first.
That would be a negative.

I just checked and with the caps off I can pick both slides and they fall back down with a nice clunk. I'll hold off on polishing them until I run out of other ideas.

So vacuum leak? Or what else could it be?
 

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are the air cuts assembled properly,when mine go south i fix them permanently
 

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Discussion Starter #20
are the air cuts assembled properly,when mine go south i fix them permanently
Permanently? Would you mind elaborating on that one? Also I'm pretty confident they're in there correctly but I'll check them next time I pull the carbs.

Speaking of pulling the carbs, I just thought of another reason to do just that. Is there any chance those little black plugs in the carb that block off a passage could contribute to my runaway problem? They didn't fit great (old/hard) when I put it back together so it wouldn't surprise me if they managed to fall out. Any recommendations on where to buy those? I see a lot of conflicting information out there on what to buy and where to buy them.

Lastly I reassembled everything today and started her up. It was basically like 1 second of idle and then the revs just shot up to about 5k with no throttle input from me. I then repeated about 5 times to verify the problem. It was kind of like if I were to roll on the throttle for normal acceleration and not roll off, it wasn't a super fast jump in rpm. Some good news is the kill switch is now working (safety first, of course). I think the throttle cable is a little tight, if I were to start it while rotating the throttle tube away from me (decel) it the rpms wouldn't run away (until I gave it a little throttle and then they would runaway and not come back down even if I rolled off the throttle entirely), but the cable is an easy fix so I'll take care of it soon (I don't think it is my root cause though).
 
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