Re: 1978 CX500 Resurrection

General Discussion

1978 CX500 Resurrection

monster813 07-13-2008, 5:48 PM
Hi All,

Being new to the world of motorcycling, I decided to dive in head first. I purchased my first bike, a 97 Ducati Monster, and had many plans for it...which all got promptly put on the back burner when a few weeks later I happen to come to own a 1978 Honda CX500. A coworkers father was kind enough to bestow her to me with nothing more than a handshake, and from there the story begins...

My intention for this bike was to get her running myself and surprise my father with it. We both got our motorcycle licenses together and I figured this was a great opportunity to get us both riding together. The bike has been off the road since 1985. The previous owner had drained the gas tank before placing it in storage, but thats about it. Everything is complete and intact with around 10k miles on the clock. I started by draining and replacing the fluids and filters(oil and air). Then I put in new plugs, a new battery, new tires, and cleaned the carbs. The starter engaged but the engine wouldn't turn. I tried rotating it by hand via the crank bolt only to find that not turning much either. I took the heads off to find both cylinders frozen with slight surface rust which I cleaned and, with the help of a mallet, a 2x4, and some gentle tapping, I broke the rust binding the rings to the cylinder walls. Now the engine spins freely, but will not start. The plugs are firing, the carb is cleaned(not rebuilt), but I get nothing. No coughing, no sputtering, no firing at all. Even after a healthy dose of starter fluid into the intake and even into the cylinders, there is still no ignition. I'm unsure of how to proceed. Considering the time it's been sitting, a carb rebuild sounds to me like a logical step, but doing it myself and resyncing the carbs may be a bit out of my league. I've been through 4 years of auto shop, so i can turn a wrench, but I'm just not sure if thats something I want to undertake at this stage of the project. Also, I've read that resyncing should only be done after everything else with the engine is in good working order, and I'm certainly not there yet. I just don't understand why there's no firing at all. I would suspect that even with dirty carbs, there would be something, especially after some starting fluid. Any help or suggestions would be greatly appreciated.
This site has proved a great resource and I hope someone can point me in the right direction.
Thanks.

Re: 1978 CX500 Resurrection

CXHOKIE 07-13-2008, 5:56 PM
your in the same boat i was in about 3 weeks ago. first, rebuilding the carbs on this is relitively easy, it takes almost as long to remove and install them as it does to rebuild them, i would find a Clymer repair manual for it, ($35 at dealership) and as far as your firing problem, you need three, well four things for a motor to run, 1)fuel, 2)spark, 3)compression, and 4) it all has to happen at the right time, you said yo have spark, your starting fluid counts as fuel at least enough to get something out of the motor, so you need to check the other two, do a compression test, a new cx500 motor is supposed to be roughly 150-180psi, if that checks out, make sure the cam chain hasn't stretched or skipped time

but the first think i would do is get a manual for the beast

LIFE IS SHORT-PLAY HARD
Its big, slow, noisy, ugly, and I LOVE IT

'79 cx500 "Tank"
'67 & '68 Mustangs

Re: 1978 CX500 Resurrection

Anonymous 07-13-2008, 6:13 PM
have you got good strong spark? did you put any oil in the cylinders?

Re: 1978 CX500 Resurrection

monster813 07-13-2008, 6:46 PM
Thanks for your quick response guys.
I have purchased a Haynes manual for it, as well as downloaded a copy of the Honda Factory Service Manual. Before breaking free the pistons, I soaked both cylinders with Seafoam and Marvel Mystery Oil. I do have spark on both plugs, although I'm not sure what a 'strong' spark should look like. My experience with engines is mainly automotive at this point, but the spark I'm seeing at the plugs of the CX is not as strong as what I've seen in a car engine. Should the spark be the same intensity on a bike as it is in a car?
Thanks for all your help guys.

Re: 1978 CX500 Resurrection

monster813 07-13-2008, 6:52 PM
If I'm not getting a strong spark, what could be causing it? I bought replacement ignition coils for it and swapped them out, but that didn't help at all.
Thanks.

Re: 1978 CX500 Resurrection

Blindstitch2002 07-13-2008, 7:00 PM
Does the choke move freely?

1978 Honda Cx500 Maggot
1979 Honda Cx500 Custom
1980 Honda Cx500 Deluxe Couch Project Bike

CX500 Factory Service Manual
Courtesy of Randall-in-Mpls

Re: 1978 CX500 Resurrection

Anonymous 07-13-2008, 7:01 PM
Check out this website,
http://www.elsham.pwp.blueyonder.co.uk/cx500
Ther is a troubleshooting procedure, and stator tests.
compression test could'nt hurt, Do you know if the bike was running when laid up or if it was laid up cause it wasn't running?

Re: 1978 CX500 Resurrection

monster813 07-13-2008, 7:26 PM
Hi Blindstitch, yes the choke moves freely.

The bike was running when it was laid up. The previous owner had a close call with a driver who ran a stop sign. With his 2 kids in mind, he chose to stop riding and bought a more fuel efficient car. As far as I know, the only thing he did before storing it was drain the gas tank.

Re: 1978 CX500 Resurrection

Randall-in-Mpls 07-13-2008, 7:27 PM

monster813 wrote:
I bought replacement ignition coils for it and swapped them out...

This brings to mind two questions:

First, are they from a compatible CX? The coils from an '82 CX500 Custom, a GL500, or any 650 will not work. They use a different ignition system. If the ingition cables can be removed from the coils, they're the wrong ones.

Second, are they installed correctly? The only visible (and actual) difference between the left and right coils is the color of the lead from the CDI unit. The left coil has a yellow lead, the right coil pink. The coils themselves are interchangeable (i'm running on two pinks at the moment), but the coil feeding the left cylinder (from the rider's perspective) MUST connect to the yellow wire under the seat. The right-side coil MUST connnect to the pink wire. If these are reverse, both cylinders will fire at the wrong time in their cycles.

Good luck,

R

'78 CX500 - The Black Maggot

CX500 Factory Service Manual
1978 CX500 Parts Manual

Re: 1978 CX500 Resurrection

Randall-in-Mpls 07-13-2008, 7:29 PM
BTW, where are you? You might find a forum member to offer some hands-on help.

R

'78 CX500 - The Black Maggot

CX500 Factory Service Manual
1978 CX500 Parts Manual

Re: 1978 CX500 Resurrection

Blindstitch2002 07-13-2008, 7:33 PM
Didn't say anything about draining the carbs. Probably looks like yellow jello inside there. Starting fluid should kick over at least one of the cylinders. Do a compression test. Maybe eventhough the piston moves the rings are locked to the piston and not flexing right. There's also the oil test where you put a litlte bit of oil in the cylinder after testing the compression to see if it went up.

1978 Honda Cx500 Maggot
1979 Honda Cx500 Custom
1980 Honda Cx500 Deluxe Couch Project Bike

CX500 Factory Service Manual
Courtesy of Randall-in-Mpls

Re: 1978 CX500 Resurrection

monster813 07-13-2008, 7:34 PM
According to the seller, they are from a 1978 Honda CX500 and are functioning correctly. We removed them one at a time and replaced them correctly, I believe. We got the same response from these coils as we did from the ones that were originally on the bike.
Thanks.

Re: 1978 CX500 Resurrection

Shep 07-14-2008, 1:45 AM
When checking the spark on the plugs I hope you didn't just touch them to the Cylinder head covers?This can blow the CDI unit.
This may not be your problem but something to remember.
They should be grounded to the frame/exhuast.
Checl all wiring under the seat.You can pick up cheap manuals off Ebay and there are some downloadable ones as well.

New Global CX/GL Forum,
http://globalcxglvtwins.hostingdelivered.com/

Re: 1978 CX500 Resurrection

monster813 07-15-2008, 3:20 PM
I did. But only once or twice. I'll remember not to do that again...

According to my multimeter, the ingition coils are operating properly. I bought a Randakks carb rebuild kit for it which should come in a few days. I figure I'll bite the bullet and rebuild the carbs, put them back on and see where I am. I have a question about timing though. When I was attempting to turn the engine by the crank bolt, and it was barely moving, could that have stretched the cam chain and thrown off the timing?

Re: 1978 CX500 Resurrection

Shep 07-15-2008, 4:46 PM

monster813 wrote:
I did. But only once or twice. I'll remember not to do that again... According to my multimeter, the ingition coils are operating properly. I bought a Randakks carb rebuild kit for it which should come in a few days. I figure I'll bite the bullet and rebuild the carbs, put them back on and see where I am. I have a question about timing though. When I was attempting to turn the engine by the crank bolt, and it was barely moving, could that have stretched the cam chain and thrown off the timing?

I doubt it.With the plugs out how hard is it to turn the engine either way using the crank bolt?

New Global CX/GL Forum,
http://globalcxglvtwins.hostingdelivered.com/

Re: 1978 CX500 Resurrection

bearmani 07-15-2008, 5:26 PM
if yer lookin for a consensus, with the way it was locked up?... my vote is the rings are prolly siezed, if not broken, depending on how "lovingly" ya hadda tap on the pistons. and if the spark is as weak as ya say, mebbe take em out dry the cyclinders out and the plugs.....might coulda grounded out the plugs with too much ether.

1981 gl500
"Rustic-225"

Re: 1978 CX500 Resurrection

mcreviver 07-15-2008, 8:30 PM
Squirt some Marvel Mystery oil into the cylinders via the spark plug holes, before you do much more cranking. You might get that running and find you have a smoker on yur hands. Where are you located? Anywhere near PA?

Ron in PA

Re: 1978 CX500 Resurrection

monster813 07-20-2008, 5:54 PM
Rebuilt carbs step by step with the Randakks kit. Starter is engaging, engine is turning, spark plugs are...sparking, but its still not starting. After spraying some starting fluid in there it sounded like it was starting to run on its own, but stops once the fluid is burned up.

Weak spark? Bad CDI? I'm unsure of what to test next and how? Im out of options at this point.
Thanks for all your help with this guys. This website has been my only salvation.

Re: 1978 CX500 Resurrection

N.W.OhioNomad 07-20-2008, 6:09 PM
Monster, still sounds like a fuel issue,if it will run on starting fluid.Do you have a fuel filter?if not get one.Although the PO drained the fuel tank there could still be junk floating around when you put in the new fuel.You can also try some SEAFOAM,its the best sh*t for cleaning dirty carbs.Where are you located,if you are close to another forum member you may get some hands on help.Good luck!

1981 cx500c "silver bullet"
"Its better to be hated for what you are than
loved for what you are not" -carpy carpenter

Re: 1978 CX500 Resurrection

Anonymous 07-20-2008, 6:19 PM
did you do the stator tests at rob's page?

Re: 1978 CX500 Resurrection

monster813 07-21-2008, 5:44 PM
Stator test came out good. Added seafoam to the tank. Float bowls are filling up, just need to find out if the fuel is making its way into the cylinders. I rebuilt the carb step by step with the randakks kit, which I had hoped would let me cross 'carbs' off the 'why this thing isnt starting' list. But I just don't know anymore. I'm going to install an inline fuel filter in the morning. I figure if I stick some paper towels in the plug holes and turn her over a couple of times, I can find out whether or not the gas is making it to the cylinder.

Re: 1978 CX500 Resurrection

LRCXed 07-21-2008, 7:57 PM
I didn't read where you ever did a compression test. After you did the heads, did you make sure the valves were going up and down? And was each cylinder at TDC and lined up on the TL & TR mark on the flywheel when you adjusted the valves? You could have the valves so tight that it wont pull a vacuum or pump up the compression! Check that all four strokes of the motors rotations line up where they should with the valve timing!

If your going to do something, do it right, don't do it half as@*d.
http://globalcxglvtwins.hostingdelivered.com/