Honda CX 500 Forum banner

Please help! 78 cx500

9K views 90 replies 12 participants last post by  jacob04892 
#1 ·
Just bought a cx500 and I dont know where to start.

I dont know if it runs beacuse they guy didnt have keys for it. I bout a new ignition lock and im waiting for that to come in.

Where should I start on trying to get it running?
 
#6 ·
I responded to your pm but this is what I typed.

Have you switched out the ignition yet and verified the new one is the right one? Some ebay sellers are selling the wrong stuff.

Beyond that if you didn't install the new switch you have two options just to see if it works. You can pull the plug back on the motorcycle by reaching up by the neck of the bike between for forks and pulling back on the plastic part of the plug. Then either plug in your new switch or jump the red to the back wire and the brown to the brown wire. That will give the bike power to try and start.
 
#9 ·
You might want to turn it by hand a few times, first. There's an access cover below the radiator (takes a 17mm socket). Under that is the end of the crankshaft. Turn it clockwise (same 17mm socket, set to tighten). This will be easier with the spark plugs removed, btw.

If it's free, crank it with the starter with the kill switch OFF until the oil warning light goes out. This will help to ensure proper lubrication for the live run.

You have already checked oil and coolant levels, right?


R
 
#11 ·
Around 2.5 liters I believe. It will say for sure in the FSM. I use Rotella 15W-40, but do a quick Google search and it will yield tons of threads on what people go with.
 
#12 ·
For a first change, just use cheap 10w-40. Change it again after a hundred miles or two. Then put in whatever you want.


R
 
#13 ·
If it hasn't run in 30 years there's a lot of stuff to do before deeming it road worthy.

Just to get it running, also check:

Tank to see if rusted, fresh gas.
Clean the carbs
New plugs
Clean/replace air filter
Put some oil in the cylinders then rotate it by hand
Adjust cam chain
Flush/fill the coolant, probably some nasty stuff in there

Sounds like you have a project on your hands!
Lots of good info/peeps on this forum.
 
  • Like
Reactions: Randall-in-Mpls
#15 ·
Assuming it moves a little, try some oil in the bores, as santafepilot suggested. If it doesn't move at all, letting some diesel fuel sit in the cylinders for a few days is supposed to help. Search the forum for "seized engine" for other ideas.

It is in neutral, correct? (Sorry, had to ask. It's the simple things that trip us up.)


R
 
#16 ·
Yes it was in neutral.

It started getting easier to turn so I went to try and crank it like you said, with it in cut off, and when I push start the lights dim but the starter doesn't even click.

Am I able to do this with just a battery charger/ starter?
or do I need a battery?
 
#18 ·
Makes me kind of nervous that it was hard to turn... you rotated it around and around, not just back and forth?

Once you get the battery, run a compression check to see if worthwhile continuing before putting more money into a smoking beast. Though it depends on how involved and what your willing to put into the bike.

I picked up an old crx250 once that looked like someone had poured handfuls of sand down the cylinder...
 
#24 ·
You need a compression gauge with a flexible hose.
Take both plugs out, turn kill switch to stop, hold throttle wide open and crank the engine over.
 
#25 ·
Can get a cheap one at Harbor Freight.

Pull plug out, put back in cap, put it (Plug end) on a good ground (not the cylinder head) and crank and look. Some guys hold it close to metal to check for spark, but I've electrocuted myself too many times...
 
#26 ·
If you leave the kill switch in the off position, you can crank the engine and the plugs will not spark.
So no need to have them in the caps or even grounded.
 
#27 ·
Mmm... second part was checking spark not compression, sry wasn't very clear.

Leave the plug for the side you're not checking compression in.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top