Honda CX 500 Forum banner

1 - 20 of 27 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
I am hoping that some one can help me out. I Just bought a 1979 cx 500. It's getting fuel, has spark, and 160 compression on each side but wont even sputter or even try to start. It turns over fine and the timing is on. I just can't figure it out. PLEASE someone help me out here, maybe it's just something stupid but i don't know where to go here. The only thing i can think of is maybe it's not sparking at the right time or spark isn't hot enough. It has a brand new battery and plugs. It won't even kick or sputter
 

·
Registered
Joined
·
3,999 Posts
Make sure that the wires coming from the cdi are routed to the correct coils. The yellow wire from the cdi must be connected to the coil on the left side of the bike and the pink wire from the cdi must be connected to the coil on the right side of the bike. Sometimes the coils get installed on the wrong sides, then if you color match the wires from the cdi to the input wires on the coils it will result in the coils firing at the wrong time.

Are you getting fuel to the spark plugs? After trying to start the bike are the spark plugs wet?
 
  • Like
Reactions: Randall-in-Mpls

·
Registered
Joined
·
829 Posts
How long did the bike sit before you tried to use it. See if starter flewed will get a kick out of it. My spelling is bad. Take the air filter out and inject the starter flued while starting and see if it trys or back fires. JUST MY THOUGHTS.
 

·
Registered
Joined
·
829 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #6
Thank you guys for responding so fast. Iv'e tried spraying starter fluid into the intake and even tried a tablespoon of fuel directly into the cylinder and it wont kick or backfire, sputter, nothing. I did try switching it out with another CDI unit but I haven't checked the wires on the CDI. I have the bike at my buddies house right now and i'm going to run over there and check that. If that fixes it i will reply right away and celebrate immediately. Thank you guys
 

·
Registered
Joined
·
3,999 Posts
So the wires were connected to the correct coils?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #9
I have the bike at my buddies garage I'm waiting for him so i can check. I really hope thats the issue. I'll respond as soon as I know
 

·
Registered
Joined
·
3,999 Posts
What does the spark you are getting look like? Is it a strong blue/white color or is it yellow/red color?
 

·
Registered
Joined
·
3,600 Posts
Check your spark plug wire caps. Unscrew them and look at your resistors. My wife and I both went through this last weekend. The resistors were shot, so we did the brass rod mod and ran iridium plugs.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #14
The spark is there, I'm new to the bike world but if it were on a car i would say i dont have the best spark. It flickers but i feel like it should be stronger. It is a white maybe yellow color. The wires look like they've been replaced recently, but i will check them out. Thank you guys for your help I really appreciate it
 

·
Registered
Joined
·
47 Posts
Recently done plug wires might be a clue. The previous owner may have been chasing the same problem. Check that the new wires are firmly attached at both ends. Clean and inspect the plug caps. Spark should be pretty impressive. With the plug out, be sure to connect its base to ground with a jumper (as opposed to just letting it rest on the motor). Good luck!
 

·
Registered
Joined
·
4,398 Posts
Is the kill switch in the "Run" position? Is the kill switch working correctly?

Sorry, don't mean to insult by asking the oblivious questions, but sometimes the answer is real simple and doesn't require a complex solution.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #18
The kill switch is in the on position. I have spark, it's definitely not impressive or anything though. I think it has to be either a weak spark or it's sparking at the wrong time, right? Like I said I'm new to the bike world but i feel like the spark should be a lot stronger. The coil is good, I replacing the CDI and had the same results. Right now I'm just checking wires and grounds
 

·
Registered
Joined
·
2,281 Posts
The timing can't really be adjusted on these bikes. Saying that, I just helped a friend with a ATV that wouldn't start, but would occasionally back fire. We went thru all the checks and finally compared the piston position to the TDC mark on the flywheel. They were about 160 degrees off. We pulled the flywheel, and there in two pieces was the Woodruff key. I don't remember any posts about shearing a flywheel key, but that can certainly throw the system out of time.

Just for easy grins, pull the left plug and drop a long wooden dowel into the cylinder. Turn the engine by the front crank bolt, and see what shows up at the timing port under the inspection cap. If the dowel is at it's peak, and the TL mark doesn't show, keep turning another cycle and then check. You should be close to the TL mark on one of the piston's ups.
 

·
Registered
Joined
·
3,999 Posts
Under the seat there is a plug that has 3 yellow wires coming from the back of the engine, unplug that plug and then try starting the bike.

If that makes no difference then try doing resistance checks on the plugs that the cdi plugs into. you will need a multimeter to do the tests. See if your numbers are comparable to the numbers in the pic below.

statortest.jpg
 
  • Like
Reactions: Darrenj
1 - 20 of 27 Posts
Top