Topic: just bought a 73 cb500four

[toyolla86]

i just bought a 73 cb500four and it doesnt run.
there is no spark as far as i can tell. (i couldnt get the stupid spark plugs out...odd size?)
it wont crank and there is no electronics. with the key to the on position, the tail light turns on but thats it.
i figured out that if i short the starter solenoid it cranks but still no start. (i because the spark issue)
i am just about lost as to what it could be. i have looked at the wiring diagrams and saw that there a few things
that could be causing no spark.
but all the electronics being out makes me think that there is a common ground open to all those things, or 12v open. anyone have any ideas as for what i should try next.
im thinking i will try and force a ground to the coils to half cut the system and tell me whether the coils are bad or if its somewhere else.

anyways. some first post huh. 

thanks for any help.

craig

[Stev-o]

Firstvoff, welcome. Yes, some first post!   First thing I would do is charge battery and confirm I have 12+ volts. Then I would check all connections and fuses (and not just visually). Then I would get the proper spark plug wrench and pull plugs to confirm spark or not. It's possible you flooded the bike and fouled the plugs.

Good luck...

[BeSeeingYou]

At this point you don't really know if you have spark.  Coils would be one of the last things I would suspect.  Don't know the particulars of your 500 but the plugs are probably metric (18mm for the 750).  Fuse, ignition switch, starter button, these things could be bad and are far more likely.  What shape is the wire harness in?  What shape are the ignition points in?  Work your way back from the starter.  It seems fine so next troubleshoot the solenoid. Are you getting 12v here on the wire from the starter button when you push it?  Maybe I am wrong but it seems the ignition switch is a common failure point of the older 500/550 bikes. This would be my first suspect.   When did the bike last run? It's unlikly a bike that has been sitting for a long time will run without a bit of troubleshooting.  Aside from the electrical issue are the carbs clean and in working order, is the tank clean with good fuel.  Plugged up carbs from sitting will also cause you to have starting problems. 

[toyolla86]

ok more details about its history,
i picked it up from a guy who let it sit for at least 1 year outside without starting it. (due to the electrical issue)
i had the battery jumpered to my other running bikes batter for power.
im certain that i didnt flood the cylinders because there was no fuel in the tank since it was drained a long time ago (i was using starter fluid)
the carbs were a little gummed up. the guy i got the bike from drained the tank but not the float bowls.
i pulled the carbs and used a mirror to see if my plugs were sparking at all. didnt see anything (i know, not the best way to check for spark)
the previous owner had it stored in a garage prior to being outside for that year; where he would start the bike every month or so and let it run. he told me that when the problem occurred that he could still kick start the bike. in fact he kick started the bike and road it to the destination where it sat for a year or so outside.
overall the bike is in really good condition. the carbs were a little sticky as felt through the throttle but i sprayed a little carb cleaner and some starter fluid and it freed up the carbs pretty good. there could be some clogged passages still. and the float needles im almost sure need replacing.

srust58-thats really what i was thinking too... the ign switch, or starter button.
i am going to get on that with a multimeter.

thank you both for your input. i really appreciate it.
pics will come soon.

[BeSeeingYou]

    If the bike started with the kicker then I would suspect the starter switch.  Another common failure point on these old Hondas.  The little button is in a plastic housing inside the handlebar control and it just falls apart from age.  I was able to get a new one for my 76F but they are not available for all years and models.  If you do a search you will find threads on other options.
     You need to get the plugs out...my guess is 18mm plug socket...got mine at Sears.  When you put them back in (new ones or cleaned and re gaped old ones) be gentle and use your hand to get them started.  Overanxious types use the wrench and bung up the threads.  Check your points, clean and set them.
     At a minimum you need to remove the float bowls and remove and clean the jets.  Some will say you need to disassemble the crabs completely for cleaning....it depends on how gummed up they are.  The idle jets in particular have a very tiny passage.  Do a search as to how to remove them, some screw in others are press fit.   The needle valves are probably fine and often the aftermarket parts are inferior so when it comes to the little brass parts in your carb use the originals if you can.  Clean them and the seats with a Q tip.  If your bike has the brass floats check them for leaks and make sure they float.  Change the oil and filter and check for a clean air filter.
     Check the inside of the tank for corrosion and clean it out if present.  Plenty of threads on that too.  After you have done ALL of this then you can put some gas in the bike and see if it will start.  And then you may want to check out that front caliper cause it will probably stick on you the second day out.

[toyolla86]

ok so i checked the starter switch and sure enough it was broken. i soldered it back together and hooked up jumper cables to see if i could get a spark then.
i pushed the starter button and nothing happened.
at this point im thinking that the ign switch (cheap aftermarket ebay one. it came with that) is bad. you can see the corrosion inside and all over it.
i want to test it by shorting the wires together. any suggestions on which colors to start with.
i was thinking i would do the red and black first since it looks like that would give me spark.

[mjstone]

i just bought a 73 cb500four and it doesnt run.
there is no spark as far as i can tell. (i couldnt get the stupid spark plugs out...odd size?)
it wont crank and there is no electronics. with the key to the on position, the tail light turns on but thats it.
i figured out that if i short the starter solenoid it cranks but still no start. (i because the spark issue)
i am just about lost as to what it could be. i have looked at the wiring diagrams and saw that there a few things
that could be causing no spark.
but all the electronics being out makes me think that there is a common ground open to all those things, or 12v open. anyone have any ideas as for what i should try next.
im thinking i will try and force a ground to the coils to half cut the system and tell me whether the coils are bad or if its somewhere else.

anyways. some first post huh. 

thanks for any help.

craig

With your first post you said you only got a taillight when you turned your ignition on.  Are you sure you turned the key in the right direction?  In one direction the ignition is on, the center is off and the other direction leaves just the taillight on.  The key can be removed in that taillight on position so people can see the bike at night parked at the side of the road.  Kinda like Flashing hazards.

MJ

[toyolla86]

oh yeah, that makes sense. i was looking at the wiring diagram and that part that youre talking about was really confusing me. haha makes sense now.

well i just now went out to the bike and checked the ebay ign switch with an ohm meter. the switch seemed bad. resistance didnt change when i would switch the key to any different setting.
so....
i took the spark plug out (i finally got one out with a super innovative process haha) and shorted the backside of the ign switch to bypass it. viola, all lights came on, blinkers, got spark. it was great. so now im going to throw the carbs back on and see if i can start it up.
i may see about getting the needles to seal first.
any tips on restoring those needles.

[Goofaroo]

Chuck the seat in a cordless drill. Then put lapping compound on the needle. Insert it into the seat and use the drill to lightly lap the needle to the seat. If you don't have any lapping compound you could get by with toothpaste. If you do a good job, it will work.

[toyolla86]

ok so its been a long time. sorry.
school and interview flyouts have been taking my time sufficiently.

i paid 9 dollars for an ebay switch (you would think that i would not buy another ebay switch since the last one that the previous owner bought crapped out on me, but this one will be put in the proper place instead of above the gas tank.)
wired it all up and vvrrrrruuuummmm! right up. started nicely. of course i cleaned out the carbs of all the gunk that was in there.
at least one of the carbs is leaking from the float bowl
and i flooded the carbs once too. the air box was leaking fuel.
also the petcock was only sufficiently getting fuel through one of the two tubes.
clarification--- it seems that both of those tubes are for fuel supply (rather than one being vacuum) since they each go to fuel rails on both sides of the carbs, feeding 2 carbs per fuel hose.
i cleaned out the petcock and the other tube got a little fuel but didnt seem like enough.
bike starts and runs but doesnt run super smooth like it should.