Author Topic: CB500 Overheating?? (Read 4589 times)

MX267 · « **on:** August 13, 2010, 05:54:08 am »

I have a 1972 CB500, my problem is, it runs great in the morning or at night when the air is cool outside. In the afternoon on the way home from work it runs like a terd about 15 minutes into my ride. It starts bogging really bad and feels like it has half power, and then eventually dies with it not wanting to start for about 20 minutes. I pulled the spark plugs and they looked pretty good, not black, a little tan with some white. Could it be running to lean? It has Uni Pods for air filters and the previous owner put huge automotive style fuel filters on it. I thought they could be restricting the fuel flow. It has a 100 main jet and I thought about going to a 105 or 110. Any help would be greatly appreciated!

Kman · « **Reply #1 on:** June 19, 2015, 04:26:34 pm »

Hello MX267

New to bikes and this forum. I have the same bike and having the exact same problem with the overheating. Did you ever find a solution?

Thanks
Karl

Tews19 · « **Reply #2 on:** June 19, 2015, 05:00:58 pm »

Kman, he posted that 5 years ago. What set up are you currently running on your bike? Pics? What issues are you exactly having? Welcome to the site and I am just north of you near Milwaukee .

Hot500 · « **Reply #3 on:** June 19, 2015, 05:07:15 pm »

What makes you think the bikes overheating?

These bikes should have a very fine gauze filter as part of the fuel petcock. They do not need an inline filter, and in fact that can cause problems as you and the OP are describing, particularly up around WOT. The larger the filter, the more fuel it can impede and slow down delivery to the carbs. Thus the bogging down, fuel starvation situation you are experiencing.

Make sure you have a good clean fuel petcock and gauze strainer, and get rid of the inline filter/s.

Retro Rocket · « **Reply #4 on:** June 19, 2015, 05:31:43 pm »

Sounds like a coil or condenser is failing when reaching operating temperature...

BobbyR · « **Reply #5 on:** June 19, 2015, 06:17:44 pm »

If you are running a Dyna electronic ignition that is likely your problem.

Kman · « **Reply #6 on:** June 20, 2015, 01:32:29 pm »

Quote from: Tews19 on June 19, 2015, 05:00:58 pm

Kman, he posted that 5 years ago. What set up are you currently running on your bike? Pics? What issues are you exactly having? Welcome to the site and I am just north of you near Milwaukee .

Thanks for getting back to me so quickly guys,
Setup: believe stock jets so 100 main and 40 pilot. No idea what oil was in the bike but topped it off with 20W-50 motorcycle oil. 93 oct gas. Battery was at 11.88 this morning, at 2,000rpm it went to 12.56. Idled at about 1000

bike sounded great when I bought it last fall. Thought I emptied all the gas out for the winter. Never really took it for a spin until a month ago. Started up fine after a carb cleaning and a trickle charge. Would take it for spins around my Chicago neighborhood and it would die out after 40 min, at this point it would be hard to shift in and out of gears and would not start with electric start or kick start. I thought it was the battery so I would walk it home and trickle charge it. Next day it started fine, rode it for 40 min and same stall out, but this time I got it home and didn't trickle it and came back to it an hour later and it started right up with both electric and kick. Took a chance and attempted to drive it to work on a ten minute highway trip. The trip started smoothly but I felt the bike loosing power and as I hit my off ramp the bike was completely shut down. i caught a faint smell of something burning and the gear shifter was really tough to move. I waited about ten minutes and was able to electric start the bike and get to work. I believe it is a overheating issue because if I let the bike chill for ten minutes it starts back up. Same thing happened on my trip back home, happened faster though and before my exit. Is it possible that the rectifier/regulated is reacting to the heat poorly?
Update: attached are picture of the bike and the spark plugs, looks like I'm running rich. But as I put the cap back on it snapped loose and is not attached to the wire anymore. Seemed very unstable because it came off so easily. Obviously this could be a factor as well.
Thanks
Karl

Tews19 · « **Reply #7 on:** June 20, 2015, 01:45:45 pm »

Screw the caps into the wire. Have you changed the oil? The bike looks to be in really nice shape. Are you running stock ignition or electronic?

I'd swap the plugs if they are not fresh. 10 bucks spent.

Kman · « **Reply #8 on:** June 20, 2015, 02:49:41 pm »

Going to get new plugs. Have not changed the oil but the previous owner informed me he got a tune up last summer which, I assume, included an oil change. I will stop assuming and just start over and change the oil and get new plugs. Do you recommend 20w-50? Do plugs usually come off that easily?
Running stock ignition with a key.
And you're right bike does look in really nice shape. I wanted something to learn on and get my hands dirty and I'm off to a good start. We'll get it working.

Kman · « **Reply #9 on:** June 20, 2015, 02:54:10 pm »

Quote from: Retro Rocket on June 19, 2015, 05:31:43 pm

Sounds like a coil or condenser is failing when reaching operating temperature...

Is there a way to test a coil or condenser?
Thanks for your input
Kman

calj737 · « **Reply #10 on:** June 20, 2015, 02:56:31 pm »

Quote from: Retro Rocket on June 19, 2015, 05:31:43 pm

Sounds like a coil or condenser is failing when reaching operating temperature...

+2 ^^^^

Plugs look fine, but check and or change the oil and filter. For Chicago summer riding, 20-50 is a great idea. But, your issue may be the battery, or a loose ground connection. Can you check the voltage of the battery after it rests 2 hours from an overnight charge? You said at 2,000 rpm it was at 12.56v. Thats low. A new battery may be necessary after some diagnosis.

Riding around Chicago, keep your revs up. Tendency is for people to idle along. These motors and charging systems don't like it one bit. Rev and ride above 4,000-8,000. This will keep the battery well charged regularly.

Retro Rocket · « **Reply #11 on:** June 20, 2015, 05:01:36 pm »

Quote from: Kman on June 20, 2015, 02:54:10 pm

Quote from: Retro Rocket on June 19, 2015, 05:31:43 pm
Sounds like a coil or condenser is failing when reaching operating temperature...
Is there a way to test a coil or condenser?
Thanks for your input
Kman

The best way is to change them out with another coil or condenser, condensers are cheap so thats a no brainer, see if there is another member close and swap coils for a test, don't change both coils and condensers at the same time, you won't know which one had the problem, do the condensers first as they are cheap... I've had these exact symptoms with both bad condensers and a bad coil....

Tews19 · « **Reply #12 on:** June 20, 2015, 05:04:13 pm »

If your coils are bad I have a set of oem you can have for free. Pm me if it's your coils.

Retro Rocket · « **Reply #13 on:** June 20, 2015, 05:17:53 pm »

Quote from: Tews19 on June 20, 2015, 05:04:13 pm

If your coils are bad I have a set of oem you can have for free. Pm me if it's your coils.

Correct me if i'm wrong but, if testing coils that break down once warm with a meter, wouldn't they still read ok whilst cold..? I'm not that good with electric components but i remember having my coils tested by a friend in a bike shop and they tested ok, once hot they failed consistently, I was lucky enough to have a few spare sets and on a whim, and still not knowing what was going on, i changed changing them out, it solved the problem...

RevDoc · « **Reply #14 on:** June 21, 2015, 08:22:04 am »

Retro, you are not wrong. With industrial and commercial electrical work I have seen many components that tested fine when cold but would fail after heating up with use or ambient heat.

calj737 · « **Reply #15 on:** June 21, 2015, 09:28:26 am »

Especially electro-mechanical devices!

Kman · « **Reply #16 on:** June 22, 2015, 12:45:24 pm »

Quote from: Tews19 on June 20, 2015, 05:04:13 pm

If your coils are bad I have a set of oem you can have for free. Pm me if it's your coils.

I've put an order in for new condensers. going to replace the spark plug caps and lines. oil change and new battery. I'll keep you posted.

Thanks for your help everyone.

Tews19 · « **Reply #17 on:** June 22, 2015, 02:49:41 pm »

What lines are you changing? Stock coils are not meant to be rebuilt but you can I guess.

Kman · « **Reply #18 on:** June 23, 2015, 02:43:56 pm »

Was Going to change the lines on the stock coils and discovered that they are not meant to be rebuilt, read your comment after i took it off. they're in really bad shape though. Took a look at the my condensers and the whole set up looks brand new, so don't think that has anything to do with my problem.

jayowen · « **Reply #19 on:** June 23, 2015, 02:48:20 pm »

i had a condenser go bad and it was about 6 months old. it caused weak spark when it got hot. so loooks can be deceiving

Retro Rocket · « **Reply #20 on:** June 23, 2015, 03:40:41 pm »

Quote from: jayowen on June 23, 2015, 02:48:20 pm

i had a condenser go bad and it was about 6 months old. it caused weak spark when it got hot. so loooks can be deceiving

+1, I've had a bad condenser straight from the shop. had me stuffed as to what was wrong and took a while to work it out....

calj737 · « **Reply #21 on:** June 23, 2015, 04:06:00 pm »

1 thing to inspect, where the GR/Yllw wire and GR/BL wire attach from the condenser to the ignition plate. Make certain the terminal clip on the end is not touching the base plate. This can cause unwanted behavior. From the picture, the #2 side looks to be awfully close-

jayowen · « **Reply #22 on:** June 23, 2015, 04:19:28 pm »

DeltaRider put this on my thread with a weird fouling issue that ended up being a condenser.

"Always start with the simplest and check the ignition (all items) and doublecheck before you move to the carbs.

Left condensor (1+4) is bad, right condensor (2+3) is good."

Deltarider · « **Reply #23 on:** June 23, 2015, 11:38:11 pm »

Quote

Make certain the terminal clip on the end is not touching the base plate. This can cause unwanted behavior. From the picture, the #2 side looks to be awfully close-

This possibility of an 'on and off' groundcontact is often overlooked as is arcing between the plugcaps/HT leads and the head (Ground). It should be routine to check this whenever the engine isn't running satisfactorily.

Kman · « **Reply #24 on:** June 26, 2015, 12:07:20 pm »

I've ordered a new condensers and coils.
One thing I can't wrap my head around is when the bike dies on me after it heats up and the clutch gets really stiff and I can't shift the bike into any gears. The bike just seams to lock up and theres a faint burning smell. After ten minutes of being off I can then shift it into neutral and kick start it. Could the transmission be binding on the engine and thats why it overheats and shuts down?

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Author Topic: CB500 Overheating?? (Read 4589 times)