Topic: Starter button and idle issues. Help needed: 1972 CB500

[DavePhipps]

it's raining today and I had to go out on the bike. I hit the starter button, the bike starts but the starter motor keeps going.This happened once before on a wet ride. It doesn't happen when it's dry.
I took the switch apart last time ithapened, cleaned the contact, installed new spring, and coated the contacts with dialectric grease.
Any clue why this is happening?

Carb issue: at idle the bike will surge to 2-3k rpm then drop down and die. Slight application of throttle will stop it from dying
Floats are set at 22-23mm, stock airbox, screws turned out 1 1/8, and a motad 4-1. From what I can tell the jetting is stock but the numbers on the jets are hard to read with aging eyes.

[TwoTired]

What's a 72 cb550?

If the starter keep spinning, there are three fault choices.
1- The slip clutch is sticking so the motor then drives the stater motor.  Revving the motor usually then destroys the stater motor from over speed.
2- the starter solenoid internal contactor is stuck and can't free or release itself from engagement.
3- The solenoid is being activated by having 12V applied across the small wires.

To diagnose the starter button circuit/wiring we really need to know the true model and year of the bike, as the activation circuits vary between years and cb500 and 550.  We also need to know of any modification to the stock wiring, as we only have access to the stock wire diagrams.


Carbs- When an engine at idle slowly slows down and stops it is likely over rich.
If the engine speeds up on its own before stopping then a lean issue is indicated.

Probably a good start is knowing the carbs are truly clean inside including the drilled passageways, and have the correct parts installed in the correct position.
Vacuum sync would be good, too. As well as a new or known clean air filter.

Cheers,

[DavePhipps]

Sorry, that's a 72 500. I'm a terrible typist.

The PO did quite a bit of wiring modification of the loom where the electric panel was on the left side of the bike.
I've attched an image of it.
I'm suspecting the button, because when I press it a few time the starter motor will stop.

Carbs.
Fully cleaned six months ago.
This started after installing the stock airbox and new filter.
I originally had the scews turned 21/2 out because I had the adjustment confused with my FZR carbs.
I then tried 1 1/2 out now down to 1 1/8 and it seems to getting better.
After the rains stops I will try 1 turn out.

The odd thing is the bike exhibiting both symptoms you described when idling.

[DavePhipps]

OK, had a bit of time to fiddle with this. It seems the leaner I go the better the bike runs. It was still idling super high, and starting was a pain.I checked the plugs and all were covered in fluffy black carbon. In a fit of frustration I removed the filter this morning and it started right up and idled well.
I think I'm going to have to get a magnifying glass so I can read the numbers on the jets
Where are the numbers located on the mains and slow jets?