Gas lock

Argh. White Norton goes dead after running a mile or so, then will start up, then goes dead after another mile. Someone suggested vapor lock. I started the bike and let it run for several minutes with the gas cap popped, it burbled away without me having to touch the throttle at all for several minutes

I can't figure out where the breather is! I read previous thread from 2012 - the photos are gone.

Can someone show me where the breather is? I tried looking at the parts book, don't see it. THANK YOU!!

Assuming standard Ceandass flip/monza type cap, then pop cap open, look closely at the brass plate that supports the sealing rubber washer. There should be a small hole in the brass plate. That is the inner side of the vent. Try blowing through that with an air compressor or if like me without such luxuries, try squirting some WD-40 or brake cleaner etc through. Should flow through the plate and out another hole on other side (I think the plate is two plates sandwiched together...a second vent hole is on the plate towards the underside of the actual chrome cap.

It is fairly easy to completely dismantle the plate(s) from the cap....some are rivetted, some are bolted. I drilled/dremel-ground off the rivet, removed the plate and got everything fully cleaned up. There is a spring between plate and cap to help exertpressure on plate against tank neck, but the real source of sealing pressure is the little bit of rubber hose on the rivet/bolt. Mine had badly perished in 50 yrs neglect and was not making for good gasoline seal. Replaced that rubber hose with a similar length/diameter modern fuel rated hose. Tapped a thread into cap and screwed in a bolt/machine screw with a washer to secure the plate/spring/rubber hose. New rubber washer/seal squirmed into gap between two brass plates. No more fuel leaks and good venting.

It’s this little hole …

Could be something else entirely, like swollen rubber seals in the petcocks.

But check the easy stuff first, like that cap breather.

Now I know! I actually looked at the underside of the gas cap today. The assembly is held together with a Phillips head machine screw.

nortonmargie said:

Now I know! I actually looked at the underside of the gas cap today.

Click to expand...

The breather holes in the plates are usually staggered so don't be too concerned if you can't poke a wire through.

nortonmargie said:

The assembly is held together with a Phillips head machine screw.

Click to expand...

Cross-head screws used on British vehicles are normally Pozidriv (including the Ceandess fuel cap screw unless perhaps it is one of the Far Eastern copies).

try riding it with cap open. that will tell you if it’s the cap.

jan nelder said:

try riding it with cap open. that will tell you if it’s the cap.

Click to expand...

that sounds dangerous. I let it idle for several minutes with the cap open. It burbled away without me having to touch the throttle

Starvation of fuel delivery ?
Remove fuel lines check fuel flow..
Remove fuel taps and check all fuel filters and fuel bowls

I have already washed out the carburetors with carb cleaner. I checked the fuel filter on the left carb, basically clean, and checked the fuel bowl, it had a little dirt and I washed it out. I was planning to pull the petcocks and check the fuel filters on the petcocks on the inside of the tank when someone suggested checking for vapor lock. If vapor lock isn't the problem, I am going to spend Saturday draining fuel and checking petcocks

ALSO: Why riding with the gas cap open is dangerous: The Antique Motorcycle Association posted an article about an older gentleman who went for a ride on a country road on his Airhead BMW. The bike slipped on something and he went down at 20 mph. Should not have been a major problem, except the gas cap came off, spilled gas on the engine, the bike caught on fire and the old guy went to the hospital with extensive burns.

nortonmargie said:

ALSO: Why riding with the gas cap open is dangerous: The Antique Motorcycle Association posted an article about an older gentleman who went for a ride on a country road on his Airhead BMW. The bike slipped on something and he went down at 20 mph. Should not have been a major problem, except the gas cap came off, spilled gas on the engine, the bike caught on fire and the old guy went to the hospital with extensive burns.

Click to expand...

Don't slip on something then.

nortonmargie said:

I have already washed out the carburetors with carb cleaner. I checked the fuel filter on the left carb, basically clean, and checked the fuel bowl, it had a little dirt and I washed it out. I was planning to pull the petcocks and check the fuel filters on the petcocks on the inside of the tank when someone suggested checking for vapor lock. If vapor lock isn't the problem, I am going to spend Saturday draining fuel and checking petcocks

Click to expand...

Its sounds exactly what mine does about a mile down the road...when I've forgotten to turn my fuel taps on...it gives you the feeling of running out of gas untill I flick them on while still running along...

Intermittent running can be the result of a corroded ignition switch.
You could try bypassing the switch.
If there is a working kill button on the bike then have a good look at that as well. Both the ignition switches and the kill switches on these bikes are known to give trouble, as with any old bike I suppose.
If in doubt you could do a temporary feed to the ignition directly from the battery. I would put a fuse in the line and a standard toggle switch.
As a matter of fact that has become the permanent setup on my 850. The switch is mounted under the fuel tank where it is out of view.

Glen

worntorn said:

Intermittent running can be the result of a corroded ignition switch.
You could try bypassing the switch.
If there is a working kill button on the bike then have a good look at that as well. Both the ignition switches and the kill switches on these bikes are known to give trouble, as with any old bike I suppose.
If in doubt you could do a temporary feed to the ignition directly from the battery. I would put a fuse in the line and a standard toggle switch.
As a matter of fact that has become the permanent setup on my 850. The switch is mounted under the fuel tank where it is out of view.

Glen

Click to expand...

Appears Worntorn was right.
Cleaned out the tank breather yesterday, bike ran beautifully on idle for about five minutes. Planned to go for a ride today. No lights/no ignition. Battery is fully charged and wiring to battery is tight. Working the kill switch does not help. Pulled several of the spade connectors under the console with the key, one at a time,and checked with multimeter. No current whether key is on or off. Assume I need to check the ignition switch and if that is good, start chasing wires.

How do I check to see if the ignition switch is OK?

What about the kill switch?

nortonmargie said:

Pulled several of the spade connectors under the console with the key, one at a time,and checked with multimeter. No current whether key is on or off.

Click to expand...

Did to check volts (not current)?

There should be battery volts at the ignition switch brown/blue terminal as that is the feed from the battery.

nortonmargie said:

How do I check to see if the ignition switch is OK?

Click to expand...

If battery voltage is reaching the ignition switch brown/blue wire terminal then connect the other wires to brown/blue.

Connecting white to brown/blue should power the ignition, brake light, charge warning lamp, horn, etc.
Adding brown/green and blue/yellow to brown/blue should power the lights.
If everything works normally, then the ignition switch is probably faulty.
If it is the same as before and nothing works then power most likely isn't reaching the ignition switch so check the two brown/blue wires are not disconnected from the 2MC capacitor.

nortonmargie said:

What about the kill switch?

Click to expand...

If the lights, horn, etc. also don't work then it's probably not the kill switch that's at fault.

Thank you all, your help is invaluable

I went down to the garage and got out the multimeter. Set on 20 DCV (=volts) checked blue/brown terminal. No voltage at all, key or on off. Need to start chasing wiring, starting at the fuse, which is weird, because I didn't do anything that should cause the fuse to blow

I also ordered a switch. If it isn't the switch, I can keep it on the shelf with my parts collection

Try wiggling the key in the ignition while checking for voltage. It's easiest with a second person, one to operate the meter and one to wiggle the key.
There is a good probability that the internal works of the ignition switch have become corroded.
If there is power coming into the switch but not out of it, then the switch is the problem.

If there isn't any power to the switch then the problem must be up the feed line somewhere.
Or you could have a bad ground at some point.

Glen

Bad fuse or fuse holder possibly.