FCRs - pilot jets?

Unfortunately, I neglected to run my carbs dry the last time I rode my Commando. A few weeks later I attempted to kick start the bike and she would not run; in fact it was very difficult to get the bike to start. Normally the bike is a 2-3 kicker! I talked with the bloke who put her back together and he recommended that I pull and clean the pilot jets on the FCRs. Well that looks simple enough! .... the problem is I can unscrew them, completely ... but they do not "fall" out. I am working on the carbs whilst they are still on the bike.

Note the pilot jets are easy enough for me to access with a small screwdriver. I did remove the fuel bowl drain bolts and they were as clean as a whistle ... I am a little stumped. I did take note of the adjust of the pilot screws prior to fiddling!

Any ideas? I am still relatively new to the Commando. I don't want to take it to anyone; as I want to fix and maintain the bike myself.

Did you put fresh petrol in?

It might just be a case of getting some fresh petrol through the system.

It maybe old fuel, but when it comes to the pilot jet, don't assume just because it is clear the small holes in the carb body are not blocked, you need to be able to blow through this to confirm it's not obstructed.

Your tank has a breather, the volatile parts of the petrol disappear out this breather over long periods, not a problem for fuel injection but for carbs it is. Without the volatile parts there is nothing for the spark to ignite from a carb. So each spring before I attempt to start any carbed engine I add a splash of thinners to the tank and wait 15 mins before opening the taps, result is no failed starts as long as the pilot jet is clear.

If you don't have any fine nose bent pliers or similar to pull the jets out, it sounds as if you'll have to take the carbs off the bike to get the jets out. A fairly quick job.

I would think that the rubber O rings on the jets are holding them in place.

kommando said:

Your tank has a breather, the volatile parts of the petrol disappear out this breather over long periods, not a problem for fuel injection but for carbs it is. Without the volatile parts there is nothing for the spark to ignite from a carb. So each spring before I attempt to start any carbed engine I add a splash of thinners to the tank and wait 15 mins before opening the taps, result is no failed starts as long as the pilot jet is clear.

Click to expand...

Never heard of that! Sounds sensible though. Will give it a try today as I’m about to drag a bike out of hibernation...

kommando said:

Your tank has a breather, the volatile parts of the petrol disappear out this breather over long periods, not a problem for fuel injection but for carbs it is. Without the volatile parts there is nothing for the spark to ignite from a carb. So each spring before I attempt to start any carbed engine I add a splash of thinners to the tank and wait 15 mins before opening the taps, result is no failed starts as long as the pilot jet is clear.

Click to expand...

That is a new one on me; makes sense to a point. I will add some fresh gas. However the issue first started after the bike sat for a mere two weeks.

Reggie said:

If you don't have any fine nose bent pliers or similar to pull the jets out, it sounds as if you'll have to take the carbs off the bike to get the jets out. A fairly quick job.

I would think that the rubber O rings on the jets are holding them in place.

Click to expand...

The hole is pretty small; however you have a point. I might be able to buy some very thin needle nose pliers. I believe the o-rings are holding them in-situ! Thanks!

74Norton920 said:

However the issue first started after the bike sat for a mere two weeks.

Click to expand...

The float bowels were full of fuel, that would have lost its volatiles very quickly next to a warm engine, leaving the difficult to burn remainder in the float bowel and then partially replaced by not really fresh fuel.

The problem is not helped by today's fuel being adapted for fuel injection which is by far the biggest user, carbed engines are being ignored. So compared to years ago the initial level of volatiles out of the pump is low, then what's left gets evaporated out of the breather.

Parts terminology is a little different for FCR carburetors.

There is no jet called a Pilot Jet in an FCR. There is a Slow Jet accessible with the fuel bowl off. It is very small and does not have a rubber o-ring. The easier to get at from the outside bottom of the carburetor Pilot Screw has a spring and an o-ring on it. It is long. You may have to take the fuel bowls off to get a tool on the Pilot Screw and pull it out, if that is what you are talking about. I can't remember if mine drops out with the bowls on. I will check later. I won't pull the Pilot Screw out, if it does not drop out. No reason for doing it on my motor.

I doubt that is the problem though. The accelerator pump sometimes takes some priming to start pumping after the carburetors sit around. You will not wash the cylinders and destroy your engine using the accelerator pump more than a couple of times if that is what it takes to start your motor.

2 weeks with the fuel sitting in the tank is not going to prevent your motor from starting, unless your spark is incredibly weak. I don't run my carburetors dry. If I knew I was not going to start the engine for a few months I would drain the bowls and tank.

Fuel Bowl removal: Be forewarned that the rubber sealing gasket for the fuel bowls can expand if it gets wet with fuel and comes out of the groove it sets in. If that happens, it is very difficult to get back in place. I would only take the fuel bowls off if I was positive that the accelerator pump was not putting fuel into the intake. Accelerator pump fuel is what starts your engine. The slow fuel and air circuits that keep it running at low RPM require a lot more vacuum than you can generate with a kick.

blah blah blah

Adjust those Pilot Screws to 5/8ths of a turn out. Take the fuel drain out of each carburetor one at a time and turn on the pet cock(s) to drain some fuel through into a container. Get rid of the fuel. Button it back up, and twist the throttle 3 times quickly. Then a 4th time, but leave the throttle wide open ignition off and kick it over. Turn on the ignition and kick again as you normally would to fire it up. If that does not work, check the plugs. If they are still bone dry, your accelerator pump isn't working that well after sitting. Doesn't mean its busted. Just means it needs to prime itself. Might only take one more twist of the throttle.

In the time it took me to type that up, you probably got it started some other way. ha

Hmmm, there is a person on the forum who has disabled his accelerator pump and his bike kick starts perfectly fine...

Fast Eddie said:

Hmmm, there is a person on the forum who has disabled his accelerator pump and his bike kick starts perfectly fine...

Click to expand...

Imagine that. That would not work on my Norton engine, but I don't have a tilted forward Commando engine. A lot less downdraught.

Maybe the person who can do this with a disabled accelerator pump could give the OP some tuning pointers on how to make it work. If it's you, share the secrets.

Not me.

BTW, I don’t believe downdraught has much impact on kick starting.

Its not clear the OP needs any tuning advice, especially if the bike ran well previously.

Fault finding first.

Stale fuel? Blocked fuel circuit? Flat battery? Duff plugs?? This is the kinda stuff that needs ruling out first IMHO.

I would need tuning advice and possibly some magic forum dust to kick start my engine cold without the accelerator pump circuit.

I can’t help there.

Living in U.K. I need some kind of cold start function which the pump seems to do well.

Schwany said:

I would need tuning advice and possibly some magic forum dust to kick start my engine cold without the accelerator pump circuit.

Click to expand...

There is an aerosol can called Easy Start, meant primary for diesel engines, but could be used sparingly inpetrol engines, I would recommend you sort your tickover first, as this can make or break an owner. . . . . .

Bernhard said:

There is an aerosol can called Easy Start, meant primary for diesel engines, but could be used sparingly inpetrol engines, I would recommend you sort your tickover first, as this can make or break an owner. . . . . .

Click to expand...

Fast Eddie said:

I can’t help there.

Living in U.K. I need some kind of cold start function which the pump seems to do well.

Click to expand...

Opps,
The comment about needing tuning help to start my engine without the accelerator pump was a insincere joke. I would have thought the need for magic forum dust would have been a clue.

I don't have any issues kick starting my Norton engine using the accelerator pump on my FCR carburetors. Using the accelerator pump is how they are designed to work.

I would never disable the accelerator pump on the FCRs. Why would anyone do it other than to say they did and get a like or two? Improve their gas mileage? Should have left 30mm Amals on if that was their end goal.

Schwany said:

Opps,
The comment about needing tuning help to start my engine without the accelerator pump was a insincere joke. I would have thought the need for magic forum dust would have been a clue.

I don't have any issues kick starting my Norton engine using the accelerator pump on my FCR carburetors. Using the accelerator pump is how they are designed to work.

I would never disable the accelerator pump on the FCRs. Why would anyone do it other than to say they did and get a like or two? Improve their gas mileage? Should have left 30mm Amals on if that was their end goal.

Click to expand...

Ha, ha, April 1st has been and gone. . . . . .