Valves or timing?

Left cylinder not running right. Plug clean and has spark.miss firing and popping .not to sure how address either problem. Soo close to 1st ride.

So many factors. Electrical or fuel. More info. Concentrics , or electronic ign ? :shock:

Favourite first port of call is blocked pilot jet. Can be cleared by simply removing the mixture screw and clearing with fine wire.
They block for fun, especially if the inside of the tank has rust or other contamination. Fuel filter highly recommended.
Quite often I get a plugged pilot jet after the winter lay-up. I must remember to run the carbs dry when I park it up...

Thereafter it's a carb strip.
If you have EI then plug, HT lead, coil in that order - swap them over and see if the fault transfers

Had only one firing on mine and turned out to be the ignition switch so "hot wire" it and see.

Points clean and set. Cleaned carbs.ran copper wire through pilot jet decent spark .out of ideas.

Points clean and set. Cleaned carbs.ran copper wire through pilot jet decent spark .out of ideas.

PJFlynn said:

Points clean and set. Cleaned carbs.ran copper wire through pilot jet decent spark .out of ideas.

Click to expand...

No you didn't.
Copper wire small enough for .017" orifice would be too limber to get in there. Dive deeper in there

Bad spark plug, plug wire or coil ? Swap sides and see if the problem remains the same. Shorted condensor ? Recheck your valve adjustment. Check valve lift.

Greg

First determine whether both cylinders have a decent compression, either by use of a compression tester, or in an emergency by your thumb over the plug hole. All other checks and tests should follow on, depending on the result.

Otherwise you can very easily end up chasing your tail around in circles

Old steel guitar strings are a favored pilot jet cleaning tool. If you don't play, you can still stop at a music shop and tell them you need a steel string .017 or smaller. It won't cost much and you can ream a thousand pilot jets with it. Any decent music store will have individual strings rather than sets for people who like to build their own set.

With that said, Amals have a small plug on the air intake side (air cleaner side) that closes off the pilot bore. One of mine was leaking. Caused me a lot of frustration until I discovered it. I dont have a photo handy of it but if you look into the mouth of the carb there are some holes across the bottom for air intake for the jets, there is a small plug that closes off one of these bores. If it leaks then the carb sucks air into the pilot assembly without going past the needle. If yours is leaking, you will never get the carbs tuned until you plug it.

Russ

Points ? Change the condensers and use a points file to clean flat the contacts then re-gap them. Plus all of the above. Buy a guitar whilst in the music shop too.

If it still does it after all of this, check the float and level. I had my float bowl warp and the float was sticking. I guess I snugged it up too tight. Same symptoms

wd40 sprayed on the intake manifold whilst running. if it smooths out, you've got a leak. Those buggers (carbs) warp sometimes of their own freen will. I had this same problem and it was air seeping past the intake manifold. Uncontrolled air = problems

Is the needle moving with the carb slide? (on both) If you have the original air filter fitted you can check for this without disturbing it by removing both float bowls and the main jet holders and see what is happening in throttle needle land

Thanks guys waiting for stay up floats and needles from old brits.will let u know how I make out.