[AzCal Retred]

Pop off the fuel line at the carb & see if you can get mebbe a pint a minute or similar, keeping tubing at that same level. The OEM taps are pretty restrictive. The wide bore alcohol taps are a whole 'nuther ballgame.

The float level needs to be OK also, I think it's 1" from the gasket surface to the top of the floats, upside down, on the Mikcarb.

Blast some spray carb cleaner in there through the passages whilst you are in there for good measure.

Hook up the fuel line to the carb with the float bowl off and SEE edzakery how much gas it passes. If it can fill the float bowl in 3-6 seconds I don't see how it can be an issue.

Spark gap can be opened up a bit if using fine-wire iridium plugs. Gives the mixture more opportunity to find a chunk of spark.

After you are sure the fuel level is proper and flow is good, feed it a new spark plug to placate the spirits & try again.

Timing shouldn't be a major issue if it's running OK most of the time. The "full retard" or "full advance" methods should get you close enough for 'gummin't work.

Keep picking at it - ACR -

PS - Your fuel cap IS VENTING, yes? You can hear it "wheeze" if you shake the bike & slosh the fuel about? It can be disassembled and the vent hole reamed out if necessary, at least my detachable cap can.

[Raymond]

Thank you AzCal - once again, some good advice and a few things for me to try.

It's all too easy to lose direction and just keep hopelessly casting about.

I know there's a good bike in there and when we're in top and it's running proper, hilarious fun.

[Raymond]

Just been out to t'garage, pulled fuel hose off carb, held measuring jug, tap on and used my pocket watch to time 1/2 a pint - 80 seconds.  That would be 2 minutes 40 seconds for a full pint, or about 200 millilitres per minute.

More than the trickle that was coming before I cleaned the tap but a lot less than a vigorous flow.

Is this slow enough to account for the running problems? Time to think about a tap with a better flow rate?

[Raymond]

And further investigation, took carb off to check float level, shows the barrel of the carb to be black and sooty, especially at the filter end. The slide also shows signs of a sooty environment, again more on the filter side. Hope the pictures show this, apologies for the out of focus image of the slide:







Black soot which readily rubs off. Too much petrol?

 

[Paul W]

I suggest you check that the inlet valve clearance is just perceptible  when cold. Looks like it might be too tight, causing slight leakage and blowback into the carb.

[Raymond]

Thank you, Paul! That much soot, never saw that in a carb before, was wondering how that could happen and the possibility of inlet not closing crossed my mind.

Still haven't checked the valves but obviously need to, I believe they should be set to just turn when cold?

Cheers, Raymond

[Adrian II]

Yes, the push rods should just spin freely on the tappets but with no up and down play beyond that, set at top dead centre on the compression stroke with a cold engine.

A.

[Raymond]

Checked the pushrods yesterday. Probably should have been in there before but anyway, both turn freely so the inlet is not being held open. There is slight up & down play which I should adjust out sometime but as my friend Elliot tells me 'a tappy engine is a happy engine.'

One condition that seems to provoke the engine holding back or giving up is riding at very small throttle and then asking for a little bit more. I suppose that's the transition from pilot to needle? So I lifted the needle by one notch - the clip was at third lowest, now at second lowest. One test run up to the next village and back, about three miles, the bike felt much happier. Tried to provoke it by giving some throttle, maybe halfway, from lowish speeds and it was fine.

Then I went for another short run and it stopped just after pulling out from a junction. Uhmm.

Still, I feel it's going in the right direction. Now wondering about investing in a new coil . . .

[AzCal Retred]

Sounds reasonable. Electrical issues are on/off usually. Make sure it's not just a bad connection - loose, corroded, or broken wire with intermittent contact, etc. Check the ground to the coil also, I usually run a dedicated (-) wire to the important stuff, frame conduction is too haphazard for my taste. Look hard at the kill switch circuit also, it's in-line with the coil (+).

One plan is to run a fused (+) jumper directly to the coil and take it out for a spin - this eliminates all the intermediate BS. If the coil/condenser is getting hot & dying intermittently that may help find it. If the solid "hotwired" system runs flawlessly for 30-45 minutes or so, maybe the issue is in the intermediate wiring.

Good Hunting - ACR -

[Raymond]

Thank you for your good suggestions. My Bullet doesn't have an earth from the coil - it earths through the points:





Should there be a separate earth from the coil?

If I understand correctly, the jumper wire would be a wire with an inline fuse, running from the battery + to the coil +?

Today, been out on the Bullet twice for a total of about 46 miles and it ran well, the engine only wanted to hold back/try to cut out twice and was able to keep it running by grabbing the clutch.

Biggest issue today was the front brake seems to want to stay on as it gets warmed up. Pulling the top actuating lever up - it only moves a tiny amount - seems to release it. But it makes me a bit wary of the front brake. The next thing I need to take a look at . . .

[AzCal Retred]

The coil has two windings - the low voltage (LV) side & the high voltage (HV) side. The LV side is powered up (+) and grounds thru the points.
The points housing conducts back to the Bat (-) thru engine cases, various bolt/washer combos, etc. until it gets there. Doesn't hurt to have an actual copper wire running back to the (-) Ground lug.

When the points break open, the LV side field collapses and HV side shoots the juice to the spark plug core, jumps the gap and comes back to the coil case. Again, paint, bolts, rust all work their voltage sucking magic. A low resistance copper wire from the bare case back to the (-) Ground lug provides a dedicated low resistance path.

Yes - a fused (+) jumper running to the coil LV (+) bypasses all the grade-school wiring. It HAS to work at that point.

The front brake cam shafts on ALL my machines have needed freeing up. Usually working them with some 3 'n 1 oil after they are apart, shoes off did the trick. Usually...

[Adrian II]

One plan is to run a fused (+) jumper directly to the coil and take it out for a spin - this eliminates all the intermediate BS. If the coil/condenser is getting hot & dying intermittently that may help find it. If the solid "hotwired" system runs flawlessly for 30-45 minutes or so, maybe the issue is in the intermediate wiring.

What my learned friend is proposing is simply what a thief would do to steal the bike! So YES, just run a wire from the POSITIVE battery terminal directly to the coil where terminal it would normally receive its supply from the ignition and kill switches. I know you rewired, but of course the OEM ignition switches are not the very best quality.

You do not want to run a lead to earth (ground) off the coil, it would simply short out the points! Leave that side of it as it is now.

A.

[AzCal Retred]

To be clear, a ground (bond?) lead to the clean metal of the spark coil case back to common (-) ground lug, not the (-) side running to the points. That would be for the HV side benefit. The LV side may possibly benefit from a bonding wire, providing a dedicated low resistance path back to the (-) ground terminal from the engine cases. Nuance stuff, only matters if the cases/frame don't have low resistance return path. The VOM will tell the tale.

[Raymond]

. . . I know you rewired, but of course the OEM ignition switches are not the very best quality. . .

The bike doesn't have OEM switches - it was my decision to fit alloy switches which led to the rewiring. Of course it means that instead off OEM switches known to be not the best quality, the bike has probably Chinese switches of completely unknown character. They seem to work.

Thank you for all the suggestions. I am trying to be methodical but I'm operating in what is for me the unknown.

I will use my multimeter to check resistance between the coil casing and a good earth point on the frame - I'm guessing the reading ought to be low?

Will fitting a jumper from battery to coil tend to cook the coil? I know you shouldn't leave the bike switched on for that reason. Though that is something i inadvertently did a wee while back.

Front brake service coming soon.

[Raymond]

Front brake service has started.

The link rod puzzled me a bit - took it out:



and what we have is, at the lower end, l/h thread, an adjuster nut and a threaded trunnion. And at the upper end, r/h thread, a small locknut, an adjuster nut and an unthreaded trunnion. It freely slides over the thread. I don't think this is right?

But more immediately, the problem is how to remove the back-plate nut. It looks like 1"AF but haven't been able to shift it. Wondering what the correct size is and what too you gentlemen use to undo this nut? Deep-access 6-point socket? #

Post scriptum - done some more reading around and it seems that my front brake has had the drilled trunnion mod. Which seems to be a Marmite subject - hope I haven't started an oil thread. But I would still like to know how to undo the back-plate nut.