Running on one cylinder

Cribby · Nov 23, 2020

So here we go again, asking for help

Just spent a week recommissioning an XS1 that probably hasn’t run for many years

I had it running a few months ago but it wasn’t firing on the left hand cylinder so I sent the carbs away for refurb to the same fella I always use (Motocarb in Liverpool). I stripped off the electronic ignition system as it was all in bits and refitted the original points based system. I spent a few hours timing all this up and setting the points gap, fitting new plugs and HT leads and I fitted a brand new loom

She started on the third kick with choke but I still can’t get it to run on the left cylinder

I have spark on both sides and if I squirt brake cleaner in to the left hand carb, it fires?

I swapped out the left hand carb for another refurbished unit and still no fire

HELP!!!

Ant

Cribby · Nov 23, 2020

Sorry, I meant to add a photo if that’s any good?

xjwmx · Nov 23, 2020

You have a compression tester in that garage somewhere.

Cribby · Nov 23, 2020

I do, think that could be it?

xjwmx · Nov 23, 2020

got gas, got spark, so makes sense

Cribby · Nov 23, 2020

But if I squirt brake cleaner in the carb, it fires?

GLJ · Nov 23, 2020

Cribby said:
But if I squirt brake cleaner in the carb, it fires?

Good point. I think I would check compression on both cylinders just to know what they are.
Drop the drain plug on the left carb to check and make sure you are getting fuel into the float bowl.
Also check for air leaks.

Cribby · Nov 23, 2020

Good points, will do tomorrow

thuban · Nov 23, 2020

I don't know what kind of brake cleaner your using but if it's anything like starting fluid, it may hit on that but not on gas with poor compression. Key off throttle full open and kick it about 4 times on each cylinder and see.
(Too late on the draw)

Jan_P · Nov 23, 2020

Thinking out loud if compression tester does not give a clear answer
First check ignition timing when running on the one cylinder,
So it is close.
Move the right hand coil + lead + plug to the left side
Left side to right.
Copper grease at all the right spots. Including ground.
Check points gap and inspect so it appears right there.
Measure voltage to points
A little oil into the left Cylinder ( improving compression )
Start outdoors because the oil will create smoke.
If no start -- take out the plugs place them against the cylinder kick so the spark is there
looking equal on both cylinders --- thereafter
might be valves.
Get back we will reevaluate

Rasputin · Nov 23, 2020

Please check the crossover tube between the carbs that supplies the starter jet (choke) mixture.
I think that early carbs have only got a choke on the LH carb.
Please also ensure you have clearance in both rockers on the LH cylinder compression stroke at TDC.

GLJ · Nov 23, 2020

Jan_P said:
Move the right hand coil + lead + plug to the left side
Left side to right.

This a points bike. Don't think it run like that. Plugs will be firing at TDE.
I could be wrong.

5twins · Nov 23, 2020

It will if you switch the points connection wires too.

Jan_P · Nov 23, 2020

Thank you Lads
I have not had points for fifteen twenty years. don't remember exactly
how it was connected. The point !!! ---Was to move the parts you know are good to the side not firing
See if one can move the problem
Tanks again. Well get there as usual with some fine spirit of cooperation

Cribby · Nov 26, 2020

Well, an interesting update!

I had a day off working on bikes yesterday but plucked up the courage for a bit more fault finding today

My mate turned up as I was opening the garage and I was explaining to him the mystery of the misfire

To demonstrate what I was talking about, I put the bike and choke and it fired 2nd kick BUT it ran on both cylinders. And when I turned the choke off, the bike continued to run on both cylinders, albeit the left hand exhaust puffing a bit of black smoke when revved

It actually ticked over!!!

Logic, what logic?

Ant

Rasputin · Nov 26, 2020

Well, just goes to show what a day off does.
Does it keep running?

xjwmx · Nov 26, 2020

I think there are several things happening, making diagnosing it confusing

Cribby · Nov 26, 2020

Yes, more days off we need!

yes it keeps running, though the tick over drops as the engine gets warm but I haven’t put the air filters on yet, that’s tomorrow’s job

Ant

Jan_P · Nov 26, 2020

Most likely the carburetors needed some " soaking "
Nothing abnormal or strange
Gas into the right places ..Float moving ..Membranes flexing
Can be a little dust and so--- when things establish themselves it fires up
And after a few miles and " Dynamic " up and down revving
Fresh gas passing through it usually runs better
Keep a look at the spark plugs if it runs uneven
And be careful since the floats can get stuck and fuel dripping out.
A gentle tapping on the outside with the handle of a screwdriver or hammer handle
can get it moving again
a Petcock is of course an advantage ,, be careful ..
Perhaps remove the tank in the beginning if indoors and left for a day or more.
Perhaps also the battery connection.

5twins · Nov 26, 2020

Puffing black smoke is a rich indicator. Slowly dropping idle as it sits there can be a slow leaking float needle and seat. The bowl slowly over-fills and chokes that cylinder out.

Running on one cylinder

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