B31 spluttering and flashing back through carb

[chaterlea25]

Hi John1168,

Are we saying that the addition of some screwed dowels  into the base of our Ariel Mag might make it fit ?

Not might it will fit

Some mags I have removed from BSA's had screw in dowels in place, rather than the more common pressed or cast in ones
I have both Ariels and BSA's and worked on more mags and bikes than I care to remember
Ariel's use a third bolt that goes into the fifth hole in the centre of the "four in a square" on more usually found mags
So if fitting a "normal" mag to an Ariel the extra hole will need to be drilled and tapped

John

[john.k]

mention of difficult hot start....... a sure sign of mag windings breaking down......a mini capacitor(aka Thorspark) will restore spark for a time ,and for the price is worth trying.........You should note that mag repairers specifically state that any supressed components in the ignition void the warranty on rewinds.....because these supressed components double the voltage at the mag coil and cause insulation failure.

[R]

Yes a difficult hot start is a sure sign of an ailing condensor, and now it sounds like something has further gone bad.

A refurbed maggie will likely make it a one kick starter, hot or cold, no need even for the leccy boot.

[Rex]

mention of difficult hot start....... a sure sign of mag windings breaking down......a mini capacitor(aka Thorspark)

Do you mean Easy-Cap? Thorspark is the replacement points assembly system.

[john11668]

https://youtu.be/bUXfzANRKdU

This is  a video of a test on the bikes mag,  taken off and driven by an electric drill. Spark is jumping a gap of about 12mm

Then we tried a spare mag which was on the shelf  and it was difficult to judge but maybe that one seems marginally better ,  so we have made the dowels for it and hopefully on monday will be in the position to give it a go.

[R]

Spark is jumping a gap of about 12mm

That doesn't sound all that faulty !
This will be interesting to hear the result,  I thought we had it nailed, for a while.

[john11668]

Hopefully will get a chance to test the replacement (on the bike ) on Monday afternoon.
Have to say though that I approach each each "test" with increasing trepidation 

[iansoady]

I agree, if it will give a decent spark across 1/2" (for our older members!) there can't be much amiss. Is it a nice blue one with an audible crack?

[john11668]

It is but the spare from the shelf has a fatter spark. so  worth a try changingthat.
If it comes down to just a bad suppressor cap, we will sure be kicking ourselves .

[cardan]

If it comes down to just a bad suppressor cap, we will sure be kicking ourselves .

Make sure that it doesn't have a suppressor cap at all - direct connection (0 ohms) only for magneto ignition.

Leon

[john11668]

Fitted  spare mag with no suppressor and  gave it a whirl.
With new carb in place it fired but would not  run.  Tickled some fuel up and try again , and same , a short burst then petered out.
Switched back to the original carb (albeit with new float) and we got her to keep running and warm up,   not bad  but not brilliant  still pops back in the exhaust when you reduce the throttle  ,  odd  spit back  at the carb. Takes quite a  time before it is hot enough to reduce the choke, and on a short run up the road it seemed to produce a fair  bit of blue smoke.

Will try to upload some videos
Not sure where to go next,   Just feel we need someone  with an experienced ear to have a look at it .
None of you guys anywhere near Cumbria are You???

[R]

The blue smoke could be from doing a lot of non-running.
A few miles under its belt might clear it out, don't do anything rash.

With the old carb it will run, and with the new it will not.
So we are back to the quality/jetting/cleanliness of the carbs again !
Obviously something is not right, seriously not right, with the new carb.

Be interesting to know if it would run OK with the old magneto.
With the amount of work involved, best you keep the current one in service until all the unknowns become good knowns.

It is permissible to set off down the road with the choke partly on.
That way the engine warms up quicker, and you can judge when the choke can be reduced.
And if it baulks give it back some choke, on the move it shouldn't conk out while doing this.
Ain't old bikes fun !

[R]

P.S. What was the source of your new amal.

As mentioned earlier, recent manufacture of new amals has had some initial terrible quality control problems,
including swarf in some of the passages and even some of the drillings not entirely completely drilled.
Needless to say, this did not make for very reliable running !!!, especially in the low engine speed side of things.

[john11668]

Not Amal but Wassel .    Supplied by Draganfly as direct replacement .
I can see your point about the quality control , but it is out if the reckoning now as she is back on her original proven carb.

Had just topped up with fuel  when the problem started  but at  our usual regular station,  and have  changed fuel a couple of times since.

[Rex]

I believe that Amal tightened up on it's quality control some years back, and certainly the last two I've bough have been perfect, unlike those bought over ten years ago which were full of swarf.
The irony here is that the Wasell stuff has a bad name now, but in this case that would appear irrelevant.