Spark plug angle on alloy head

[limeyrob]

Anyone happen know the angle of the spark plug thread on an A10 ally head?
I want to check the timing and i have tool that slips in the plug hole so I need to do a bit of trig to get the correct reading.
I have level but the shed floor slopes and its a faff so if anyone happens to know the actual answer that would be great.

[Rex]

My tool that slips in the plughole is a short wooden pencil with TDC and the correct timing mark scratched on it.
No trig required...

[Billybream]

Found this sketch in my bike folder

[limeyrob]

Thanks! That's 42 deg, makes sense. I'll try that.

Timing
In           mm        rod mm
3/8         9.53       12.82
11/32     8.73        11.74
5/16       7.93        10.66

[chaterlea25]

Hi All
The diagram is only approximate 
It also depends on the shape of the piston crown
A degree disc will find the correct firing point then make a piston stop using an old plug which you can then use whenever you need to check the timing

John

[limeyrob]

I set it all up with a degree disc and depth gauge as a double check, but I'm having a problem and so firstly I want to check whether something has slipped, and secondly I may need to take the mag off so I'll loose all my careful work.
Its proving impossible to start after its rebuild.  It did start on the kick starter a few times and ran for around 5 mins several times before I shut it down to do some adjustments. Now it won't restart so I will be checking the carb fully, resetting the float level, checking the timing and cleaning the points.
The spark is OK ish but not really strong, the plugs are a bit wet but not really as wet as they should be. Its not running cleanly on both cylinders.  Compression check is good.
So its back to first principles and go over it all again, but since I have the plug gauge I'll use that to avoid taking the chaincase cover off.
When I did the timing with the head off I compared the piston height to the degree disc expecting the degree disc to be easier, but it made no difference so I'm happy to work off piston height.

[bikerboy]

Hi Limey

I find doing the timing is definitely a two man job. One on the points and one on the advance/retard end. If you need a hand give me a shout you are only down the road and I can dive over and set it with you if necessary.

[limeyrob]

Thanks, I got it done with a bit of trickery. It ended up with the mag being duff, seemed fine on the bench but really only a decent spark on one cylinder.  Built a spare mag out of box of left over bits and it turned out much better.  I set that up on the bench then locked it by putting a dowel in an old earth brush, put that on. got the engine at 5/16 (I'm playing safe) before TDC and gave the mag gear a tap on.  Worked a treat. Here's hoping I can leave that bit alone for a while!

[muskrat]

G'day Rob.
When you get the timing just right make a stopper out of an old spark plug. Any time work is done and needs to re-time just screw the stopper in and bring the piston up to it. https://www.a7a10.net/forum/index.php?topic=18137.msg157127#msg157127
I use this even on the Boyer to get it set up, then use a strobe & degree wheel.
Cheers

[trevinoz]

Limey,
When I bench test a magneto I use an adjustable spark gap and give it a run. Firstly, if I can get a constant spark across 4-5 mm I go to stage two which is put the magneto into the oven and heat to about 80 degrees. Back onto the spark gap and see what happens. A good one will work but usually to a smaller gap, a bad one won't spark at all.
This is only for old armatures, I don't bother with rewound ones.