can't start after setting timing

[pdg]

I've got a 1949 A7 Star Twin. I've set the timing but can't get it to start and I'd like to check some things with all wise and enlightened.

When I was finding TDC on the right hand cylinder I found that the cam/crank timing markers were aligned when I could move inlet and outlet valve stems suggesting that I was on the compression stroke. Is this coincidence correct?

[Triton Thrasher]

Did it run before?

At TDC, one cylinder is at the top of the compression stroke, so there's clearance at both valves.  The other cylinder is at the top of the exhaust stroke, with both valves held slightly open.

If the HT leads are crossed, the engine will not start.

You have to re-check the ignition timing after tightening the drive onto the taper.

[bsa-bill]

 Excuse me suggesting the following but believe me I don't know any A owners who haven't done some if not all of the following

1.  timed it to fire on TDC, depending on your bike it needs to be timed a bit before it.
2. got the leads the wrong way around
3. forgot to wedge the AA unit in the advanced position

if you knew all that my apologies, if not ask away for anything else

[pdg]

Many thanks for the replies.

I set the timing 35-36 deg advanced with the ATD wedged, and I checked it after everything was tight, so I don't think it's that.

I get a good spark, so the mag seems ok. When looking at the mag from the primary case side I've got the left lead going to the left cylinder, which is how it was when I took it off.

I noticed that after I'd done up the ATD bolt with a new C washer and took the wedge out I had to manually push the ATD back to the non-advanced position. The springs couldn't do it, which seemed wrong to me?

[chaterlea25]

Hi pdg

I noticed that after I'd done up the ATD bolt with a new C washer and took the wedge out I had to manually push the ATD back to the non-advanced position. The springs couldn't do it, which seemed wrong to me?

This is fairly normal, kick the engine over and the atd will return, its the pull of the magnets in the mag that keeps the atd open (usually??)
Its easy to get the mag timed to the "other" cylinder so try swopping the plug leads..

To identify which cylinder is firing remove the rear pickup and look at the slip ring with a mirror at tdc,
when you can see the brass segment  that is the lead that is firing, bring this to the cylinder thats on the compression stroke (tappets loose)

HTH
John

[pdg]

Many thanks. I've also noticed that when the mag was rewound the ring that contains the points has been put back 180 deg round from where it was originally. Would this also put the firing order 180 deg out?

[bsa-bill]

it would make it 180 deg out from where it was before, and 180 deg out if before was correct, but it's kind of irrelevant as it's just the same as swapping the leads so again the answer would be to try the leads around the other way.

Have you done any other work on the bike other than rewind the Maggie

[wardleybob]

Hi peter you should be approximately 5/16 befor TDC fully advanced. If your stuck give me a ring rob.

[pdg]

Swapped the HT leads and we're up and running. Thanks for everyone's help.