Timing plate and piston position

[LoHo]

When the marker in the pickup coil assembly points to F, number 1 cylinder should be at TDC, correct? And then it should be TDC again at 180 degrees out, right?

She cranks and tries to catch, but then backfires like a 12 gauge without starting. Could I be getting spark 180 out from what should be? I've done so much to this bike over so long that I'm not sure what all might be different from when it ran fine all the time.

[Rasputin]

T is TDC and F is when engine running at approx 1000 rpm for timing light use.

[LoHo]

My error, I see that the plate spins once for each piston cycle.

My #1 piston is bottomed out at the T mark. I had the plate off for a while and may have put it on 180 degrees reversed. But all else being the same, that wouldn't change the timing, it would only change what showed on the plate, or am I fouled up?

[natemoen]

In theory you cannot put the plate on wrong. It is supposed to be notched so that it can one be assembled one way. I however will admit it can be put on wrong. It is easier to put on right though.

[Rasputin]

While I am not that smart with electrickery things i would definetly move the timing plate to its correct position. It may have something to do with the reluctors and that would cause your problem. It could also be that you have the pick ups switched bass ackwards but again I am not sure on that so wait for someone who knows better to chime in.

[LoHo]

Yeah, it looks like it can be either right or 180 wrong, but I don't think it affects timing.

[Rasputin]

I was wrong as the reluctor is on the ignition advance unit so the timing plate should not affect it. But hey if it is not showing T as TDC then why not change it so it does so. The timing plate only will fit on properly one way that is correct.

[IanDMacDonald]

Umm, I have not had the opportunity to look at my timing plate for the 11, but, I know on the 750 it is possible to put the plate 180 degrees opposite of what it is supposed to do if you accidentally push in the timing pin as I have done. And, it's not fun doing that! I believe it's the timing pin that prevents you from putting the plate on backwards.

[natemoen]

The notches on the back are ever so slightly off center, but it doesn't take much to overcome the slight off center.

[DGXSER]

Loho,

Yep, it can be put on 180 deg out, but it typically will be noticable it is not quite sitting right. I am anal enough I would have to fix it, but not it should not effect the actual timing.

Since this tells me you did remove the timing setup, it is entirely possible you put the pick-up coils on reversed. Which would then signal the coils in reverse. Easy way to check is go up to the coils and swap the grey and orange wires. On the 78-80 bikes these are separate wires, on the 81 and probably the XJ, each coil has a two wire connector that has an orange or grey wire with the red/white wire, the red/white are the same wire in either case.

Hope this gets your beast back to running strong.

[bikerphil]

Also, the reluctor tab should be pointing towards the top pick up coil when the #1 piston is at TDC. If you took the centrifigul weight mechanism apart to lube it, it is possible to put it back together 180º out. JAT

[clcorbin]

As has been said, that notch is offset by about 25 thousands per my measurements. So the timing plate will drop into position pretty easy one way, but WILL hit when going in the other way, but you can force it if you really want.

I have found that installing the bolt and screwing it in until it is JUST touching the bottom of the timing plate allows me to easily spin the timing plate until it drops on the notch with no force. Then I know it is in the correct position. What ever you do , don't use the bolt to "pull" the plate into position.

If you took the advance mechanism apart to clean and lube it (like I did a couple of weeks ago), be sure you get the bronze trigger back onto the advance mechanism the correct way. I got mine 180 out the first time I put it together and the backfiring through the carbs was indication I had to pull that part off again (thankfully a fast and easy job).