Topic: Weber + ARD Mag setup no start issue

[scottly]

The 6mm stud that holds the stock advancer?

[valt]

The 6mm stud that holds the stock advancer?

No, the only thing that holds the lower shaft to the motor is the two set screws and the mag body. This is a picture of the lower shaft, the body of the mag holds this shaft to the motor.

[scottly]

Can timing marks be made on the larger diameter area of the "lower shaft"? IIRC, the pin that keys a stock advance is at TDC. Would it be visible with the pulley installed?

[valt]

Can timing marks be made on the larger diameter area of the "lower shaft"? IIRC, the pin that keys a stock advance is at TDC. Would it be visible with the pulley installed?

No because loosening the lower pulley set screws and moving that pulley is how you adjust the timing.

[scottly]

No, I mean having a timing mark on the part that is pined to the crankshaft. At least then you could see where the crankshaft is at the instant the points open. Now you are blind.

[valt]

No, I mean having a timing mark on the part that is pined to the crankshaft. At least then you could see where the crankshaft is at the instant the points open. Now you are blind.

I will get a video showing the timing process and it will make more sense afterwards why that wouldn't help. A mark on the lower shaft wouldn't help me as there would be no reference for it. The two marks on the upper pulley and housing let me know when the mag is firing. So all I have to do is roll the motor over with the stock advance mechanism on so I know when fully advance is. Then put the mag on and align the two upper marks.

[scottly]

The lower shaft has a pin that indexes it to the hole in the crankshaft like the stock advancer, correct?

[scottly]

So all I have to do is roll the motor over with the stock advance mechanism on so I know when fully advance is. Then put the mag on and align the two upper marks.

Try setting the advance at the F mark on the stock advance instead of the full advance marks; full advance is not needed at starting RPM.

[valt]

So all I have to do is roll the motor over with the stock advance mechanism on so I know when fully advance is. Then put the mag on and align the two upper marks.

Try setting the advance at the F mark on the stock advance instead of the full advance marks; full advance is not needed at starting RPM.

I have tried this as well.

[scottly]

And?? You mean absolutely no difference? Have you tried going the other direction, with the stock full advance marks to the left of the crankcase mark?

[valt]

And?? You mean absolutely no difference? Have you tried going the other direction, with the stock full advance marks to the left of the crankcase mark?

Sorry I think in my original post I mentioned that I tried different timings but the only one that gets it to do anything is the full advance timing.

[scottly]

What about +/- 5 or 10 degrees from full? You only get anything from full advance? You mentioned at some point the timing felt retarded?

[valt]

What about +/- 5 or 10 degrees from full? You only get anything from full advance? You mentioned at some point the timing felt retarded?

In an effort to trouble shoot the timing issue. I set it at full advance so I would know where it was. Then I walked it back in very small increments and got nothing. Then I set it back to full advance and walked it forward in very small increments and got nothing.

[scottly]

BTW, I have only had a couple of experiences with magnetos, and they never gave me the grief you have been going through.

[turboguzzi]

In response to Turboguzzi:

I don't have easy access to a full points setup with coils and stock plug boots. I have verified spark on both the big bore motor and other motors I have put the mag on. So I am confident spark is not the problem, that being said you certainly have a point. It could still be a timing issue, which a stock points setup would eliminate since I would be able to set it without full advance and be confident in my timing settings.

quick check shows that points plates and coils with wires sells for 20$ (each) used on ebay.... just an idea to at least eliminate a part of the madness...

[valt]

In response to Turboguzzi:

I don't have easy access to a full points setup with coils and stock plug boots. I have verified spark on both the big bore motor and other motors I have put the mag on. So I am confident spark is not the problem, that being said you certainly have a point. It could still be a timing issue, which a stock points setup would eliminate since I would be able to set it without full advance and be confident in my timing settings.

quick check shows that points plates and coils with wires sells for 20$ (each) used on ebay.... just an idea to at least eliminate a part of the madness...

Unless I can find a known good working setup. I don't want to bother with the money and time to buy random ebay stuff that I'm going to assuredly have to fix. I'm going to scrounge around and see if I can at least find a points plate and coils. I'm buying another motor next week so I will see if he has some as well.

[valt]

Alright so an update on this. I finally had enough of it and brought it to a local shop to see if they could find anything wrong. I can't believe I never noticed this being that I had the valves in and out of the head several times. But All of the exhaust valve guides are extremely worn. What they believe this causing is intermittent compression, which is why that doesn't show up in a compression tester.

I pulled the head off my other running motor and brought it to them so they could throw it on and see if actually runs. I have attached a video showing how bad the wear is on the guides, he hadn't pulled the intakes so not sure if they were this bad but its likely.

[scottly]

All of the exhaust valve guides are extremely wor n. What they believe this causing is intermittent compression, which is why that doesn't show up in a compression tester.

I'm not buying that explanation. You mentioned before that none of your timing lights worked consistently with the magneto, so maybe the spark from the mag is what is intermittent. 

[754]

If I have the rockers or cam cradles off a head, I give the valves get wiggle test. You can see them move if they have a lot if clearance.

[scottly]

Even extremely worn guides will not cause a significant and "intermittent" loss of compression, such that the motor won't run. I had a VW motor once with exhaust guides with 2mm wear, and it ran. It made a lot of noise with the valve cover off, as when the valves first opened, the exhaust blew out through the guide.

[valt]

All of the exhaust valve guides are extremely wor n. What they believe this causing is intermittent compression, which is why that doesn't show up in a compression tester.

I'm not buying that explanation. You mentioned before that none of your timing lights worked consistently with the magneto, so maybe the spark from the mag is what is intermittent.

There is nothing wrong with the mag (I have tested it several times and verified it works on known good motors). New timing lights cannot pick up the signal from the mag very well which causes them to intermittently show spark.

I'm not sure I agree that the extreme valve guide wear is causing it not to run either. But it certainly is not helping it. I pulled the head off the other running motor and we are going to put it on the big bore motor and see if it does anything different.

[Don R]

 I had a bad #1 plug on a motor and it caused the inductive timing light to intermittently not light, I assume the plug wasn't firing. After I replaced the plug it lights fine now. That's just my bike, not saying it applies to your situation.
  My light's pickup has an arrow pointing towards the plug. I always wondered if our ignitions having opposite polarity on each side of a coil affected that.

[scottly]

Valt, any chance the cam timing was off?

[valt]

Valt, any chance the cam timing was off?

Cam timing was verified by myself and 2 separate people who are familiar with 750 cam timing. So it was as correct as it could be.

[valt]

Well after swapping the heads the motor still won't run. I'm going to pick it up this weekend since the next steps are going to be tearing the thing down further. I am starting to feel that its way to tight and I want to double check my ring gaps and make sure the motor turns over nicely with the head off.

The motor seems to tight and I think that is causing problems with getting it started. Plus I need to get new valve guides installed on my head since they are super worn out.