Ironhead Advance Unit Springs Broke, Sloppy Shaft

[arisaka]

Hello everyone! I'm having an interesting issue with my 77 XLH. I've worn the search function out, so I'll have to resort to starting this thread. Same old story, the bike is running like crap backfiring through carb. Looks like I have points opening on the narrow lobe but not the wide lobe. Okay, reset ignition timing (again) only to find that the cam doesn't reset itself. Further investigation revealed that both of the advance weight springs were broken. So, naturally I need to figure out why they are broken. It looks like they are rubbing against the back of the breaker plate. So, I take a look at the advance unit on my 73 (not messed with by the P/O) XLCH for reference. On the non-molested XLCH, if you replace the bolt that holds the advance unit in, and tug on it, there is no movement. So, very little to no endplay. On the (aggravating) 77 XLH, I can pull it in and out a bit and it makes a clacking sound. Definitely some endplay. Furthermore, the oil seal is leaking oil into the points area. So, here are some questions for the Ironhead gurus here:

1) Will a new oil seal take up the slack (endplay) that is causing the advance weights to rub on the breaker plate?
2) If not, do I need to shim the cam, or replace the bushing? (hope not)
3) Is there a simple way to keep the weights from rubbing on the breaker plate?

I appreciate the help very much, I'm sure after I'm finished working on this bike I'll know enough to help others on this board. BTW, I have the factory service manual for the bike, problem is it starts at section 3-31. The front cover and a portion of the book are lost to time.

Thanks again!

[arisaka]

Here are a couple of pics of the bike so far:

[big andy]

Hi nice lookin bike if it was mine I would replace the complete advance unit They are not that expensive and if you put new springs it may still not work correctly and you will be forever trying to tune it without success .Replace the whole unit and put a new oil seal in behind it and you will have no more problems

[arisaka]

Thanks, glad you like the bike. If I replace the advance unit, would that keep the weights from rubbing the breaker plate? I traded advance units between my two bikes and the end play is the same with either unit. Should I not worry about the in and out movement? I'll try and post pics of the movement later using a dial indicator.
Thanks for the reply, I appreciate the input!!

[Hopper]

Sounds like you have too much end float in the camshaft that the advance unit bolts on to. How much does it move in and out?

Could be your camshaft end float shims have disintegrated - not an uncommon problem. Best to open up the timing cover and retrieve the pieces of shim before they go through the rest of the engine.

On later models, HD put out a service bulletin recommending the discontinuation of shims on the cam spindles. Seems there is some debate as to whether this applies to the earlier models or not.

[arisaka]

Hi Hopper, I'll put it on the dial indicator later today and post the results. I'm about to order parts, do you think I would need a bushing, or is shimming going to give acceptable results? The cheapo in me wants to space the breaker plate a hair out with washers to prevent the rubbing. Bad idea, I know.

[Hopper]

Bushing should be ok unless there is up and down movement evident in the shaft.
No, dont space the plate out, begging for trouble.
Check the manual for 77, they did set the end float pretty sloppy. Maybe as much as .015" but I can't remember for sure. But at that setting, it won't be rubbing the plate.

Check too that the auto advance unit was seated properly on the camshaft. The tiny tiny little roll pin on the back of the advance unit that goes into the slot in the cam shaft can get mashed up and cause the unit to not seat properly.

[arisaka]

So..... advance unit out, retaining bolt screwed in, dial indicator series. When I pull out, I'm showing around 62 thousandths end play. There is also a few thousandths up and down movement. I have a feeling that a 5 thousandths shim won't help....

[arisaka]

Could the bad seal have a hand in this sloppiness?

[Hopper]

No. Seal does not control endfloat. Excessive movement of the shaft will chew up a seal though.

Time to open up the cam gear case and do the cam shimming thing.
It may be too that you have a cam bushing chewed up allowing too much end float.
You can take out the pushrods and the lifter blocks first and take a look down in there and see how much the cam is moving on all four - but you already know this one is bad so you have to open it up anyhows.

Take a good read of the workshop manual before you dig into it. And be sure to remove pushrods before taking the cam gear case cover off.
And just by luck there are a couple of current threads on here about putting it all back together. Plus I am sure there is stuff in the Tech Stickies Index about it.