Could someone confirm (or deny) this for me? I have removed the timing plug on my '73 ironhead and am kicking the bike over slowly, very slowly, looking for the timing marks. It looks as if there are two different ones: a single "dot" and a "double dot". These are the timing marks, correct? Single dot is the front piston at tdc and the double dot marks the rear cylinder at tdc? I'm going to adjust the pushrods and want to make sure that this is what these marks are.

thanks,
Chris

 

According to my factory manual the front cylinder advance timing mark is a single dot. Rear cylinder advance timing mark is a double dot. There is also a slot, and it is used with a strobe connected to the front cylinder to set the timng. With the bike at 2000 rpm, strobe connected to front plug wire, and aimed at timing hole, the slot should be visible in the hole, with the front cylinder dot superimposed on the slot.

 

Thanks for the clarification. My Clymer's manual isn't as descriptive as it could be. Is it still possible to buy a factory manual for an old ironhead?

I ended up finding tdc by putting my thumb over the spark plug hole and, when I was on the compression stroke, placing a straw into the hole and watching it for the high point. Adjusted the pushrods (they did seem a little loose compared to the descriptions that I've read of what they're like when they're properly adjusted). Is there a trick for putting the covers back in place?

 

ChrisB.......poco is right on about the timing marks. The slash mark is for the front cylinder using the timing light. At 2000 rpms, the timing is perfect when the mark is centered in the hole. However, if the mark is toward either the front or rear of the hole it is close enough. As long as the mark is in sight you are good to go.
Regarding adjusting the pushrods I would like to offer this:
The engine has to be absolutely stone cold before you adjust these. Do not use the timing marks to adjust. What you need to do is raise all four covers on the pushrods. Hold them in place with paper clips and a rubber band on each.
Rotate the engine until one of the intake pushrods is at it's highest point. Now adjust the like pushrod on the other cylinder. Reverse this for the other intake pushrod. Do the same for both of the exhaust pushrods. The intake rods are closest to the carb of course...........pg

 

Thanks for the help, folks. I appreciate the information.

Do any of you have a trick for getting the pushrod covers back in place? Those springs are stout!

 

Sure....the way I do it is to put the end of a thin shank screwdriver between two fins on a cylinder. Pick a spot close to the tube (#7) Spring Retainer shown in the stack up.
Place the shank of the screwdriver across the top of the retainer and pry downward. When you have compressed it far enough, put the Cover Spring Keeper (#2) in place.
I choose to put the top edge in first and then move the bottom edge inward to the tube.
It is going to take a good bit of compressing to enable this keeper to go into place, but after you do the first one you will know what to expect for the other three.........pg


Edit Note: I attached a jpg of the stack up of the pushrods so you can tell what I refer to on items #2 and #7.

[IMG]local://upfiles/8331/1A60E60D33E743BBA4F70099CC32827F.jpg[/IMG]

 

I got the pushrod adjustment finished and it seems to be running better. It still makes a heck of a lot of noise, but I really don't have any frame of reference for what these motors are suppossed to sound like (valvetrain). I can't really describe how it's running better, but as soon as I fired it up, I could tell that it was better--slightly different sound.

I am still getting an occasional cough out of the carb and so I suppose that the timing is next on the list. Do I need to have a tach to time it or can I estimate the rpm?

 

ChrisB.......An ironhead is a fairly noisy engine if you compare it to a big twin. If you want to compare it to a Honda, then it becomes a threshing machine as far as noise goes. If the engine gets quiet, then you may have some problems coming. Noise is good in the case of an ironhead.
I would definitly check the ignition timing next. You will need a timing light. You do not really need a tachometer.
You do need to run the engine at 2000 rpms (approximately) however. The reason is because the engine has to be turning fast enough to produce enough centrifugal force to allow the flyweights on the advance unit to advance the timing so that you can set it correctly.
A normal idle is about 900 rpms. Just roll the throttle a very little bit and the engine goes to a slight racey sound, or is about double what the idle speed sounded like. Hold the throttle there and check the timing. You will be close to 2000 rpms at that point.

Be sure to check the points gap on the contact points before doing the timing though. Check both cylinders (the ignition cam has two lobes on it) and the difference between both should be .004 OR LESS. The correct gap is .018. If you find that the gap difference between the cam lobes is greater than .004, and I doubt that you will have this, but if so this indicates that the cam is not runnung concentric. Remove it, inspect and reinstall it if all looks OK...............pg