So I just bought a 1981 Ironhead and it isnt running right. I bought new plugs coil and points for it. (it was converted to points). I began to put the new points and condensor, I then went to gap it and static time it and noticed a few things that caught my attention. when the bike shows the straight line in the viewing hole its at top dead center, (which is normal). the small lobe was not facing the points though so I thought maybe the advance unit was 180 degrees off, but i then tried agian and did another rotation back to the straight line agian in the viewing hole, agian it was top dead center, but the wierd thing is, is that the small lobe was now agianst the points which was the way its suppose to be. can some one explain this? I am wondeing why a full rotation from the straight line at top dead center all the way around to the line agian only turns the cam 180 degrees and not 360. PLease some one help im at a stand still.

 

Check out this YouTube video ...

http://www.youtube.com/watch?v=mKVh4pbyh2A

 

Some things you might have missed / overlooked:

• first, in your comments, you don't say which cylinder you're looking at.... front or rear. I imagine you're looking (correctly) at the front cylinder but just in case..... we are talking about the front cyl.
• circuit breaker cam runs at 1/2 (one half) engine speed...... aka the crankshaft/flywheel rotates through 2 complete revolutions (completing 1 compression stroke & 1 exhaust stroke), while the circuit breaker cam rotates through 1 complete revolution.

Not too likely the advance unit is 180 degrees off...... more likely, your front cyl was on the exhaust stroke not the compression stroke.

You have correctly discovered & rotated the motor so the front cyl is on the compression stroke. Now you should be good to go.

BTW, most do not use TDC of the front cyl to do ignition timing. Most use the ADVANCE TIMING mark on the flywheel, so you might be wise to locate the ADVANCE TIMING mark for the front cyl.

But it's your ride, do whatever works for you.

 

Yes, the TDC mark is useful if you are using a dial-back timing light to set timing to a specific value, such as 35`. Otherwise i believe you have to use the front cylinder advance timing mark.

Additionally, you should never assume that the marks are what the book or any other person says they are. You must always set the front cylinder to TDC and look in the hole to see what is that mark. Unless you have some way of knowing that the flywheels in the engine have never been changed.

 

Key?????

 

Your #2 cam which operates your points rotates at 1/2-turn for every one rotation of the flywheels...Both plugs fire at the same time...Comprende?

 

Thanks for the comments everybody. Thats what I wanted to hear....Thats what I was hoping, that the #2 Cam rotates at 1/2 a turn for every full rotation of the flywheel. Thanks agian everybody.

 

so I installed my new points, condensor, coil, and spark plugs....set the gap and tried to start her but there was nothing the starter is just clicking as if the battery went dead. so I charged the battery tried agian and now the motor turns as if it wants to start but theres no spark at the plugs or the points. I am sure i put all back together the same....so im at a stand still agian. before I put the new coil points and plpugs in it would at least start....what could be the problem. I have a single white wire going from the coil to the push button start. and the other side of the coil is the wire that goes to the points.

 

Check that there is 12 volts at the white wire at the coil when you push the start button.

The circuit is red wire from batt+ to MAIN circuit breaker, then red wire to B terminal of key switch, then white wire from IG terminal of key switch to IGN circuit breaker, then gray wire from IGN circuit breaker to start button, then white wire from start buton to coil.

 

I don't have an '81 to compare to but this doesn't sound right. Have you confused "push button start" with "kill switch" ?

I would expect that wire to run thru the "kill switch"..... but please correct me if I'm wrong.


Regardless, another simple test you can do..... put your bike into RUN mode by:

• turn the ignition key on
• ensure kill switch is off (if your ride still has the kill switch)

Do you have 12v at the white wire at the coil ? If not, something is wired wrong.