Me me, I an airhead

[coastranger]

Originally Posted by Milkjug

Thanks for the responses gents. The bings have coarse threaded adjustments which makes them sensitive. I will double check for runout at the cam nose with a dial indicator, I just set points and I'm running a dyna booster, valves are set, I get 44mpg, running fresh brad penn 20w50 with a napa filter (which is very high quality). I'm gonna change wires, check for that damn ghost and if he's spooking my timing. I agree with the guy who said if you have a carb issue, check ignition. My mileage is correct by the way. Carbs have matching number plates and same throat size, but I don't know the condition of the diaphragms. Could it need a timing set??? Hope not and how would I know?

NAPA sells a filter for these things ????
live and learn
that is if a person wantsw to learn, never looked at napa for a filter, if I dont look, I cant learn :)

[Milkjug]

By timing set I mean chain and sprockets. I have Noris points that I set with the small gauge in the tool kit and a dab of the Bosch grease so I'm good on that. Im going to order the Beru wires from eubmw and rebuild kits for the carbs after checking runout on the cam nose. Bike really idles poorly.

[disston]

I was told that checking the run out didn't really matter. What matters is the double timing image. Sometimes changing the advance unit can fix the image.

Duane Ausherman's web site explains all this and more. He works mostly on /2es but the principles are the same. I fixed mine with a hammer and a long brass drift. I whacked the advance unit a couple times, looked at image again and whacked it some more. I now have an even running engine. Two years ago at one of the Maryland Tech Days the Maryland Air Marshall said to me, "Charlie, your bike sounds good." I think it was so bad before it didn't sound good.

[Milkjug]

Originally Posted by disston

I was told that checking the run out didn't really matter. What matters is the double timing image. Sometimes changing the advance unit can fix the image.

Duane Ausherman's web site explains all this and more. He works mostly on /2es but the principles are the same. I fixed mine with a hammer and a long brass drift. I whacked the advance unit a couple times, looked at image again and whacked it some more. I now have an even running engine. Two years ago at one of the Maryland Tech Days the Maryland Air Marshall said to me, "Charlie, your bike sounds good." I think it was so bad before it didn't sound good.

Did you whack the cam nose, or the mechanism itself and where, no pun intended

[Milkjug]

[IMG][/IMG] here's a pic of my r90 on a nice day, been windy and foggy for a month now. Napa filter for airheads PS4945; whole kit was $8.00 and a really high quality filter IMO.

[disston]

Originally Posted by Milkjug

Did you whack the cam nose, or the mechanism itself and where, no pun intended

I pretty much did it the way Duane describes I think. I tried to do it his way. But I was confused about where or in which direction to bend the cam tip. So I spent some time with my trouble light checking the opening of the points and tried to figure which side was opening the points earlier, so to say. I puzzled for some time with this and then when I figured I had figured which way to move the tip I placed my long brass drift from the left side onto the advance unit. I was able to work against the solid piece of the advance unit and I gave it one good whack. I was using my 2 lb small sledge or drilling hammer. When I say a good whack, I mean enough to have effect but not enough to move anything very far. I played with this for 30 mins or so the first day. I did this on maybe 3 different occasions. Each time checking the timing again in between each whack. I was able to see which way the timing was moving and by how much. I may have gone on even longer but one day the timing marks were really close and one more small bump I was home free.

I haven't checked it this year yet but should probably do that. I put a Dyna Booster on it last year (the same one I took off over ten years ago)

I wouldn't say that trying to figure the direction needed with the trouble light did any good. I think Duane says to hit it any ole way and if not right then hit it the other. Maybe it didn't matter like he says but I felt I should try to move it intelligently. Like stated I worked on this a couple of three times and always quit when I got tired of it or figured I wasn't doing any good. Sometimes it was better but not close enough. In the end it might have been just luck, I don't know.

But I got what I wanted, one dot of light in my timing window. I never would have found the original problem if I had not looked for it. My timings marks were so far apart that there seemed to be only one. Then when I raised the idle the second mark would appear. And now my German motorcycle doesn't sound like Patatoe-patatoe-patatoe.

The cause of all this is not important maybe. Some say it's the large gear on the cam. But I haven't changed mine or any other so I can't say.

[MotoKaw]

WOW MilkJug, that's a great looking BMW! Thanks for the filter tip. Now please tell us a bit about that solo seat - home made?

- Bob

[Milkjug]

Originally Posted by disston

I was told that checking the run out didn't really matter. What matters is the double timing image. Sometimes changing the advance unit can fix the image.

Duane Ausherman's web site explains all this and more. He works mostly on /2es but the principles are the same. I fixed mine with a hammer and a long brass drift. I whacked the advance unit a couple times, looked at image again and whacked it some more. I now have an even running engine. Two years ago at one of the Maryland Tech Days the Maryland Air Marshall said to me, "Charlie, your bike sounds good." I think it was so bad before it didn't sound good.

You must be a lucky person, if I started whacking the mechanism with a drift it would break, I hope you buy Lotto tickets. I'm gonna use my dial indicator and zero it and turn the engine to see if the needle moves, then whack it. If that doesn't work, I'll go to the next step and the next and the next. I hope it goes from potato to pot with no tato.
For the seat I cut a rusty denfield pan in half, por 15'd it and riveted on the seat you see by the vinyl. The seat is mocked up in that pic. It's not as nice as village idiot's seat, but my ass doesn't mind.

[disston]

I still have some of the other timing woes of an Airhead motorcycle. Using the Booster is a big plus but I do set the points to work on their own before connecting the booster. So if I should have a problem on the road I can just unplug the box.

After I get the dwell where I want it I try to time the engine with moving the point plate. I always end up with a fine adjustment of rocking the advance unit on it's D slot. Works for me.

I guess those points are now in there for a couple of years. But I'll check them once in a while.

You might find that the dial indicator works better than what I went through.

[Milkjug]

Disston, can you explain what rocking the advance unit in the d slot means. Do you set timing with the engine running, the book and local BMW guy said small taps, shut down, start, check. Sounded like a crapshoot way to set timing to me.

[disston]

The bending the cam tip is a sort of crap shoot. That's my experience. It may not be the cam tip is bent, not at all. My own personal theory is that it is the cam bearing on the front of the cam shaft that is worn. This is the part holding the cam in the block. I proposed this favorite theory of mine on another list once and was yelled at because "Everybody knew the problem was the large gear for the chain that was worn." Mean while another Guru maintains that the large gear is never worn, can not wear because it works in a bath of engine oil.

The bottom line: Nobody has the definitive reason for why the older Airhead has the ghost timing image. It may be several reasons or a combination of worn parts.

The tip of the cam shaft has a D shape that locates the advance unit. When new the advance unit fit pretty tight. After many miles most of them are worn so that when fitting the advance unit, before tightening the small nut on the tip, the advance unit can be rotated several degrees. I think it is best to locate the rotation all the way clockwise or counter clockwise. Then remember to replace the same way. When timing the engine on my bike I found that one way works and the other way I can't get it timed properly. I have to play with this any time I have touched the timing or removed the advance unit.

I always time my bike with a timing light at full advance. This also works out to be the correct place for idle because I have blue printed the advance curve. If I was broken down on the road and had to do this with out the timing light I guess I would still get it with the trouble light but I find it easier to use the timing light at home.

I also have another problem that one Guru says is uncommon. I have to set the timing and tighten the screws then check where it is. It will not be where I thought I set it. So I have to guess the amount of change and tighten the screws then check again. It has been like this for so long I think it's normal. Said Guru says I have a bent point plate but I checked and it is not bent.

After all this I think my bike is beyond worn out and is really a rolling wreck on the highways of America. So I get out on the nearest freeway and blast down the road at a hunert miles per hour till I see some cops. Then I slow down and go home.

[_cy_]

welcome to the madness ... airheads are simple, but some things are done slightly different from other machines. there's a steep initial learning curve, learning what those differences are.

for instance... there's a LOT of aluminum threads used on airheads.
if torque spec's is 6-8in lbs, it means it.

if you are not the original owner, odds are there's a few stripped bolts waiting to happen.
bolts barely holding that strips at the first sign of torque.

if doing all of the above to fix and vibration at XX rpm doesn't go away.
it could be pistons/rods out of balance.

as it was explained to me factory piston/rods can be out of balance by a significant margin.
my R80 G/S was balanced to 1/10 oz and runs pretty smooth.

[disston]

The bending the cam tip and consequently the position of the advance unit is to deal with a ghost timing image as seen in the timing window when using a timing light. I sometimes call it a "ghost". It is also called a double image. Usually the second light is in a blank part of the flywheel so it's sort of invisible. If checking at idle the mark for one cylinder will show the mark you want and the second firing being in a blank area of the flywheel will not show. Tricky. You have to watch very carefully as the rpm is raised and the timing marks start to move.

There is also some jumping around of the timing marks from bouncing points and whipping timing chains. You have to factor these out. The ghost image you should look for is very regular and will appear in the same places as rpm is raised and lowered.

I am not an expert on anything but I learned about the ghost timing issue when I discovered this problem on my R90/6. I fixed it the way described by Duane Ausherman on his web site. I don't know how common a problem this is. I've not heard of too many others. The biggest issue with this particular problem was a lack of performance and the lopey idle. Saying it sounded like a Harley is the most descriptive way I can put it. But the image with a timing light was very convincing.

I guess there was some improvement of vibration issues but not much. After the timing was fixed tho I was able to balance the carbs better which improved vibration issues even more.