First off I own a 1997 Fatboy. I have had it for quite a while but am starting to hear some noises from the primary that I have not heard before.

The first noise is almost like a knocking sound. I tightened the chain and changed the oil and it only makes the knocking sound when at idle. As soon as you rev the engine slightly it stops. I also hear this noise when turning the engine off. just as the final revolution takes place.

The second noise which concerns me more because it just started the last two rides is during engine breaking. As I let go off the throttle and the engine breaks i am hearing a grinding noise. almost like you would when breaks go on a car or when a wheel bearing on a car is really bad. It starts and stops but seems to be getting worse very quickly. This noise also seems to be coming from the front of the primary case and there is a vibration in the foot pegs when this occurs.

I have researched this a got different results and have checked all the basic reasons this might be happening. Any info will help...Thanks everyone!

 

Just an opinion but so a far all I have. Could be many things. However, as the primary chain wears, it does not do it equally and evenly. Probably a long way from wearing out it basically has short and long areas if say you went down the chain and measured the distance in length between 5 rollers at different areas. This makes the chain run tight and a little loose. When you set the tension, did you check for this? Won't hurt anything, but it does make for a rotary tiller noise in a gravel bed. Mine does it. Do not set the chain too tight. Harley says the chain is worn out when the tensioner runs out of travel. Another guess is the alternator rotor spline has sheared off and is slipping but still being driven by the spring pressure of the compensator. However , it has worn so much on the face, it has let the sprocket move over and the front to rear chain alignment is off and the side of the links are nipping the edge of a sprocket. (mine did this also) If this is so, you should be getting a lot of metal on the oil plug magnet..a sure sign

 

What would be considered a lot of metal on the drain screw? Since around March of this year I have changed my primary oil twice. Once for regular change and the second just a few days ago. The drain plug both times had metal filings on them. I have put probably 1200 to 1500 miles on it since the first primary oil change.

I did notice that i tightened the chain one day. Took it for a ride about a mile or so and then checked it again and it seemed it had loosened a little.

How would I check to see if the alternator rotor spline is worn?Is this a fairly easy repair?

 

What is the shaft assembly called that the rotor attaches to? I looked up rotor replacement and found that there are teeth or splines on the rotor and those match up to a shaft that extends out of the bottom of the motor. Is there a chance that shaft may need replacement and if so what is it called?

 

YOUR'S IS DIFFERENT BUT NOT THAT MUCH FROM MY 04. Look here.. click OEM parts and then click the Motorcycle and it will let you pick your year.


http://partsfinder.onlinemicrofiche.....asp?make=hdmc

The alternator rotor is on the crank. That is it hiding behind the chain in the second picture with the writing on it, Do not strike. If you hit it, the magnets will fly off from the epoxy glue since it's like glass.

The magnet will have a hairball the size of the hole coming out.

You really need a service manual and a few special tools to go in there. Including heavy duty stuff for the compensator nut. This is not the place you want to learn how to fix mechanical stuff.

 

Well maybe its a good time to take things apart and replace seals. Could be your IPB bearing. Older model primary's are pretty sound but bearings do go bad.

 

I didn't read all of the responses, so I'm just going to jump in here.

Sounds like the compensator nut is loose and the spring pack in not fully compressed.

 

Does the engine have a rough idle also (shake excessively)? Pull the primary cover NOW. Either have a Mechanic do it or do it yourself. I am betting your Compensator nut is Very loose. You don't say how many miles are on the bike so it is hard to guess how much damage has been done. My guess is a lot. Mine had worn the teeth in the rotor as well as both mating surfaces. The Large spacer and Crankshaft Thrust washer looked like they had been rubbing each other also. Don't wait.

 

I'd put money on the comp nut or sheared rotor teeth. It's happened 3 times to me, exact same sound, vibe in the foot.

 

Just had to revive this 2 week old thread. I rode the bike in from work and heard a slight knocking sound when idling at the stoplight about 2 miles from home. I swear it sounded like a rod noise, and at my mileage anything's possible.

I gently drove it to the house and noticed that at speed it sounded fine, so it couldn't be the rods.

In the driveway it had gotten louder, the sound traveling from the primary across to the cam cover. I was picturing a blown up primary on the left side and my gear drive cams flopping around on blown inner cam bearings on the other.

So I pulled the primary cover this morning. Sure enough, the compensator nut was loose enough to turn by hand. I remember using blue loctite last time I reinstalled it (I replaced the drive belt last fall,) and this time it went back together with the stronger red loctite.

Everything seems fine again. ( It sure did make a racket though!)