Auto primary adjuster 03-RKC
randy
Not sure what auto tensioner you are talking about.....? Did you use an aftermarket tensioner....?
If you're talking about the Harley Auto Tensioner, introduced in the '07+ models years (I think I got that date correct), there is good reason for the skepticism....
The early version(s) #39929-06 were causing numerous primary belts to over tighten. That would put stress on other areas of the primary causing issues. There were many reports of collateral damage from an over tight primary chain.
I forget the year ('11ish), Harley redesigned it, part #39929-06B. Since that version has been released, there are very few issues with the HD auto tensioner...
In this pic, the older version is on the bottom and the newer version is on the top:
You can see the older version (bottom) has a "thinner" base/ramp, and the adjusting teeth are larger, covering the entire top ramp. The combination of the those two designs allowed for it to ratchet up very tight and over tighten the chain.
The newer version (top) has a thicker base/ramp and smaller teeth covering a small area of the top ramp. It looks much more robust than the older one and with the smaller teeth it would increase tension in smaller increments. This newer one has been almost trouble free, compared to the older version.
Last edited by hattitude; Feb 2, 2019 at 11:19 AM.
randy
randy
You mention your auto tensioner moves... The HD auto adjuster is supposed to automatically adjust to the proper tension spec for the chain. It' not like a Hayden Tensioner, where the chain is tight, and then the tensioner "gives" for the proper chain tension spec.
Generally speaking, a "whirring" sound is frequently a chain that is too tight. Primary chain adjustment specs from my service manuals:
From my '03 manual, for the manual chain tensioner, upward tension on a cold primary chain should be 5/8" to 7/8".
From my '16 manual, for the auto chain tensioner, upward tension on a cold primary chain should be 1/2" (.500") to 5/8" (.625").
So you should have some upward movement on the top of your primary chain, midway between the clutch and the compensator sprockets. Also, as chains wear, they get "tight spots" so you should check the chain in several different spots, and adjust it at the tightest spot.
I would suggest that your chain is too tight if I understood your explanation of its measurement. Based on the Service manuals, you should probably be at 5/8" upward play of the chain, cold, for proper adjustment....
Not sure what auto tensioner you are talking about.....? Did you use an aftermarket tensioner....?
If you're talking about the Harley Auto Tensioner, introduced in the '07+ models years (I think I got that date correct), there is good reason for the skepticism....
The early version(s) #39929-06 were causing numerous primary belts to over tighten. That would put stress on other areas of the primary causing issues. There were many reports of collateral damage from an over tight primary chain.
I forget the year ('11ish), Harley redesigned it, part #39929-06B. Since that version has been released, there are very few issues with the HD auto tensioner...
In this pic, the older version is on the bottom and the newer version is on the top:
You can see the older version (bottom) has a "thinner" base/ramp, and the adjusting teeth are larger, covering the entire top ramp. The combination of the those two designs allowed for it to ratchet up very tight and over tighten the chain.
The newer version (top) has a thicker base/ramp and smaller teeth covering a small area of the top ramp. It looks much more robust than the older one and with the smaller teeth it would increase tension in smaller increments. This newer one has been almost trouble free, compared to the older version.

Hattitude, you can't get a better show-n-tell than this.......... thanks for the write up!
randy
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randy
Thanks for the info....
I see by the video, they use a special auto tensioner bracket, that allows for the newer auto tensioner to bolt into the older inner primary. I didn't know that bracket existed...... The bolt holes that bracket provides are cast into the newer inner primary covers...
Good to know the auto tensioner is an option for the older bikes......
The Best of Harley-Davidson for Lifelong Riders
randy
Last edited by cajun1957a; Feb 3, 2019 at 01:00 PM.









