Sportster Primary Chain (Remove and Install)
Article and Pictures by Mark Trotta
Removing the primary chain from your Ironhead Sportster requires several specialty tools. All can be bought and most can be fabricated. A service manual is always helpful.
Read: Ironhead Special Tools
Remove the hand clutch lever. On 1977-up models, loosen the chain tensioner from underneath the cover. Drain primary cover oil and remove cover.
Note that their are different length bolts holding the cover. I use a piece of cardboard to keep the bolts in order.
The clutch assembly comes out next. For a step by step how-to, refer to the Remove And Install Clutch page.
There are at least three different timing chain tensioners for the Ironhead motor:
- 39975-52B - 1957 to 1976 XL and XLH
- 39975-54A - 1958 to 1969 XLCH
- 39975-75 - 1977 to 1980 ("old style")
- 39975-80 - 1980 to 1985 ("new style")
On pre-1977 models, remove the bolts from the primary chain adjusting bracket. This will leave the adjuster loose behind the chain.
Sprocket Locking Link Tool
A tool is needed to keep the two sprockets from turning while you remove the hub nut. You can either borrow one, buy one, or fabricate one. The tool fits in between the clutch hub and the large nut. After the tool is in place, bend back the tabs of the lock washer so you can get to the hub nut.
The picture below shows the sprocket locking link tool holding the clutch basket and compensating sprocket.
A 1-1/2" socket is needed to remove the large nut. An impact gun can also be used to remove this nut, instead of using a locking tool. Either method works.
To remove the compensating sprocket shaft nut (front pulley) another specialty tool is needed. One can be made, but they're pretty cheap to buy.
Order of compensating sprocket shaft assembly is sprocket shaft nut, sprocket spring, sliding cam sleeve, sliding cam, and sprocket shaft extension.
The compensating sprocket shaft nut, clutch shell, and primary chain will come out together.
Inspect all parts for wear. Clean and blow dry with compressed air. While it's visible, inspect the clutch shell for any wear or damage. Look for worn sprocket teeth or damaged ring gear teeth.
The primary chain runs in an oil bath and generally does not wear out. Unless your bike was abused (raced), a Sportster primary chain may outlive you.
Inspect the chain adjuster plastic shoe. If it has deep grooves (like the one in the picture below) or it's worn (less than 1/4" of original thickness) replace it.
Install Primary Chain
The hub nut and lock washer (use a new one) go back over the clutch gear splines. Install the lock plate tool to tighten the sprocket shaft nut. The clutch hub gets tightened with a socket, and needs to be tightened to at least 150 foot/pounds. To do this, it's OK to strike the socket handle with a soft mallet.
After tightening, bend the ears up on the new lock washer to prevent it from loosening.
Primary Chain Adjustment
Whichever chain tensioner you have, the chain should have 3/8" to 1/2" movement at it's tightest spot. To re-install clutch assembly, refer to clutch remove and install page.
Reinstall primary cover with new gasket. Gasket sealant is optional.
To adjust the clutch, unscrew the large assess plug. (using the side of a wrench is better than using too-small a screwdriver). Loosen the locknut. With a flat-blade screwdriver take up the free play on the adjusting screw, then back off a 1/4 to 1/2 turn. Basically you are turning it in until you feel pressure, then backing it out some. The backing off is to make sure the clutch is fully engaged. Tighten the locknut without moving the adjusting screw. Make sure there is an o-ring on the back of the assess plug before re-installing (to prevent a possible oil leak).
After your bike is together and running, listen to the left side of the motor. If you hear a whining noise coming from primary, the chain is too tight. If the chain is too tight it will stretch.
If the primary chain is too loose, you may hear a rattle. It's better that the chain is a little loose than a little tight.
Read: Harley-Davidson Classics