Sportster Cam Bushings
If you've ever listened to an old Ironhead idling, chances are you've heard a lot of clacking noise. It's probably not a valve adjustment, more than likely it's the cams riding in worn bushings. The noise doesn't really effect the way the bike runs and will not cause engine damage. But if you have the engine apart and would like less cam noise, replacing and reaming the cam bushings is in order.
The most common reason to replace Sportster cam bushings is because they're worn. I replaced mine because I had the old chrome removed at a plating shop, and the bushings got contaminated from the acid.
An Ironhead's cam cover, also known as the gear cover, is made of aluminium, and has six bronze bushings pressed into it. It is a load-bearing cover, as it supports four cams, the pinion shaft, and an idler gear.
Ironhead Cam Bushings
There is no problem finding new replacement cam bushings for your Ironhead Sportster. Aftermarket kits usually come with new bushings, cam plates, bushing pins, and four cam bearings. There are two kits available, one for 1957-1976 XL models, and one for 1977-1985 XL models.
Cam bushings are offered by several different manufacturers. Avoid foreign-made parts and buy U.S. quality bushings. I paid $105 + shipping from an ebay store.
Cam bushing removal isn't that hard, nor is the cam bushing installation. The difficult part is properly reaming the new bushings once they're installed. Again, the key word is "properly". By this, I mean following the procedures laid out in the factory service manual.
New cam bushings are made to size, but the bushing I.D. usually distorts during the press-in procedure. This is corrected during the line-reaming process.
Line-Reaming Cam Bushings
Sportster engine cases and their cam covers were matched on the assembly line, before the engine was assembled. The cam bushings in the cover were not only reamed to fit the camshaft, they were also line-reamed with the right-side engine case. This process allows the cams and idler gears to spin as freely and quietly as possible.
Do I Need To Ream New Cam Bushings?
There are plenty of Sportster owners in the past who have replaced their cam covers, perhaps for a chrome one, without reaming to fit. Or perhaps changed a cam bushing or two and not reamed the new bushings to size. Yes, your bike will still run, but there's potential danger.
If one or more of your cams is riding too loose, they're just noisy, but a cam running too tight spells trouble. If there is not enough minimum cam-to-bushing clearance, the running friction builds up heat, causing tooth surface failure or worse.
A cam will let you know it's too tight by making a whining noise when the motor is running.
The six bronze bushings in your Sportster cam cover are known as blind bushings, because you can't get to them from the back side. This makes getting them out a little harder.
Idler Gear Bushings
Just below the generator mounting hole, there are two idler gear bushings. One of them is in the cam cover and the other is in the right-side engine case. If you're replacing the cam cover bushings, replace the one in the engine case, too. The idler gear bushings do not get line-reamed.
Cam Bushing Removal Tool
There is a Harley-specific tool called a "crankcase cam gear shaft bushing remover". This tool carries part number #96760-36, and has only one function--to remove cam bushings. Of course, the factory-designed tool would be nice to have, but not really needed, because there are other ways to remove Sportster cam bushings.
The method I chose was to employ tools that I already had, which was a 5" air-sander, an electric die-grinder, and a 24" slide hammer. It also helps to have a solid workbench vise.
Read: Ironhead Special Tools
Cam Bushing Pins
From the factory, 1/8" pins were installed in each bushing to prevent it from spinning in it's cavity. Before you remove the old bushings, mark where the pins are. This can be done with either a scribe or a black felt-tip marker. Also note which way the oil grooves face on the four bushings that have the oil slot. They need to go back in the same way to maintain proper engine oiling.
Removing Bushings From Cam Cover
This is the method I used to remove my cam bushings. First, I carefully ground off the bushing collar (the part that sticks out) with a 5" air-sander. I worked slowly and stopped every 5-10 seconds to check my progress. You don't want to take off any unnecessary metal from the cam cover.
Once the bushing collar is ground off flush, the rest of the bushing should come out easily with a few raps of a slide hammer.
As bad luck would have it, only two of mine came out easily. The others required much more time and effort.
To get the other cam bushings out, I ground off each collar, then carefully ground down the length of the bushing I.D. with an electric die-grinder. This was done in a vertical position with the cover secured in my workbench vise. Working very slowly, I ground down just enough in one spot of the I.D. until the bushing split.
Once the bushing was split, I was able to pry it loose with a thin flat-blade screwdriver--just enough to make it loose enough to fall out of the cavity. This was a slow and tedious process. I was constantly stopping and checking my progress to make sure no damage was being done to the bushing cavities.
After all the old bushings were out (including the one in the engine case) I sprayed everything down with brake parts cleaner, wiped the cover clean, and dried with compressed air.
Install Cam Bushings
If you don't have availability to a hydraulic press, here's another way to install cam bushings. Put the bushings in a freezer overnight. The next day, heat the bushing cavities slightly with a propane torch. By freezing the bushings and heating up the cam cover, they should go in pretty easily. A large C-clamp may come in handy.
Remember to line up the oil grooves on the four bushings that have the oil slot.
Bushing Pin Replacement
New holes are needed for the new bushing pins, as they will not fit tightly back into the old holes. This is done to insure the bushings don't spin in the cavities.
With a #31 drill bit, drill a hole through the cam bushing flange and into the aluminum (#31 is .120", 1/8" is .125"). The hole should be 9/32" deep.
Jims Tool makes an excellent tool to help with this.
The factory manual recommends drilling the new hole at least 1/8" from the old one. Or you can simply drill the new pin opposite to where the old pin was.
Once the new pin is in, make sure its below the surface level of the bushing face. After pinning, slightly distort the top of the pin with a chisel and hammer. This is called peening.
Generally, line-reaming is done when rebuilding a new engine. Remember that the cam bushing is not just reamed to fit the camshaft, the bushings need to be line-reamed with the case as well. This aligns everything together--the right-side engine case (cam bearings) and the bushings in the cam cover.
Proper cam bushing reaming requires either splitting the engine cases or having an "extra" right-side engine case. Old school motorcycle shops used to keep a donor engine case specifically to ream new cam bushings after they were pressed in. If you happen to be doing a bottom end rebuild, you'll have the cases apart anyway.
The cam reaming process is not that difficult, but the reamers can be expensive if you don't have them. Three different sizes are needed, plus you'll need pilot guides. Unless you're planning on rebuilding another Sportster or two, these will be costly one-time use tools.
Read: Ironhead Special Tools
Ream New Bushings To Size
- Insert the reamer pilot guide into the right-side engine case.
* Using a T-handle or crescent wrench, turn the reamer clockwise at a steady pace.
- Once you feel it is all the way through the bushing, stop.
- Continuing the clockwise motion, slowly pull the reamer out.
After the new cam bushings are installed, reamed, and pinned, run a hand-held drill bit or something similar into the cam bushings that have oil drain holes. You want to make sure the holes are clear to properly drain the oil.
Cam Gear End Play
Mount your cam cover with a new gasket, and install and tighten 4 or 5 cam cover bolts. Through the lifter bores, check cam gear end play with a feeler gauge.
From the factory, Ironhead Sportsters were fitted with shims between each cam and it's bushing. Clearance should be between .001" to .006" and can be adjusted by adding or removing shims. Some techs will set the rear intake cam to no more than .004" and the other three cams to .005". Although minimum end play is critical, maximum end play is not.
Service Bulletin M-680
In 1985, Harley-Davidson put out Service Bulletin M-680, discontinuing the use of Sportster camshaft shims. Factory testing revealed that too much end play neither increased engine noise nor affected engine performance. If you had shims when you dismantled the motor, you can re-use them if you want. Just be sure to check minimum end play before proceeding.
Cam Bushing Clearance
Minimum cam-to-bushing clearance is critical. This can be checked by measuring the I.D. of the cam/gear bushing and the O.D. of the cam/gear, then subtracting the two. The factory service manual calls for .0005" to .002" clearance for the cam gears, and .0005" to .001" for the idler gear.
When satisfied with the fit, install and torque all cam cover bolts with an inch-pound torque wrench.
Replace Sportster Cam Bearings
If you have engine cases split, this would be an ideal time to install new cam bearings. There is a Harley-specific tool, an inner bearing puller, which allows you to remove the bearings without separating the engine cases. But if you have the bare right-side case in front of you, they can be pressed out on a shop press.
If you look closely at the four cam bearings in the right-side engine case, you will see that they are slightly thicker on the numbered side than on the non-numbered side. When installing new cam bearings, press them in from the numbered side of the bearing. The bearing numbers should face outward towards the cams.