Camshaft Sprocket Swap

[wickermann]

Has anyone here ever swapped over a camshaft sprocket? If so what is the best way to do it? Is it heat shrunk on?
I have a 1972 XS-2 which I am converting to XS650 engine internals (533 crank, pistons etc) but I believe the XS-2 camshaft is better than the later cams, so I would like to keep it if possible.
Dave.

 

[XSLeo]

You need a press to just press the sprocket off and on. A bit of heat probably won't hurt unless you get things hot enough to affect the hardness of the parts.
Getting it back on in the right place is the tricky part.
Hugh at Hugh's Handbuilt has done this to use the 256 cam in his rephased engines.
Maybe contact him or he may see this thread and respond.
Leo

 

[650performance]

Leo's right. It's just a press fit, but the trick is to mark the desired location very, very carefully and then press the sprocket on just a bit ... perhaps 1/8" ... eyeball the alignment and if it's right, continue on to the stop. If not, then it's easy to get off without overworking the bits.
Also, you can get an adjustable cam sprocket which eliminates the problem. Just press it on within 5 degrees or so and you can dial the cam timing in later.

 

[Brian902]

If you look for threads by mrriggs, you'll find he recommends heating the sprocket to about 200 F and it will drop on with a moment to adjust it before it cools and locks on. Heating method was just a propane torch.

Installing bearings we often freeze the shaft for several hours and heat the bearing to get a slip fit that locks when cool.

Not sure if he heats them to remove.

I would think too many removals and installs would eventually loosen the fit.

Found this, good read;

http://www.xs650.com/forum/showthread.php?t=6867&highlight=camshaft

 

[mrriggs]

You definitely need a press to get the sprocket off (no heat) but I don't recommend using the press to put them back on. Besides being more difficult to line up the sprocket, you run the risk of cracking the cam.

A shrink fit is much safer and easier. Like Brian902 mentioned, I use a propane torch to heat the sprocket until it just starts to turn a straw color (~400°F). Direct the flame towards the center of the sprocket, not at the teeth. With the cam mounted securely in a bench vise, the sprocket will drop right on and you will have a few seconds to move it around and line up scribe marks. I handle the hot sprocket with welding gloves. If you measured your marks accurately then it's a cinch to get the sprocket dialed in on the first try.

 

[5twins]

My question is how are you determining the scribe marks on the 447 sprocket? Is it simply marking it in line with the notch on the 447 cam before removing it and then just lining that up with the notch on the 256 cam? Is that all there is to it or is there more, like having to use a degree wheel? This is something I'd like to try but this alignment part is holding me back.

 

[wickermann]

now all I need is an XS650 camshaft sprocket, anybody help me out, would prefer it in a camshaft, a worn out camshaft is fine as I wont be using it ?????

 

[mrriggs]

My question is how are you determining the scribe marks on the 447 sprocket? Is it simply marking it in line with the notch on the 447 cam before removing it and then just lining that up with the notch on the 256 cam? Is that all there is to it or is there more, like having to use a degree wheel? This is something I'd like to try but this alignment part is holding me back.

I prefer to mark it on the back side where the "dot" is on the sprocket. Scribe a line on the sprocket and cam that correspond with the dot. On both the 256 and 447 this dot is directly inline with a sprocket tooth. This is convenient for the sprockets that do not have the dot. You can simply count teeth to figure out which tooth is 90° from the notch then scribe in line with that tooth.

Marking it on the notch will also work. It's just a little more awkward getting the sprocket back on since you have to fixture the cam "sideways" to be able to see the notch. With a conventional vise, this requires making a mandrel to hold the cam.

When you mark it on the dot side, you can just throw it in the bench vise (clamp on the cast part of the shaft, not the lobes or bearings) then drop the sprocket straight down.

I've done several of these swaps and can usually nail it the first time.

 

[5twins]

OK, that sounds simple enough. Thanks for the info, especially about marking the "dot" side. I probably would have realized that as I went along but it's nice to have it confirmed.