Ironhead Advance Unit Springs Broke, Sloppy Shaft

[iNSaNeSHaNe]

another thing you may do is put the bushing in dry ice that's how I shrink them down for installation 5 minutes on dry ice and they fall in the case makes it easy to line up the oil hole without any damage to the bushing just check to make sure you have close to .005 interference too much and you may have to hone the inside of the bushing to fit the cam. still not a big deal. good luck

[Hopper]

Originally Posted by arisaka

Cool, this type of work is right up my alley, my other hobby is building rifles. Pressing, honing, and pinning is all pretty familiar. I'll check out the bushing when iget it. Thanks for all the info, ill mic the case and see how she looks

That's good. Main difference with rifles is the material. Aluminum shears, or forms a pressure wave ahead of the bush, if bushing is pressed in cold, so you get a looser fit than if you heat the aluminum to expand it first.

And even though you don't want the bushings to spin, putting too much interference in the fit could crack the aluminum or deform it enough that you don't actually get a good grip resulting.

I would think .005" a bit heavy in this application. I would stick more with the tried and true .0015" per inch of diameter. So more like about .002" interference, with the above suggested red Loctite.

The bushings usually come undersize on the ID and need to be reamed or honed to final size. To be done properly, should be line reamed or honed using an old engine case as a guide jig, but if you can set up square in a drill press or mill, you can get away without line-reaming.

[iNSaNeSHaNe]

I agree Hopper. I was trying to remember the clearances since I don't do machine work every day anymore. and again yes Heat the cover I didn't state that when I was typing.
funny how I have seen so much stuff monkeyed with when I was doing repairs at the machine shop. I had a gear case come in with coke can layered inside the bearing journal before to hold it tight so nothing surprises me too much. and another thing I have done but don't recommend is when at the track doing repairs I once put in a bushing and reamed it with an old cam polished up with a spiral cut in the bushing area. not the best but it got the job done and we went on racing later that day. funny though we never did replace the bushing again..

[laborer8113]

had same trouble with my 71 what happens is the cam is jogging up against the shoulder of your cam bushing therefore your shoulder is now thinner and allows the advance system that is connected to that cam to rub plate and break springs! i bought brass shim paper and made a few shims to space it out to finish the riding season! winter time came and i changed the bushing! your seal will not change the spacing! good luck!

[Hopper]

The other thing you will need to look real careful at is the condition of the hole in the cover where the bushing fits. If it is worn egg-shaped, or tapered, or both, from the spinning bush, there is not much point punching an oversize bushing into a cattywumpus hole. Will need to be machined back to round and straight.

Which then raises the question of if the newly finished hole is concentric with the original.
Which is where the factory remommended method of line-reaming the new bush after installation comes in right handy, but still does not guarantee original alignment as the reamer still follows the new hole.

[arisaka]

Just waiting on parts guys, I'll post up pictures and a rundown here as soon as they arrive!