Motorcycle Repair: 1982 Yamaha XS400J Maxim Cam and lifter dammage while adjusting valves, valve shims, cam lobes

Question
Hello again, Mark. You helped me some time ago with a missing gear problem and some engine noise. The missing gear was fixed by using good, heavy-duty deisel engine-oil (Rotella T non-synthetic). It worked like a charm until I decided to try to adjust the excessivly-tight valves. I've described what happened below. Any help would be really appreciated.

It was the first time I had ever tried this, and since I do not have any extra valve shims, I thought it would be easiest to simply remove each of them at once and replace them all at once (rather than temporarily removing them one at a time in order to read the number on the bottom of each of them, replacing every one before removing another).

This caused some damage to the cam lobes and the lifters. The damage is on the outside edge of the cam lobe and the inner ring of the lifter (the edge of the cup that the shim sits in). Of course, what had happened is that turning the cams without the shims forced the outer edge of the cam lobes against the inner edge of the lifters---crunch.

The cam lobes are missing about 1-2mm of material on either side of the lobes and the inside of the lifter have been cut up enough to make insertion of a new shim difficult without a bit of filling.

I own a complete parts bike, so I can replace everything… But I was planning to overhaul the engine next winter anyway and would prefer to patch things up for the summer before removing the engine. (I want to ride, not wrench, this summer)

I think the following are my options. could you advise which you think is the best option and let me know what are the risks?

1. file enough material off of the inside of the cup of the lifter so that I can squeeze the shims back in and ride it out for the summer. (do you think that the cams would be able to withstand the stress as they are?)

2. replace the cams and lifters. Is it possible to do this without completely dismounting the engine and removing the head?

(I'm pretty new to motorcycling, but I'm getting a very quick introduction to the frustrations!)
Allan Pollock


Answer
Hi Allan,

Sorry to hear about the damage to your Mc. Unfortunately, the parts are ruined and must be replaced. Camshafts are machined to mate with their journals and wear accordingly. Swapping cams will not work. The head must be replaced which requires partial tear down.

Let me know how it goes.

Mark