I replaced the collapsed lifter this past weekend, got everything back together, and now it all runs much better.

While replacing the lifter, I discovered a couple things. 1. The cam lobe was a bit worn. Not much, but noticeable. Then, I also noticed those jeep lifters that are a $3 alternative to the $125 lifters from the yamaha dealer are a different height. The jeep lifter is roughly 1/16th of an inch shorter. I should have measured with my micrometer before I put it in, but I wasn't thinking at the time. Well, that combined with the slightly worn lobe, and I'm talking less than .3mm of wear off the lobe, there's a noticable difference.

Now, when I'm out riding, I noticed a couple things.
1. The R* is fast as hell. Seriously, I got it running on one 800cc cylinder. Something sounded missing, but I didn't think it was a whole cylinder, just bad combustion or something on one of them. I had mentioned that my top speed was about 70mph, it was hard to get faster than that. I found myself accidentally doing 70 in 3rd gear about 50ft after turning on to a side road. There's a huge steep mile long hill, called mile hill. It's a pretty steep grade too. I was in 4th doing 50 up it, rolled the throttle, and it just roared and shot me up the hill extremely quickly.

2. I had a terrible tapping noise coming from the engine. My best guess is the rocker arm for the intake cam slapping against the valves, because of the clearance created by the shorter lifter, the shorter cam. Can anyone say whether this is probably it or if it's something else? It's pretty loud. Will this tapping damage anything if it's the rocker it's tapping against? I was thinking about adjustable pushrods, telescoping pushrod covers for adjustment without removing the top layers of hte head, new cams, and new lifters all around as a winter project.

Justin if you noticed wear with your eye on the cam chances are it's more wear then what you think. I would not continue to ride it! You need to take it back apart and mic the cam lobe. I have only worked on harleys so I'm not sure if they make adjustable push rods for the R* engine. If the jeep lifter is 1/16" shorter add to that the wear on the cam this is a problem. The lifter can only take up a certain amount of slack. If your guess is right and the push rod is loose enough to slap around think for a minute what could happen if it slips out enough to bind on the rocker? Just think of the damage that could occur cause now it's too tight and binding. Just my .02

If your cam had a noticable differance it needs to be replaced. By the way your old lifter looked the cam would also be worn beyond limits. The cam is only hardened a little past the surface. Once your past the harden surface it needs to be replaced. As far as noise if you didn't adjust everything properly, especially with a worn cam and the wrong lifter (shorter) your asking for problems. Don't try and cut corners on internal eng repairs. Cut yourself short on the chrome.

Just FYI.... adjustable pushrods

The cam wear was noticable only through discoloration on the surface. I wasn't able to notice visible size difference, and it was only on one side of the lobe. I don't plan to ride anymore really this season, it's put up in the garage for the winter where I'll break it down.

My plan was to get the kit half way down this page:
http://www.pacificcoaststar.com/pcs/road_star_engine.htm

That has the cams, lifters, and push rods, as well as the springs, and the chrome retractable pushrod covers. $1400 for a more agressive cam profile, adjustable pushrods, covers, good spec lifters, seems like a pretty good deal to me.

looks like a good way to go!!

I've had the aftermarket lifters since almost day one. I have no idea if mine is shorter (what is the product number on yours) but the 1/16" difference in height is easily taken up by the hydralics of the lifter.

Worn cam is not good ... it will just destroy the lifter.

Doc