Tearing down the motor... again

Finally had some time this weekend to start tearing down the engine. I could have just been satisfied to get it to the point where I could re-torque the head bolts, but no, If I'm going into this engine again, there are going to be some changes!

Another thread details my ported head and new Thumper Racing 83mm 3-ring piston.

So, I've got her torn down to the piston, and I've been checking everything for unusual wear. Cams, cam journals, cylinder wall and piston all look great. Even the spark plug looks good with a nice medium to light brown color. Looks like the fueling is right.

Don't know how far I will get today. Installing the wrist pin clips in the new piston will be a bitch for sure. Hopefully, a technique for compressing the cam chain tensioner that another member told me about will make that easier.

In the meantime, here's few pics:

Got the new Thumper Racing piston (actually a CP piston) on. Had to stop working on the bike early so that I could take my son to the airport.

The piston and wrist pin clips went on easily compared to installing the Athena piston, and keeping true to form, the Athena piston was a bitch to get off. Had to drill access under the clip on one side in order to get my tiny screwdriver under it to pry it out.

Here's a pic of the new piston installed. The tape is on there to keep the rings indexed properly until I can slide the cylinder back on. More tomorrow.

No progress to report today. Started with a round of golf (my normal Sunday morning routine), and after a couple of beers at the 19th hole and some yard work at home, I was done and watched a movie instead (Moneyball).

The WR is as it's last reported state, with the new piston installed, waiting for me to slip the cylinder back on and tighten down the head. A couple of shop rags cover the exposed components until I can get back to it

Regarding the cylinder, although it looked good, I decided to de-glaze it with a scotch-bright pad. I'll feel better about putting it back on that way. Also, since the head had a complete valve job in addition to the porting, I did a valve clearance check on the bench. None of the old shims are now appropriate, so I had to source new shims. If you can believe it, none of the 4 Yamaha dealers within a reasonable distance from me had all of the right shims in stock, so I had to order two 1.75mm shims. Won't be able to button it up until they come in.

So, I'm at a bit of a stand-still. Feeling confident about the rebuild though. With the former BB kit intall on the WR and my more recent BB kit install on my KLR, tearing down top-ends is getting to be routine. Still looking forward to getting the X back on the road soon.

What's the reason for going with the Thumper piston vs. the Athena?

chuckP wrote:

What's the reason for going with the Thumper piston vs. the Athena?

Lighter (less vibration), and 3 rings vs 2 (longer service life).

Interesting. How many miles do you expect to get out of these big bore pistons?

I can't wait to hear you opinion on how they compare.

I assume that they are as good or better than the stockers. With normal maintenance, the new piston should go for a long time.

Benefits of the Big Bore option? That's a whole 'nother thread.

I got the WR back together today. The BIG disappointment was that the Thumper Racing piston turned out to be too small. At the urging of HighFive over on ADVrider, I checked the TR piston vs the Athena and the TR was clearly at least 2mm smaller in diameter than the Athena. The Athena kit has an 83mm piston and the TR item measured out to 81mm. Scratch that idea. I put the Athena piston back in.

Fortunately, the TR piston was free to me, so I'm not out any $$$, but I'm disappointed that they couldn't get it right. The first time they sent me a piston, it was for a YZF! (five valves) This one was definitely for the WR, but obviously not big enough for the bore. Oh well...

Another thing I discovered is that there is a glitch in the shop manual, which contributed to my leaky head gasket and base gasket. There are 4 head bolts. One is longer than the others. The manual has you installing the longer bolt in the wrong hole and it bottoms out before bringing the head to the proper tightness. For those attempting a top-end job, the longer bolt goes in the left side rear location rather than the left side front location, which is what is indicated in the manual.

The bike had a chronic off-idle hesitation before this rebuild. No matter how I adjusted the PC5 & Autotune, I couldn't diminish the problem. With this rebuild, I discovered that I may have used the wrong timing marks on the rotor to set the timing. There are 3 marks, they are very close together, and only one is correct. I think I used the correct one this time as off-idle hesitation is now all but eliminated.

"What about the ported head?", you ask. Well the jury's out on that one, but time with the Autotune will reveal any advantages gained by that. My couple of short test rides today suggest that there is more "umph", and maybe even more to be had with proper tuning.

Anyhoo, it's been a long 6 months without the WR and I'm glad that it's back in the fight. I'll update this thread as I gain more info. Right now, it's time for a Dogfish Head 60 minute IPA!

Fini!