Valve timing question (with pics!)

[TwoManyXS1Bs]

Interesting! Your XS2 cylinders have NO bridge. Noted!
Now, where is the aluminum flaking coming from. Have a close look at the cases, where the flywheels spin. A separating crank would have a flywheel dragging in there, making flakes. Otherwise, I haven't a clue.

I see the offset wear pattern on your rockers, and have a theory. But, I'm running out of me. I need a shop full of flunkies to do my bidding, to pursue this theory.

... I checked the cam timing 3 different ways. Intake at .003", .006" and .012"...

This service bulletin notes that ALL valve timing be checked at 0.012" lash.
(At the bottom)


So, you can ignore the timing readings from those other clearances...

 

[Marlin72xs]

Yamaha neglected to send me that memo. I get no respect! Thanks.
The flakes... Should have the bottom half open tonight. Spent all last nite removing the bottom gasket. Oh, what fun.
There was no drag or side play on the crank and the trans feels like butter. If it is the crank, good, because I'm replacing it anyway. Rumor has it that there are balancing plugs in the 256 cranks that can fall out. Ever hear of that?
How about the oil pump? Never dismantled one. Are there AL parts in it?
Do you see the spots on the rockers? And yet the surfaces are smooth. Come on, spill it, what's your theory? The rocker bearing surface could be worn. I'll try to yank that tonight also
The cam chain tensioner and guides are all in good condition. Hard as rocks though and no damper washer on the tensioner plunger.

 

[TwoManyXS1Bs]

Yes, there's a couple threads in here showing balancing plugs slipping out.
Here's a good one:

http://www.xs650.com/threads/any-guesses-what-is-stuck-in-my-crank.27461/

Good idea to check that, if you have them.

The oil pump cover, and, of course, its base (which is the right sidecover) are aluminum. The rotors and shaft are steel. It would have to be a seriously chewed-up pump before you'd start to see any aluminum flakes from that.

The thing with the rockers is the nature of the shafts to hammer themselves upward against the miniscule/narrow shaft bores in the camcover. When that happens, there's no guarantee that the shaft is still parallel with the cam, and offset wear on the follower pads can happen. A good indicator of this condition is if you have to *grunt* the shafts outta the camcover. Many posts in here on that, and MikesXS even offers a slidehammer tool to yank those rocker shafts out.

Now, that ain't supposed to be!

In the manual (including my experience on my other XS1B) the rocker shafts are supposed to be a smooth sliding fit, easily withdrawn.

I have an eBay head with rocker shafts that had to be *grunted* outta the camcover. The battered aluminum in the shaft bores swaged itself outward and around the end of the shafts, making them difficult to withdraw. Close examination of the shaft bores in the camcover found that I could wiggle lift/lower the shaft in there at least 0.010", not all the same, but seriously loose. That's gotta make some uncomfortable ticking sounds.

Deep in some dark/damp corner of my head I've been contemplating another exotic fixture, for some sort of bore repair, sleeve maybe. Just not there yet...

 

[Marlin72xs]

Well, (large pause), didn't split the cases yet, but was fiddling with the rod side play and began spinning the crank and shifting the rods from side to side and felt and heard the right rod scraping, then noticed the large what appears to be lead plugs. There are definite radiused scrapes on the plugs. I know I'm old so occasionally I repeat myself, but 65K miles is still pretty fu_king amazing. Come on, even cars in 72 were considered over the hill at 60K miles.
Thinking back, the flakes were thin and thin flakes of AL can bend easily, now I know it was the lead. Smedley mentioned that they had a tendency to come out.
As always, if any of your IM people are... Wait, as usual, thanks for your input and the related thread. Picts in a few days.
Oh, and the upper rod bearing diameter is huge compared to the 447's.
And, I've never inspected the oil pump, but I will pull that apart, along with anything else that was not inspected.

 

[TwoManyXS1Bs]

... I know I'm old so occasionally I repeat myself, ...

You, me, and DADDYG are all the same age, within a few days.

I don't mind repeating, 'cause I have the complimentary ailment,

Fergettin'...

 

[TwoManyXS1Bs]

...the upper rod bearing diameter is huge compared to the 447's...

You've heard of the rod/stroke ratios bantered by the engine builders?

There's also the lesser known wristpin/bore diameter ratio.
Seems that with improved metallurgy, the rule-of-thumb for that ratio changed somewhere in the '70s, which I think may have influenced the 447 design...

 

[grizld1]

2M, I've always suspected that the fat, heavy 22 mm. wristpin had a low tech origin, an artifact of Yamaha engineering's initial rookie screwup with the first run of XS1s. Maybe I'm wrong, but what it looks like to me is that when they eliminated the fragile needle bearings in the small end of the rod they just stuck in a solid pin with the same OD. Being a dirty minded kind of guy, I also suspect that reducing wristpin diameter to 20 mm. at the same time they detuned the cam had a bit of a low tech origin too; those 256 motors had a way of stretching the small end of the rod when guys got on that cam, hence more meat in the small end and a cam that made the motor less happy near redline.

 

[Marlin72xs]

Picts will have to wait, it's Mother's Day. I forgot that too. So without a cute little gift, I am sworn to be a "Honey Do" today.

 

[Marlin72xs]

Here r a few Picts, not my best work. A gentle push to the side was all it took for the rod to scrape the lead plugs.
I've ridden 2, 71's and a 72, in the past and for some distance and all of them had a lot less vibration than mine.

 

[TwoManyXS1Bs]

Yup, looks like you found your "flake factory".
Can't help you with that, but your planned 447 crank replacement will settle that...

 

[Marlin72xs]

It gets better. I pulled the crank and the plugs are actually loose. I can rock them back and forth with my finger nail.
I wonder if the started racing the XS in 1970. I went to a 1/2 mile flat track race at Roosevelt stadium in NY in the early 70's and they were promoting Keith Mashburn and his Yamaha. I believe there was only one race there because the track had a rubber base with little nubs and it was covered with sand or clay. I walked on it because my photographer friend had pit passes and we were allowed on the center of the track. I was about 21 and I was in heaven. Look up Keith Mashburn and/or motorcycle racing at Roosevelt stadium. There were several Yamahas and a few Nortons. Did I say Norton... That's weird.

 

[TwoManyXS1Bs]

... what it looks like to me is that when they eliminated the fragile needle bearings in the small end of the rod they just stuck in a solid pin with the same OD.

... those 256 motors had a way of stretching the small end of the rod when guys got on that cam, hence more meat in the small end and a cam that made the motor less happy near redline.

Griz, here's something to chew on.

The small end needle bearing was discontinued at s/n S650-003269.
To accomodate the 22mm wristpin, the conrod was also changed at s/n 003269. From p/n 256-11651-00 to 256-11651-01. The wristpin and pistons remained the same, so the conrod had to be changed.

I've not seen an early -00 conrod, but my -01 conrods' small-ends don't seem to be that thin.

So, we actually have (4) different conrods in the XS650 history. I have pics of the (3) more common ones provided by one of our members, the shortest 447, the 256 -01 version, and the 533 conrod.

I haven't seen any pics of the earliest 256 -00 conrod.
Could that one have the thinner small-end?

70-72 Crank/Piston parts listing attached.

 

[Marlin72xs]

Hey 2m, check out this link. There's one photo of bikes taking off from left to right. There are 2 obvious xs's in the foreground. 1971.

https://books.google.com/books?id=G...d Roosevelt raceway motorcycle racing&f=false

 

[TwoManyXS1Bs]

Hey 2m, check out this link...

Yes, I see them.
Race frames and suspension, only thing XS is the engines...

 

[grizld1]

2M, I had a -00 motor from a parts bike bought for $50 25 years ago from a clown who'd chopped it and holed a piston. Wish I had the rods to send for your collection, but that stuff is long gone. I didn't know whether to laugh or cuss when I found those needle bearings in the small end, so I did some of both. Why Yamaha's engineers couldn't break their 2-stroke design habits when they did that top end is a mystery to me. Surely somebody in that shop knew better!

 

[TwoManyXS1Bs]

... that stuff is long gone...

Well, maybe someone will post a pic, someday...