Valve timing question (with pics!)

[TwoManyXS1Bs]

...No telling what 65k miles has done to it...

Hey, Marlin72xs. Something to look for. Our early engines have a cylinder "bridge", which isn't as tolerant of stretched camchains as the 447/later open tunnel cylinders.

Check for chain grinding on the top and backside of the bridge.

5twins' pic of the later 'open tunnel' cylinders.
Lookit how far the chain tensioner can move.

 

[TwoManyXS1Bs]

More tunnel *grinding* pics:

 

[Marlin72xs]

Yes, check the cam timing before you remove the chain and cam. Do it with the chain tensioner applied (adjusted). With the rotor mark set at TDC, what you'll be looking for is how far off from vertical the notch in the cam sprocket is.

Oh, yes I will, and thanks for the encouragement. I'll be getting things lined up and ready to go. Thanks again.

 

[Marlin72xs]

More tunnel *grinding* pics:

View attachment 115849 View attachment 115850 View attachment 115851

Yes, about a year and a 1/2 ago I went to the Iron Horse with JetmechMarty and pushed it a little hard, then, took a quick work trip and pushed it again. I changed the oil shortly after and discovered big Al flakes and you pointed out the bridge. Upon riding my baby easier after that, no flakes occurred. And yes, the cam chain was adjusted properly the whole time. It's too gosh darn easy to do to not do it.
And speaking of easy, it's not easy changing the oil, let's face it, it sucks. I'm gonna go with Howard Smedley's oil filter conversion for the bottom strainer. If you haven't seen it, go to smedspeed.com or UK. But I'll bet you guys know something better, so gimme please.
I'll be in touch. Thanks again.

 

[5twins]

That oil filter set-up looks interesting. It seems you have to send him a sump plate to modify? Let us know the particulars if you get one, especially the cost. I don't see that mentioned on his site.

 

[Marlin72xs]

Two months ago he quoted £63.00 which is about $89.00. That ain't bad. I mean really, I can change the oil in my F-150 quicker.
Some may say that the filter protrudes down too far. It might. I once cracked the strainer plate going up a curb slowly with one hand. OK, alcohol was involved, I had a beer in my clutch hand. I was 26. The oil was gone in about 2 minutes. Anyway, I don't go up curbs any more. If I had to, I would stand up and use 2 hands. When in doubt, ride it like a motocross bike.
You guys can email him any time, he answers all questions and seems to know his stuff. He can also show you where to get 256 pistons.

 

[Marlin72xs]

Oh, and yes, you send him your sump plate. I'm sure you have a couple of spares.

 

[Marlin72xs]

More tunnel *grinding* pics:

View attachment 115849 View attachment 115850 View attachment 115851

Some one mentioned once in some forum, that the sprocket on the 256 tensioner guide is a better idea because it keeps the chain in line. I agree. I bought the Mikes guide and the contact point for the tensioner in concave vertically only. There is no shoulder to prevent side to side movement. The 447 from my 75 is concaved 360 degrees. I wonder, did it press into the rubber over time or did Yamaha create it that way. Does anyone have pictures of other new ones?
Perhaps I should create a different thread, or I'm sure that you guys can point me to one.
Great picts by the way.

 

[TwoManyXS1Bs]

Marlin72xs's rear slipper discussion continued here:

http://www.xs650.com/threads/front-...ain-tensioner-arm-assembly.29541/#post-543897

 

[Marlin72xs]

Yes, check the cam timing before you remove the chain and cam. Do it with the chain tensioner applied (adjusted). With the rotor mark set at TDC, what you'll be looking for is how far off from vertical the notch in the cam sprocket is.

Well, it's been over a month, just started on the rebuild. Engine on the bench and attempting to check the valve timing. Didn't pull the head cover yet.
My dilemma, I'm using the specs from an XS1-B, that's the manual that came with the bike along with and addendum for the starter and disc brake. XS1-B valves are spec'd at .006 and .012. I have them set at .004 and .006.
The XS1_B book says the intake valve should start to open at 47deg BTDC. I get an average reading of 55deg. OK, from here, if the camchain is stretched, the valve shud open retarded or late or less than 46deg, right?
Sometimes I suffer from inverted thinking.
Jap manuals in the 70's need some interpretation. On the closing of the intake, did they mean start to close or completely close. And it says 67deg after BDC. My #s are way off here.
Does anyone know if the 72 cam is different from a 71? Smedley says it's hotter than later model cams, in fact he recommended using the 72 cam with the 750 kit, but what about 70 and 71?
And, yes, I checked and double checked my TDC.

 

[Marlin72xs]

Marlin72xs's rear slipper discussion continued here:

http://www.xs650.com/threads/front-...ain-tensioner-arm-assembly.29541/#post-543897

Hey 2M, I'm good with the rear guide now, thanks. Now I need you in on my latest quest. Read the above to 5twins.

 

[grizld1]

The cam grind didn't change until 1974 (first 447 motor, TX650A). Inspection valve lash is .012".

 

[gggGary]

No documentation but I thought the cams were "milded down" a bit 71ish? Yamaha was figuring out that street 4 stroke riders were different from dirt 2 stroke riders,

 

[Marlin72xs]

Gary, that's very possible, since they may have realised that the XS wasn't gonna beat a CB750, so let's make it easy for the college kids and newbies to ride. My good friend had a 71 and he always beat me off the lights. Maybe his was a 750?

Grizld1, I will set my valves to 72 specs, but the intake for it is .006", the exhaust is .012". That's what the 71 book said. I will check it tonight. Wondering if .003" changes the angle much.

 

[grizld1]

Valve lash for cam timing inspection is not the same as operating valve lash. I thought all 256 cams had the same grind, but maybe not!

 

[Marlin72xs]

I may be wrong, (my wife always says I am), but the book says that at 47deg before TDC the valve should be about to open. At that point, the valve clearance is closed to 0". In a perfect world, the .006" clearance should get me to 47deg, but the .003" should be, well, 50 or 58 degrees before TDC. Am I not interpreting this properly?
If I read you correctly, operating valve lash is the clearance at operating temperature and all the parts involved have expanded to reduce the lash closer to 0"?

And yes, it would be logical that all 256 cams would be the same.

 

[grizld1]

Nope. Operating valve lash is the cold setting that you use for valve adjustment before you run the engine. Inspection valve lash is the setting that Yamaha specifies for checking valve events for cam timing. Check valve lash with a dial indicator on the rocker arm; if the valve stem is cupped, a feeler gauge will read the edges, not the true contact.

 

[Marlin72xs]

Gotcha!

 

[Marlin72xs]

[/A

Hey, Marlin72xs. Something to look for. Our early engines have a cylinder "bridge", which isn't as tolerant of stretched camchains as the 447/later open tunnel cylinders.

Check for chain grinding on the top and backside of the bridge.
View attachment 115847

5twins' pic of the later 'open tunnel' cylinders.
Lookit how far the chain tensioner can move.
View attachment 115848

Hey 2M, Guess what. No bridge on the 72. I guess the AL chips were coming from somewhere else. I'll be biting my fingernails as I open the bottom tonight.
Notice the weird pattern on the rockers, 65K miles of carbon on the Pistons and the chain guides look good. Who wudda thunk it.
The 2 upper rings had their gaps almost on top of each other and the oil rings had very little spring left in them.
The cam looks OK. I measured the cam lobe height of the 72 vs the 75. The 75 is .015" taller, but the 72 appears to be fatter or faster rise.
I also noticed that the springsteel breather baffle cover is not present.
Here's something weird, when I pulled the head there was a strange odor that filled the basement and partial main floor.

 

[Marlin72xs]

Yes, check the cam timing before you remove the chain and cam. Do it with the chain tensioner applied (adjusted). With the rotor mark set at TDC, what you'll be looking for is how far off from vertical the notch in the cam sprocket is.

OK. I checked the cam timing 3 different ways. Intake at .003", .006" and .012", but unfortunately, I left my book and degree measurements at home. However, at TDC, the notch is 90deg +/-2 or 3deg to the horizontal, as it should be.
I do remember that at .003, it was about 55deg BTDC. @.006 approx 50deg, and @.012 it was like 39deg BTDC. So the cam chain stretch will retard the valve opening but the smaller valve clearance brought it back. Then my guess is that the low compression on both cylinders accounts for the slower acceleration. Well?