Valve Clearance Question

I've seen that web page and also read some posts on another board saying kinda the same thing - larger valve clearances give more power. After I installed my elephants foot adjuster screws I tried them. I couldn't tell any difference in power or performance, they just made more noise, lol. Yes, even with those elephants feet screws, they made noise. I've experimented with various larger setting but eventually worked my way down to '78 stock specs - .004" intakes and .006" exhaust. I can now run the intakes at .004" quietly.

What I did discover running these elephants feet screws is that the "foot" portion remains stuck to the valve top from oil cling and the "lash" movement takes place between the foot and ball on the end of the screw. I figured it probably wasn't a good idea to have huge clearances or I'd be subjecting that area to more wear.
 
Excellent 5Twins since I have the elephant foot adjuster screws on my motor too! I'll be re-adjusting the intakes to .004" then.

Thanks
 
Lash depends entirely on cam grind, so go with what's recommended. Too tight and you're taking the valves off the seat for too long and getting no benefit from it, so you get all the drawbacks of a huge cam (ugly idle, et.c) and none of the benefits (power). Too loose, and you're not taking up the slack gently with the lash ramps, you're slamming the tappets into the valves on the opening ramp and beating things up. Playing around a few thousandths either way might reveal good things for your combo, but it's not gonna be far off.

Shell #1 was .006" intake, .012" exhaust, right?
 
DirtyErnie said:
Lash depends entirely on cam grind, so go with what's recommended. Too tight and you're taking the valves off the seat for too long and getting no benefit from it, so you get all the drawbacks of a huge cam (ugly idle, et.c) and none of the benefits (power). Too loose, and you're not taking up the slack gently with the lash ramps, you're slamming the tappets into the valves on the opening ramp and beating things up. Playing around a few thousandths either way might reveal good things for your combo, but it's not gonna be far off.

Shell #1 was .006" intake, .012" exhaust, right?
Click to expand...

I have seen .003 and .006 exhaust, I have seen what you mentioned. Is a 71 considered xs1 or 2?
 
1970 = XS1
1971 = XS1B and XS1F
1972 = XS2

The service bulletin that came out in 1972.

72-03-20_S288-01_ValveClearanceChange.jpg

Also, have a look at peanut's post #7, about SmedSpeed, and the following posts.
http://www.xs650.com/threads/1978-xs650-engine-knocking-noise.45277/#post-452426
 
Last edited:
5twins said:
Bigger is better as far as oiling goes. I wouldn't recommend .002", not much oil will get in. Try at least .003". My '78 recommended .004" for the intakes but they clattered at that setting. Closing them up to .003" got rid of the noise.

I have no idea why Yamaha changed their specs so often. As you mentioned, the motor wasn't changed much, if at all, after '74. The general consensus is bigger is better for the clearances. It allows better lubrication of the valve stem top and adjuster screw contact patch. Even so, those 2 parts do wear, especially the screw tip. No sense speeding that up by running the clearances too tight.
Click to expand...
Question @5twins , what did you set your exhaust at? I just reset all my valve clearances and they chatter.
 
I pretty much stick to the stock .006" spec for the exhausts. That's bigger than the intake specs so hopefully enough oil is getting in there.
 
It shouldn't. Do you have stock adjuster screws and if so, have you checked them for wear on the tips? Once they get all beat up and worn, setting accurate clearances can be difficult.
 
glennpm said:
Hi,

I started my engine up for the first time after my rebuild and re-phasing and am real happy so far. A couple of nights this week, I re-torqued the heads and adjusted the valves. I wanted to do some more research on the valve over laps and what is a good compromise for setting clearances, performance, noise and avoid burnt valves!

I have a 1979F so have set my valves to the latest specs of 0.0024"(0.06mm)...0.006"(0.15mm). I notice that 5twins said to use, though but earlier in this thread mentions using .003" for the intakes,

"Bigger is better as far as oiling goes. I wouldn't recommend .002", not much oil will get in. Try at least .003". My '78 recommended .004" for the intakes but they clattered at that setting. Closing them up to .003" got rid of the noise."

I pulled up an old article that I saved a while back written by Bob Bertaut, http://www.650motorcycles.com/isky.html. He has some great actual measurement data and is biased toward larger clearances, maybe even using the original XS650 factory specs of .006" and .012" for intake and exhaust respectively.

Looking at the actual measured data that I edited a bit, not the values though.

XS 650 Intake Cam Actual In Motor Specifications
Acronyms:
Intake valve opening = I.V.O., Intake valve closing = I.V.C.
Exhaust valve opening = E.V.O., Exhaust valve closing = E.V.C.

I.V.O.@ .002" @ 95 degrees B.T.D.C.
I.V.O.@ .004" @ 70 degrees B.T.D.C.
I.V.O.@ .006" @ 50 degrees B.T.D.C.
I.V.O.@ .040" @ 11 degrees B.T.D.C.
I.V.O.@ .050" @ 8degrees B.T.D.C.

Max. Intake Lobe Lift @ .000" lash = .388"

I.V.C.@ .050" @ 43 degrees A.B.D.C.
I.V.C.@ .040" @ 46 degrees A.B.D.C.
I.V.C.@ .006" @ 78 degrees A.B.D.C.
I.V.C.@ .004" @ 98 degrees A.B.D.C.
I.V.C.@ .002" @ 124 degrees A.B.D.C.
------------------------------------------------
Stock Intake Cam Lobe Center = 107.5 degrees

Intake Cam Duration @ .002" = 399 degrees
Intake Cam Duration @ .004" = 348 degrees
Intake Cam Duration @ .006" = 308 degrees
Intake Cam Duration @ .040" = 237 degrees
Intake Cam Duration @ .050" = 231 degrees


XS 650 Exhaust Cam Actual In Motor
Specifications

E.V.O.@.002" @ 127 degrees B.B.D.C.
E.V.O.@ .004" @ 120 degrees B.B.D.C.
E.V.O.@ .006" @ 91 degrees B.B.D.C.
E.V.O.@ .040" @ 44 degrees B.B.D.C.
E.V.O.@ .050" @ 41degrees B.B.D.C.

Max. exhaust Lobe Lift @ .000" lash = .388"

E.V.C.@ .050" @ 11degrees A.T.D.C.
E.V.C.@ .040" @ 14 degrees A.T.D.C.
E.V.C.@ .006" @ 53 degrees A.T.D.C.
E.V.C.@ .004" @ 71 degrees A.T.D.C.
E.V.C.@ .002" @ 88 degrees A.T.D.C.


Stock Exhaust Cam Lobe Center = 105 degrees

Exhaust Cam Duration @ .002" = 395 degrees
Exhaust Cam Duration @ .004" = 371 degrees
Exhaust Cam Duration @ .006" = 324 degrees
Exhaust Cam Duration @ .040" = 238 degrees
Exhaust Cam Duration @ .050" = 238 degrees

Note the camshaft duration at the valve lash settings of .002", .004", and .006"!
Setting valve lash to the stock cam specs just contributes to reversion and lost compression with these old design dead slow cam lobe opening and closing rates

I also put together the chart below doing an overlap of the curve from Doug Meyer, http://www.muzzys.com/articles/lobe_centers.html

My other concern with opening up the gaps too much would be the impact and wear potential when the adjusters close with the valve stems. The ramps are gradual though and this is probably not a big deal for the XS cams. I can deal with the noise it I get noticble performance improvement. I wear ear plugs anyway ;-))

So any constructive XS650 experience based comments?
Click to expand...
 
glennpm said:
Hi,

I started my engine up for the first time after my rebuild and re-phasing and am real happy so far. A couple of nights this week, I re-torqued the heads and adjusted the valves. I wanted to do some more research on the valve over laps and what is a good compromise for setting clearances, performance, noise and avoid burnt valves!

I have a 1979F so have set my valves to the latest specs of 0.0024"(0.06mm)...0.006"(0.15mm). I notice that 5twins said to use, though but earlier in this thread mentions using .003" for the intakes,

"Bigger is better as far as oiling goes. I wouldn't recommend .002", not much oil will get in. Try at least .003". My '78 recommended .004" for the intakes but they clattered at that setting. Closing them up to .003" got rid of the noise."

I pulled up an old article that I saved a while back written by Bob Bertaut, http://www.650motorcycles.com/isky.html. He has some great actual measurement data and is biased toward larger clearances, maybe even using the original XS650 factory specs of .006" and .012" for intake and exhaust respectively.

Looking at the actual measured data that I edited a bit, not the values though.

XS 650 Intake Cam Actual In Motor Specifications
Acronyms:
Intake valve opening = I.V.O., Intake valve closing = I.V.C.
Exhaust valve opening = E.V.O., Exhaust valve closing = E.V.C.

I.V.O.@ .002" @ 95 degrees B.T.D.C.
I.V.O.@ .004" @ 70 degrees B.T.D.C.
I.V.O.@ .006" @ 50 degrees B.T.D.C.
I.V.O.@ .040" @ 11 degrees B.T.D.C.
I.V.O.@ .050" @ 8degrees B.T.D.C.

Max. Intake Lobe Lift @ .000" lash = .388"

I.V.C.@ .050" @ 43 degrees A.B.D.C.
I.V.C.@ .040" @ 46 degrees A.B.D.C.
I.V.C.@ .006" @ 78 degrees A.B.D.C.
I.V.C.@ .004" @ 98 degrees A.B.D.C.
I.V.C.@ .002" @ 124 degrees A.B.D.C.
------------------------------------------------
Stock Intake Cam Lobe Center = 107.5 degrees

Intake Cam Duration @ .002" = 399 degrees
Intake Cam Duration @ .004" = 348 degrees
Intake Cam Duration @ .006" = 308 degrees
Intake Cam Duration @ .040" = 237 degrees
Intake Cam Duration @ .050" = 231 degrees


XS 650 Exhaust Cam Actual In Motor
Specifications

E.V.O.@.002" @ 127 degrees B.B.D.C.
E.V.O.@ .004" @ 120 degrees B.B.D.C.
E.V.O.@ .006" @ 91 degrees B.B.D.C.
E.V.O.@ .040" @ 44 degrees B.B.D.C.
E.V.O.@ .050" @ 41degrees B.B.D.C.

Max. exhaust Lobe Lift @ .000" lash = .388"

E.V.C.@ .050" @ 11degrees A.T.D.C.
E.V.C.@ .040" @ 14 degrees A.T.D.C.
E.V.C.@ .006" @ 53 degrees A.T.D.C.
E.V.C.@ .004" @ 71 degrees A.T.D.C.
E.V.C.@ .002" @ 88 degrees A.T.D.C.


Stock Exhaust Cam Lobe Center = 105 degrees

Exhaust Cam Duration @ .002" = 395 degrees
Exhaust Cam Duration @ .004" = 371 degrees
Exhaust Cam Duration @ .006" = 324 degrees
Exhaust Cam Duration @ .040" = 238 degrees
Exhaust Cam Duration @ .050" = 238 degrees

Note the camshaft duration at the valve lash settings of .002", .004", and .006"!
Setting valve lash to the stock cam specs just contributes to reversion and lost compression with these old design dead slow cam lobe opening and closing rates

I also put together the chart below doing an overlap of the curve from Doug Meyer, http://www.muzzys.com/articles/lobe_centers.html

My other concern with opening up the gaps too much would be the impact and wear potential when the adjusters close with the valve stems. The ramps are gradual though and this is probably not a big deal for the XS cams. I can deal with the noise it I get noticble performance improvement. I wear ear plugs anyway ;-))

So any constructive XS650 experience based comments?
Click to expand...

GlennPM
Is the Bob Bertaut content still available somewhere else? I'm not getting a connection to XS650motorcycles I'm trying to find lobe centers for early XS650 cams.
 
GlennPM
Is the Bob Bertaut cam article still available somewhere else? I'm having trouble connecting to XS650motorcycles. I'm looking for cam lobe center data for earlier XS650 cams
 

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