Exhaust Valve hitting valve cover?

[shitsnack]

I have a 1978 I picked up for a song, and I'm in the process of getting her on the road. I did a cam chain adjustment, and the vavle adjustment(.006 intake, .004 exhaust). There is a weird knock that sounded like the right exhaust valve was hitting the valve cover, so for kicks i took the cover off and started it, and the noise pretty much went away. I rechecked my valve clearences and they're good, so I'm a bit stumped. Any idea what might be going on? I wish I would have found my camera for a video...

 

[TwoManyXS1Bs]

I have a 1978 I picked up for a song...

That should be your first sign. Check EVERYTHING!

... the vavle adjustment(.006 intake, .004 exhaust)...

Sounds kinda backwards, double check this.

...Any idea what might be going on?...

Mystery 'ticks' are always fun, here's an example:

http://www.xs650.com/forum/showthread.php?t=28536

 

[shitsnack]

Whoops, I meant .006 exhaust, .004 intake. I'll read up on that thread, thanks!

 

[5twins]

.004" is the spec for the '78 intakes but they usually tick if set that big. Try .003" on the intakes. The valves shouldn't move enough to hit the cover. Check the adjuster screw and make sure it's an original. Maybe someone swapped a different, longer and incorrect screw in there.

 

[dirtymike]

I thought the clearance for XS C and on was 0.0024"(0.06mm)for intake and 0.006"(0.15mm) for exhaust. This comes from the adjustment video from Littlebill31. sorry i made a copy error it reads
Tappets - model... inlet...exhaust
...XS1- B 0.003"(0.076mm)...0.006"(0.15mm)
...XS 2 0.006"(0.15mm)....0.012"(0.30mm)
...XS B........ 0.0024"(0.06mm)...0.004"(0.10mm)
...XS C-on... 0.0024"(0.06mm)...0.006"(0.15mm)

 

[XSLeo]

Yes, they tried several clearances over the years. Mostly to make thing quiet. This quiet often leads to other problems. The .003 I .006 E has been found to work about the best.
Leo

 

[TwoManyXS1Bs]

Yamaha Service Bulletin #220, in 1972, revised the previous confusing valve lash specs:

 

[gggGary]

remove that lash screw and look at the end and the head of the valve stem. It is common for one or both to be badly spalled making setting at the correct clearance impossible.
Sorry, new camera I don't have close focus hammered yet.



This engine had marks where the screw had been hitting the cover..... nut probably wasn't tight letting screw back off.



Dated 1974 FURTHER valve clearance clarification!


Random SB

 

[dirtymike]

Aint nothing like doing things 4 time. I set the valve lash at cold engine after the cam chain tension step. Set points then timing. done. Dirty