Topic: Valve issues! argh!

[DirtyUnderWhere]

So the other day my bud comes over to turn some wrenches on my bike. Before we begin I tell him to take it for a ride. He and I go waaaay back and he hasn't been on the bike since I've done the mods, so I wanted him to evalute the differences in power, handling, etc. As he's leaving the neighborhood I hear him running the bike a little hard. Much higher reving than I ever use. So I get a little worried. Anyway he comes back five minutes later and I can hear the tapping before he gets to my driveway. He asks "Has it ever done that before?" and I'm all "uhhh, NO."
 The purpose of the visit was to change the oil and filter out, as the bike was overdue (not much). Long story short, he leaves, we didn't change the oil. Now I'm not mad at him, the bike's nearly 40 years old, these things happen, and I knew it could happen while he was riding.
  My question is What do i do now? I changed the oil today and when I cranked the bike after the tapping was still there. I'm currently waiting an hour or so before I crank it again to see if maybe the new oil has helped the issue.
I've never done work on valves before, and I don't know where to begin or how to troubleshoot. Any  help would be greatly appreciated!

[mystic_1]

Sounds like a valve lash adjustment is in order.  It's a relatively simple procedure, check your shop manual for the procedure.  Must be done with engine cold.  Necessary tools are a feeler gauge set with .002" and .003" feelers, a wrench for the tappet covers, and wrenches and/or a screwdriver for the tappet adjusters.

What model bike is this?

mystic_1

[DirtyUnderWhere]

1972 cb750

[DirtyUnderWhere]

Is the bike safe to run with this problem? I definately don't want to grenade the engine, or do any more damage...

[mystic_1]

Since it came on suddenly, I personally would not run it too much until you get it sorted.  Are you sure the noise is coming from the valves?  I'd at least pop the tappet inspection covers and eyeball everything.  How's it running?

mystic_1

[DirtyUnderWhere]

runs like a top! When the negine is cold, the sound is barely audible, as it warms up, it gets louder.

[OldSchool_IsCool]

Any exhaust smoke at startup?

[DirtyUnderWhere]

no smoke. The only difference is the tapping.

[DirtyUnderWhere]

When I pop off the tappets, what would I be looking for?

[ofreen]

A few runs to redline shouldn't cause any problems with the tappet clearances if everything was adjusted and tightened correctly.  But what if they weren't?  So check your clearances.  

Another possibility is an exhaust leak at the head and exhaust header.  Many times I've heard leaks there that sound all the world like mechanical ticking or tapping.  If the exhaust was a little loose already, some hard revving could well have developed the leak.

[mlinder]

You really need to hit over 12k to do actual damage to the valve train, assuming nothing was too far out of whack when it was over revved. Don't ask me how I know.
Adjust the valves, see if it still exhibits the sound.

[OldSchool_IsCool]

With the tappet covers off,
- the innards should be oily.  Dry is a BIG warning!!
- take off the points cover
- with a 22mm wrench, slowly rotate the crank clockwise via the nut under the points cover
- with a finger on the #1 intake tappet, feel it lower then rise again
- after it rises, look through the hole at the top of the point plate.
- rotate the crank some more until T 1.4 lines up with the timing pointer
- your #1 cylinder is now at TDC of the power stroke.

Wiggle the tappets.  #1 intake, #1 exhaust should wiggle.  So should #2 exhaust and #3 intake.  All other tappets should feel hard and non-wiggly.

Watch the timing pointer again and rotate the engine 360 degrees until T 1.4 comes back to the pointer.  #4 intake, #4 exhaust, #2 intake and #3 exhaust sould now be wiggly and all others firm.  

This isn't exactly how you adjust tappets, but just a quick inspection.  If you want to adjust tappets at this time, the wigglies should be set to .002 (intake) and .003 (exhaust).

[DirtyUnderWhere]

Okay, so i just checked and it's not an exhaust leak.
Is there a tutorial here or anywhere on adjusting the valves on these bikes? this is beyond my scope of mechanical knowledge as of now. But like I told my bud, At the worst at least I'll get to learn more about working on the bike.

[OldSchool_IsCool]

I like your attitude!  See my Sig.  Learn to DIY whenever possible!

[mystic_1]

Okay, so i just checked and it's not an exhaust leak.
Is there a tutorial here or anywhere on adjusting the valves on these bikes? this is beyond my scope of mechanical knowledge as of now. But like I told my bud, At the worst at least I'll get to learn more about working on the bike.

You best bet is the procedure in the workshop manual.  Got one of those?  If not, go here and download one:

http://forums.sohc4.net/index.php?topic=17788.0

You could also search the forum for "adjust valves" or "adjust tappets" and probably find several nice threads.

The good news about this procedure is, there's very little disassembly involved, mostly popping off covers and pulling the tank.  Again make sure to do this with a cold engine, since thermal expansion will change the clearances.

mystic_1

[DirtyUnderWhere]

Thanks for all the help guys, I'm downloading the manual, and I'll refer back to this thread as I go through everything. If anything positive happens, I'll post it here! thanks again.
Alex

[turboguzzi]

hei alex

Not trying to knock you off, really, just trying to understand.....

You've done performance mods to the bike for improved power and handling and yet don't know how to adjust your valves or what to check even.... strange

something doesn't add up here, what kind of mods have you (or others?)  done? are you sure they are not the cause?

Maybe give us more details about the work

Cheers

TG

[DirtyUnderWhere]

 Well I put cone filters on, changed the exhaust from factory 4into4 to 2into1 drag, and that's been it as far as performance, as far as handling goes, I put some avon roadrider tires on and put a homebuilt cafe seat on, thus lowering the center of gravity and reducing weight, I've also removed lots more unnecessary weight(fenders chainguard etc.). Oh and I painted lots of stuff black which should be good for like 10hp...
And I've done all of the work myself. I know the carbs need to be properly jetted, and that was to be my next project before this valve rattle... Could the intake and exhaust changes have been the catalyst for this? The pipes are baffled as they were extremely LOUD upon installation.
And you can check out the build in the projects section if you want. 

[Spanner 1]

Plus one on check tappet clearances....but sudden startup of tappet noise sounds to me of a sticky valve..i.e. valve spring unable to close valve until cam has already released its ' sweep ' on the tappet tapping home ' late' behind the cam release.? Anyone else ?