Topic: valve timing - I'm sure this is right?

[pae]

I can't see where this is wrong, but it's not absolutely correct either - what do you think.

'79 CB650Z, when I line up the timing mark the notch in the end of the cam should be horizontal. Well mine 'nearly' is, but the bottom face of the notch is actually in line with the gasket face. So it's sort of right and not far enough out to be a whole tooth wrong - or is it???

I'm not happy as it doesn't feel right. Is there a way of getting this together and having it subtly out by this small amount? Or am I overdoing the worry? Comments please...

regards, Phil

[Tom Stark]

Not real familiar with this bike motor, (built over 4500 car motors, no bike motors).  As I look at your photo, I do not know which way is the direction of rotation.  I do know that the chain looks really loose on the right side of the photo. 
If the notch is supposed to be horizontal, that is how it should be.  More than likely you made a mistake somewhere.  Perhaps you do not have the crank lined up as well as you think.  Manufacturers are pretty good at this stuff.  While timing marks are seldom "exactly where they are supposed to be" they are most often less than a degree off.  They are so close, (usually), that without a dial indicator to TDC the motor, you would never know they were off. 
Step back and look at what you have done.  Make sure you are looking straight at the timing marks on the crank, make sure you have the cam chain tight on the tension side, etc.  It should line up exactly like they say it should. 
Now, all that being said, as I sit here and think, have you taken a bunch of meat off the jugs or head?  That will change the center to center distance of the cam and crank, but your problem does seem like a little more than that. 
Hope this info helps you.
Tom

[SOHC steve]

To be honest,it looks like an old chain?If so the mark is probably as good as you could expect.Have you had it apart or just checking it? Was it running OK? To give you an idea on just how much a long timing chain can stretch,I recently rebuit a 4cyl OHC chain driven mitsubishi (our family driver).It ran OK but was down on power and burned oil.After reassembly I degreed in the cam (I just cant help it  ) and the TDC mark was pretty much spot on.Out of curiosity I put the old chain on to see how bad it was,it is a bit hard to explain without pics but the chains have timing marks on the links as well as on the gears,but basically I would have had to move it one complete tooth to make it even close  .The new chain was very close,but still not spot on,ended up modifying the cam gear with a new dowel hole to get it spot on and allow for the stretch/wear over time. 

[crazypj]

If you have all the slack out of front run its one tooth off. Should line up with the middle of notch.
 Rotate engine two turns to get back to where you are now and see what it looks like (tension chain first)
PJ

[Ibsen]

crazypj gave you a good advice. It's the center of the index mark(notch) that should align with the gasket surface.

LINK 1

LINK 2

I took these pictures for reference before I removed the cam and the cylinder head on my 650.

[pae]

crazypj gave you a good advice. It's the center of the index mark(notch) that should align with the gasket surface.

Hi Ibsen! Yes, I realise it should be the centre, which is why I suspect something is not correct. But the notch isn't far enough out of place to be a whole tooth wrong on the chain, and I can't see what else could be out of line by a small amount.

I didn't take a close look at the alignment before dismantling so can't say for certain how it was before.

I think I'll pull it apart again and see if there's anything obviously wrong and then re-assemble.

regards, Phil

[merc2dogs]

is the gear on the cam reversible? and if so would reversing it alter position of the teeth enough to shift the cam any?

 I know with certain cars, a head gasket that is thicker or thinner than stock will alter cam timing, more if it's coupled with a thin base gasket, as will shaving the head. not by a huge amount, but enough to alter position and valve timing.

 Is all the slack out of the chain?
is it a new chain or the original one?

 Ken.

[pae]

I wondered about the gear being reversible, but I'm sure it's not. I'll take a look at it later.

It's got stock gaskets and nothing shaved off the head as far as I know. If I'd checked before removing it I'd have known if it was always like this or not before 

It's the old chain, nothing has changed other than a new head gasket.

regards, Phil

[Ibsen]

I don't know what brand head gasket you have used, or if you used the stock Honda gasket, but I have seen after market head gaskets for my Kawasaki engines that have been 0.5mm, to be exact 0.53mm, thicker than the stock gasket.
You should have the the two small punch marks on the cam sprocket facing towards the left hand side.

[pae]

Doh - it was a tooth out  

Mislignment on  a small shaft never looks much, but before I started to tear it apart I thought I'd just sit quietly and have a good think.

So, out with the calculator (yes kids - keep up with your maths at school because a bit of trigonometry IS useful in life   )

First, with a 22mm shaft and a 4mm notch, a 'half-notch' misalignment is actually 10.5 degrees out - WOW! I couldn't say for sure how far it was out, but it was close to the edge of the notch and certainly not past it - so somewhere about 10 degrees. Next count the teeth - 46 of them, which makes each tooth 7.8 degrees. Uh-oh, pretty close to what I'm looking for.

And yes, after redoing it (properly) it's bang on.

Just shows, don't assume - measure! and stop and think when stuck. Thanks for your help all. Have taken pics if you're interested.

regards, Phil

[Ibsen]

That's good news Phil. And you did a fine job, both with solving the problem, and with the maths. 

[pae]

... the notch isn't far enough out of place to be a whole tooth wrong on the chain....

live and learn, live and learn...  

regards, Phil

[medic09]

Doh - it was a tooth out 

Mislignment on  a small shaft never looks much, but before I started to tear it apart I thought I'd just sit quietly and have a good think.

So, out with the calculator (yes kids - keep up with your maths at school because a bit of trigonometry IS useful in life  )

First, with a 22mm shaft and a 4mm notch, a 'half-notch' misalignment is actually 10.5 degrees out - WOW! I couldn't say for sure how far it was out, but it was close to the edge of the notch and certainly not past it - so somewhere about 10 degrees. Next count the teeth - 46 of them, which makes each tooth 7.8 degrees. Uh-oh, pretty close to what I'm looking for.

And yes, after redoing it (properly) it's bang on.

Just shows, don't assume - measure! and stop and think when stuck. Thanks for your help all. Have taken pics if you're interested.

regards, Phil

Honestly, if someone had taught me math was that applicable and importand in HS (over 30 years ago), I wouldn't have had to start relearning it as an adult.  I'm emabarrassed to say I wouldn't have known to do that!

Good for you, Phil.

Pay attention to Uncle Phil kids, he's a good example.