Topic: 78 cb550 TDC timing marks mismatched

[howdisrespectful]

I am finishing up a top end rebuild on my cb550 and as I begin to check valve clearances I notice the marks for TDC are completely off.

I turn over the engine until intake valve #1 begins to raise so I can line up the T marks however the numbers to the right read 2-3.

I assume this means The cam is 180° out of alignment? How do I go about getting the correct marking to line up? Should I open the cover back up and detach the cam chain?

I have attached a (poor) picture showing how the ignition plate looks when valve #1 is on its way up. You can see the cylinder 2-3 marks to the right.
I thought I was following the directions to a T (no pun intended) so where did I go wrong?

[jaytee-nz]

There are separate timing marks for cylinders 1/4 and 2/3. Rotate the crank until the marks for 1/4 come in to view - what is no. 1 valve doing then ?

[scottly]

There is no such thing as a cam 180* out on these motors. Turn the crank 360 degrees and the cam rotates 180*.

[howdisrespectful]

There are separate timing marks for cylinders 1/4 and 2/3. Rotate the crank until the marks for 1/4 come in to view - what is no. 1 valve doing then ?

As the 1/4 marks come into view there is slight wiggle and on the intake valve #1. Once I line up the “T” marking the valve loses all wiggle and becomes very tight.

The valve only moves up and down just before the 2/3 marks come into view

I also retracted the valve adjustment screws a bit for installation of valve cover - not sure if that has a drastic effect on the wiggle of the valves. .

[Scott S]

 Use a straw in the #1 spark plug hole and find TDC. See where your timing marks are and if both intake and exhaust are slightly loose. If not, go one full revolution and check them again.

 If both valves never get loose, you have the tappet adjustment way out of whack.

 OR..... The timing is off on the cam/gear. Did you line up the slot on the end of the cam when you did the top end?

[Bodi]

Odd. I don't think the advancer can be 180 out, since it locates and drives with a pin on the advancer that goes into a hole in the crank end.
The cam itself can be put out of sync with the crank by engaging the chain on the sprocket incorrectly, but it can't be 180 degrees out as it turns at 1/2 crank degrees. You can be a sprocket tooth (or maybe two) out without crashing pistons and valves together.
I would confirm that it's at TDC 1-4 by eye or a straw to check that the 1-4 marks are in play. If not... well, that should not be possible.

[howdisrespectful]

Use a straw in the #1 spark plug hole and find TDC. See where your timing marks are and if both intake and exhaust are slightly loose. If not, go one full revolution and check them again.

 If both valves never get loose, you have the tappet adjustment way out of whack.

 OR..... The timing is off on the cam/gear. Did you line up the slot on the end of the cam when you did the top end?

I will check with the straw asap!
I did line up the cam parallel with the top end, I made sure to.

Now that I think about it, in order to line up the cam sprocket screw bolts with the cam itself I had to pull the chain link by link until the holes matched up. I think I may have possibly spun the timing 180* during that process before tightening the bolts. If that is even possible.

[Scott S]

 You can't be out 180*. It doesn't matter if the notch on the cam faces forward or backwards, as long as it's even with the edge of the head when you are on TDC.

 You can be off a tooth or two.

 You can be WAY out of adjustment on the rocker arms.

 Did you use the rubber band trick when installing the rocker cover?

[howdisrespectful]

You can't be out 180*. It doesn't matter if the notch on the cam faces forward or backwards, as long as it's even with the edge of the head when you are on TDC.

 You can be off a tooth or two.

 You can be WAY out of adjustment on the rocker arms.

 Did you use the rubber band trick when installing the rocker cover?

The cam was even (although for a day or two I was thinking I must've made a mistake.
Turns out I was way out of whack on the rocker arms. I did not start with the rubber band trick and it led to a whole day of confusion. Once I brought out the rubber bands everything fell into place.

What really set me on the right path was when I brought out a chopstick (didn't have any straws lol). It showed me I was reading my ignition marking wrong and ended up confusing myself.
everything was put together correctly and I was the cause of my own worry.
Thank you for the tips they really helped me out.

[howdisrespectful]

Just as an update everyone's contributions was exactly what I was looking for and my bike is now up and running!

I have rode it around the block a bit and everything seems to be running better than ever!! This is not only my first top end rebuild but my first time working with any kind of engine, and it wouldn't have been possible without the collective knowledge and resources SOHC4 provides.

Thank you all 100x over.

I am now going out to enjoy the last of this sunny day.

[scottly]

I did not start with the rubber band trick and it led to a whole day of confusion. Once I brought out the rubber bands everything fell into place.

You are very lucky you didn't bend any valve stems.