Topic: Cb550 valve-TDC question

[work9to5]

I just want to double check myself on this one. Re doing the top end on a 550. If the cam is in this position (pic below) with both lobes facing up this is the cylinder that is at TDC, correct? Assuming that timing is right and crank is turned to T1-4, which it is.

I'm double checking myself because I'm about to do a valve adjust after an engine overhaul and this is something I've screwed up/questioned myself after the fact if in fact I did it right. If lobes are both facing up and timing is correct this is the cylinder that is at TDC the one I valve adjust first, then do a 360 rotation and adjust the other side T1-4 correct?

[Bootsey]

There should be a slot in the other end of the cam (right hand end).

Take the points cover off, and turn the engine over using the stator bolt. Rotate it until the T 1-4 mark on the advancer lines up with the notch in the crankcase, the engine should be at TDC in this position.

Now at this point of rotation, you need to have the slot in the end of the cam parallel to the head surface. Then you fit the chain, making sure that the slot stays parallel with the head. Once it's fitted, you can rotate the engine 360 degrees, and the slot should line up on the opposite side. If it's not parallel to the head, then you're off by a tooth or two.

If you haven't already, grab yourself a copy of the service manual.

[work9to5]

There should be a slot in the other end of the cam (right hand end).

Take the points cover off, and turn the engine over using the stator bolt. Rotate it until the T 1-4 mark on the advancer lines up with the notch in the crankcase, the engine should be at TDC in this position.

Now at this point of rotation, you need to have the slot in the end of the cam parallel to the head surface. Then you fit the chain, making sure that the slot stays parallel with the head. Once it's fitted, you can rotate the engine 360 degrees, and the slot should line up on the opposite side. If it's not parallel to the head, then you're off by a tooth or two.

If you haven't already, grab yourself a copy of the service manual.

Bootsey, I do appreciate your answer. Everything that you mentioned has been done. Notch is in the right place, timing is set correctly. I am and always do work with a manual open next to me. I just want a better understanding, Clymers and Haynes are a bit cryptic (at least to me who learns through working rather than reading as I'm sure most of us on here do) on their valve adjustment process. I'm just looking for a little clarification on which valve set to adjust if the cam is in the position mentioned. With Haynes' kinda ridiculous X and O chart, and Cylmer's directions not taking into consideration that it's not an adjustment situation but a rebuild where rockers always have a "wiggle" it can get a bit confusing.

If engine is set at T1-4 and both lobes are facing up (on cylinder 4) do you ajdust the valves on the cylinder 1 in this position or cylinder 4?

[wowbagger]

Whenever I start questioning myself on TDC I just pulla spark plug and very carefully stick a long screw driver into the cylinder through the spark plug hole. You can then rotate the engine (CAREFULLY, so that the screw driver doesn't get bound up) and the piston will then raise or lower the screw driver until you see where TDC is.

[jonda500]

Hi work9to5,
#1 & #4 pistons both go up and down together (as do #2 & #3 -180 degrees apart from 1&4).

In your picture the other end cylinder (#4) is on compression and is ready to adjust, after turning 360 degrees the one in your picture will be on compression stroke (lobes down).

To find out which is which with the cylinder cover back on you can hold your finger over the #1 or #4 spark plug hole and turn the engine until you feel compression pressure then keep turning until the 1.4 timing mark lines up.
Or look at the rocker arms while turning the engine back and forward to find the spot where the exhaust valve is still closing while the inlet valve is starting to open and adjust the other end cylinder.
John

[work9to5]

thanks Jonda, exactly what i thought was going on and needed to know