See my comments below.
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> followed the Haynes manual, I have very carefully removed the rocker arms > & rods, springs and seals, together with the camshaft itself. Photographed > it all and stored it very carefully. I couldn't remove the hydraulic cam chain > tensioner. The Haynes manual says I should do this, does it need to be done to > replace the chain?
You do not need to loosen the cam chain tensioner to replace or rotate the camshaft. It can be quite a task to remove that cam chain tensioner with the engine in the car. Here is what I have found:
a) if you remove the cam chain tensioner, you should be able to change the chain's position on the cam without removing the cam holders.
And you will also be able to replace the cam chain with a split chain and a master link, too.
b) if you don't want to remove the cam chain tensioner (I don't like to remove it when the engine is in the car since it is too much work to get at the lower bolts on the fan housing and you have to remove the carb, too), then you will find that a good cam chain and a good tensioner does not give you enough space to change the cam chain's position on the camshaft. So, you will need to remove the left and right cam holders. When you do this, you end up taking out the valve train components (the rocker arms and springs and rubber plugs). This gives you enough space since the camshaft will drop down enough to change the camshaft or change the chain's position on the cam.
I will put the chain in the position which I think
is correct, remove both spark plugs, put the cam holders back on the camshaft but don't reinstall the rocker arms and springs at this time. Rotate the crank over until the notch in the camshaft is appearing in the cam holder and check if the mark on the pulley is aligned with the "T" on the engine case. If not, move the cam chain to another position on the sprocket and turn over the engine again (using a wrench on the pulley bolt) until the camshaft notch appears in the cam holder.
Again, check the pulley notch to see if it is aligned with the "T" on the case. Keep doing this until you have the correct alignment of the crank to the cam.
I also double-check that the piston is at TDC when
the mark on the pulley is at the "T". Since it will be difficult to get a dial indicator on the dome of the piston, I use a low tech method. I stick a long dowel rod or a screwdriver with a long thin blade into the spark plug opening when the piston is approaching TDC. I watch
the movement of the rod and see if it peaks at TDC while I watch the mark on the pulley. After TDC, the rod will change direction on its movement.
Since the rocker arms are not installed,
when you are turning over the engine you are not in any danger of damaging the valves if the cam chain is out of position. Why? Because the valves are not opening. That is why I removed both spark plugs ..... so the cylinder compression does not make it difficult to turn over the engine by hand.
Once I know my pulley mark is correct and
the "T" on the casing is actually referring to TDC (because I checked the piston movement) and my cam is aligned to the crank, then I remove (or rotate) the cam holders and insert the rocker arm parts. Do all of this with the engine at TDC. Make sure the cam chain does not change its position on the sprocket when you reassemble. When you are done, double-check the timing of the cam to the crank by rotating the engine over by hand.
c) if you are replacing the cam chain, cut a link on the old cam chain (or remove the master link if it has one). Split the chain and attach the new cam chain to the old using a new master link. Rotate the crank so the new chain is pulled into the engine and the old one rotates out. I also attach a wire or string to the new cam chain which is one or more links away from the end. While I am trying to attach the new cam chain using the master link, the string is long enough so that if I accidentally lose the chain and it falls down into the engine, I can use the string to pull it back up.
When installing the new cam chain, you will find it
easier to work on if the camshaft and valve train components are removed. Especially if you have not removed the cam chain tensioner. I also stuff some rags in the center where the chain comes through so I do not drop things into the engine (you don't want to lose your master link).
> I am assuming that the chain needs replacing as it will have > stretched and let the timing slip, is this correct or can I infact just > reallign the cam and crankshaft using the existing chain? My car has done > 55000 miles.
The chain may not need replacing (and I am guessing it is probably ok because your car has been working ok even though someone did not properly time the crank to the camshaft) and your engine has not bent a valve yet. Here is some advice which was offered by Bill Colford to someone in February 2009:
If you don't mind, I would only add
that due to wear the cam chain may be stretched to a point it needs to be changed. A test for this is to put the timing mark (on the pulley rotated to the "T" on the case) and then while watching the cam (through the oil fill port - with the cap removed) move the mark on the pulley from the "T" back toward the rear of the engine to the "F" mark. If the cam does not move by the time the mark in the pulley reaches the "F" the cam chain is stretched and needs to be changed. Also the point breaker plate shaft may be warn which will keep the points from maintaining the correct gap. The static test is good and I would always try and get a .016 on the points gap. Then rotate the crankshaft several times and check the gap to see if it changes. I have noted as much as 10 thousands change on a warn assembly.
Caution, if you disassemble the breaker
plate do it in a plastic bag, there are small bearings that will fall out. Also, there is an article in the text pages of the ANZhonda600 yahoo group site to fix this. I have repaired several and all of them are still working to this day.
> If I do need to replace the chain, Miles said I can to use a > 108 Link DID Brand chain which is available in the UK, but is it possible to > obtain and add my own split link to fit it, or am I better off trying to get a > 1973 Honda CB450 motorcycle chain which has the split pin but which I will > need to cut down? I have tried my local bike shop for the Honda CB450 chain > and they couldn't help.
> Removing the cam shaft was a pretty big deal
> for me and if I have to reomve the crankshaft also to fit a chain without a > split, that would be quite scary for me.
Yes, you don't want to have to pull the crankshaft apart to replace the chain. A new chain using the master link is the easier method. Someone on this newsgroup has the part you need or has found an aftermarket brand which will work. We will have to see what the others say.
> Thank guys, I look forward to hearing from you.
> Ross,
good luck,
Dale