The CAM CHAIN is the chain that drives the engine camshaft.  When adjusted correctly with the piston stroke, valve train and points in time, the engine will perform as it is supposed to.  Often a stretched cam chain can add as much length as an extra link in the chain.  A worn cam chain can cause incorrect valve adjustment, point gap and timing in general.  First:   Before making any of the tests listed check to ensure the engine is in time or in some cases not in time.  From the Honda Shop manual (commonly referred to as the Big Blue Book, downloadable from this page) page 2-3; “When cam chain noise is high, the cause is either an inoperative hydraulic cam chain tensioner or excessively stretched cam chain.  Incorrect valve timing or valve clearance, or both, are often the main cause to poor compression, low engine power, engine overheating, hard starting, unstable idling etc."  "Incorrect valve clearance attributes not only to higher valve noise performance as well. If valve clearance is excessive, the valve opens too late and closes too soon, causing poor engine output, increased fuel consumption, and valve noise.  Further, wear of the camshaft lobe is accelerated because the rocker arm is unable to follow the pattern of the camshaft lobe, causing a shock contact. If the valve clearance is too small, the valve opens too early and closes too soon causing poor compression, rough engine idling and back firing.  0.003 - 0.005 in is the normal setting." 

Other problems can come from points and a worn points breaker plate shaft.  If the breaker plate shaft is worn the point gap of between 0.012-0.015 inch cannot be maintained.  Will the engine run, yes, because it will run with a point gap that can shift between 0.012-0.015 inch.  When the wear exceeds the gap variance then the point gap can't be maintained and there will be poor idling, rough running, over heating etc. as stated above with a worn cam chain. The same is with the Valve adjustments and maybe piston ring wear can come into the poor performance issue too. 

Here, we are addressing the Cam Chain.  

To find out if your cam chain is worn there are simple checks that can be taken to find this out.  The following is from an article I wrote back in July 1996:

 The first question is: - how do we know how much the cam chain has stretched?  Second: - what do we do about it?  The first is really simple, with the engine off,  (Remove the oil fill cap) using a flash light move the crank shaft until the timing notch on the cam is centered in the cam-bearing notch.  Then look at the notch on the timing pulley, it should be on the "T".  Now move the pulley back toward the "F" mark on the same housing as the "T" mark. The cam notch should move the same distance as the pulley notch.  If it doesn't, measure the distance from the "T" mark to where the cam starts to move.  Add that to one and one sixteenth inches and you will know how much your cam chain has stretched. When will this take place?  Depending on the use you give your Honda 600, rough or with care.  The chain will give the rough user, (tire spins, 0-65 down the free-way or street) about 40.000 miles.  If you warm the engine up and use discretion in your driving habits, leaving the jackrabbit starts to the Jack Rabbits.  Around, 65.000 miles can be obtained.  However, you should check this every time you adjust the timing, set the spark, change the plugs etc... 

Additionally there are some visual checks that can be performed. 

Remove the valve/cam box cover and look at the chain.

Here is a worn crankshaft main bearing cap tab

Along with the chain being worn is the area between the teeth on the cam itself. 

Here is a cam showing wear from the chain moving lower between the teeth due to stretching

Please see Shop Manual page 4-26 for the repair limit.  Using a heavy duty chain with a slightly larger roller will improve this condition.  Often the slipper (top and bottom pins fitted in place using JB Weld epoxy) will keep them in place and save the slipper. 

This cylinder with the pins epoxied in place was used on an engine for over 10 years.

The heavy duty chain has thicker links along with the rollers taking up the wear between the teeth to get your engine timing back.  The original Honda chain comes packed in grease the other is packed in light oil.  Caution should be taken when choosing a replacement chain.  The chain designation is 219T and is 108 pins long.  Some can be purchased for as little as $23.00 a chain with another $5.00 for the split link.  However many of these chains are used as Go-Cart drive chains and not made for sustained high RPM's like needed on the Honda 600.  The heavy duty chain shown costs quite a bit more but will fit, remove the effects of the worn space between the teeth on the Cam and the Crankshaft and put your cam back in the proper timing range.  Another question; how do you keep your engine clean? The picture above of the Crankshaft Bearing Cap not only shows the effects of a stretched cam chain but the overheating of the oil which caused the baked on tar like coloring of the aluminum bearing cap.

But that is for another letter...

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