greenjeans
Well-known Member
How to get your cam timing marks dead on. With help from 66Sprint.
Over the last month or so, I’ve been taking a whipping on a ‘72 CB450. Luckily, I found this forum & Steve aka 66Sprint. I tried an EK timing chain and a Honda timing chain. I was having a heck of a time getting the marks to line up when putting the chain on. It’s easy to get the cams in the correct position, but what kept happening to me was: When the chain was on the cams, the front of chain run it wasn’t tight. And, if you pulled the chain tight, it wouldn’t fall into the teeth on the cam sprocket. So, on it went, slightly loose, but with the marks lined up. This is why everyone thinks you “skipped a tooth”. So... when I’d rotate the motor, the lower crank sprocket would turn before the cam would - not by much. About 2-3mm after the mark. This was because the front run of chain was not tight. I wasn’t noticing. So, when I’d turn the motor over a time or two to check, my marks would be off. The factory manual does not mention how to fix this.
Over and over I did this. Same results. Then with a little suggestion from Steve, it started to make sense why. The front run of chain HAS TO BE TIGHT when lining up the marks. Steve told me that was mandatory. He said I’d have to rotate the crank backward slightly, then back forward. Finally, the lightbulb was starting to glow. I would back the crank up about .25”. This actually makes the chain looser. Then, I would move the exhaust cam back 2-3mm before the mark. Then, put the chain back on the cam sprocket - gaining a tooth. I’d do this a time or two until the crank sprocket and the cam sprocket were in a position where the front run of chain was TIGHT. Then, as you rotate the motor forward, the timing mark and the cam timing mark will line up when you get to their marks. Then, you can feed the chain through to the intake side. The intake side will line up because it has the same amount of teeth as the exhaust cam. The key - the crank sprocket has fewer teeth than the cam sprocket. Remember, the crank makes 2 revolutions for each revolution of the cams. The crank rotates more than the cams. Think of a bicycle. Your pedal stroke is not the same as your wheel rotation (unless both sprockets have the same number of teeth)
I hope this makes sense. Many thanks to this forum and guru Steve 66Sprint.
And, always try to use a Honda (D.I.D. T chain)
It is possible to get the marks right on the money.
Over the last month or so, I’ve been taking a whipping on a ‘72 CB450. Luckily, I found this forum & Steve aka 66Sprint. I tried an EK timing chain and a Honda timing chain. I was having a heck of a time getting the marks to line up when putting the chain on. It’s easy to get the cams in the correct position, but what kept happening to me was: When the chain was on the cams, the front of chain run it wasn’t tight. And, if you pulled the chain tight, it wouldn’t fall into the teeth on the cam sprocket. So, on it went, slightly loose, but with the marks lined up. This is why everyone thinks you “skipped a tooth”. So... when I’d rotate the motor, the lower crank sprocket would turn before the cam would - not by much. About 2-3mm after the mark. This was because the front run of chain was not tight. I wasn’t noticing. So, when I’d turn the motor over a time or two to check, my marks would be off. The factory manual does not mention how to fix this.
Over and over I did this. Same results. Then with a little suggestion from Steve, it started to make sense why. The front run of chain HAS TO BE TIGHT when lining up the marks. Steve told me that was mandatory. He said I’d have to rotate the crank backward slightly, then back forward. Finally, the lightbulb was starting to glow. I would back the crank up about .25”. This actually makes the chain looser. Then, I would move the exhaust cam back 2-3mm before the mark. Then, put the chain back on the cam sprocket - gaining a tooth. I’d do this a time or two until the crank sprocket and the cam sprocket were in a position where the front run of chain was TIGHT. Then, as you rotate the motor forward, the timing mark and the cam timing mark will line up when you get to their marks. Then, you can feed the chain through to the intake side. The intake side will line up because it has the same amount of teeth as the exhaust cam. The key - the crank sprocket has fewer teeth than the cam sprocket. Remember, the crank makes 2 revolutions for each revolution of the cams. The crank rotates more than the cams. Think of a bicycle. Your pedal stroke is not the same as your wheel rotation (unless both sprockets have the same number of teeth)
I hope this makes sense. Many thanks to this forum and guru Steve 66Sprint.
And, always try to use a Honda (D.I.D. T chain)
It is possible to get the marks right on the money.
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