Britbike forum Forums British motorcycles in general Bsa gold star forum Check Cam Timing - DBD

I have timed a lot of motorcycle cams with an engine on the bench - head off - using two dial indicators.
I want to avoid that to check cam timing on a problem bike.

Suggestions on how to check cam timing without pulling the head?
I have Keith Johnson 1/2 mile cams so any markings on the cams may no be correct.
I have the settings so just want an easy way to see if the cams are correct.

This can be done....as long as you have an accurate valve lift profile graph. Using the graph, pick an appropriate checking lift, a common one is 040". Calculate the "lift" at the lifter (where you check clearance on a DBD). Set the clearance to the checking lift clearance plus standard tappet clearance. Now set the engine position to overlap where each lifter is at 0 clearance and 0 lift. Compare that position to the graph. It's not as accurate as checking with dial indicators, but it's better than not checking.

I have an A65 that I wanted to check the valve timing on. With a degree wheel hooked up and a buddy rotating the crank with a socket on the nut at the end, after a couple of tries, we were able to get repeatable results as to when the pushrods would start to get tight and were able to determine that, yes indeed, I had a bad cam (20 degrees late on intake opening and 30 degrees early on closing on one cylinder). I wouldn't use that method for precision work, but if you are just trying to verify that the timing is approximately where it ought to be, it should work for you.

Ed from NJ

You can make the above 100% accurate.
Pick a wide tappet clearance say 0.040" as above but then check at both ends of the opening and closing where the push rod can just be rotated and note the numbers on the degree disc. Exactly half way between these 2 numbers is the lobe angle and is usually in the vicinity of 100 degrees
The lobe angle can be calculated from the camshaft spec opening and closing points
eg The cam opening point is 60 BBDC and closing point is 40 ATDC so total duration is 60 + 40 + 180 = 280, the mid point will be 140 which is 100 degrees BTDC lobe angle