John :
I believe it's a definite possibility. I once helped a friend who had
assembled a motorcycle motor (which was a 4-stroke) with the timing chain
off by one tooth, and it would consistently foul plugs in just a few minutes
of running.
However, it's not hard to check cam timing (with the stock cam) with just
the rocker cover removed. If you trust your TDC mark, it's even easier.
Assuming the TDC mark is good :
First turn the engine until #4 exhaust is just closing, and the crank is at
TDC. Set the valve lash for #1 intake and exhaust to .050". You can stack
multiple feeler gages together for this. It doesn't matter if the value is
not exactly .050", as long as they are the same. Now turn the crank forward
one full turn, coming back to TDC and stopping. You have to stop on the
mark, you cannot turn the crank backwards (or the reading will be
inaccurate). If you do pass the mark, turn it two full turns forward and
stop on the mark. Now measure the lash on #1 intake and exhaust (without
moving the crank). If they are equal, then the cam is perfectly timed. If
the intake is tighter than the exhaust, the cam is retarded.
I don't recall the slope offhand, but one way to find how far it is retarded
(or advanced) is to split the difference of the readings (assuming one of
them is not .050"), and then turn the crank another two turns, stopping when
the readings are equal. You can now measure how far the mark is away from
TDC, and compute the angle from that.
When you are done, turn back to TDC with #4 intake closing, and reset the #1
valves to .010".
Randall
> Could the timing chain have slipped a cog? Looking at the manual,
> and spinning the crank to see when the valves open/close it
> appears to be off (it's late), but not by much. Can this sympton
> be caused by timing error? I'd hate to open up the front end of
> the engine just to find out it's just fine.
/// triumphs@autox.team.net mailing list
/// To unsubscribe send a plain text message to majordomo@autox.team.net
/// with nothing in it but
///
/// unsubscribe triumphs
///
/// or try http://www.team.net/cgi-bin/majorcool
|