QuestionI have a near pristine 77 GL1000 ( they still looked like motorcycles back then
!) with 17,000 original miles. A couple of weeks ago I replaced the cam belts
and at the same time, Installed a Dyna electonic ignition module.
Setting the timing proved to be a bit of a beast but I finally managet to get it
to a sasfactory level.
As the bike was now able to Idle quite a bit lower (950 RPM), I immediatly
noticed engine rattle that I hadn't before. I was unsure as to weather this was
new noise or if it was old noise that had previously been masked by the
engine running at higher (1200-1500)RPM.
After 70 miles or so of enjoying the new smoothe ride I noticed that the
engine rattle/clacking had increased. Next thing, going about 25 MPH the
bike died out as the crunching/clacking/rattling noise increased. I managed
to restart the bike and slowly ratlle a few more blocks to the top of a hill (I
live in San Francisco which is full of hills) at which point I was able to kill the
engine and coast the rest of the way home. I have been in a deep melancholy
since.
My real question however, is how to go about diagnosing the problem in a
systematic manner.
I don't want to fire up the enginer if there is risk of damage. I figure I
should examine the belts to make sure they are still there but other than that
... shoud I pull the cylander heads off ? Could the timing / ignition module
have slipped or malfunctioned ?
AnswerJosh, I don't usually go into a lot of GW questions, as there are numerous Wing websites that specialize in the details of these rather complicated machines.
http://www.classicwingclub.org/ is a good one.
That said, I will share my thoughts, based on your comments and my overall experience about how things go wrong and why. This may be useful or not...
First, I'll assume the bike was running well before you began to work on it. Yes?
Changing the belts/ignition should not make the engine suddenly run at a lower idle, if they are set to the original specifications. Correct cambelt installations won't affect the engine running/idling afterwards. Be sure that the idler pulleys are still okay.
GW ignitions run of the end of the camshaft and thus are subject to being affected by the cam timing, which is controlled by the cambelts. If the cambelt installation was off one tooth, then not only does the cam timing suffer, but the ignition timing as well. If the cam timing is off on just one bank (ignition side), the valve timing is incorrect for that bank, but the ignition timing is off for the whole engine.
Your "difficulty" in installing the ignition system, which have been around for years and should be a direct install, leads me to believe that your camshaft timing is not correct, at least for that side, thus causing ignition timing errors.
Incorrect ignition and cam timing sends incorrect vacuum signals to the carburetors, which can no longer meter fuel/air to the cylinders as designed. Either the spark plugs get fried from too lean mixtures or get fouled from too rich mixtures.
On top of this, cam timing errors can/do cause interference between the valves and pistons. This can lead to bent valves and/or damaged pistons. The increased noises you are hearing could be valve/piston collisions and are certainly also coming from the primary chain tension, which is easily upset when the engine is no longer in dynamic running balance, due to cam timing, ignition timing and carb synchronization issues arising from the belt/ignition timing errors. Cause and effect....
What to do: First pull the spark plugs and get a reading from them... fouled or fried or showing particles of metal on them from the mechanical collisions that may be happening.
Next, pull the cam covers and recheck the cambelt indexing.
Correct as necessary.
Then, check the valve clearances. If the valves have been hitting the pistons, they will bend and loose their sealing faces and the valve lash clearances will change in a big way.
Finally, check the compression readings to see if all cylinders are the same. If you had to correct cam timing and one bank of cylinders has much lower compression than the other side, then the head will have to come off for damage appraisal and repair. If the pistons are damaged, you are in pretty deep trouble, work-wise and $$$-wise. If only the valves are bent and the pistons are just nicked a little, then you can do a valve job on that side and put back together again.
If the cam timing gets corrected and the compression gets back up to normal, then redo the ignition pickup again, back to where it was designed. With a fresh set of plugs, even compression and ignition timing back to where it belongs, you should be good to go again.....
I'll keep my fingers crossed for you...
Bill Silver
