Idle troubleshooting checklist? (Back after a long break)

[DJM]

Why didn't you swap the needles, tops and slides, until you do you can't rule out the problem being carb related.

Swap the other carb bits over and see what, if any , difference that makes.

Amal MK1 concentrics were a half decent carb but were built down to a price and not noted for longevity, they can wear quite quickly especially if run without an air cleaner. Quality of the original Keihins is much better. If you still have them you could try putting them back on.

If the problem is still there I would be inclined to refit the points and condensers if you still have them to rule out t a faulty ignition. Do you have good compression on both sides, are valve clearances (tappets) both OK?

These engines ran very well when stock and many still do, shame you're still having problems with yours.

[Jlovvorn]

Will swap the slides needles and tops and see what happens.
Ignition is electronic. Might try putting the points back in.
Valves were set after rebuild but I will check them.
Stock carbs are shot.
Thanks for help with the troubleshoot!

[Jlovvorn]

Increase in advance timing cleared up my trouble. So much so that I tried it on my 550 as well, with great results. Both bikes were rebuilt with new cam chains, timed static and with gun, and then stored for five years with maybe one start a year.
I guess the question is - how much is too much advance?
I am sure I am beyond the spec. (Today I slowly increased advance until the bike would idle and run acceptably. Tmw I will put the light on it and see how far out of spec I am)
These bikes never see more than 50mph, nor revs over 4K, nor more than an hour of riding in one day.
Maybe I can get away with a little extra advance?
Or I am going to overheat, seize or blow piston holes?

[redblk63]

My guess is that your SuperHot (per Brendan) will at least overheat and seize. Also, the spark plug electrodes will likely erode away before the pistons melt. Don’t ask how I know all this.

Check your timing is correct static and at full advance.

Larry

[Jlovvorn]

Thanks. Superhot sounds really bad.
I guess the question is how far I can push it and there is no one answer.
I think I need to find whatever problem the advanced timing is covering up and fix it.
Sigh...
Report on static and strobe timing still coming later.

[Jlovvorn]

Timing report.
Strobe only as the electronic ignition I use (bought from this forum) is strobe only.
As I had it set (ie, best starting and running yesterday at 55 degrees) idle advance was half way past TDC towards first round image that appears under strobe.
Full advance was well past the two marks, half way to the next round image.
BUT Today was much warmer (70+) and the bike would not return to idle at any timing setting advanced past F.
It just races up to 4K and stays there. But won’t idle reliably at F.
I think I need to either pull the head and replace the advancer or look into the electronic unit from Germany.
The price is steep but the many hours of my time pulling the head and cam, waiting to send it off to repair, then zipping everything up, is probably worth it if the Sachse system does the same thing as overhauling the advancer.
I am not convinced the advance is my only problem, but I also think it needs to get sorted before I have any chance of sorting out the carbs.
Without predictable advance I could chase this forever.

[DJM]

PM me with an EMail address and I'll send you a 'report' I had almost exactly the same problems with my CL77 and yes it was the advancer that was U.S. over advancing by around ten degrees although 'spot on' when static timed.

The good news is that although it ran very hot it didn't seize or do any other damage but the bike was a whole lot better to ride after I got if fixed.

Mine also sporadically raced up to 4,000 rpm which made for interesting town riding!