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Hi All, I have an problem setting the timing on my R80g/s and just wanted some advice before i start stripping any parts off. The bike has clocked 162000 mls which i think is relevant to issue.
I have recently stripped the ignition bean can to check/clean/lube the advance unit and fit new springs .Prior to this the valve gaps and carb balance was checked , both fine .I hav’nt checked the timing for a very long time though as the timing should not change unless the advance unit is sticking, and the bike has been running fine for years.
I refitted the beancan and set the static timing with the led tester hall tester.
The flywheel marks are correct at tdc. Once warmed a little it idles ok.
When idling i can only see the Z full advance mark but it is not clear .When i increase the revs the Z mark disappears and can only be roughly seen when the can is fully retarded .I cannot see the S mark at idle speed . The bike revs pick up fine.
Does this all point to a worn out crankshaft sprocket as it has never been changed . The timing chain was replaced 7000 miles ago.

There is something very not right here. You should not be able to see the 'Z' at idle. The 'Z' should only show at full advance (i.e. at - say - 3000 rpm or more. At idle you should be looking at the 'S' mark which should be aligned with the timing notch on the edge of the timing hole in the crankcase.Full advance is 26 degrees so it's highly unlikely that issues with the timing chain or the sprockets are the cause (not saying the sprockets couldn't do with replacement... at 162k miles that's quite probable... If a new chain was put on 150,000 mile sprockets it's quite probable that it will have issues as well) but it isn't the main cause of this issue.

The obvious answer is that the advance mechanism is sticking so I think you need to revisit your work on the bean can to see if something has slipped or isn't assembled right.

I'n assuming that the bike has run well since the timing chain was replaced... If not, you might need to check to see if the new chain was fitted a tooth out... however, the fact that you static timed it on the 'S' mark makes a sticking advance much more likely.

Rob

Rob Frankham wrote: ↑Tue Mar 28, 2023 7:54 am...
The obvious answer is that the advance mechanism is sticking so I think you need to revisit your work on the bean can to see if something has slipped or isn't assembled right...

Following the often mentioned philosophy of checking the recent work done to correct a new problem...
A quick way to check that is via substitution with a known good bean can. That's not always that easy though. Giles B, do you know someone with a working spare?

SteveD wrote: ↑Tue Mar 28, 2023 10:15 pm

Rob Frankham wrote: ↑Tue Mar 28, 2023 7:54 am...
The obvious answer is that the advance mechanism is sticking so I think you need to revisit your work on the bean can to see if something has slipped or isn't assembled right...

Following the often mentioned philosophy of checking the recent work done to correct a new problem...
A quick way to check that is via substitution with a known good bean can. That's not always that easy though. Giles B, do you know someone with a working spare?

A good point. I do have a spare working bean can and would be happy to lend it for testing, however, I am a considerable distance away. We would have to come to some agreement about postage and it isn't for sale so I'd need to have it back...

Rob

Giles,

You know I have a bean can nearby but it's points so I can't see how that would help.

If the static timing is ok on the S mark with the led tester but not when tested at idle then could the timing light be faulty ? Now I've written that I see it doesn't make sense because if you are seeing Z at idle instead of S then the timing light would have to illuminate earlier rather than later and that's not possible even with an adjustable delay timing light. Anyway the curious thing is the led tester and timing light don't agree so the problem must lie somewhere in the method unless idle speed is enough to move the advance mechanism which seems unlikely.

Hi All, thanks for your input. As you say it does seem to point towards an issue with the advance mech. I decided anyway to have a look at the alignment of the crank/ cam sprockets any they are fine , plus the cam sprocket wear which does’nt look too bad. I stripped down the bean can again and could not find any evidence of the advance mech sticking. On checking it I cannot see any way I of assembled it incorrectly and have cross checked it with pics on web sites. I do have another beancan but was similar when fitted . .I have been wondering now if its something to do timing light or the process as you have said Barry. Will have to get the gaskets and re assemble the timing case , and get back to you as i would appreciate some help.

What sort of timing light are you using? From your description, it would seem that you have a LED tester for the Hall Effect switch and for static timing. I would also assume that you have a strobe timing light of some description and that this is different.

Concentrating on the strobe. If it's a simple 'single pulse/single flash' strobe, then it's very difficult to see how it can cause the timinmg to misread. The strobe can only flash at almost the same instant as the ignition current is switched (and the plug sparks). If it's a more sophisticated strobe system with delays controls and other circuits installed, then it's possible (if unlikely) that it is malfunctioning in that way. What I'm saying is that I think it unlikely that the issue is with a strobe timing light but the acid test would be to try it on another vehicle and/or try a different strobe on yours.

The other thing that occurs to me, although it doesn't really fit you symptoms, is that it is possible to fit the entire bean can upside down which makes timing impossible. Worth a check.

Otherwise, grasping at straws a bit. My 'instinct' still goes for a sticking advance... doesn't make much to prevent the bob weights from returning as the revs die...

Rob

Hi Rob, I have just connected the shaft of the bean can ( without the outer case ) so i can see the advance mech rotate at speed . The bob weights spin out and return back perfectly without any problem . On with the investigation !

Hi Rob, The strobe is a Gunson Tachostrobe ,old but it has worked ok in the past . It connects to the battery with 2 croc clips and signal wire / connector which attaches to the top of the spark plug and then the plug cap. The led hall tester is one I made years ago with a led bulb / resistor and 9volt battery which connects to the cans 3 pin plug . The bean can can only be fitted one way. Will have to try another strobe . Onwards and hopefully forwards!

Giles B wrote: ↑Thu Mar 30, 2023 8:23 am Hi Rob, I have just connected the shaft of the bean can ( without the outer case ) so i can see the advance mech rotate at speed . The bob weights spin out and return back perfectly without any problem . On with the investigation !

Sorry I don't understand, how have you achieved that? the bean can and base is a solid casting.. you can't see the weights when they are inside. Not being funny but is that a stock bean can?

Rob