175TS Narrowcase Timing Help

[Samurai]

Hi Guys,

Story so far in brief.

I've completely stripped and rebuilt/refurbished the engine, shimmed all the timing gear correctly, following all the combined wisdom on here and from Nigel Lacey. I've read all the various threads in the flywheel marking and find that mine is correctly marked and is now set at the required 13-15 degree advance for this model.

I'm now at the stage of checking and adjusting the static and advance timing, following the advice given on the vintage veloce website from a link I found under the Technical section on here.

Now the issue. I've followed the process to the letter and everything seems to make sense to me. However, I'm finding that whilst I gap the points correctly (0.3 and 0.4 mm) and can get the static advance smack on at 13 degrees BTDC (with the AAU fully retarded), when I check the fully advanced timing, it is too advanced at 46 degrees, whereas it should be between 40 and 43 according to the manual?

All the springs seem fine, everything lightly lubricated, moving easily and as far as I can tell, the points appear to be fairly new.

Is this a case where the springs have just stretched with age, the points are just worn or badly made or am I missing something else?

Having only ever had belt drive Dukes and other modern bikes before, points ignition is a new thing for me, but I'm guessing that the extra 3 degrees of advance could be damaging long term?

Any advice would be very welcome!

[Bevel bob]

I run a 250 with similar system, I find 36 degrees adv plenty and 8 static to give better starting with little kickback and better idle. It also gives the big end an easier time. I would start with this and then compare with result from a few degrees more adv , If no improvement go back to less adv. Look at and read the markings on the plug earth electrode .

[Jordan]

I've seen AAUs that had been modified to reduce the advance range, with small blobs of weld, filed.

[Samurai]

Hi Jordan,

That's interesting. Is it a reasonably common thing for a 28 degree advance AAU to be outside it's supposed maximum advance range by 5 degrees then?

I guess that back in the day, spring tensions and manufacturing techniques were obviously not as accurate, or it's just wear and tear?

[Samurai]

I run a 250 with similar system, I find 36 degrees adv plenty and 8 static to give better starting with little kickback and better idle. It also gives the big end an easier time. I would start with this and then compare with result from a few degrees more adv , If no improvement go back to less adv. Look at and read the markings on the plug earth electrode .

Hi Bob, thanks for the info, but I may not have explained myself terribly well!

My concern is that my 28 degree AAU is apparently capable of giving up to 33 degrees of advance!?

I didn't know if it might be just wear, me over stretching the springs capacity whilst trying to lock the cam in place, or something I've overlooked?

[Bevel bob]

What you have is a 14degree unit that is giving about 16 degrees (doubled by the gearing) , If you read back history you will find that the extra range is just what some of us want and go to extra work to achieve just what you have!. You can just time the motor to give say 38 to 40 degrees and still have happy kickback free starting ,you lucky B------.

[Jordan]

Hi Jordan,

That's interesting. Is it a reasonably common thing for a 28 degree advance AAU to be outside it's supposed maximum advance range by 5 degrees then?

I guess that back in the day, spring tensions and manufacturing techniques were obviously not as accurate, or it's just wear and tear?

I think Ducati points ignition hardware is quite good quality, but could wear eventually.
Spring condition has no effect on advance range.

[Samurai]

What you have is a 14degree unit that is giving about 16 degrees (doubled by the gearing) , If you read back history you will find that the extra range is just what some of us want and go to extra work to achieve just what you have!. You can just time the motor to give say 38 to 40 degrees and still have happy kickback free starting ,you lucky B------.

Well that's good to know The only problem is that I can't regard the AAU any more as it is already back as far as the slots allow. So I'm kind of stuck with pretty much what I've got.

From what you guys seem to be saying I should just get the static timing as low as possible and not worry too much over extra advance at the other and of the scale?

[Jordan]

Is it the correct AAU unit? The range of movement could vary according to the part number. Can you measure it?
I would time at factory recommended degrees BTDC for full advance, either with strobe light or by locking the AAU.
If then the full retard timing is later than spec, it won't hurt anything and could make idling and starting nicer if it has battery ignition.
If full retard timing is earlier than spec, it may not matter. But if it makes starting difficult, you could time it for more retard but it will then not go to the specified full advance degree figure, so performance may suffer.

[Samurai]

Ok, I've had one more go and fiddled the points gap to the absolute minimum I would be comfortable with and this gives me a static reading of 12 degrees BTDC (minimum spec according to the manual) and a full advance of 45 degrees (2 degrees more than spec).

So I'm going to leave it for now and see what it's like once it's finally running, as from your comments it seems I maybe overthinking this.

If all else fails then I gueas sourcing another AAU would be the only way forward.

Thanks for all your advice guys, it's really appreciated