lets talk about timing wheels

[MotoMike]

Looks like i should have a timing wheel. I see what appears to be a nice one on ebay from a tool shop in Australia. over a hundred bucks though.
I see that it has o ring and oil seal to keep the case sealed while using it. I see EuroTrash has the arbor without the wheel. not sure if it can be used for strobe testing.

How hard is it to make one? anyone got pics of their home brew. How important is it that it is sealed against the case? what wheel did you use?
Mike

[Bevel bob]

I still have points so i can time it with a plastic disc and the Pazon has a blink light on it,I set my timing about 5 to8 degrees static - . this gives about 33to 36 degrees full advance, if it kicks back too much i open/close up the points a thou to fine tune it!! Looking at the heat line on the plug electrode this seems to be a touch retarded so i can have easy starting or full performance ---but not both. If you want to strobe you will need the kit you mention. I would do it my way then use the strobe pointer and mark the cover so to make it simple to check or play with , nice if you could just buy the pointer, no seal needed.The pointer locks into the crank slot

[MotoMike]

Thanks Bob
that sounds good. I think that even the advace can be checked statically. Not functionally but the degree of the full advance.

That little pointer I see in the old manuals for strobe timing. I have never seen one of those for sale anywhere. Do you know of a source.

Mike

[Jon Pegler]

Barry Jones at Classic Ducati sells them.
They are easy enough to make. The pointer just has to be aligned with TDC.

[DewCatTea-Bob]

" I set my timing about 5 to8 degrees static - . this gives about 33to 36 degrees full advance, if it kicks back too much i open/close up the points a thou to fine tune it!!
this seems to be a touch retarded so i can have easy starting or full performance ---but not both. "

____ Thanks for your input B.Bob !
__ You're certainly one who understands why the 28-degree mech.advancer-unit is not sufficient for both best-performance & avoiding kick-back in the 250s !
So have you not yet checked into thinning the width of the fly-weights of your advancer-unit, so as to add some extra swing into the twisting of the points-cam ?
As you must understand that that would then allow for some amount of extra auto-advance range, for you to take advantage of.
__ It should also be understood that besides yielding a couple extra degrees of swing/twist, that the lightened weights would then also delay the full-advance RPM-point... However that may be somewhat canceled due to the aged return-springs possibly being weakened. _ But even if the full-advance RPM-point is altered from the stock set-up's INTENDED 3000RPM-point, then that really wouldn't be a bad side-effect of lightened fly-weights... Cuz keep in mind that the originally heavier fly-weights were required to move the ign.timing from 8 to 36 degrees between idle & 3000-RPM, while the modified AAU would hopefully (possibly for instance), advance the ign.timing from 5 to 39 degrees between idle and about 3500-RPM,, which would actually be the same as getting 3 additional degrees to further increase the maximum-advance as the RPMs exceed the regular/intended 3000-RPM max.advance-point.
So all that should be realized as a win/win-situation, since not only could kick-back be kept towards a minimum, but also the maximum/standard barrier-point of '36-degrees @ 3000-RPM' could then be (advantageously!) surpassed, with a new (estimated) figure of '39-degrees @ 3500-RPM'.
So where a stock-250 would top-out at just 36-degrees BTDC, your modified-250 could then gain an additional 3-degrees over the next 500-RPM (past the std.3000RPM-point).
__ I've never bothered to fully calculate-out the exact outcome of any intended modification to the fly-weights, cuz it just seemed more concrete to just go-ahead & make the mod & measure the results.
I always wanted to try this modification-idea to a AAU but, it was unfortunately one (of many) projects which I never got around to, back when I was still in my active-years with DUKEs.


DUKE-Hopes,
-Bob

[Bevel bob]

Too busy to play with the 250, I have two 860s in bits.The timing pointer usually has a nib that locks into the crank slot,so once you have got the timing right and the case strobe-marked it will be childs play to check the timing or adv/retard a touch.No need for timing discs.

[JimF]

I have a generic timing wheel. No gasket.

I attach a piece of thick solid copper wire to the bike to use as a pointer. I use a TDC finder in the spark plug hole and then bend the wire to locate a TDC mark on the timing wheel.

You don’t need to mark any certain degree on the wheel, you will just be looking to rotate the engine a few degrees away from whatever point on the wheel you establish as TDC.

[Bevel bob]

I too use a generic disc and wire pointer to set up the timing initially, It is however difficult to accurately measure tdc due to the piston shape and so i only do it when the heads off,its also a pain to get the AAU to hold in the full advance. It is however very easy and accurate to strobe check the timing with the crank pointer once the case is marked .I have more recently used plug electrode readings to keep tabs on the timing and fine tuned with points gap adjustments, this does take practise and needs a clean running motor and a bit of fast riding!!.

[LaceyDucati]

Hi Bob (and all)
It's actually quite easy to find TDC accurately with the head on. Firstly you cannot use a clock gauge as the gauge will hit the piston at an angle and the ensuing drag and sticktion will result in poor repeatability. The other problem is even if you were 90 degrees on, movement is very slight and there can be an element of dwell on the reading.

The best way to set TDC accurately is to make a positive stop using an old spark plug. The usual method of making one of these is to bash the middle out of the plug and braze/weld a nut (10-12mm) on the top end of the remaining steel part and then fix a stud and lock nut into the plug body. The end of the stud will need to be rounded to prevent marking the piston and the stud should have a hole in it to allow air to escape from the cylinder.

Install the postive stop in place of the plug with the piston to one side of TDC, then turn the engine until the piston rests against the stop.

Take a reading on your degree disk which you will have set to TDC approximately by eye.

Remove the stop, turn the engine past TDC, replace the stop and return the piston back towards TDC until it rests against the stop once more.

Take another reading on the degree disk and compare it to the original reading the other side of the stop. If the reading is the same then the disk and pointer are set correctly.

If there is a difference in the readings move the disk or pointer half the difference and then repeat the exercise until both readings are the same. The actual figure is irrelevant and is only a result of how far the thread stop is screwed in. Somewhere around 20 degrees will work well.

The reason I recommend removing the stop either side of TDC is if you turn the engine over and you have the stop too far in, there is the danger of running one of the valves into the stop. If you are only using the stop on the one engine next time you have the head off you can check that the stop clears the valves and of course then you can turn the engine through from one side of TDC to the other quite safely. When placing the stop in, it should be nipped up by hand so that the stop does not move and if you carry out the check either side of TDC a few times you will prove to yourself that you can remove and replace the stop with good repeatability. At all times during this operation the engine should be turned slowly and in a controlled manner. Jerking the engine over with the back wheel is not to be advised!

This you will find is an extremely accurate way of setting a degree disk to TDC. Another word on degree disks, is to check the the degree disk is running true. Although for ignition timing this will not matter too much, if you are checking cam timing and the disk has a lot of run out on it, when you are about 90 degrees to your TDC mark, you could be a few degrees out.

Best Wishes

Nigel

[MotoMike]

parts manual shows a grub screw in the end of the crank at that end. does it need to be removed? not clear from the picture if it is deeply sunk in the crank or near the end. what size bolt and thread?

thanks for all the good info here. I have a little flash light (torch) that I will modify to make the test light. I guess just checking the point gap as I had been doing, leaves a lot to be desired.