Advance mechanism

[JimF]

My 250 cc daily driver is running great. I get waves, honks, thumbs-ups and the like all the time. I take it to work every day weather permitting - it's that reliable.

The oil leak is lessened if I don't try to fill the crankcase to the line on dipstick.

My question has to do with the advance mechanism, or in my case the lack there-of. When I was setting the points I took them out and and the plate below and found I had no advance mechanism whatsoever.

The bike runs great, starts easily, pulls strongly, etc.

What concerns if any should I have since my timing is not being compensating for engine RPMs?

Thanks

Jim

[Bevel bob]

You must be missing a chunk of horsepower , if the timing were set to give full power you would be getting some serious kickbacks. What is the general state of tune?.

[JimF]

It does kick back a little, but not a lot.

How do I quantify the state of tune?

[DewCatTea-Bob]

By: JimF...
" My 250 cc daily driver is running great. "

____ So I guess you expect everyone to already know that your "daily driver" is an older 250-Mk.III ? _ (Is that correct ?)


" The oil leak is lessened if I don't try to fill the crankcase to the line on dipstick. "

____ Perhaps you have some blow-by effet which pushes some oil-slosh out-through from behind the drive-sprocket.
Does your motor employ any type of PCV near the crankcase-breather exit-opening ?


" My question has to do with the advance mechanism,
and found I had no advance mechanism whatsoever.
What concerns if any should I have since my timing is not being compensating for engine RPMs? "

____ I'm left to assume that you've previously set your engine's static-timing as if you had assumed that the engine included a (stock-type) AAU ?
If so, then the ign.timing is always maintained at 21 to 23 degrees BTDC, (is not that the case, for you ?).
__ For the older Mk.III (& Motocross) 250cc.Duke-models without any AAU, the ign.timing is supposed to be set at about 40-degrees BTDC.
Bevel-Bob has already covered your possible results.


DUCATIly,
-Bob

[Bevel bob]

Hi Jim, by state of tune I meant,compression ratio,carb size ,cam type and valve size. Every single I have ridden has been in Mach 1 or higher spec so starting has always been "fun"!. I find it difficult to understand how a manufacturer could expect you to kick start a bike with 40 degrees fixed adv.I don't think we got that spec in the UK. No wonder Americans walk kinda funny!.My 250 also leaks a little from the drive area if the oil level is right up there.My bad work I think.I would have altered your bike to Battery Mach 1 spec ignition.

[DewCatTea-Bob]

" by state of tune I meant,compression ratio,carb size ,cam type and valve size. "

____ Early/pre-65 Mark-III (not 'Mark-3') models had 10:1 ; 27mm-SSI ; Red-cam ; 36 & 33mm valves. - (That's of-course ASSUMING that that's the Duke-model [which Jim has not yet bothered to confirm for us].)


" I find it difficult to understand how a manufacturer could expect you to kick start a bike with 40 degrees fixed adv. "

____ Keep-in-mind that the ign.systems which are not powered by stored-up battery-juice, do-not as easily produce an adequate ign.spark quite as well (as the bat.powered ign.systems do) during SLOW kicking-speed,, so-therefore when there's then* insufficient ign.spark-power produced, there's then little chance for any 'kickback' ! - (Much-unlike if a battery-powered ign.system were to be set with such extremely advanced static-ign.advance/timing.)
(* "then" meaning when purposefully working starter-lever SLOWLY.)
__ The kick-starting method for the non-battery models, is to use the starter-lever to (slowly) bring the engine to comp.TDC (which becomes too difficult to quickly continue-forth at about the same point as when the ign.spark is set/timed to occur [at 40-d.BTDC], so at that point there's then insufficient alt.power-production to produce sufficient ign.spark),, then after (relatively slowly) bleeding-off the built-up compression (without going-past TDC too far), then-next the kick-lever is reset (for maximum advantage), and THEN fully -(forcefully & fastly) jumped-on,, thus-THEN providing proper kick-over speed to produce sufficient alt.power (for producing an ign.spark) and sufficient flywheel-effect to prevent/avoid 'kick-back', (and press-onward past comp.TDC, for successful eng.starting) !
__ If the above suggested kick-starting method is not followed and rather done with some-other (non)- method of-which just-happens to leave the kick-lever randomly associated with the crankshaft-location, then such (non)- practice will result with random (and more likely !) incidents of 'kick-back' & failure to start-up.


Dukaddy-DUKEs,
DCT-Bob

[Bevel bob]

Thank's Bob for the clarification, now i'm sure I don't want one!!, relying on a feeble ignition to not kick you seems very hit and miss.In the UK battery less bikes were viewed with much suspicion after the very public failures of competition bikes in the ISDT . Also most bikes were bought to use as regular transport including night use and traffic manners. The American market was as different as night and day.

[DewCatTea-Bob]

" Thank's Bob for the clarification, now i'm sure I don't want one!! "

____ Your reaction has now led me to think that perhaps I did-not get my entire intended conception fully/properly expressed, so I've just-now edited the wording of my previous-post, (for improved "clarification").



" relying on a feeble ignition to not kick you seems very hit and miss. "

____ As my now improved previous-wording should better help make-clear, it's not that the stock magneto-type Ducati ign.systems are "feeble", but rather that that type of ign.system won't produce a sufficient ign.spark WHEN you're NOT trying to produce a spark !
__ However it is indeed a "hit and miss" type of starting-situation whenever ya don't practice a nonrandom type of kick-starting method ! _ As THEN ya're quite likely not able to produce a consistently constant kick-over speed (try after try).
In-other-words,, producing spark & starting the engine without any kickback will be a certain hit & miss affair, whenever kicking-over of the engine is done without any regard as-to whatever the relationship happens to come to be between the starter-lever & the crankshaft-location.
So if one wishes to avoid such hit & miss poking-around, then they should make the effort to properly setup the stater-lever's relationship to the crankshaft, before each kick-start attempt.
__ This kick-starting concern is of-course not so much an issue for the Duke-models with battery-powered ign.systems.


Dukaddy-DUKEs,
-Bob

[JimF]

Hello Bob and Bob and others,

OK, I must be a dolt. When asked about the "state of tune", the meaning of that phrase which is quite a common thing to ask just passed through my brain as if there was nothing there. That should tell me something.

I have no clue as to its state of tune. The bike came to me with 2000+ miles on the odometer. I was told that I am the third owner. I was told the first owner crashed the bike (hence the low mileage and its non-stock forks and front fender) and the second owner never got it to run well (mostly owing to a grossly mis-jetted Mikuni carb) and the bike sat in his living room as a display piece. This is true as I had seen it there on numerous occasions.

I've been told it was a Diana, but here in the States the label "Diana' label is tossed around about every 250 Ducati to the point that it is almost a generic term for any and every narrow case Ducati 250. So I make absolutely no claims as to my bike's provenance.

Now with just over 3000 miles on the engine if I can believe the odometer, I don't want to take the engine apart to document its internals and thus its state of tune. Here is what I do know: narrow case, street bike frame, 250 engine with no special suffix stamped into the motor, 5-speed gearbox, AC voltage electrical system, no advance mechanism and an aftermarket Mikuni VM 26 fitted. The original toolboxes and seat are also gone.

I do know that the second owner fitted the Mikuni, the fate of the original DelOrto it was said to be wearing is unknown. When I was trying to resolve the issues of it not being able to rev past 6,000 RPM I asked the second owner if he ever set the timing. He replied that he did not which makes me sure that he did not pull the advance mechanism out. The carb was at fault for the 6K rev limit, not the timing.

So here's my dilemma:

On one end I am handcuffed by having a full-time job and two part time jobs so I have not a lot of time for wrenching.

On the other end the climate here is miserable and makes for what is always a too-short riding season so I don't want to decommission the bike long-term until November at the soonest. Similarly I wouldn't want to implement an afternoon repair that leads me to transform a well-running, reliable and easy-to-start bike into a poor-running , unreliable or hard-to-start bike.

At this point in time I could:

1) Add an advance unit and re-time the bike.

2) Re-time the bike from its current 21 degrees to 40 degrees so as to better suit the timing to the ignition system.

3) Do nothing. This tack aligns with the school of thought that "if it ain't broke, don't fix it."

If I am risking the chance of incurring engine damage from running 21-degree timing when I should be at 40 degrees, I would not hesitate to change the timing.

So I am just looking for well-meaning and informed advice from the people on this forum for which I am grateful for their help.

[Bevel bob]

You could try a little more advance on the points plate, you can always put it back if the kickback is too much. I'm not sure that the mag ignition would work well with the AAU.