250 primary gears.

[Bevel bob]

My primary gears are noisy and have a tight spot,anyone else had this problem? also clutch center notched by plates causing drag,can this be reconditioned?

[DewCatTea-Bob]

" My primary gears are noisy and have a tight spot, anyone else had this problem? "

____ Not really, (not me anyway)...
Do you know if both of your primary-gears are both the original factory-matched pair, or did you possibly get one or the other thru eBay, from some seller who didn't know better or care enough to list the factory-matched set within the same auction-listing? ... (Often I notice that many such sellers will use a separate auction-listing for each gear -(of a Ducati-factory matched-set), and then uninformed buyers will win & buy one of the gears but yet not also win the other!)
I myself have always used only matched-sets, but I know that unmatched gear-pairs may run-into such problems as you've brought-up.
Mismatched primary-gears most always eat power.


" also clutch center notched by plates causing drag, can this be reconditioned? "

____ I'm not really too clear on what you might actually mean but, if you happen to mean that the flute-slots on the clutch-hub, or the slot-surfaces (between each of the 8 finger/ear-tabs) of the clutch-drum/basket, have developed indentation/wear-marks caused by the teeth of the clutch-plate/disks, which have somehow become deep enough to cause interference with the otherwise smooth sliding of the teeth though/across their involved mating-surfaces,, then yes, you could do some careful reconditioning by hand, using a drill-stand with emery-paper wrapped around a shaft (installed in the drill), that should then properly fit the flutes of the hub, or emery-board to fit through the drum-slots, so that you could then decrease the difference between the (extra worn) valleys & the original (less worn) surfaces, (which the plate/disk-teeth mate against) _ That should help reduce the sliding-resistance somewhat.
Sorry I don't know of any standard machine-work job for either of these two particular reconditioning-jobs. _ As it's not a common enough problem that gets quite so serious to such a degree that it requires any real attention. _ I've only ever tried doing this fix just once, to a less than perfect degree,, and then got rid of both the hub & drum, cuz I assumed that they would not last much longer.
__ You could then try converting to the 6 plate/disk system that Eldert claims works so well, so as to keep the issue from returning as soon.


DUKE-Cheers,
-Bob

[Bevel bob]

No way of knowing what orriginal on this bike,the wear on the clutch is another indicator of race use.As the gears show play for 3/4 of rotation then a tight spot i'm looking for bent shafts etc ,missmatched gears would most likely be tight or loose all round?.I have a set of Lacey thick plates to fit,after sorting the problems.

[DewCatTea-Bob]

" As the gears show play for 3/4 of rotation then a tight spot i'm looking for bent shafts etc, missmatched gears would most likely be tight or loose all round? "

____ I agree that mismatched gears are probably not the source of your particular issue.
I'm not sure if I recall ever noticing a meshing problem exactly like yours.
__ When you state "3/4 of rotation", it's then expected that you mean 270-degrees of the crankshaft's rotation but, I'm thinking that your actually mean about 270-degrees of the clutch-drum/basket's rotation.
Off-hand, that would seem to indicate a bent main-shaft but, I'd then expect extra tight meshing for about 90-degrees, followed by about 90-degrees of near normal-tightness of meshing, followed by about 90-degrees of loose meshing, followed by another 90-degrees of near normal-tightness of meshing. _ Those two 90-degree arcs of near normal-tightness would also be subject to abnormal meshing of the gear-teeth (if due to a bent shaft), so I'd thus expect notable resistance to meshing for closer to 270-degrees -(about 3/4 turn), with the remaining 90-degrees being loose meshing (yet also somewhat of a poor mesh alignment)!
Also, in order for a shaft to get bent, I'd expect that something hard got eaten through the meshing teeth,, and something hard enough to bend a shaft would also put some noticeable dents into the teeth, yet I assume you saw no such damage.
__ So since what you state about your particular issue is not exactly like what would be expected with a bent shaft, it would seem that your drum-basket has warped but, that seems even less a possibility.
I've been assuming that you've already tried to check into this issue a fair amount and thus have removed, inspected & reinstalled your primary-gear set, only to then find that the problem still remains. _ But if you haven't yet tried that, then I'd highly suspect that one of the drum-basket's two bearings has gone bad !
__ Since this motor has been well modified for racing, I wonder if it happens to have a 'straight-cut' gear-set installed, as well !? - Are the teeth straight-across, or just the stock-type slanted cut teeth?


Hopeful-Cheers,
-Bob

[Bevel bob]

Std bevel primary set, and as yet I've not seen inside the cases,box shaft turns true and the basket bearings are sound and in straight,I have heard that clutch baskets can be machined wrong and as its one of the last of the n/cs perhaps the tooling worn out?I've got a dial gauge now so may show up something, crank pinion was a little loose on the shaft.Basket shows no wear but center does,so maybee unmatched.5th gear weak on these boxes perhaps it ate one.Plenty of other signs that the Bike shop that built this bike were numpties.

[DewCatTea-Bob]

" I have heard that clutch baskets can be machined wrong and as its one of the last of the n/cs perhaps the tooling worn out? "

____ I'm afraid I'm ignorant of any such tales of such poor drum/baskets being installed by the factory !
(Perhaps fellow-member Eldert has come-across such?)
Those same 60t baskets continued-on to still be used for all the wide-case 250s as well ! _ So it's extra doubtful that worn-out machine-tooling is responsible.
__ I'd suggest that you look for a 350/450-model 27/57t primary-set for your modified 250.


" crank pinion was a little loose on the shaft. "

____ Not good! ... The pinion-gear can shear it's key in half, if the crankshaft-nut is not kept tightly torqued-down !


" Basket shows no wear but center does, so maybee unmatched. "

____ Maybe so, but the clutch-hub/"center" is not hardened as the drum/basket is !


Hopeful-Cheers,
-Bob

[Bevel bob]

Good to know that 350-450 sets fit, I have passed over a few thinking NBG!! Never come across a drive sprocket or gear that only used a key to carry the power,this is not considered good practise,I'm tempted to link the gear to the flywheel to take advantage of the taper ,has anyone done this,could be done by putting recesses in the back of the gear to line up with the flywheel rivet heads.I've sseen a few damaged keyways so others have suffered from this weakness.As the motor was only designed as a 175 perhaps it was sufficient.

[DewCatTea-Bob]

" Good to know that 350-450 sets fit,"

____ I've always installed the 27/57t sets on all my highly suped-up 250s.


" Never come across a drive sprocket or gear that only used a key to carry the power, "

____ Actually, the key is not depended upon to carry the entire load ! ... The friction-pressure (placed on both sides of the pinion-gear), caused by a properly torqued crankshaft-nut, spares the key from having to solely transfer all the power ! _ (Still, if I had been the designer, I would've used 2 keys spaced 120-degrees apart.)


" I'm tempted to link the gear to the flywheel to take advantage of the taper, could be done by putting recesses in the back of the gear to line up with the flywheel rivet heads. "

____ You're a good thinker, however if you throughly thought-out that idea, you'd then see that doing such as that would limit the phasing of the flywheel-rotor to the crankshaft (alright to do if all worked-out ahead of time), and also, a thinner spacer-shim would then be needed behind the drum-basket, (so that the primary-gears would once again re-align, better).


" I've sseen a few damaged keyways so others have suffered from this weakness. As the motor was only designed as a 175 perhaps it was sufficient. "

____ I agree that once these motors grew to 250cc, that their single key set-up is a "weakness", to have to be trusted upon.


Hopeful-Cheers,
-Bob

[Bevel bob]

With my alt/batt/coil system flywheel phase not important, setting the drive pinnion back a tad would also line it up with my clutch!! see what i mean about the numpty bike shop!.Spacers and shims HUH!!. I wont be happy till i get it all to bits,but I can't stop riding it.

[Bevel bob]

Problem sussed, the crankshaft is not turning true!! , I took the clutch plates and crank key out and spun the gear pair,with the crank keyway facing the clutch --nasty tight spots, after turning the crank 180 degrees(keyway facing away ) everything spins free.The crank must have a good wobble on it.Lets hope my crank man can sort it.The vernier caliper says 7 thou wobble,more than enough .