450 SCR engine rebuild

[LaceyDucati]

Wolf.

The flywheels are ground as an assembly, so the chance of two odd flywheels running true as a pair is slim....who knows you may get lucky!

The 350 and 450 cranks have the same stroke but are balanced differently and fitted with different rod lengths. You can use 350 flywheels with a 450 rod (140mm) in a 450 as long as you balance them accordingly. All the stoked race 450's I have built used 350 cranks very successfully.

Never needed a key in the taper on any race 450's I've built (all with heavy flywheels), so I conclude it's not necessary. Probably more likely to cause issues. The taper needs to be good, nut tight (70 lbft)and I use a tab washer and a bit of 243 nutloc (on the thread) for good measure.....35 years building Ducati singles and I've never had a crank nut come loose.

As a test I always tighten the nut, then undo it and test the flywheel fit with a puller, if it jumps off easily, it's probably no good. If you have to strain or it comes off with a crack, then it's good.

Nigel

[themoudie]

My apologies to Wolf and all others reading this thread, if I implied that there is a woodruff key in the alternator rotor taper of my 450 engine, this is not so. The woodruff key is located where the helical drive gear is attached, taking the drive to the clutch drum gear. I hope this clarifies my last posting.

Good health, Bill

[LaceyDucati]

I would add that not all the tapers are perfectly the same from the factory....so if you are unlucky sometimes the two components don't fit together well even when both are good. In which case they might look good, but they wouldn't pass my fit test. Either a case of rectification or mix and match.

Nigel

[Duccout]

Brilliant reply there from Nigel, real, practical knowledge and advice; if racing does not show up a problem, then nothing will.

Years ago when 450'S were in their hey-day, there were a lot of owners who had experienced trouble with the flywheel taper and there was a lot of disparaging discussion about it in the pages of the Owner's Club magazine. Basically people accused Ducati of being stupid in not fitting a key to the taper, and most people who experienced trouble had their tapers modified to fit a key, when most likely the problem was caused by the nut not being tight enough and a poor taper fit.

I am guessing that the extra thump of the 450 is what causes the flywheel to spin on the taper compared to the 250 or 350? After all of the talk about loose flywheels years ago, one of the first things that I check when I buy a new Single is that the flywheel nut is torqued up tight. Does anyone think that it is good practice to lap the flywheel taper with grinding paste?

Cheers,

Colin

[blethermaskite]

Rightly.....or.......wrongly if there is even a hint of a dodgy fit on 'any' taper fit I give it a wee lap with very fine grinding paste, a very light test lap will also act as a tell tale re the actual mechanical fit of the components relative to one another, if the test lap shows bad contact I would be reluctant to try and repair by further lapping as positional tolerances can get messed up. Certainly with Ducati single flywheels at a minimum I always lap with Tcut or brasso......I have never had one come loose, needless to say any lapping compound needs to be scrupulously cleaned from all surfaces before assembly.
Cheers,
George

[Jordan]

I'd hazard a guess that many problems with loose flywheels were caused by unclean parts.
I've owned 6 singles, all second hand, and most had been enthusiastically barstardised and had scored tapers.
DIY is so much fun! But that taper should be scrupulously clean at assembly time.

[Wolf]

...thanks a lot so far for all the valuable input! I think my next step is waiting for the left hand part of the crankshaft. With the possibility that that may not work out I will go for the 350 crankshaft solution.
I will keep you updated
Cheers
Wolf

[LaceyDucati]

Fine with all that George, a light lap with fine paste is okay with me, as long as caution and cleaning is observed...Also as you say any more will end in a compromised gear position. It's amazing how a few thou from a taper will result in large movements of the flywheel.

I would agree with Jordan too, in fact many problems with engine builds stem from poor cleanliness!

Nigel

[Wolf]

...meanwhile I've found a 350 crankshaft in good condition and ordered a rod kit and flywheel from Nigel, a new lay shaft is also ordered and everything seems to make good progress...

[Duccout]

Looks good!

Hope it goes together well.

Cheers,

Colin