Another no-Monster build thread

[MonsterHPD]

I've just sent the crank / Carillos / Pistals off to the Crank Man for balancing, and when I get them back (eventually ...) I need to get the Carillos properly attached to the crank. My experience on mounting con rods is purely car and very old. What's your best tips on assembling the conrods, and how to get the correct bearing clearances?

I will of course check the Duc workshop manual, but shurely there's a lot of experience out there, and I'd like to get this right first time .... your advice would be most appreciated.   

[koko64]

Although you are very skilled, I would consider having the bottom end put together by an expert who will shim up the bottom end and gear box to track specs and finish the top end yourself. You will have plenty of other work to do I'm sure. But that's just me.

[ducpainter]

             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                   This!

Ducati bottom ends have a fair amount of black art associated with them.

[MonsterHPD]

Although you are very skilled, I would consider having the bottom end put together by an expert who will shim up the bottom end and gear box to track specs and finish the top end yourself. You will have plenty of other work to do I'm sure. But that's just me.

Well, you flatter me by sayaing I'm skilled, but basically it's mostly a matter of finding decent info, and letting things take the time they take. One should also no forget that mostly things that went well will end up in a forum thread like this one, the screw-ups tends to get less publicized   

Anyway, I've actually already made a couple of bottom ends, with the help of some advice from Brad Black, and a lot of time. It was my plan to write a manual for myself and next time, when I had the process in fresh memory, which I of ourse did not do .... but getting the shimming set-up pretty OK is not so much black magic, really. I'll put some info in this post as I go, and we'll see if you find that rerasonable.

But I have so far not made the big ends, so any advice on that would be much appreciated.   

[Duck-Stew]

Although you are very skilled, I would consider having the bottom end put together by an expert who will shim up the bottom end and gear box to track specs and finish the top end yourself. You will have plenty of other work to do I'm sure. But that's just me.

+1

[koko64]

The last bottom end rebuild I did was a '78 Corona

[MonsterHPD]

Well, memory deteriorates with age, so I've had to ponder this for a few days before I could say too much about lower end assembly. When I was in the process of building my track-ST2 motor, I discovered more metal on the magnet plug than I really liked, so eventually I ended up with the motor completely disassembled. I found nothing amiss, but I ended up assembling 2 motors in pretty short succession.

Since I had an ST2 disassembled at the same time, and since the M900 has a close-ratio gearbox and the ST a wide-ratio one, I decided to swap sine I never liked the close-ratio for the street. So I had 2 lower ends I had to assemble.

At the same time, my mate was also assembling lower ends, so it turned out to be a bit of a common do-and-learn thing, with the odd advice kindly provided by Brad Black. In the end, it's not so much a black art as patience and some proper tools (and some proper advice).    

Many years ago, I read an article by Kevin Cameron in Cycle Magazine, where he described a cure for hard-to-shift gearboxes:  â€¦. Set a few hours aside, dissemble your motor …. And gearbox …. And lap the gear dog end faces ….”. I always wanted to test this, so I did it when everything was in pieces anyway.  

DSC_0191 by torbjörn bergström, on Flickr

Dogslipning01 by torbjörn bergström, on Flickr

Dogslipning2 by torbjörn bergström, on Flickr

As always, some learning is done the hard way, especially when you do things you knbow will not end well, and do them anyway …. Always use the right sort of pliers for the locating rings; some parts of the shaft are very brittle:

Utgående axel by torbjörn bergström, on Flickr

There are quite a few shims needed to get it right; it helps that my mate has a small flat grinder

Shimsning by torbjörn bergström, on Flickr

I will have to re-learn the proper order of doing this, I seem to remember that the shift drum is assembled with (at least) upper-tolerance clearance, then proper clearance is done one shaft at the time with the shift drum and associated fork(s) in place, and in the end everything is installed to get as much gear overlap as possible which might require shifting shafts this way or that but I don't quite remember anymore. It will be trial-and-error again I suppose.

The 900 motor ran and shifted very well after the re.build, the ST has not been started yet ….

DSC_0002 by torbjörn bergström, on Flickr

Was the dog-grinding worth the trouble ….? Naah…., don't think so, really.

I have also heard afterwards that it is possible to shift the gears for 5th atnd 6th and the box still works, a friend is said to have discovered this on the dyno when the shift pattern turned out to be 1-2-3-4-6-5. I hope I have not done so on the ST, but I can't be sure until I start the ST motor …. the 900 was OK   

[koko64]

Bugger. Good to have handy mates.

[DucHead]

Great thread, thanks!

What surfaces are the "gear dog end faces"?

[MonsterHPD]

Great thread, thanks!

What surfaces are the "gear dog end faces"?

Thanks, I hope someone will find something useful somewhere in my ramblings.

Gear dog end faces:

Dog markerad by torbjörn bergström, on Flickr

The idea is that by polishing these surfaces, the will slide easier when they are brought in contact when you change gear, thereby making shifting smoother. When I tried them by hand, on the shafts, it did feel smoother, but I can't really say if it was any better on the running motor.   

[DucHead]

Cool, thanks!

[koko64]

 
Maybe you might feel the difference when making clutchless up shifts. I have to remember that you have a substantial off season to work on bikes.

[MonsterHPD]

Maybe you might feel the difference when making clutchless up shifts. I have to remember that you have a substantial off season to work on bikes.

Believe it or not, it's too short ....

[MonsterHPD]

When I bought the bike, it came with the stock 749R linear rear linkage and shock, and a new but not 749R-spech Öhlins front fork.

Trying out all the adjusters, it turned out the rebound adjuster on the shock would just turn half a turn, so I had to dismantle the shock, really all the way, to get at the rebound adjuster. As it turned out, the adjuster wheel has got a good whack that had destroyed the adjuster:
P6290024 by torbjörn bergström, on Flickr

P6290024 (2) by torbjörn bergström, on Flickr

A bit of work, but once diagnosed, just a few spare parts away.

I don't have too much experience with shock shimming, but from what I know, the shimming seemed very stiff:

P6270044 by torbjörn bergström, on Flickr

The five shims closest to the piston is quite a lot .... but not having ridden the bike, I left it all in place.
 
Springwise, both ends came with stupendously stiff springs, 10.5 N/mm front and 120 N/mm rear. That might be OK if you're in the 100 kg leage, but I'm 62 or so, and on the first track day, on a small twisty track, the bike would chatter as soon as we went anything but straight ahead. Presumably, the tires were doing the suspension work as well, so that would be mostly some springiness but no damping.

Digging into my pile of used springs, I found some 9.2 or so N/mm fork springs, and a 100 N/mm rear spring, and the improvement was immense. The rear shock, however, really is very stiffly damped, so that will have to be corrected during the winter. Some correction here, and the suspension should be quite OK.     

[Speeddog]

Wow, a 120 spring and that shim stack.
I think the previous owner nicked that shock off of a dump truck. 

That sort of shim stack seems pretty common, I have yet to see any reason for it.
PM me when you open it up and we can discuss what you've got.