Motoscrubs.com

We've made some progress the last week or so on our pair 250 narrow cases and learned a few thing about them. The first thing we learned is that we will need a new set of bevel gears for the 1964 Monza:



The next thing we learned is that the piston is indeed stuck just as the seller said:



It is now sitting in a 50/50 mixture of ATF and Acetone (I read that this is upposed to work even better than Kroil).

We found traces of the original "Kingfisher Blue" underneath all the black paint on our late '63 Scrambler:



And we also found out that, contrary to what the seller told us, the piston is NOT stuck!:



And the bevel gears have no missing teeth!:



The bad news is that the cylinder has a broken fin that I did not notice before:



So now I'm wondering if you all could answer a couple questions for me. How tough are these cylinders to find? Is there a difference between narrow case and wide case cylinders or are they interchangeable?

Is there anything I need to watch for in picking up a used cylinder other than broken fins?

Does anyone make new cylinders?

If I find a used cylinder I can either have it bored out or buy a new liner for it, is that right?

Anything else I need to know on this topic? Thanks for any info you can give me.

Jon

Part numbers from factory spares books will tell you if the cylinders are interchangeable. I think you'll find they are.
You can get the broken fin repaired, if you find a similar one that you can cut off another bike - not necessarily a Ducati - and have it welded on.
It won't be as nice as a complete good cylinder, but sometimes if done well the fix is virtually invisible when the engine's assembled.

Jordan

I second Jordan's statement about fin repair. I have a bunch of friends that ride BMW airheads. When they have a broken fin they send it off (and I can find out to who) and the results are perfect. You can't find the repair to save your life. I am thinking that their "go to guy" for fin repair has some donor BMW jugs on-hand that he takes from, so you'd best source a crappy cylinder as the donor.

Jim

Thanks for the fin repair idea guys, don't know why that didn't occur to me. Sometimes I just assume the worst-case scenario when working on old stuff. Jim, if you could get that information, that would be great, thanks!

Those cylinder liners can be pretty easily swapped at 410 degrees.

Bruce

A new liner costs nearly the same as a complete cylinder.

The fins are, almost without exception, broken in the same place so you may have a hard time finding a donor cylinder. You might be able to use the next fin down or one from the opposite side of a donor cylinder? A piece of 6061 aluminum of the proper thickness could be cut and shaped to fit, then welded on. Grind the weld flush and you are good. Once the engine is reassembled it will be impossible to detect. That would save you from buying a donor cylinder.

Cylinders do turn up on Ebay. They seem to show up in waves. Research piston sizes/options first, then try to find a cylinder that has enough meat left to bore to an available piston size. You may have trouble getting the piston that you prefer if the bore is already way oversize. Have the seller take a rough measure of the bore if possible.
-Jim

If you go the fin repair route, my BMW friends go here:

http://www.cycleworks.net/index.php?mai ... cts_id=246

Once again, they do BMW heads. Maybe they are used to fielding requests to repair other makes. I have a broken fin on a 750 roundcase so when the cylinder comes off for any reason I am going to implore these guys to do the fin repair for me because I know the magic they are capable of and I will supply the donor barrel.

Thanks for the link!

By: guzzijon...
" The next thing we learned is that the piston is indeed stuck just as the seller said: "

____ THAT piston is not a stock Borgo-piston, it's an aftermarket 10.5:1-CR forged-piston made by 'MC Supply' .
(StocK CR for Monza is 8:1, and 9.2:1 for the 250-Scr.)
__ I'm wondering why the tower-shaft tube-housing is still in-place, even though the cyl.head is removed ?




____ THIS piston looks to be a stock-type piston, (but can't see it's dome to be certain of it's CR.


" How tough are these cylinders to find? "

____ Not too tough actually, they (usable ones) often sell for around 60-bucks on eBay.
And I think I-myself have one or two to spare.


" Is there a difference between narrow case and wide case cylinders or are they interchangeable? "

____ They're interchangeable, however the n-c.cylinders come in three slightly varying heights. _ So it's possible to end-up with a piston/cylinder combo which won't allow the piston to fully reach the top of the cyl.sleeve,, or even perhaps conversely, a combo which requires a cyl.spacer-shim (to be placed underneath cyl.jug).


" Is there anything I need to watch for in picking up a used cylinder other than broken fins?

____ Other than the particular bore-size, of course,, any cracks in the sleeve, (although that's not usually a concern with 250-sleeves).


" If I find a used cylinder I can either have it bored out or buy a new liner for it, is that right? "

____ Yes, the cyl.liner/sleeve can be bored (out to as much as 76.6mm, safely),, however finding a new (stock) cyl.sleeve may be pretty-difficult.


Duke-Cheers,
-Bob

Thanks for your feedback Bob! Here's some better pictures of the piston we found inside the '63 Scrambler:




The dome seems at least as big if not bigger than the one on the '64 Monza, doesn't it? And the valve reliefs seem deeper to me. Also, is that little flat spot a relief for the spark plug?

Thanks for any insight you guys can give. The archaelogical detective work is part of the fun for us.