Millyard Special

[Duccout]

I've just been watching a video of the amazing Allen Millyard and his incredible small Honda vee twins. Watching him assemble the engine has left me wondering......The Honda engine has a vertically-split crankcase and the main bearings are ballraces that are pressed onto the crankshaft, which is then lowered into the crankcase, with the uppermost half lowered onto that, so that the outer races are a sliding fit into their housings. So, my question is, how does that work? What stops the outer races spinning in the housings?

I know that some Japanese engines with horizontally split crankcases have small pegs on the outer races that keep the bearings from spinning in their housings, but that is not possible on a vertically-split case, or is it?

[Ducadini]

Dismantled a couple of Honda singles (few decades ago but first are never forgotten) and indeed the bearings were always on the crankshaft.
Just took that japanese way of working for granted. It simply worked.
Imagine my surprise when I opened my first Ducati : shims everywhere.

BTW : still think Millyard should've used a CB50 cyl and head for the rear pot. And original SS high pipes.

ciao
ducadini

[Duccout]

What is also interesting is that the Honda big-ends have paired rollers: two, side-by-side in each cage slot.

[Jordan]

What is also interesting is that the Honda big-ends have paired rollers: two, side-by-side in each cage slot.

I remember reading that having more than one row of rollers can help them stay "on track" better.
A degree of variability existed in this aspect of engine design.
'50s AJS has 3 rows of rollers, caged.
'64 AJS has a single row, caged.
Panther has 2 rows, uncaged.

[LaceyDucati]

Ducati used double row rollers in both the last singles and the early twins, many suffered early failure and the evidence I've seen on bevel cranks is the failures starts at the edge of the rollers in the middle. On the basis all modern manufacturers use single rollers, I wouldn't think the use of doubled up rollers was a solution to long life. I'm not saying doubled up rollers won't work in conjunction with other well engineered parts, but I don't think it's a solution that worked for Ducati or is it necessary for a reliable bearing.

Nigel

[Duccout]

I'm not sure that I explained about the rollers clearly - the little Honda has two rollers laying parallel to each other in each cage slot, like two people laying next to each other in bed. I'm surprised that it works, I would have thought that the rollers would rub against each other, although the aluminium cage would probably wear them more.

[LaceyDucati]

Ah yes I do recall Honda doing that with early XL's, maybe a way of getting more rollers (increased load rating) and maintaining thicker (stronger) cage supports. Anyway I think Honda had good reason at the time, but probably an idea long confined to history.

Nigel

[Eldert]

dont know about old Honda Xl's but the CB 500 T1 twin has a bearing cage with 2 parallel rollers .

and guess what the rollers have the same 13.8 X 3.5 dimensions as a Ducati single .

cage is 34 x 41 and no longer available from Honda

had a Ducati single on the bench last year that had a Carrillo rod with that Honda bearing

Eldert

[double diamond]

The first Honda XL250 (1974?) used the same size bigend rollers as a Ducati single. Also the bore/stroke was the same if I recall correctly.
Matt

[Duccout]

Another thing that is surprising about the little Honda engines is that the cam chain drive sprocket is an interference fit onto the crankshaft, with no woodruffe key (as far as I can see, anyway).