600 750 900 Inlet tubes

[Nasher]

Evening all

There has been discussion on here before about the differences between the inlet tubes on 600, 750 and 900 carb fed engines.

The situation is made worse by some breakers, particularly on ebay, purporting to be Ducati specialists who advertise inlet tubes as being suitable for all three engine sizes.

Having built up a 900 engine from parts, and purchased a 600SS already dismantled to use as a donor to build a 900 bitsa special, I’ve ended up with a set of 600 inlet tubes and a set of confirmed 900 ones.

I can confirm they are very different - See the images,

At first glance they appear to be the same casting externally, but are different in length, and all the angles are slightly different.
But the most significant difference is that the bore is MUCH larger at the head end on the 900 ones.

Nasher.
http://i1277.photobucket.com/albums/y481/Nashersimages/inlets%203_zpsuq8ljdlh.jpg (http://s1277.photobucket.com/user/Nashersimages/media/inlets%203_zpsuq8ljdlh.jpg.html)
http://i1277.photobucket.com/albums/y481/Nashersimages/inlets%201_zpswm9xtndf.jpg (http://s1277.photobucket.com/user/Nashersimages/media/inlets%201_zpswm9xtndf.jpg.html)
http://i1277.photobucket.com/albums/y481/Nashersimages/inlets%202_zpsvov8lvxi.jpg (http://s1277.photobucket.com/user/Nashersimages/media/inlets%202_zpsvov8lvxi.jpg.html)

[DrD]

Thanks - so now I know they are different and not just suspected so.

[Wasta]

A bid difference when viewed end on.

[utopia]

Hmmmm.
I wonder which my 750 has.
Or maybe I'm being unkind in assuming that there isn't a dedicated 750 version.
Either way, I'll be in there fairly soon to fit the new carbs, so we shall see.
Any chance you could measure the two bores ?
Maybe I can consider "optimising" mine while I'm at it.

[Dukedesmo]

Hmmmm.
I wonder which my 750 has.
Or maybe I'm being unkind in assuming that there isn't a dedicated 750 version.
Either way, I'll be in there fairly soon to fit the new carbs, so we shall see.
Any chance you could measure the two bores ?
Maybe I can consider "optimising" mine while I'm at it.

I don't know this for sure but would think the 750 is as per the 600, because AFAIK the engine is the same 'block' (other than bore and stroke)?

If they are, and you want to do any 'optimising' - then I have a pair of the 600 tubes lying around that you are welcome to have a go at with grinder/polisher etc. so that if it does go wrong you've still got your good ones. as backup. :thumbsup:

[utopia]

Ever thoughtful and helpful.
Much appreciated.
I'll bear it in mind.
:)

[Nasher]

Any chance you could measure the two bores ?


No worries, will measure them tomorrow.

Nasher

[Nasher]

I wonder which my 750 has.


The Stein Dinse website has 3 different part numbers for the 600, 750 and 900

Nasher

[Dukedesmo]

The plot thickens. I knew 600 & 900 were different, I would say the 750 must be the same length as 600 but maybe a bigger bore?

[Dirty]

I don't know this for sure but would think the 750 is as per the 600, because AFAIK the engine is the same 'block' (other than bore and stroke)?


Is the 900 not pretty much the same basic block as well?

[Dukedesmo]

Is the 900 not pretty much the same basic block as well?

I think there are some differences in the crankcases but maybe not too much?

More specifically the cylinders (other than bore) are the same on 600/750 but not on 900, which is longer due to the longer stroke.

This is one reason why the intakes and exhausts are different - the 900 cylinder/head combo is longer so the ports sit in a different location, meaning the intakes and exhausts are longer because the ports are further apart.

[Darren69]

900 is large crankcase (888/916 etc) w/- 6 speed box. The 750/600 is small crankcase (Pantah) 5 speed box. Both derived originally from the Pantah design however.

[Nasher]

Managed to measure both sets of tubes today.

The Flange end where they bolt to the head is obviously the difference we're concerned with. They are a different length and shape as well.

On the 600 ones the diameter does open up very sharply after the actual flange bit, suggesting the flange itself could be machined differently for two versions, 600 and 750 maybe??

The bore of the flange end is obviously machined on both, not as cast, and strangely tapers out slightly towards the outer edge. So even the 900 ones could be opened out slightly so the smallest diameter was at the outer edge of the flange not the inner edge.

Anyway - Flange bore diameters:

600 Set
At outer edge of flange - 28mm
At inner edge of Flange - 27mm

900 Set
At outer edge of flange - 34.5mm
At inner edge of Flange - 33.5mm

Hope that helps somebody.

Nasher.