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Discussion Starter · #1 ·
Whenever I look up torque specs or other info relating to the motor internals (which is often since I'm in a tear-down right now), I've noticed different torque values between Monster and SS motors. Also other things like checking rod bearing/crank journal clearances with Plastiguage on one motor and direct measurement on the other.

Since the motors appear pretty much identical to my eyes, does anyone know why some of the specs differ?

It has always puzzled me because of the "parts bin" nature of the subassemblies built in house by Ducati. It would seem that all carbed 2-phase 900 motors should be the same; all 3-phase motors the same; all FI the same; etc.
 

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Dunno why they're different, other than the standard answer: "It's a Ducati". [laugh]

I'd go with the plastigage on the rods, unless you happen to have a direct reading bore micrometer.
Place I used to work had a set of Mitutoyo bore mikes, they read to tenths....really nice but *really* expensive.
 

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Discussion Starter · #3 ·
I'm shopping around for a mic to to do the journals. Just this morning found a nice Starrett 1-2" conventional micrometer at a pawn shop, still in the box with paperwork - well cared for. Priced $49. It has the pointy anvil and ram though, and I like the flat version better. I already have a set of telescoping snap guages to take the raw bore diameter. So once I get a mic, I may check this motor both ways just to see what I get.

I'm trying to find a decent dial caliper so I can check things up to 6", but don't want to break the bank.

I have learned, though that sometimes overchecking can run you crazy when you get unexplainable differences between methods. The you stress over which to believe.
 

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I've got an 8" Mitutoyo dial caliper, it's bitchin'. [thumbsup]
McMaster-Carr Part#2325A25 $113, page 2111.

They've also got a Mitutoyo 1-2" mike, reads to tenths, $92.

The telescoping snap gages are a bit of a PITA to get accurate results with...if you use one *all* the time, I'm sure it's easier.

+1 on the 'overchecking', takes me forever to do my valves... :p
 

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i just use plastigauge. the torque specs/method for rod bolts varied with later years. early ones were just a torque. then they got angle tension as well. the bolts may have changed also, altho they all use the same part number still. probably depends who wrote the manual and how much they copied from the last one.

they are all basically the same, excepting the w headed motors and the close ratio box in the 900m ie
 

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Mark1305 said:
It has always puzzled me because of the "parts bin" nature of the subassemblies built in house by Ducati. It would seem that all carbed 2-phase 900 motors should be the same; all 3-phase motors the same; all FI the same; etc.
If the cams are different you'll get a different power curve.

I know for sure that the ST2 has a different cam than the Monster, and that an ST2 cam is the better way to go for a high performance Monster engine. Other than a slight difference in displacement with the Monster being 904 CCs and the ST2 being 944 CCs, the 1997 Monster that I used to own had a power curve different enough that you could feel it compared to the ST2. The Monster, even when tuned for top end, didn't want to rev past 9000 rpms. The ST2 pulls strongly to the rev limiter at 9500 rpms. Even after three years and 12,000 miles, I'll still hit the rev limiter in the lower gears when I'm trying to accelerate hard and not looking at the tachometer. The Monster had a bit more power in the midrange around 4-6000 rpms.

Cam differences, valve size differences, intake tract differences can all affect the powerband.
 

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there's nothing parts bin about them. all carb 904 engines are the same excepting w headed monster engines, with some variations for some years - 6 spline cranks, narrow cranks on ss compared to 906/907, etc. same as the 4v evolution pretty much. the injected 904 engines are all the same excepting the 900m ie and mhe having the close ratio gearbox. the 944 st2 is unique in cams (which are not that different to 900 ie), but the same otherwise given it's a water cooled single pickup injected engine first released with a 2 phase alt.

any short manifold engine will rev out much better than a long manifold carb engine.
 

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Discussion Starter · #8 ·
brad black said:
there's nothing parts bin about them. all carb 904 engines are the same excepting w headed monster engines, with some variations for some years - 6 spline cranks, narrow cranks on ss compared to 906/907, etc. same as the 4v evolution pretty much. the injected 904 engines are all the same excepting the 900m ie and mhe having the close ratio gearbox. the 944 st2 is unique in cams (which are not that different to 900 ie), but the same otherwise given it's a water cooled single pickup injected engine first released with a 2 phase alt.

any short manifold engine will rev out much better than a long manifold carb engine.
I'll take that as an authoritative answer, since you've probably seen the insides of 2 or 3 motors ;) I guess some of it goes back to a statement above that some of the differences in assembly specs could be attributed to different tech writers at different times.
 
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