Another eng swap thread:(Edit: no longer considering EFI, upgrading 750 engine

[LowercaseJake]

A guy I used to ride w/in SoCal begged and begged me to install 11:1 Ferracci piston in his STOCK HEAD equipped 750.  Finally, mostly to shut him up, I did it.  What a mistake.

The stock 750 heads lack the flow to get air in and out which is used to somewhat reduce the static compression ratio of the pistons.

The bike made more torque, yes.  But to do so, it took the highest octane fuel and the torque was over-and-done-with in short order.  Bike also ran very, very hot.  My stock headed 750 ran just as hard as his high-comp bike did.

I used to cut apart 750 heads to make "demo" units so that people could understand how desmo works (w/o the top of the head getting in the way).  That's about the most practical use for them.  There isn't anything about the 750 head that's good.  Nothing. 

695 heads run 7mm valves, same as the later 800 heads do.  Get them if you get the pistons.  Consider it a package deal.

DS, thanks you just saved me a lot of money, time and frustration. The issue I'm having is deciding *which* heads to go with and with *what* pistons. Various forum anecdotes talk about compression dropping big time if doing an 800 head swap with 750 pistons, *even 11:1 Ferraci pistons*. So, just to clear some things up and I guess start over;

I want the quickest, easiest, most inexpensive route to a modest bump in top end power for the 750 and the ability to easily power wheelie in first gear. Porting the stock 750 heads sounds like a waste of money. So - what about 695 or 800 heads, untouched from stock aside from a nice valve job, plus 800/695 jugs and / or 800/695 pistons?

Honestly at this point I'm inclined to fit the already smoothed out long manifolds/intakes I already have, install a light flywheel + 14t sprocket and call it a day. I would hope the cleaned up rough casting of the intakes + LW flywheel + FCR39's would be sufficient for occasional hooligan behavior.

But the engine is sitting on my bench right in front of me. If I can source 695/800 heads complete with jugs and pistons for cheap (a few hundo) and significantly improve the performance of the bike it's a no brainer. I bet I could find a low mileage set of jugs complete with pistons AND their respective heads for cheaper than the Ferraci 750 pistons alone.

[LowercaseJake]

Also, somewhat off topic - does anyone know the size and thread pitch of the OEM flywheel nut on 98+ Ducs? it seems smarter to buy a pair of inexpensive hardened jam nuts from McMaster Carr (if possible) than $40 on the Nichols and other jam nut pairs being offered.

[ducpainter]

<snip>
I want the quickest, easiest, most inexpensive route to a modest bump in top end power <snip>

Fix the 900 and re-install it.

[Duck-Stew]

DS, thanks you just saved me a lot of money, time and frustration. The issue I'm having is deciding *which* heads to go with and with *what* pistons. Various forum anecdotes talk about compression dropping big time if doing an 800 head swap with 750 pistons, *even 11:1 Ferraci pistons*. So, just to clear some things up and I guess start over;

I want the quickest, easiest, most inexpensive route to a modest bump in top end power for the 750 and the ability to easily power wheelie in first gear. Porting the stock 750 heads sounds like a waste of money. So - what about 695 or 800 heads, untouched from stock aside from a nice valve job, plus 800/695 jugs and / or 800/695 pistons?

Honestly at this point I'm inclined to fit the already smoothed out long manifolds/intakes I already have, install a light flywheel + 14t sprocket and call it a day. I would hope the cleaned up rough casting of the intakes + LW flywheel + FCR39's would be sufficient for occasional hooligan behavior.

But the engine is sitting on my bench right in front of me. If I can source 695/800 heads complete with jugs and pistons for cheap (a few hundo) and significantly improve the performance of the bike it's a no brainer. I bet I could find a low mileage set of jugs complete with pistons AND their respective heads for cheaper than the Ferraci 750 pistons alone.

If you want my direct instructions:  "Honestly at this point I'm inclined to fit the already smoothed out long manifolds/intakes I already have, install a light flywheel + 14t sprocket and call it a day. I would hope the cleaned up rough casting of the intakes + LW flywheel + FCR39's would be sufficient for occasional hooligan behavior."

Do that. ^^^

[Speeddog]

OEM 695 pistons are too tall, and OEM 800 pistons are too short, to work with the 750 crank, as the strokes are shorter and longer, respectively.

695 heads are identical to the 7mm valve 800 heads, same part numbers, same valves.

[koko64]

https://www.hordpower.com/gallery3/index.php/Dyno-Charts/album07/750ss
Hi comp 750's. (JD Hord), with stock Vs 900V cams.

Then he goes nuts.. 900 inlet valves, porting, 900 cams, big bore pistons.
https://www.hordpower.com/gallery3/var/albums/Dyno%20Charts/album07/795ssIgnition.jpg?m=1416607249

You guys are lucky to get 695/800 motors/ heads so cheap.

[Duck-Stew]

You guys are lucky to get 695/800 motors/ heads so cheap.

You could "hit" one of us up and have some online auctions watched for you.  Then, if we win, it's a personal shipment from a friend to another friend...

Perhaps that's an option, just sayin'...

[koko64]

That's a cool option. . A whole 800 motor with 6 gears would be cool.
Sounds like it's not too hard to fit some Ferracci pistons and 800 heads (with swapped cam pulleys).
I wonder how consistent the port casting has been between model years? Iirc, Lofgren reckons the early 900V heads were worse than 93 - 99V heads in the ports and then 900ie heads a bit better again. Is it possible this is the case with 750 heads over the years?

[Duck-Stew]

That's a cool option. . A whole 800 motor with 6 gears would be cool.
Sounds like it's not too hard to fit some Ferracci pistons and 800 heads (with swapped cam pulleys).
I wonder how consistent the port casting has been between model years? Iirc, Lofgren reckons the early 900V heads were worse than 93 - 99V heads in the ports and then 900ie heads a bit better again. Is it possible this is the case with 750 heads over the years?

I dunno...  Could be.  I'm guessing that Ducati improved castings by about 2000-2002 and held at least that same level of improvement going forward.

[LowercaseJake]

If you want my direct instructions:  "Honestly at this point I'm inclined to fit the already smoothed out long manifolds/intakes I already have, install a light flywheel + 14t sprocket and call it a day. I would hope the cleaned up rough casting of the intakes + LW flywheel + FCR39's would be sufficient for occasional hooligan behavior."

Do that. ^^^

Will probably do this I guess, but I was sorta hoping for a fun winter project that didn't break the bank and, may not be worth the *time*, would be worth it to me, at the right price.

DP I've ridden bone stick 900's compared to a 750ss and was very underwhelmed by the difference in power. But that's just my opinion. And I already parted out my "hot" 944 in disgust.

I'll probably never chase power out of one of these old Ducati twins again tbh. The fun lies in how unique classic Monsters are and how fun they are with well sorted suspension and brakes. Next time I crave power I'll buy one of the many cheap gixxers "laid down on a test ride" (yeah right) in the local craigslist. And for Italian thunder I like the new Brutale Dragster.

BTW I stripped the heads and jugs today. Heads are in fine shape, the pistons have play in every direction up down sideways. Evidence of rod end bearing bits in the sump. And I noticed for the first time my vertical head wasn't aligned on the studs evenly. I wonder if that misalignment  stressed the big end bearing on the vertical head and eventually caused it to blow. I wouldn't think that would keep the crank from moving a single mm, and there's also no damage to the cylinder walls but what do I know. In retrospect I probably shoulda bought a cheap 900 bottom end and transplanted the top end. But I got a nice price for the heads, enough to pay for the new engine and I don't hate the 750 motor, at all.

[LowercaseJake]

Nichols no longer offers or manufacters the 3 phase carbie flywheel, but instead of ordering the one from Kaemna (which I'm sure was fine quality and priced right)  I tracked down a brand new Nichols for $200 which includes the lock nuts.

Other updates include the L & R engine covers being dropped off at my coaters, eBay headers scrubbed down, prepped and primed for VHT, and a pair of MIVV X-CONES.

https://photos.app.goo.gl/lAEiM2ONvXZ5OMF42

https://photos.app.goo.gl/qNcQB3pzhjBjhqr03

Genial Motor Italia supplied the exhaust (great service and only 2 business days door to door), they are wonderful and highly recommended now that PJ's Parts is no more (RIP, great company also).

[koko64]

How's it goin'?

[LowercaseJake]

Hit a lump in the road. I attached the new Nichols FW and simply... Can... Not... Get it to slide onto the crank properly. In my frustration, I accidentally pulled the primary crank gear loose. I know it rides on a keyway so can only go one way but now I'm nervous I screwed my cam timing up and am considering hiring this job out along with new belts and a valve adjustment. Here a photo - I see no marks indicating where this gear should line up in accordance with the larger primary:

https://photos.app.goo.gl/uIP5mB2jOoE3g36h2

Side covers are at my powder coaters, I figured I couldn't possibly F this "easy" job up but apparently I did. The Nichols FW with the sprag bolted on simply will not slide up the crank and seat its gear with the starter motor gear. I've no idea what I could be doing wrong and I'm afraid of damaging the delicate aluminum splines on the FW.

But the cam timing potentially being off now is a bigger concern. Actually they are both concerning.

Also I realize I'm supposed to align the dot on the FW with the groove in the crank but which one? There's 2 grooves as opposed to only one on my older single phase motor.

[LowercaseJake]

New FW assembled to the sprag according to Nichols instructions

https://photos.app.goo.gl/d4W3kUsed9MX6U9n1

[LowercaseJake]

The large gear slides on no problem and aligns with the starter motor gear perfect. The gear also slides into the sprag, which is bolted to the FW, NP. The whole assembly however will not easily slide black into place. It stops just short of being snug with the small starter motor gear. I removed the entire ignition trigger bracket and made small sharpie dots so I'd be sure to get it back where it was.