Hi all,

After sharing my happy trackday pictures this topic is to share the pain and get me back in the happy place by rebuiilding my Santamonica engine. What happened and what is the plan?

After 35 years of abuse, 3 gearboxes and 60k kilometers my Santamonica engine got some serious damage when the piston of my horizontal cylinder broke in 2. The result is a bend crank, damaged cylinder, some damage on the cases and the top part of the piston kissed the valves. I should have, could have, I know but the bike really ran perfect and I didn't want to mess with that but the momenbt we all know when you race came and its now about bringing it back to its second life.

In anticipation I started to collect some spare parts past 15 years so I have a 650 Engine, Paso cylinders, prepared heads to fit on the 750 squish sizes but thus far it looks that the heads are OK. But after all those kilometers and racing its time to refresh the valves, guides, etc.

What am I planning to do:
- exchange the cranckshaft for the 650 or as suggested see if I can reuse the original crankshaft and replace the rods
- replace the pistons with similar characteristics as the Santamonica ones
- refresh all bearings
- I am still dabling if I would use the Paso horizontal cylinder or source a F1 one to make sure I restore the engine back to its orioginal state (ish)
- refresh valves, guides, etc
- while I am at it repaint the engine that look 35 years old (and we know the quality)
- also refresh my oil cooler hoses
- and few small things or things I forgot so far

I have been rebuilding engines past years including rebuilding this Santamonica back after being years in parts but I am not an expert and this project is getting into new territory for me and I miss my support network and mechanical shops and dealers in the Netherlands. So I do need this community of experienced builders.

What questions I want to begin with:
- very simple, what is the conrod screw head size so I can remove them and check my crankshaft?
- any tips about removing the paint and painting the cases, cylinders and heads?
- where can I find valves, pistons, etc. for the 750 Santamonica in the USA? Europe is option 2!
- what do you guys think, Paso cylinder or source a 750 one?

Thats it for now, Ron

PS, if I can figure out how to upload the photo's on my phone I will share some of the offers to the gods of racing!

Ron, the con rod bolt should be 10mm, 12 point socket.
Good luck, I do t think you should have too much trouble sourcing g parts needed.
Good luck!
Paul

Hey Ron.....
Sorry to hear ya blew the thing up!!!! It seems the vertical cylinder is the one that always goes, but you did the opposite :-0

Clay

Thank you Paul, now i can search for the right tool and start to remove the cranks and check the crankshaft tollerance.\\

Hi Clay, yes the engine blew up, its the horizontal cylinder and my heads are undamaged so it could have been worse as happened with Richards F1.

Ron if you need cylinder replating, this is the company I have recently used great service and good turnaround time,

https://millennium-technologies.com/millenniumrepair/
Paul

More general thoughts, based on the belief that F1B, M, LS, and SM models all used the same piston/rod/crank parts. F1As were different.

Finding NOS F1B pistons will probably be impossible (unless a hoarder appears). Many here and in EU sell Pistal 88 and 90mm versions. There may be some HC Wiseco sets out there somewhere. F1B pistons (stock) weigh about 17oz (HC bump); 750 Paso, Sport, and SS about 16oz (flattop); and 82mm 650CC about 13oz. Ring sizes on all the stock 750s are "same". I would normally say avoid used pistons unless they really look good!

Paso cylinders are "same" as the F1 except that the V cylinder has the exhaust cutout in back. Your H will be fine if it is good and you decide to use it - and you find one piston to use. Replacement F1/Paso sets available a few years ago had the V cylinder exhaust cut in both directions. They seem to have disappeared from the market.

Rods are all over the place; new/used, good/bad. All the 750cc rods weigh "about" 17.5oz. Carrillos about 15oz. Finding NEW half-shell bearing will be the challenge now. That topic has been discussed here without any resolution.

The 750 F1B, Paso, 750 Sport, and 1990s 750SS cranks are the "same", but vary by one or two ounces. Most 9lbs and 7oz. Used ones are out there, and now and then a new one shows up in the EU ebay or...

Valve guides for 750cc are available in US from Ducati and after-market sellers like Kibblewhite and A & V. There are some small length and shape differences, and using oversize, or not, adds to the decision making. Same for seats if those are needed. The 41 and 35mm valves are the "same" length for all the 750 heads; +/- 97V/95H mm. Some say this is not true for the (P) Montjuich, LM and SM cams, but I have not had any problems using the standard lengths. Once I bought two new 41mm intake valves in a Ducati box marked Montjuich, and they were still 97mm or so. Ducati can still sell them, I think.

Except for the rod (half-shell) bearings no problem with that part of a rebuild.

MikeV

Now let the corrections begin.

Rob bearings are available from Stein Dinse, be prepared for a shock.
You may also find some though a Ducati dealer,
Good luck!

Who could possibly resist your invitation for corrections Mike.
Cranks not all the same... Sport had a slightly smaller wheel dia for the lighter lower compression pistons.
Actually works well with the lighter Pistal pistons.
Rods not all the same... Monti and Laguna a little bit lighter... I think hand worked with more attention at factory. Carrillo rods a reasonable priced insurance plan for a track day build.
All this is irrelevant when building a fresh race motor as one should balance the assembly with what ever your using.
The P cams require the deeper valve cutouts that some aftermarket pistons don't support. Finding the round dome pistons can be challenging. I have run bathtub style pistons with the round chambers and still can achieve reasonable compression ratio. Just be careful to measure the squish angle. That changed over time by a few degree. You want that squish to expand slightly to the center of the combustion chamber. Rod bearings are still available from Ducati... just stupid expensive...but hay you can still get them.
I believe Bruce Meyers still has a stock of bathtub style Pistal pistons with enough crown material for the P cams. Just got to do some cutting.
-Crank-

Hay, at least we got you out of the cave! Perhaps I should have used "similar" instead of "same". It was meant to be generalities. These things can be put together, and work. But you are right, balancing them is always good. MikeV

Thank you all, missed a push message from the forum so apologies for being silent and actually will travel coming week so cannot dive into it yet. BTW, first travel for work but after that going to the AHMRA races in Laguna Seca combined with a small road trip on my Multistrada. Any from the forum in Laguna?

Rods are off the crankshaft, the tool worked perfect, and they are indeed a bit polished with attention looking a bit more well treated then the 650 rods.

Ron