Hello all,
I hope 2021 has started OK for everyone. Here in the UK we are firmly locked down again without much movement allowed. So those of us with garages are very lucky!...
I'm building a 750 engine from a 650 bottom end and 350 heads modified by J Precision:
I've started rebuilding the heads and have a question about the orientation of the left hand bearing seal, and whether it's needed.
The Pantah donor engine has the external oil feed type of bearing carrier per the photos.
I'm pretty sure the bearings I took out had an oil seal on the external face.
So my question is: with the external oil feed should you retain the oil seal on the external face of the bearing?
I seems to me that this would just divert the oil flow down the drain hole...
Apologies if this has been discussed before but a search didn't find anything.
Hopefully there won't be too many more questions going forward.
Thanks a lot.
Cheers
Rob

Hi, with the bearing closed the oil pressure will go all inside the camshaft, remember to close the flow that comes from inside the cylinder, otherwise you will have to give the engine oil a play map to get to the cylinder head.
I was skipping, what I was saying before just so as not to remove engine oil pressure from the important parts of your engine block.

Thanks Carlo, that makes sense!
Must think harder before posting
Cheers
Rob

Carlo is correct
Make sure that the original path to heads is blocked.
Oil feed lines to the head should also get restriction.
1.2 mm to each head.
Oil from the pressure switch tap is unfiltered.
Ducati used it this way on original F1 and Elefant.
-Cranky-

Grazie Kranky, I forgot to mention the shrinkage on the cam axle oil flow screw, I made the 1 mm hole in my Moretti hypermotard with carburetors and it's amazing how the heads are filled with oil, 1,2 is the right size, sorry my English.
Greetings from Italy, Carlo.

Thanks guys,
The feed through the barrel to the heads is blocked off ok.
But I didn't know about the 1.2mm restriction required in the head external feeds.
That's good info.
And thanks for taking the time to reply.
Cheers
Rob

Hi Desmorob.
Great and interesting project.
If I can ask, how you planned to solve the piston clearance on main 650 engine case. I'm asking because I have a 650 engine too and ( on a far future) planning to rebore to 750.
Enjoy your project.
Ciao
Filippo

Hello Filippo,
I have had the 650 casings machined to accept 750 barrels.
And I have bought two 750 barrels and 88mm Pistal pistons.
I'm not sure that you can rebore the Nikasil lined 650 barrels. But I could be wrong.
I have had the cylinder heads worked by JPrecision in Canada to 750 spec and they now have 43mm/36mm valves.
Now I am starting to rebuild the heads, and finding out how expensive valve shims are!...
Ciao
Rob

Hi Rob, Filippo

I've done more or less the same approach with a 650 motor. To my surprise the gearbox was completely worn out - I've hoped the 650 motors were already equipped with a better gearbox generation. Nope. The gears of the later 350 Pantahs is of much better quality which I'm using now.

I've used a 750 horizontal cylinder head, the vertical head of the 650 was machined to the specs of the 750 motor by a local tuner. The Jprecision company appears to me as very attractive, but is a bit fat away for me living in Europe. I thought that they do not anymore the conversion of Pantah heads but obviously they still do it. What kind of cam shafts are you planning to use - in case they are a high lift geometry - was this considered in the location of the valve seats? If not you are in need to use very large opener shims, this was the case for my heads. Would you be so kind to show some pictures of your machined heads?

And yes - the valve shims are very expensive. Sometimes it is interesting to buy complete cylinder heads and you obtain not only the rockers in good conditions but also the shims. I'm using the opening rockers of the more modern motors because the adjustment of the valve closer shims is much easier...

Cheers

Wolf

Hi Wolf,
Sorry for the delay but I was having some problems with with the resizing software on my computer, (to make them less than 2MB for posting) which keeps 'squashing' the picture. I've sorted that now
JPrecision also welded up and slightly relocated the spark plug hole as a 12mm one. And also provided the valves, nicely lapped in.
But not cheap. (I sent my heads to Canada from the UK)

I actually bought a 350 Pantah, that someone had converted to 539cc using 650 pistons and the original 51mm stroke. But I separately bought some 650 crankcases (from an Elephant I think) as they have slightly stronger cast webs around the main bearings, and I read that this was a better option. But I am having to modify the swinging arm pivots to match the 750 Sport Verlicchi swinging arm I am using.

I also bought a pair of what I hope are Santamonica cams (I won't know for sure till I check the valve timing..) That will be a while yet. Looking at Ian Falloon's book, it seems that if I advance these cams approximately 7 degrees, then the valve timing should pretty much match the race spec TT2 cam timing. I'm not sure if that's good or not.
Reading some of Brad's articles on Ducati cams it sounds like I should probably throw them in the bin!

Anyway, it should be fun makings sure nothing touches, with the Pistal high compression pistons installed.

I have a pair of 40mm Dellorto's to try to fuel it.
And I have bought a later (wider tooth) 750 gear set too
I'm planning for the bike to be a classic track bike, as I get older...
It's all taking a long time as I work abroad a lot and don't get to attend to things regularly.
But at the moment with UK lockdown rules I'm mostly in the garage.
Cheers
Rob