Hi Desmorob
Wow that heads are a work of art!
Intersting shape they give to the inlet duct.
Please Keep us updated!!

Ciao Filippo

The JRP heads look very nice, and I knew they were doing this again. Now I see valve sizes up to 43/36 from the 42/35 that they did before. So, I have some concern, especially if you think you are going to use P cams (is that what you have?) from a SM: What is the distance in mm between the valves at rest in their seats? If it is not 5.7 to 5.9mm, or more, then there could [will] be a problem with V-to-V contact. This always seems to surprise people. 4.5mm or a bit more (stock) will let you use two H 900ss or ST2 cams, but not any of the old style"race" cams.

I have just finished a set of 900 heads using Montjuich (P) cams with 5.8mm resting clearance and I ended up with .022" moving clearance on both heads. Going to test the limits on this. Posting soon in the TT/F1 string.

MikeV

Thanks for the info Mike!
I can't measure completely accurately with my calipers but it looks to be approx 4.8mm between the valve OD's in the head.
I'm building them up and when I get the right shims I guess I'm going to find that I can't turn the cam over because the valves clash then? That's a bummer. But better to know now.
I'll let you know.
Modern cams will also need machining to fit the old style right-hand side bearing arrangement I guess?
Cheers
Rob

Hello Rob

Like you I used 750ss front head and 650 rear head
Two front 900 ie cams fit without problems

Graeme

Hay MikeV that .022" is a little to close for comfort.
1 mm or .040" is min with these cams.
1.2mm with high lift variety (St2)
I find it best to stay with 41/35 combination with the P cams.
-Cranky-

Hay Cranky. You must have been napping in June 2019 when Boucher and I had a two-man discussion about this —- valve overlap clearance. I do appreciate your concerns, and have faith in your recommendations, so will approach this carefully. I have not fired it up yet. MikeV

I fully agree with you, I had the honor of speaking with Giorgio Nepoti, NCR, and he told me, that the exhaust valve, the bigger you put it, the slower the speed, the bike goes. .
The right recipe, according to him, was this.

Hay Mike I've been napping much longer than June 2019... kinda like Rip-van-winkle.
Now have some time and access to this site to cause trouble .
-Cranky-

Hi all, I realized I hadn't closed this one out on the Forum here.
Just FYI, the P cams did produce the predicted clash with the large valves, of course.
So I bought a pair of the ST2 style cams from Ducati Kamna in Germany, (and ate the invoice evidence...).

I've built the heads with these now.
They provide approximately 1.6mm minimum overlap clearance, with the valve clearances taken-up with feeler gauges, which should be sufficient I think.
Not much other progress due to life and having too many other bikes (not a bad problem to have for sure )
I hope all is going well with all the other projects out there!
Photo attached just for info.
Thanks for the help everyone.
Cheers
Rob

I think this is what Carlo is saying to do with the carb jets. Since Dellorto jet sizes are in mm, a 120 main jet is 1.2mm. Makes it easy to get the correct size. The threads on Dellorto jets are m5x.75 for pilots and m6x.75 fpr mains. These are main jets.