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Over pressurized crankcase Cal III

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Vecchio Lupo:
I know this thread is pretty old and maybe not much interest anymore.   Well I’m torn…….after much consultation and all different opinions, I’m exactly where I started.

I believe I can hone / save the original cylinders. I’ve got 1 good original and 1 NOS piston, that would seem the easy thing to try, but……….

I’ve also got the 1100 cylinders that have been milled down .20 and they fit into the case so smooth and nice, I’ve also measured the distance from the wrist pin to crown of piston….exactly same on 1000 and 1100 pistons. This makes me think that the Cal III con rods will be fine. The head measures good and the 1100 pistons weigh 41 grams more than the 1000.

Assuming I don’t have clearance issues with valves, right now I don’t think I will. I’m tempted to fit the big bore set up.   

Problem is, I can’t find where people have been doing this and I know for a fact I’m not the smartest guy on this stuff, there must be a reason it’s not being done. I mean; the 850cc to 1000 kits are common on the loop frames.

What Am I missing? Should I just fit the 1000 stuff and see how far I get? Should I trail blaze and see what happens?

Vecchio Lupo:
What do you guys think about what to put on the piston crown for witness marks? I do t think I’ll have valve issues with the 1100 but I remember old timers saying a super thin layer of playdoh or some kind of putty.

Pescatore:


--- Quote from: Vecchio Lupo on April 30, 2025, 04:56:32 PM ---What do you guys think about what to put on the piston crown for witness marks? I do t think I’ll have valve issues with the 1100 but I remember old timers saying a super thin layer of playdoh or some kind of putty.

--- End quote ---
Yep, I used regular play-doh. First rub a small drop of oil on the piston, so you can easily lift the play-doh to take measurements.

Moparnut72:
Modeling clay was the product of choice by hot rodders. Play-doh is a good idea too.
kk

Vecchio Lupo:
Everything coming together, I’ll post pictures tomorrow.   Super big shout out to member MattP , for jumping in. The parts he had to help me out are in excellent condition and they were half of what some EBay parts hound would have charged, plus he did the machine work for me and they fit perfectly.   Thank you to the Guzzi community for talking me through this minor hiccup. My first new Guzzi was an 89 CalIIi dresser , I loved that bike but I traded it in on a restored V7 sport and a LeMans SE (yeah the red and white one ) too bad about the 16” front wheel, but it was still great. I was so happy to find this 90 Cal III dresser in the same color even. Anyway, I’ll report on the fitment , I don’t have rings or a head gasket but maybe I can at least bolt together and check valve clearance.   

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