Carlo; dont forget that Federico Martini also designed the Gilera Piuma!

Your job looks excellent, really! Do you know what happened to the GPM that was on tje museum in Stockholm and was sold on the auction a year ago? Can you keep track of the bikes?

/Björn (the guy with the friend who has the primary gears...)

Hi Bjorn, I participated in the restoration by giving the right colors and trying to give the best advice, I don't know who bought the bike, but I know it took a lot of money.

That motorcycle there (that of the Swedish museum) has the rear frame with a parallel tube that raises the rider's seat by about 5 cm.
I know the driver who was driving it, a certain Donato Battistoni, and he told me that being big in stature he had to make this modification in order to drive better.

From what I've been told it was supposed to be the only bike that had this modification on the rear of the frame.
The bike that I am restoring has the usual modification, identical identical .... then I ask myself the question .... which is the correct motorbike?

Surely they are both very beautiful and original.

My GPM has the let's say traditional chassis.
I am looking for clues to the bike I own, and I believe it was the bike 2 or Fabio Barchitta or Tardozzi.

Who sold me the bike is a friend of Tardozzi and went to his house to show it to him, he found that it is original but after a long time it is difficult to say if it was a bike that he rode, however he found the originality of a GPM of that historical period, and this finding is enough for me.

Thanks for the information Carlo, that was very interesting!

Do you know an Andrea Bregna? He is a collector of classic racing bikes, and racer I think. I dont know if he has any Ducatis but for sure two-strokes like RG500 etc.

/Björn

his name doesn't tell me anything, but you know ... among Passionists we always try to remember the person on the basis of the bike!

work in progress...I will make the pistons based on an original Ncr, but we will put two piston rings and an oil scraper ... much better.

work...Hi guys, I worked the heads and the intake and exhaust ducts, I created 5,20mm thicknesses with c40 steel, with a very wide collar, so that I can put steel washers inside and make the right adjustment from 010 , 015mm.
Of course, the steel thickness I warmed it up to become incandescent and I threw it in water.

Thanx for posting!!

There is not much room between those valves! What did GPM manufacture/produce as far as engine/motor parts? Did they primarily modify Ducati parts or make their own?

Thanx,
Clay

Ciao Carlo.

What size valves did you install? Did you keep same valve seats?

I see valve-to-valve clearance is small, but OK. What cams are you using?

Grazie, MikeV

PS: that is one beautiful jig you made to hold the heads while working on valves.

Ciao Clay, when you manage to reach more than 0'8 mm, you're done, reaching 1.5 mm would be safer, but sometimes the castings are not all the same, sometimes you find valve seats positioned higher compared to the upper part of the cylinder head, GPM, he was the adversary par excellence together with Moretti, from NCR, the engine block workings were done in the usual way, using "P" or ncr7 cams, with 35- -41-- for the 600.
GPM has produced parts of the chassis, marking them with its unmistakable initials, such as dry clutches, footrests, magnesium valve caps, exhaust pipe flanges, etc., etc., but as reproductions of cam axles, I believe they used what the NCR provided.

Ciao Vecchio mio, I have used valves 41-35, and axle it to cam a "P" like the monthiuich.
I have found a person who has replicated them, and they are done very well.
The template for removing the valve seats was a challenge !!
Yes I have left the original valve seats, I have had the experience of my Moretti TT1 750, and its valve seats are even more tapered, but I have found that if we mill the first part, going very slowly with the tool, and the final part we use the PEG, orbiting stone grinding, the valve seat does not get stressed and if the material allows it we can use the original valve seat.
Of course if we use bigger valves, we will throw all this talk into the toilet.