hi all 1986 v65sp there is a round hole 25/30 mm in the right hand case aft or the right hand cylinder what was/is it for and should it have a blank in it thanks
so you can see the timing marks on the flywheel. You should have a rubber bung in there. 
Or the cork from a bottle of Borello, like mine has .
Cheers
Nice one.
sorry i did not ask about the hole to get at the fly wheel for the timming marks it is behind the r/h cylinder
Well I don’t have that on my 750 Breva.
Nor me on my V50. Still sounds like what Chris said. Picture?
Is it like this?
This is the timing hole as mentioned.
Oil pressure sensor isn’t 25-30mm dia though, my money is still on the timing inspection hole 
i have tried to put a photo on but no joy if you look at the photo that has been put on by iansoady if you look at the bell housing bolt above the timing hole it is above it in the case behind the cylinder not the bell housing thanks
Could be the oil pressure sensor then as suggested by Al, but as said that’s only 10mm diameter. You need to be careful as the adaptor the sensor screws into also locates the rear camshaft bearing…
it is a hole in the case behind the right cylinder not the hole for the timing marks and it is not in the middle and there is no thread in it and it is not for the oil pressure switch look at the case and it is under the carb inlet area .thanks
On the later big blocks there is a blanked hole where the distributor used to sit, could it be that?
Can you send the photo you have to one of us and hopefully we can put it up on here to work out what it is or you. my email address is in my profile
thanks breva-al thats the one now what is it blanked with plastic bunk or metal plug now some one must know what used to be there in the past thanks all
A parts list is always a good thing to turn to on such occasions. They are available in various places, but this one - on the Fowlersparts.co.uk site will surely show you what you need to know.
Not a 100% certain, but looks to me like Part #17 in that diag is what your photo shows - GU19017120 : “cover” NLA.
If it’s the right bit, or when you find the right bit, a bit of Googling with a combination of ‘Guzzi’ + ‘GU19017120’ (or variants of that number) might win you a goldfish.
Interestingly, my downloaded parts book (19 92 00 01) doesn’t show or list that part although otherwise the diagram is the same.
I’ve just been out for a (chilly) run on my V50 and checked my bike. There is no plug or hole in that position. Mine is a 1982 engine.
I can only think that what you have is a core plug used to block a hole introduced for some machining operation that is carried out on later bikes than mine.
yes i think it is that part i would like to know what it is plastic or metal then i can make one but i cannot find one to look at thanks
To have a look at one, now armed with the part number, all you have to do is Google it, then select images. You can pretty much always find what you’re looking for, if you persevere, and when you recognise that a Guzzi part number might be, for example: GU19017120, 19017120, 0019017120, and so on.