Scooterotica

The mugello 225 v4 piston has a completely different crown to a normal style lambretta piston. It has the same crown profile as a super monza and normal monza, so an MRB style piston will fit but you either need a new head (as the mugello head is profiled to fit the mugello piston) or see if your head can be re profiled.
If you are using the mugello head with the rt piston your squish and compression will all be way out.

nelson pk wrote:The mugello 225 v4 piston has a completely different crown to a normal style lambretta piston. It has the same crown profile as a super monza and normal monza, so an MRB style piston will fit but you either need a new head (as the mugello head is profiled to fit the mugello piston) or see if your head can be re profiled.
If you are using the mugello head with the rt piston your squish and compression will all be way out.

Hi, thank you for confirming this. I called MB and he suggested this head http://www.lambrettaspares.com/spares/b ... m0384.html. I think this has the same recess of the mugello head (1,2mm) so it might work straight away with the actual set up: 2mm base and 1mm head- although i'm thinking that probably with 3mm base and no head gasket might be a better set up for both the port timings and the head centering.... I don't think the piston sitting 1mm below the exhaust port is a big problem after all. Let's see...

As long as your new head is profiled to that piston crown if you set your squish between 1.2 and 1.5mm you should be ok compression wise and squish wise although it is always good practice to work out your volume when piston is at top dead centre to double check. Your piston at bdc should be level with your exhaust port or at least about 1 mm over a fully open exhaust port. What you dont really want is your piston to be lower than your exhaust port fully open if you see what i mean.

The AF head wouldn't be a bad option. Less than a third of the price and the correct crown profile for your piston.

servetakid wrote:The AF head wouldn't be a bad option. Less than a third of the price and the correct crown profile for your piston.

Too late, the MB head is on its way... I wonder if there's some relevant difference in weight between the 2 pistons if there's a possibility to lighten it somehow or if its better to leave things as they are... Hopefully i'll get more power with the MRB piston+MB head compared to a standard Mugello...? ( i wish... ). Also ordered a Kytronik.

With 2mm base packer the piston is level with the exhaust port at bdc BUT this way i also lower the port timings... hmmmm.... or i could dremel the exhaust port 1mm down and fit the 3mm base packer... not sure about the nikasil quality thou...

Today i checked the port timings... Mugello 225 V4 with 58x110 crank and 2mm packer plate (piston aligned the exhaust port at bdc):

Intake : 152
Tranfers: 125
Exhaust: 175

Noplastic wrote:Today i checked the port timings... Mugello 225 V4 with 58x110 crank and 2mm packer plate (piston aligned the exhaust port at bdc):

Intake : 152
Tranfers: 125
Exhaust: 175

I think MB would say that those are just about perfect for a nice road going scooter