mallossi type porting

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sean brady scooters
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Location: Ripon, North Yorkshire

Fri Sep 25, 2009 12:45 am

hopefully those of you that are as familiar with vespas as lambos may find this interesting
its something taken from malossi kits in particular that we are trying out on lambos........
please dont scoff... :lol:
theres no denying the fact that malossi know whats what,their kits are great for vespas.........
if only they made kits for lambos eh...?
anyway,as i say..if you have ever checked out say a malossi 166 kit or 210 kit,you will have noticed how short the transfer passages actually are,and how far below gasket surface of barrel they are....
and also that the pistons have 2/3 holes in each side approx 1cm below rings..
at BDC these holes in the piston match up with transfer passages providing flow from under piston crown directly into transfer ports.........
presumeably to not only aid overall cooling but to make the most of flow ,converting an otherwise dead spot into a working area.
(the 172 kit for some reason has the facility to do this ,but not without further porting.......although the holes are already there in the piston..)
any way.........i showed this all to mick abbey the other day to see what he thought....
he also found it quite interesting although as yet he has not seen anything similar on bike motors..........
never the less we both agreed that it must be worth a try on lambos,if only for the piston cooling benefits.....
and we will asap try this out as soon as we get the chance/opportunity...
but meanwhile,i was wondering if any of you had also noticed this and had maybe tried something similar on a lambretta kit.
Sean Brady Scooters - 01765 690 698

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Location: Cambridge

Fri Sep 25, 2009 7:25 am

Hi Sean
I have a top end prepared by the late Dave Betts of SES and this is basically the same principal as you describe here. It has 3 boost ports feed trough the piston holes which line up with new transfers ground into the liner. I believe that the V3 Mugello has 1 fitted opposite the exhaust port but mine has 2 more either side of the ring pegs. Its not unlike Mick's 150 project except its feed trough the piston not the original transfer passages. I have looked up this principal in various 2 stroke tuning books and it does give good results when set up correctly. I have also seen these piston windows feed transfers that joint up with the main transfers for extra flow rates and also will help cooling the piston and little end at the same time.
It will be interesting to see how Mick's 150 performs, it may be even more interesting if these freshly cut ports were feed via piston windows as to not dilute the main transfer flow.
TBH I have spent many hours pondering how to get the maximum transfer flow into the top end (sad I Know) however I've had a few very interesting ideas before you take the exhaust into account as this is another science of its own.
Best Regards


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Location: 40 miles north of Vienna

Fri Sep 25, 2009 1:16 pm

I think on P2´s Malossi did a very good job finding a way to get more charge through the tiny transfers in the casing. Also making the transfer passage longer and transfers opening at slightly different times (mains first, secondarys second, boost last) is very good - both for midrange power.

On the other hand I am not sure if this is beneficial on an aftermarket Lambretta cylinder, because you might destroy the flow on the inner transfer wall as long as you don´t put serious amounts of liquid metal or epoxy into the port (see inner wall on a Malossi).
Could think of doing it to a standard Lam cylinder with nearly parallel (to bore) inner walls...but, ports can be opened more on a Lam engine anyway :)

Looking forward to the results, I got very good ones with additional boost ports - so anything that helps making more timearea can´t be to bad.
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