“We are getting almost to the point where every Lambretta engine component weak link has been solved. Except one.”
As part of the forthcoming Complete Spanner’s Lambretta Kit Book I’ve been dyno testing and fitting tons of cylinder kits. In doing so I’ve encountered a few anomalies that I’ll be sharing as YouTube videos to accompany and promote the book.
Lambretta head cowlings are still very much in the dark ages because kit manufacturers rarely seem to consider how they affect the cooling of the kit. More than that, you need to understand how the cowling design works with the bodywork of the scooter.
Forward with Avanti
A big shout at this point should go to Ron Moss for being the first kit manufacturer to carefully look at the cooling system of the Lambretta barrel and head, and to see if it could be improved.
Ron’s Avanti kit maximised both the fin area of the cylinder and also the head design, and as such it required a dedicated oversized head cowling made from fibreglass.
After fitting Ron’s heads and finding that they dropped the temperatures of other kits, AF Rayspeed developed their own oversized Mammoth cylinder head which has even more fin area than the Avanti head. Rayspeed have subsequently produced a dedicated oversized head cowling in steel to suit it.
What about kits with ‘normal’ size heads?
It doesn’t take much investigation to discover that almost all of the reedvalve kits on the market compromise the airflow within a standard Lambretta cowling.
Sometimes the blown air is allowed to escape through massive holes.
Sometimes the air is obstructed from certain fins by the placement of the reedblock casting.
Perhaps worst of all is that with some kits the design of a standard cowling actually prevents hot air from escaping.
Hack and slash
What the video covers is our adaptation of a Lambretta cowling to make it work correctly with a kit that features a head with radial cooling fins.
This is not a commercial project, just a home-brew solution by someone with all the welding skill of Joey Deacon performing a circus balancing act between high voltage pylons.
Forgive the workmanship, just concentrate on the why the modifications are needed.
VIDEO: Head cowling modification
This is the first of a few videos that I’ve put together as both promotion and to illustrate some technical points for the Complete Spanners Lambretta Kit Book.
The book is aimed at not only helping Lambretta owners find the right kit, but also making sure that they run as safely as possible.
In this episode we address an often-overlooked item – the cylinder head cowling – and how one might be modified to improve functionality with the latest breed of Lambretta cylinder kits.
This is not a commercial modification. It’s something my son and I knocked-up at home to solve a problem with the cooling system. I’m sure that in the future, commercial solutions to this problem will be available but for now, anyone who wants a cowling that works will have to modify their own.
If you make a tidy job of it and want to sell them then let us know.
SLUK Cooler
Not long after Sticky wrote this article back in 2020, we decided to make a cowling taking some of Sticky’s thoughts on board. He helped with the design of what was to become the SLUK Cooler. Originally designed around my own Quattrini 210, our version of the head cowling has around 10mm extra space around the top of the cylinder head to increase air flow and heat dissipation. The cutout on the exhaust side has also been enlarged to allow heat to be expelled.
In practice, using this cowling on my Quattrini lowered the temperature by 31ºC. I’ve been running the protoype cowling for four years with no problems. The production version is virtually the same, other than having a reinforced top fixing hole for added strength.
They’re available in cream or black from the SLUK Shop and cost £55 each.
Iggy
