Scooterotica

i run the original AF rayspeed lightened 80's flywheels with both extended and short innocenti cowls. never been an issue. those early AF flywheels are fecking awesome. rev like chainsaws. theres enough of a vortex of air in the cowl to do the job. the system isnt particularly good anyway. i dont think the cowl is the major problem with an overheating Lambretta barrell.

(Some of you may have seen this post on the LCGB forum)

I have had a good look at the cowling, and realised that on the RHS of the barrel on MY barrel, the fins between the inlet manifold and the are complete isolated from the fan. If that is the case, why are these fins covered by the fan cowl if the fan cannot possibly blow any air over them?

Therefore, I have cut-back the cowling so that the fins are exposed to the air, rather than covered by a steel cover.


On the photo on the left, you can see I have put a black dotted on the lowest fin that the air from the fan can reach.

This can only help these fins to cool. Even though this area is not a notorious hot-spot, anything that helps the barrel to cool has got to be worthwhile.

(These photos look fine on my laptop, but are rotated and distorted on my tablet. Sorry if you are getting the same distorted view, but I can't do much about it)

Please discuss the value of this mod.

I have got a new kit with a new billet head. It is a longer stroke and needs plenty of cooling.

I have acquired and lightened a long-fin flywheel, and I am using the deep flywheel-cowling, which has been fettled to eliminate cavitation.

I have been working on the head cowling too, partly to make allowance for the wider flywheel cowling, but also to make a bit more space beneath the cowling for the air to flow. I am happy with my reasoning for this, but I thought I would start a thread on the forum so people could join in with my "fettle, learn, share" approach to re-engineering the Lambretta.




Let's have a discussion about what the air should be doing inside the cowling, how long it should be there, and how it should be allowed to escape.

Here are the photos of my fan cowl with the anti-cavitation ring fitted inside the cowl, and a photo of the three fixing points made for the ring on the outside of the cowl.

I recall a thread some time ago pointing out that the AF light alloy flywheel sits below the lip on the mag-housing and you should cut away about 5 to 6mm from the mag-housing lip from the 6 o'clock position to the 9 o'clock position.

has anybody in the last 40 years actaully done a airflow-test on a Lambretta flywheel cowl (+ head cowl) with different flywheel types (short finned/ long finned / lightened) to show the differences in airflow and what easy optimisations can be achieved?

Well, it'll either work or blow up.

Fruitjuice wrote:has anybody in the last 40 years actaully done a airflow-test on a Lambretta flywheel cowl (+ head cowl) with different flywheel types (short finned/ long finned / lightened) to show the differences in airflow and what easy optimisations can be achieved?

Yes , Ben @AF did some extensive testing a couple of years ago with airflow / temperture testing equipment , from what i remember he found out that there was very little difference in cooling over the various ways of fitting head and flywheel cowlings and different flywheels , what he did find was that the larger heads made a big difference in lowering running tempertures and thus why they have now produced the Mamouth head.

And got some stick for it. But common engineering problems always evolve towards a common solution.

fairspares wrote:

Fruitjuice wrote:has anybody in the last 40 years actaully done a airflow-test on a Lambretta flywheel cowl (+ head cowl) with different flywheel types (short finned/ long finned / lightened) to show the differences in airflow and what easy optimisations can be achieved?

Yes , Ben @AF did some extensive testing a couple of years ago with airflow / temperture testing equipment , from what i remember he found out that there was very little difference in cooling over the various ways of fitting head and flywheel cowlings and different flywheels , what he did find was that the larger heads made a big difference in lowering running tempertures and thus why they have now produced the Mamouth head.

Are these similar to the Moss heads theyve been using for a few years.