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These new mam­moth Lambretta heads from AF Rayspeed are a di­rect re­place­ment for the stan­dard sized cylin­der heads but of­fer a sig­nif­i­cantly larger heat sink. The im­proved cool­ing re­sults in a lower run­ning tem­per­a­ture.

This has of­fered an in­creased safety mar­gin to help en­gines bet­ter re­sist seizure in ad­verse con­di­tions. AFR noted on ser­vic­ing en­gines fit­ted with these heads that top ends are cleaner and in bet­ter con­di­tion than their coun­ter­parts. They at­tribute this to the two-stroke oil ben­e­fit­ing from the slightly lower run­ning tem­per­a­ture.

The head will ini­tially be avail­able to suit 200cc (66mm), 225cc (70mm) and 250cc (72mm). A small block vari­ant for the RB20 will follow soon.

The main de­sign fea­tures of the New AF Mam­moth Head in com­par­i­son to a stan­dard head are: 1: Sig­nif­i­cant in­crease in the sur­face area for heat trans­fer. More and larger fins with fins on the un­der­side of the head as well. 2: Holes be­tween the fins around the cir­cum­fer­ence of the head to im­prove air flow. 3: Around 67% in­crease in the mass (880g to 1470g) over a stan­dard 200 head, mak­ing the head more ther­mally sta­ble. 4: Tem­per­a­ture sen­sor mount­ing point cast in to the head, to suit SIP/KOSO type sen­sors. 5: Cut away sec­tion to al­low a stan­dard club­man to fit with the big­ger head. 6: Com­bus­tion cham­ber de­signs op­ti­mized to 7000rpm with com­pres­sion ra­tios of 10:1 with a 1.2mm squish clear­ance. Al­ter­nates are avail­able through ma­chin­ing.

These heads are ob­vi­ously not a ne­ces­sity as en­gines with­out these heads have been, and con­tinue to be re­li­able. How­ever they do im­prove the cool­ing in com­par­i­son to the stan­dard head which leads to a typ­i­cal 20ºC to 40ºC drop in run­ning tem­per­a­ture, and an im­proved re­sis­tance to sud­den changes of tem­per­a­ture. This may save an en­gine from a seizure and will im­prove the per­for­mance of the two-stroke oil.

AF Rayspeed Tel: 01944 710693 Email:­

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