MB BIG HEAD

Anything related to Lambrettas... ask tech questions, post helpful info, or just read and learn.
Joe Swoonara
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ive finally finished repairing (long story i wont bore you with at present) my TS 240 fitted it with a MB big head and finless flywheel question is what egt temps are people getting ??
Warkton Tornado No.1
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I am sure you know your stuff & have made your decision about cooling the cylinder assembly rationally.

The fact that racing Lambrettas in Group Four are only air scoop cooled is because of several factors. Apart from their time sitting in the holding bay, where the sensible riders just keep their engines running @ a fast tick over with the occasional blip, the machine is constantly having air blasted over the cylinder assembly with sufficient volume. That air is also able to escape via adequate routes. Having very little under the panels apart from a fuel tank & some electronics helps matters, though often panels will have 'bigger than necessary' cutouts for carbs, rear sets etc to aid flow through.

The exhaust bleed will be of adequate size to prevent head build up.

However, the fundamental ingredient to help sustain a cooler running engine from the inside is the use of Avgas. It is a very stable fuel & allows lower temperature burn. The trade off is that petrol can create more power, but when finishing a race is the priority, Avgas is the natural choice.

I mention this as I wouldn't fancy sitting in crawling or 'stop-start' traffic with no other means of cooling than an air scoop...... ;)
gaz_powell
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Great heading..... was expecting a different topic!!???
Warkton Tornado No.1
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gaz_powell wrote: Sun Sep 20, 2020 9:40 am Great heading..... was expecting a different topic!!???
:lol:

I had hoped that I was not the only reader that thought that!

What with it being a Sunday, should we bow down & say three "Hail Mary"s whilst shuffling backwards?
gaz_powell
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Naaahhh!
vega125s
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Currently running an Avanti with an MB big head , no scoop and little body work , no more than 320f ,hot day standstill in traffic 340 max.
vega125s
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Sorry there cht temps,Doh !
Warkton Tornado No.1
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vega125s wrote: Thu Sep 24, 2020 1:13 pm Currently running an Avanti with an MB big head , no scoop and little body work , no more than 320f ,hot day standstill in traffic 340 max.
Is that with or without a fan to cool the barrel?
vega125s
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Yes no fan , runs a little cooler than my TS at 60, but I guess you need to take into account no side panes and very short rear runners , so good for air flow.
Warkton Tornado No.1
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Much depends on air flow but also the engine itself in addition to the way it is ridden.

An alloy barrel with a good, tight squish running with an exhaust with a large enough bleed will tend to lose power if it gets hot, rather than seize as a cast iron barrel would, it will expand but lose power.

However, it's swings & roundabouts.

It used to be mandatory to try to gain every ounce of power by omitting the fan for sprinting, say.

That's no longer the case, as Eric Cope has proven, no doubt the fan contributing to consistency enabling a greater state of tune......
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