Lambretta Stage Four Tune Setup?

[sean brady scooters]

bangs for bucks ,its still hard to beat a good stage 4 tune ...as many folk are now realising .
18 plus bhp is quite easily obtainable whilst still retaining a good MPG .

[Lamaddict]

The SIL MB ones are good : Tidied up ports, profiled head and an RT piston all for less than anyother 'kit'. Love mine, did have a 25mm Dellorto on but have just put a 28mm Dellorto. Using an AF/KBA Clubman but might put on one of the new MB BGM Clubmans on when they come out. On it today at work and just loooking out the window at it

[Darrell Taylor]

can anyone explain what stage 4 tuning is ?
is it the 4th most expensive option?
is it a tune that youll have to pay the full price for again if you want it taking to the next stage?
ive never really understood the stages in relation to the end result

i always tune a cylinder to its full potential and state that it will have a characteristics that will either be trials/mx/road race or low/mid/high rpm peak for the given engine type

[sean brady scooters]

thats a very good question darrell and one that i have also asked many times before as it seems that there is no definitive answer LOL
and like you probably ,my tunes have always been done and suited to the customers requirements

[soosh]

I think originally it was classed as a touring tune,the last step before a jap conversion using an expansion and 28/30 carb.

[sean brady scooters]

well yes in a way it was regarded as that back in the old days ,but with no standard of BHP/torque figures to back it up ...and so many shops offered this so called "stage 4 tune " without any reference or comparrison to any other stage 4 tunes by others .
and so ,...many old stage 4 tunes do vary a great deal ,depending on who did them .

[Spanish Fly]

can anyone explain what stage 4 tuning is ?
is it the 4th most expensive option?
is it a tune that youll have to pay the full price for again if you want it taking to the next stage?
ive never really understood the stages in relation to the end result

i always tune a cylinder to its full potential and state that it will have a characteristics that will either be trials/mx/road race or low/mid/high rpm peak for the given engine type

According to MBD.......

LAMBRETTA CAST CYLINDERS

1. STAGE ONE. Basically clean up ports, keep standard carb and exhaust.
2. STAGE TWO. Clean up ports, raise exhaust port slightly to increase port timings, use either standard or slightly larger carb, Standard or Clubman exhausts.
3. STAGE THREE. Lower inlet port slightly to increase port timings, raise exhaust port, flow transfer feeds. Increase carb to 22 – 26mm, Standard, Clubman or a touring expansion chamber.
4. STAGE FOUR. Increase inlet size and port timings to match to 28 – 30mm carb, raise, widen and open exhaust port to larger big bore gasket. Flow transfer ports. Use a clubman or touring expansion chamber.
5. STAGE FIVE. Increase inlet size and port timings to match to larger carb 30 – 34mm, increase exhaust port size and port timings to slightly larger than a stage 4, use a full expansion chamber.
6. STAGE SIX. As above but perhaps larger port timings to increase power higher up in the rev range, also increase size of transfer passages. Use 32 – 36mm carbs and full race spec expansions. (Usually classed as a full race tune.)
7. STAGE SEVEN. As per stage 6 but with a reed valve fitted and the extra work needed.

The above would be some kind of standard to say a 200cc stud pattern engine, 190cc and below would more likely run smaller carbs as it is harder to get reasonable port sizes. It is not uncommon to see engines with mismatched settings i.e.; a stage 6 cylinder with a standard carb and exhaust or a standard cylinder with a 34mm and expansion. I’m not saying they will not work but common sense says they might not set up as good in this way! Other factors come into the equation like cylinder head design and compression ratios, crankshafts, crankcase modifications, ignitions, clutches, gearboxes, clearances etc but are not too relevant to the STAGE of tune but to how the tune is to run.

SF

[Darrell Taylor]

i also find whats defined as a torquey set up doesnt refer to high or low torque figures but is a reference to how soon or how lower rpm the power is delivered from
eg a pipe that shows a sharp rise (comes onto pipe)with say 10 torque from 3000 rpm would be ridden and described as having loads of torque
where a jl4 with say 20 torque that comes onto pipe at 5500 would be described as having no torque

perhaps "comes onto pipe" i should rephrase roll on the jokes

[sean brady scooters]

and yes again ,that also confirms customers expectations of a tune like you say.
its almost as if most customers now are expecting their two stroke motors to perform like a 4 stroke one ,prefering no power band effect but just a smooth pull through .
hence the popularity of the MB touring tunes i guess

[Darrell Taylor]

thanks spanish fly for the breakdown

Sean
i guess the touring tune is most popular as thats the largest % of end user
travel from a to b at a relaxed touring speed at an rpm where the engine is most sweet whilst maintaining reasonable fuel economy
when i print a dyno graph for touring users i sometimes point out the rpm where peak torque is made and ask the customer to check gearing to see if its within the cruising speed range that they ride at/or the motor is capable of