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RB 20 zorsts...

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RB 20 zorsts...

Postby Andy B.L.C. » Fri Oct 01, 2021 11:20 pm

After much agonising (the, on hold since 2016, Pacemaker project will have to wait...), doing the math & deciding an SS200 (however much I may be gagging for a pure HOOLIGAN I.T.A. engine!) is not for me, ta Mart! (the complete spanners Lambretta kit book). So unusually for me, having finally saved up the necessary squids I won't be going down the not quite known path but will be going for the tried & tested RB20 to reanimate my funk as puck cutdown.

Thing is as far as I'm aware, due to the unique exhaust port angle, there's only 3 pipes available, right? So there's the AF NK & Tornado pipes + the PM fat Mamba, any more? Being a cutdown the PM pipe would aesthetically work best on a cutdown, but how does it perform compared to the AF, designed for the kit, pipes? Also would cutting & shunting upwards the AF pipe affect performance negatively?

Call me superficial but IMVHO an exhaust that protudes beyond the backwheel on a cutdown looks total gash ;)

With many thanx in advance for any input
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Re: RB 20 zorsts...

Postby Andy B.L.C. » Sat Oct 02, 2021 1:16 am

Soz... Being a bit fick... Forgot to mention the CST
& Franspeed pipes, & the SIP (as I've just heard about) new kid on the block...

OK to expand this question some more...

Do any cutdown specific pipes exist, DJ copy's exempted, & do they work? (nb this question has just gone beyond RB specific as I'm sure others out there have the same question...) Ta!
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Re: RB 20 zorsts...

Postby gizmo » Sat Oct 02, 2021 8:23 am

This sounds like me. As yourself I've been looking at and pondering Rb, Ss and quattrini. One week it's one and next week another. The casa kit doesn't seem to have a great deal of feedback and doesn't seem widely used so I abandoned that one. The Rb always came out on top and not being far from Frannies it's easy to pop in for a natter and advice. But the big thorn in the side is the blooming quattrini kit. Not heard a bad thing and it's also apparently not a pig to ride around town and in traffic. I need to hurry up as time is not on my side :lol: Watching the Rb's at Caldwell they are quick. Good luck
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Re: RB 20 zorsts...

Postby Warkton Tornado No.1 » Sat Oct 02, 2021 1:31 pm

If I were in this scenario agonising over choice, I'd have to agree with this:

gizmo wrote:This sounds like me. As yourself I've been looking at and pondering Rb, Ss and quattrini. One week it's one and next week another. The casa kit doesn't seem to have a great deal of feedback and doesn't seem widely used so I abandoned that one. The Rb always came out on top and not being far from Frannies it's easy to pop in for a natter and advice. But the big thorn in the side is the blooming quattrini kit. Not heard a bad thing and it's also apparently not a pig to ride around town and in traffic. I need to hurry up as time is not on my side :lol: Watching the Rb's at Caldwell they are quick. Good luck


I think that the MQ would win my selection because of it's geometry. Plain & simple truth is that it can run with an air filter with full bodywork. A 'proper' system, though I doubt OEM would cope. However 'F'ooligan' we feel @ times, protecting an engine from itself emulating an industrial vacuum cleaner in a slow process of suicide is a good idea, especially as a good carburettor & air filter will only affect performance by a nat's.

Anyway, in response to the original question, I hope this kinda helps.

I was given a blankish canvas @ the request of a friend in that his TS1 was cooked. What he expressly didn't want was an RB as he'd been there & found the TS1 to be far more user friendly without the necessity for constant gear changing. Now, this guy only knows how to ride like he stole it. The engine I built is a TS1 (yawn...?) but by way of being from a certain auction site, it possessed additional 'porting' due to throwing a rod. The upshot is that the 70mm bore still being good, the slots were tidied & extended/widened to communicate direct with the boost port via the inlet. The boost port is raised & widened. I can't be doing with those 'lady boy fingers' that other's adopt, so a new non-Dykes DT250 piston with relocated top ring allows a generously sized boost. BTW, it runs a Harry Barlow (the thousands in cash in carrier bags one) 60 mm stroke crank, long rod & I can't fault it.


Anyway, despite my best efforts ( :D ) it works extremely well. I just hope he pays me before he kills himself.

Bear with me. I'll cut to the chase now :roll:

This engine is being restricted by it's - how you say - "zorst"

On 'our' shopping list for primary consideration are:

PMT Fat-Lady Mamba
Mick Abbey bespoke
Pipedesign
A N Other*

What I think is important is to capitalise on 'what is already there' (as happened with the blown up TS1 cylinder) & in the case of the RB, the exhaust port is already heading in a good direction to better encourage the signals required for cylinder filling via the transfer/boost ports. So I'd be looking for a good flow following that lead with no abrupt changes in direction. If you look @ those depicted in Scootering magazine, you will see what I mean. Mentioning no names or numbers, there are "zorsts" there that I simply would not want to use. The 'entry angle' of the exhaust port & the piston crown is very, very influential on the performance of an engine. Just how important & what the optimum is, I don't know precisely, but there are a few tuners that do. They probably won't tell you because they may have worked long & hard to discover it. But personally, I feel knowing that there is an angle that makes an engine work better is worth pursuing. It can only help. You can bet your bottom dollar that in the last two decades, the 'science' I speak of will be a factor in the best competition engines, be they piston ported or reed. Just look @ last week's Cadwell footage & see the difference between night & day......

* I've told him I'm not doing it
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Re: RB 20 zorsts...

Postby Andy B.L.C. » Sun Oct 03, 2021 10:49 pm

gizmo wrote:This sounds like me. As yourself I've been looking at and pondering Rb, Ss and quattrini. One week it's one and next week another. The casa kit doesn't seem to have a great deal of feedback and doesn't seem widely used so I abandoned that one. The Rb always came out on top and not being far from Frannies it's easy to pop in for a natter and advice. But the big thorn in the side is the blooming quattrini kit. Not heard a bad thing and it's also apparently not a pig to ride around town and in traffic. I need to hurry up as time is not on my side :lol: Watching the Rb's at Caldwell they are quick. Good luck


Innit... The Quattrini kit sounds perfect (however perfection doesn't exist in the real world, piston wobble at bottom stroke seems suspect, draw your own conclusions...!) SS200 is up in the same price range, but while knowing several peeps running them they (AHEM...) wouldn't ever be part of the 'Euro roadcrew'... So the price of an RB + dedicated zorst (always put me off, as if I'm paying up I would prefer to, for the money spent, have a top end interchangeable unit...) is becoming a deal breaker, & while in no way 'nationalistically' inclined (I'm a Koelner & proud ffs, look it up! clue there's a euro scoot emporium nearby...) the thought of a British made kit, with 'local' backup if things go wrong, + the BSSO footage is making this a no brainer...
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Re: RB 20 zorsts...

Postby Andy B.L.C. » Sun Oct 03, 2021 11:00 pm

Warkton Tornado No.1 wrote:If I were in this scenario agonising over choice, I'd have to agree with this:

gizmo wrote:This sounds like me. As yourself I've been looking at and pondering Rb, Ss and quattrini. One week it's one and next week another. The casa kit doesn't seem to have a great deal of feedback and doesn't seem widely used so I abandoned that one. The Rb always came out on top and not being far from Frannies it's easy to pop in for a natter and advice. But the big thorn in the side is the blooming quattrini kit. Not heard a bad thing and it's also apparently not a pig to ride around town and in traffic. I need to hurry up as time is not on my side :lol: Watching the Rb's at Caldwell they are quick. Good luck


I think that the MQ would win my selection because of it's geometry. Plain & simple truth is that it can run with an air filter with full bodywork. A 'proper' system, though I doubt OEM would cope. However 'F'ooligan' we feel @ times, protecting an engine from itself emulating an industrial vacuum cleaner in a slow process of suicide is a good idea, especially as a good carburettor & air filter will only affect performance by a nat's.

Anyway, in response to the original question, I hope this kinda helps.

I was given a blankish canvas @ the request of a friend in that his TS1 was cooked. What he expressly didn't want was an RB as he'd been there & found the TS1 to be far more user friendly without the necessity for constant gear changing. Now, this guy only knows how to ride like he stole it. The engine I built is a TS1 (yawn...?) but by way of being from a certain auction site, it possessed additional 'porting' due to throwing a rod. The upshot is that the 70mm bore still being good, the slots were tidied & extended/widened to communicate direct with the boost port via the inlet. The boost port is raised & widened. I can't be doing with those 'lady boy fingers' that other's adopt, so a new non-Dykes DT250 piston with relocated top ring allows a generously sized boost. BTW, it runs a Harry Barlow (the thousands in cash in carrier bags one) 60 mm stroke crank, long rod & I can't fault it.


Anyway, despite my best efforts ( :D ) it works extremely well. I just hope he pays me before he kills himself.

Bear with me. I'll cut to the chase now :roll:

This engine is being restricted by it's - how you say - "zorst"

On 'our' shopping list for primary consideration are:

PMT Fat-Lady Mamba
Mick Abbey bespoke
Pipedesign
A N Other*

What I think is important is to capitalise on 'what is already there' (as happened with the blown up TS1 cylinder) & in the case of the RB, the exhaust port is already heading in a good direction to better encourage the signals required for cylinder filling via the transfer/boost ports. So I'd be looking for a good flow following that lead with no abrupt changes in direction. If you look @ those depicted in Scootering magazine, you will see what I mean. Mentioning no names or numbers, there are "zorsts" there that I simply would not want to use. The 'entry angle' of the exhaust port & the piston crown is very, very influential on the performance of an engine. Just how important & what the optimum is, I don't know precisely, but there are a few tuners that do. They probably won't tell you because they may have worked long & hard to discover it. But personally, I feel knowing that there is an angle that makes an engine work better is worth pursuing. It can only help. You can bet your bottom dollar that in the last two decades, the 'science' I speak of will be a factor in the best competition engines, be they piston ported or reed. Just look @ last week's Cadwell footage & see the difference between night & day......

* I've told him I'm not doing it


Ta WT1!

So cutting & shunting the longer, up to tailpipe angles, would have a potentially negative/not worth risking resuslts (kinda what I imagined)?
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Re: RB 20 zorsts...

Postby Warkton Tornado No.1 » Mon Oct 04, 2021 7:38 pm

Andy B.L.C. wrote:
So cutting & shunting the longer, up to tailpipe angles, would have a potentially negative/not worth risking resuslts (kinda what I imagined)?


I think you have the wrong end of the stick about my previous response. Ideally, the exhaust port should have a sloping floor & roof, as depicted here:

Exhaust port.png
.

The continuation of the 'downdrafts' shown above in the port floor & roof requires the pipe to follow similar angles.
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