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If ron moss designed this kit without a reed why add a reedvalve? what is the most simple basic spec for an avanti i have one to build and want to end up with a reliable tourer........
what other set ups are running at present it seems to have went all quiet on the avanti front in recent years, is RT kits and quartrinis the way to go, is the avanti old hat?

I re-built a top end for a mate a bit back, think he had a 30mm delly, I can get you the rest of his specs if you want bud?

Probably too cut down on the spit back
Also strong clutch required as it puts out ooddles of torque

hullygully wrote:I re-built a top end for a mate a bit back, think he had a 30mm delly, I can get you the rest of his specs if you want bud?

yes that would be good, be interested to find out how it has performed to date.
cheers

ULC Soulagent wrote:Probably too cut down on the spit back
Also strong clutch required as it puts out ooddles of torque

Spitback hopefully wont be a problem if it is set up to Rons original spec........thats what i,m looking for his idea of exactly how it should be run,,,,,,as for a clutch i would be hoping a 5 plate red read speed should do the job. if not then LTH.
ciao Shaneo

I have an early (No 9) Avanti which I ran with a 30 phbh, JL3 which suffered from spitback to th extent that I gave up n using a filter as fuel would collect whilst idling and then it would bog as I pulled away. It was set up in accordance with Ron's instructions but in the end I fitted a reed valve and it was transformed. I cut windows in the piston and trimmed 3mm off the bottom of of the skirt but did not bother with a finger port. The reult was dramatic, all the spitback problems disapeared and it would pull cleanly from 20mph in 4th. It now sits on the naughty shelf in the garage as I burn holes in 2 pistons due to air leaks in the reed manifold (ScootRs). I did love the cooling from the increased finnage though so might resurect it but with a different reed manifold.

Clutch wise, I used a Reedspeed 5 plate budget clutch as a base but had to swap out some of the steels for 1mm ones in order to get sufficient clearance. It was always a struggle though, If I adjusted the cable up to make selecting 1st easy and not drag then it would slip under acceleration in 4th. I always had to get it in neutral before I stopped in traffic

coaster wrote:I have an early (No 9) Avanti which I ran with a 30 phbh, JL3 which suffered from spitback to th extent that I gave up n using a filter as fuel would collect whilst idling and then it would bog as I pulled away. It was set up in accordance with Ron's instructions but in the end I fitted a reed valve and it was transformed. I cut windows in the piston and trimmed 3mm off the bottom of of the skirt but did not bother with a finger port. The reult was dramatic, all the spitback problems disapeared and it would pull cleanly from 20mph in 4th. It now sits on the naughty shelf in the garage as I burn holes in 2 pistons due to air leaks in the reed manifold (ScootRs). I did love the cooling from the increased finnage though so might resurect it but with a different reed manifold.

Clutch wise, I used a Reedspeed 5 plate budget clutch as a base but had to swap out some of the steels for 1mm ones in order to get sufficient clearance. It was always a struggle though, If I adjusted the cable up to make selecting 1st easy and not drag then it would slip under acceleration in 4th. I always had to get it in neutral before I stopped in traffic

Thanks for that coaster........food for thought

A friend has just had an engine built by Ron, after using his "standard" Avanti for several years. Ron used a 60mm crank and altered the piston, that coupled with a new Ron Moss ex-box has created a nice touring scooter. I believe Ron is building another motor with the same spec'

My own Avanti, one of the first on the road, is still going strong. It's had 2 re-plates, one my fault (air leak) and the other a bit of a mystery (excessive wear on the plate ?). Spit back has been issue although i've run various carb's exhausts, timing systems and filters. Never-the-less it's still a pleasure to ride and has no real issues.

It's been dynoed at 23hp yet i only run a 4 plate clutch (LTH plates with Malossi springs).

Not really considered a reed valve although i've had another barrel steel lined but not yet fitted.

shamrockexpress wrote:

hullygully wrote:I re-built a top end for a mate a bit back, think he had a 30mm delly, I can get you the rest of his specs if you want bud?

yes that would be good, be interested to find out how it has performed to date.
cheers

got his spec bud :-
no. 080, my mate had a Indian GP200 g.box, 20T x 47T, 5-plate surflex with fox hat spider, Indian stator @ 17deg BTDC, Franspeed exhaust?, 30mm delly (jets?) Indian crank with Yam 34 rod - 110mm lg, 2-ringed 1mm thk 70mm piston with extra lube holes for gudgeon & 2 lube holes for bridged exhaust port, 3mm thk barrel spacer, paper base gasket, no head gasket, Ron Moss central squish spiggotted head,

I think there's a 'Parallel Universe' type thing going on & it may be of use to look @ Scooterotica 'Winter Upgrade' which besides yours truly as a contributor of advice, has only had comments from the OP. Hopefully, there may be some information of use there

To reiterate my stance, my only involvement with piston ported cylinders having the addition of reed valve manifolds is with a Rapido, but I've never considered them essential & I run one on the road.

However, the 'science' of the reduction of spit back appears to apply to the Avanti & Rapido, both of which IMO are still relevant in the field of tuning Lambrettas. Not everybody wants an engine with the carburettor in place of the battery tray They not be perfect kits, but they were conceived some time ago, & it is clear that the designers put a lot of thought into that process. They didn't just emulate the OEM Lambretta cylinders in alloy with a Nikasil bore/iron liners but incorporated additional transfers.

I have no connection with Ron, but the ethos of his kits appeals to me. Obviously he does not have the resources available to him that bigger manufacturers enjoy & he is no spring chicken but it's a Hell of an achievement to have launched a very 'British' kit onto a crowded Lambretta upgrading market.

From my understanding, if there is a fundamental flaw, it may be just the 'Old School' inlet duration. Well, that's part of this & the other Forum discussion & TBH, how many of us don't incorporate a new crankshaft with any major engine build? Some of us have been long stroking for decades but it's beginning to gain favour these days as surely one of the cheapest upgrades, say, comparing the cost of a 60+ mm stroke versus 58 mm.

I would imagine a well set up, piston ported Avanti 70 x 62 mm to be an absolute stump puller......

MickYork wrote:A friend has just had an engine built by Ron, after using his "standard" Avanti for several years. Ron used a 60mm crank and altered the piston, that coupled with a new Ron Moss ex-box has created a nice touring scooter. I believe Ron is building another motor with the same spec'

My own Avanti, one of the first on the road, is still going strong. It's had 2 re-plates, one my fault (air leak) and the other a bit of a mystery (excessive wear on the plate ?). Spit back has been issue although i've run various carb's exhausts, timing systems and filters. Never-the-less it's still a pleasure to ride and has no real issues.

It's been dynoed at 23hp yet i only run a 4 plate clutch (LTH plates with Malossi springs).

Not really considered a reed valve although i've had another barrel steel lined but not yet fitted.

Well Mick that all sounds reassuring, i will be putting this motor into a series 2 for touring standard trim with either a fran race or ex box.
thanks for the encouragement.
regards Damian

hullygully wrote:

shamrockexpress wrote:

hullygully wrote:I re-built a top end for a mate a bit back, think he had a 30mm delly, I can get you the rest of his specs if you want bud?

yes that would be good, be interested to find out how it has performed to date.
cheers

got his spec bud :-
no. 080, my mate had a Indian GP200 g.box, 20T x 47T, 5-plate surflex with fox hat spider, Indian stator @ 17deg BTDC, Franspeed exhaust?, 30mm delly (jets?) Indian crank with Yam 34 rod - 110mm lg, 2-ringed 1mm thk 70mm piston with extra lube holes for gudgeon & 2 lube holes for bridged exhaust port, 3mm thk barrel spacer, paper base gasket, no head gasket, Ron Moss central squish spiggotted head,

Thanks again Hully, will be running very similar to above but with a tv175/sx200 gearbox,,,,,,,,,will be building over the xmas holidays will keep ya all posted.....

Warkton Tornado No.1 wrote:I think there's a 'Parallel Universe' type thing going on & it may be of use to look @ Scooterotica 'Winter Upgrade' which besides yours truly as a contributor of advice, has only had comments from the OP. Hopefully, there may be some information of use there

To reiterate my stance, my only involvement with piston ported cylinders having the addition of reed valve manifolds is with a Rapido, but I've never considered them essential & I run one on the road.

However, the 'science' of the reduction of spit back appears to apply to the Avanti & Rapido, both of which IMO are still relevant in the field of tuning Lambrettas. Not everybody wants an engine with the carburettor in place of the battery tray They not be perfect kits, but they were conceived some time ago, & it is clear that the designers put a lot of thought into that process. They didn't just emulate the OEM Lambretta cylinders in alloy with a Nikasil bore/iron liners but incorporated additional transfers.

I have no connection with Ron, but the ethos of his kits appeals to me. Obviously he does not have the resources available to him that bigger manufacturers enjoy & he is no spring chicken but it's a Hell of an achievement to have launched a very 'British' kit onto a crowded Lambretta upgrading market.

From my understanding, if there is a fundamental flaw, it may be just the 'Old School' inlet duration. Well, that's part of this & the other Forum discussion & TBH, how many of us don't incorporate a new crankshaft with any major engine build? Some of us have been long stroking for decades but it's beginning to gain favour these days as surely one of the cheapest upgrades, say, comparing the cost of a 60+ mm stroke versus 58 mm.

I would imagine a well set up, piston ported Avanti 70 x 62 mm to be an absolute stump puller......

Thanks Warkton i have been reading your posts with interest you sure are a man who has been on the Dyno road of life with plenty of knowledge always pointing towards simplicity.............point taken.
Regards Damian

I put a reed block on my Avanti when I had it, simply to lessen the spit back from the carb.

I did work in that respect, I didn't do it expecting any performance gain and I cant say as there was any noticeable performance gain.

Leotech wrote:I put a reed block on my Avanti when I had it, simply to lessen the spit back from the carb.

I did work in that respect, I didn't do it expecting any performance gain and I cant say as there was any noticeable performance gain.

actually good to know,,,,,,as i want to keep it piston ported only because of the reed gremlins i had with the GT kits,,,,,,,,,,,,so one less thing to fail especially driving thru europe

shamrockexpress wrote:

Leotech wrote:I put a reed block on my Avanti when I had it, simply to lessen the spit back from the carb.

I did work in that respect, I didn't do it expecting any performance gain and I cant say as there was any noticeable performance gain.

actually good to know,,,,,,as i want to keep it piston ported only because of the reed gremlins i had with the GT kits,,,,,,,,,,,,so one less thing to fail especially driving thru europe

What was your Reed gremlins with the GT Kits ?

Toddy just the same as every GT kit out there, kept eating reeds until i doubled them up which solved the problem but always in the back of your mind it was just a bad design which there was never an admission to it being designed wrong!!!!
anyway no Gt kits for me now i have moved on...

shamrockexpress wrote:

Leotech wrote:I put a reed block on my Avanti when I had it, simply to lessen the spit back from the carb.

I did work in that respect, I didn't do it expecting any performance gain and I cant say as there was any noticeable performance gain.

actually good to know,,,,,,as i want to keep it piston ported only because of the reed gremlins i had with the GT kits,,,,,,,,,,,,so one less thing to fail especially driving thru europe

The reed block that was fitted to the Avanti about 5 years ago has been fitted to an RT225 for the last 3 years and it's the same reeds and petals with zero issues.

I had issues with GT reeds but only in the GT240, my GT200 has been a wonderful piece of equipment. I doubled them up in the 240 and it stopped it but it affected the mid range power delivery, it was never quite as strong.

shamrockexpress wrote:Toddy just the same as every GT kit out there, kept eating reeds until i doubled them up which solved the problem but always in the back of your mind it was just a bad design which there was never an admission to it being designed wrong!!!!
anyway no Gt kits for me now i have moved on...

There is a potential reed problem with the GT240 if you use an expansion but not with a box pipe. Mine runs a BGM 3 and went to Adria and back then Soria and back on the single reeds that came with the kit so around 6k miles. I've changed them since and doubled up but havent personally noticed any difference in the running.

coaster wrote:

shamrockexpress wrote:Toddy just the same as every GT kit out there, kept eating reeds until i doubled them up which solved the problem but always in the back of your mind it was just a bad design which there was never an admission to it being designed wrong!!!!
anyway no Gt kits for me now i have moved on...

There is a potential reed problem with the GT240 if you use an expansion but not with a box pipe. Mine runs a BGM 3 and went to Adria and back then Soria and back on the single reeds that came with the kit so around 6k miles. I've changed them since and doubled up but havent personally noticed any difference in the running.

Certainly one of the lucky ones , my mate only got 1500 miles when his GT200 kit broke the reed going to a rally........suppose every situation is different so just carry spare reeds