S & S port data

[mickdale]

got a new old kit for a lambretta
its the yamaha 200 kit for 200cc lambretta from dave websters scooter and scooterist book

tv 175 conrod (116mm) with welded up yamaha dt175 piston (and spare unwelded piston)

1) question - is it a good performing set up?

2) can i get an equivalent piston that hasnt got ports for a reedvalve?

3) is it worth using the piston with cutouts and trying to get a piston port reedvalve ? (are there major modifcations needed)

thanks for any advice
mick

[J1MS]

Ran on one of these pistons, its the first Jap conversion I had... Fitted mine to a GP rod and had the barrel shortened 7 and 2... was fairly revy and pretty reliable.. but from one piston to the next, the welding caused more or less deformation of the piston, that is... no two were the same...

Then I ran them with the windows un-welded and fitted a reed block, I used both the webster and Taffspeed reedblocks.. The reedblock cleaned up the bottom end and the pistons lasted longer (no welding) but I always ran them on shortened barrels... Biggest problem was the size of the reedblock meant you had to cut half your panel away.... But one of the best cast iron barrels I had.... got about 4000 miles out of a welded piston sometimes less, but alot more out of the standard (un-welded)...


Probably not as fast in reality as I remember it (rose tinted spectacles)... but back in the late 70's early 80's where I lived, not alot of road going scooters were faster...

[Speed Demon]

I've got an LTH reed manifold to test that should work sweet with that set-up. If you can get the scooter up and running with the welded-up piston and fancy some time on the dyno we can test both with and without the reed. If you are interested then send me a PM.

[jonny snatchsniffer]

i had one a few years ago that was done by dave (well it had name and number on it) and at the time i was very impressed, when the piston wore out i used an asso piston and a packer, still went well tho

[J1MS]

I've got an LTH reed manifold to test that should work sweet with that set-up. If you can get the scooter up and running with the welded-up piston and fancy some time on the dyno we can test both with and without the reed. If you are interested then send me a PM.

I liked the finish on the LTH manifold very well made... What size carb are you fitting to the manifold..??

[Speed Demon]

I think it takes a 30mm

[J1MS]

I think it takes a 30mm

Its a very compact little unit with what looks like a high flow low area so the reeds look like they will be working hard... They do look the mutts nutts... Ive still got three old style Manifolds that I once used, which ran the TZR type Reedblocks I think one of the is a 6 petal kawasaki Reedblock... I think they always looked better on a cut down, or race style scooter... but on a full bodied scooter they look just too big...

[mickdale]

thanks speed demon for the offer - need to build the engine first and am getting the bottom end internals together (was thinking 4.8:1 gearing)

are there two piston ported reedvalve housings available on the market (just been told there might be a mb developments and a taffspeed one?)

looking at the port timings:
transfers 120 degrees - port height 12mm - height over port 47mm - i suppose that means i cant use a rapido due to excessive transfer timing?

can i use one of those ali steel linered barrels off ebay or are their transfers too big to start with?

cheers
mick

[J1MS]

I ran 128 transfer timings On a Yam IT Piston 66mm with the reed block, on a 180+ exhaust timing & 360 inlet. So I wouldn't say 120 was large.

[mickdale]

thanks for the info jims

did rayspeed sort out the exhaust flange? (heard the exhaust port was cast wrong way round)

also were there any issues with steel liner hardness?

cheers
mick