Gs 160 stage four tune

[guygrrr]

cheers gents!
the gs160 and ss180 cylinders are basically the piston ported predecessors of the p200.


general port layout


intake and transfers


exhaust and transfers

exhaust was open to 60%, these thick rings make me nervous. the head'll be recessed in to the bore to up compression a bit.
should be fun.

[soosh]

I took my GS150 to Readspeed and he was thinking of sticking a liner in and starting again.He did a very littel bit of work to the barrel but the best thing was he done a center plug head.Was well worth it and it could be worth speaking to him.

[jonny snatchsniffer]

yeah those transfers look small dont they, the bottom feeds more so, where are the ring pegs ? i take it both down the inlet side, you would get away with 65% with the cast 2mm rings but looking at the barrel you would have to do one side more than the other for the reasons mentioned earlier, the windows on the piston could probably be enlarged to improve flow, as your rescessing the head you will not only increase compression but will alter the squish and to get that right you might need more gasket under the barrel which will raise the ex and trans timing but decrease the inlet, however this is something you can play with with certain packers and head gaskets if need be to get what you want, along with the porting
what out of curiosity do you hope to get out of this ?

[guygrrr]

yeah those transfers look small dont they, the bottom feeds more so, where are the ring pegs ? i take it both down the inlet side, you would get away with 65% with the cast 2mm rings but looking at the barrel you would have to do one side more than the other for the reasons mentioned earlier, the windows on the piston could probably be enlarged to improve flow, as your rescessing the head you will not only increase compression but will alter the squish and to get that right you might need more gasket under the barrel which will raise the ex and trans timing but decrease the inlet, however this is something you can play with with certain packers and head gaskets if need be to get what you want, along with the porting
what out of curiosity do you hope to get out of this ?

i was curious how well the stage 4 lammy tunes would apply to a piston port vespa but there's always a concern about loosing bottom end. so, i'm just looking to get a bit more out of it, more torque and a few more horses. i have to send the head off to get re-profiled but i'll post up some follow up pictures and what not when it all comes together.

as it stands right now, i- 150, t- 123, x- 170. turns out i did need to raise the cylinder to get the transfers about right.

cheers for all the input.

[nicsar]

Nice project! Going to be interesting to see how it goes. I have SS motor on the shelf thats going to get some kind of treatment at some point. When I was looking into this I came across this page, http://www.vespaio.net/Vespa180SS%20-%20VSC1T.htm , good pics of a scauri worked SS topend.
Also the reedmanifold prototype that Grand Sport came out with seems interesting.







"First pictures of the new GRAND-SPORT reedvalve manifold for VESPA GS160 / SS180. CNC machined and set up to use the known Tassinari V Force 3 reed valve Minarelli (Order nr: M1002).

Currently this is only a first prototype, the space is scarce, given the angles and the mainfold for the carb is still missing until now - maybe that would be a nice job for Basti MRP.

The reed valve is screwed by means of an adapter plate to the original 3 cylinder studs, no additional drilling required. For the prototype I have to cut the lowest cooling fin on the cylinder at the inlet side for 3 - 4mm, that's it.

With a reedvalve manifold it is be possible to use an available modern and improved pistons, like the PX 200 GRAND-SPORT piston. BigBore with 66.5 mm gives 208cc and would no longer be a problem! With the conversion exhaust manifold you can run a PX sport exhaust - please note, maybe you need to rework the original exhaust bracket.

The GRAND-SPORT reedvalve manifold for VESPA GS160 / SS180 was manufactured in Germany at the company MMW, thanks to Harald for their support.

Price is not yet clear, this is only a first prototype. QUESTION: Is there general interest because, feedback is welcome, thank you."

[jonny snatchsniffer]

all that inlet but so little transfer area, its not really ideal unless there is boost ports cut in and/or the transfers widened quite a bit
but i suppose with a piston and decent rings the porting could be a bit more wild, together with a decent pipe and 185/125 timings it could be fun

[nicsar]

The reed inlet combined with porting in this style would be interesting.

[nicsar]

Is it on the road yet? How does it go?

I´m waiting on a GrandSport piston for a p200. I´m gonna have the hole welded and bore out the ss180 barrel to the piston. What clearance should I have it bored to?
Its going to get a sip road exhaust and a bored out 27/23 carb, if that makes any difference.

Cheers,

n

[guygrrr]

i'm still waiting to get the head back from the machine shop, but then, he was waiting to get it from me in the first place. what i've heard from a reliable source, is that you don't actually need to have the port in the piston completely sealed with weld. i was advised that a piece of aluminum in the window to obstruct flow would be fine. i haven't tried it my self but there you go. i usually go for .003" clearance but the guy who actually does my re-bores knows better than i.

are you planning on opening the cylinder ports at the base like the above photos? i've done this on a p2 and liked the results, but then it was also an other wise stock barrel bored out to take a polini piston, so....

does the grans sport piston use thin rings?

check this out too if you haven't already
http://scooterotica.org/forum/viewtopic.php?f=8&t=13641

[nicsar]

Thanks,

Yes, I´m planning on opening up the ports in the base of the cylinder like the pics.

I have this on its way with the piston.


The piston is with 1.5mm rings (std px200 2.5mm) so they should cope with wide xport. GS makes it exlusively for SIP

http://www.sip-scootershop.com/en/produ ... +_12090000

What kind of timings did you end up with?