GT125 upgrade with Pinasco 2port?


I'm thinking of upgrading my GranTurismo '67 engine to give it a bit more power. I've heard a lot of good things about the Pinasco 2-port kit ( I already changed the crankshaft to a Mazuchelli one, and the ignition has been replaced by an electronic ignition. The exhaust is a Sip Road.

I would use the Pinasco plug-and-play without adjusting the ports, but there seems to be some discussion about the carb. At the moment I'm using the original 20/17 carb, but I still have a 20/20 spare (P125X) carb somewhere. Would this be sufficient (off course i'll have to adjust the main jet)? I was also thinking of buying the Polini air intake system, but maybe this would be an overkill on the 20/20? What about the spark plug and ignition timing?

Thanks in advance!

my stock LML 150cc with a sito+ i run a 100 main jet. my stock LML 150cc with a SIP road exhuast and a modified reed block with a GGR carbon fiber single reed pedal i run a 108 main jet. both have 20/20 carbs with p200 air filters. i don't think the pinasco 2 port kit is super aggressive, but i would think you'll have to start with a bigger then 108 jet because of the extra displacement... always better to start with too big/rich a jet and work your way down. better to fowl a plug or two, then to seize an engine. let us know what you end up with. good luck.

I'm sure the carb is fitted correctly :)

the minimum main jet I installed so far was a 106, but I could hear it "choking" when I opened the throttle.

I already played a bit with the throttle screw, but I would have to open it only 0,5-1 turns to have a decent result, which doesn't seem a lot. I still have a P200 SI24/24 and a T5 SI24/24G carburettor lying around that I was planning to use for another rebuild, but maybe I'll try to install this one and see what happens.

Although I'd still prefer to use the SI20/20

I always start at 1 1/2 as well, but so far I haven't adjusted it. I tend to leave the mixture screw as it is

well... it seems like you have tried every thing else with the carb. it's up to you, but the mixture screw is there for a reason - other wise the carb wouldn't have it. i've made small 1/8 turns on mine to make it a little richer (to the left/loosen) or a little leaner (to the right/tighten). just very small adjustments and check to see how it runs and what the plug looks like. besides that, about the only thing that seems to be left is a new/different carb or take it to a good shop to have them check it out.

sorry i couldn't help more.

My jets are clear and cleaned, that's not a problem.

How do i know if my engine gets to much or to little gasoline? Since it dies out at low rev, I don't know if it gets an overflow or if it doesn't get sufficient... And if people mention a too rich mixture, does this imply to much gasoline or to much air?

Thanks for the feedback!

hi, be care to fit correctly the carburetor , also, can i know the min jet you used?


besides the main jet i left the others as stock, being atomizer BE3, air 160 and idle 60 (no ratio as 55/160 is indicated on the jet...)


Thanks for the help anyway

I just ordered some spare parts for the T5 carb that is hidden somewhere in my garage. I'll try to install it this weekend and see what happens. Although I've heard that it's difficult to set a T5 carb on a non-T5 engine...

the 20/20 carb should be sufficient seeing that you're not totally 'hot rodding' the engine. (after all, some of the p200 models came with a 20/20 carb.) i don't think the polini venturi kit would be "overkill" so that's up to you. i'm not sure about the plug or timing for the pinasco kit... but i will say i've had pretty good luck with NGK plugs. i've also been really happy with the SIP road exhaust on my genuine stella 2T. (a.k.a. LML star 2T.)

I finally managed to install the kit on my Vespa. However I have some problems setting it.

I currently have the following set-up:

- Pinasco 2-port 177cc kit (carters not adjusted in any way)

- ignition timing set to 20° BTDC (standard = 22°)

- carb = SI20/20D, with main jet currently at 110

- exhaust = SIP Road

- P200 air filter with both air holes drilled open above jets

- spark plug = NGK B8HS

I can't seem to get the bike running smooth at idle, it always dies out if I don't touch the throttle. Installing a bigger or smaller jet doesn't improve anything.

I haven't taken it for a ride yet because I first want it to run at idle without stalling.

Anyone got any advice?

my understanding is to rich means too much gas/oil.

what other jets are you running? atomizer, air, and idle? i'm running a BE3, 160 and a 55/160 with a 108 main on my stock LML cylinder with a P200 air filter on a 20/20 carb. and a B7E plug. with the SIP road exhaust.

thought of one more idea... have you adjusted the air/fuel mixture screw on the back of the carb? i usually start with it 1 1/2 turns loose and then adjust it with small 1/8 turns.

personally i would try adjusting the mixture screw before doing all the work of switching carbs and starting from ground zero jetting wise... but, let us know how it all turns out. good luck.

thanks for the reply. I think I'll try to run it with the 20/20 carb. I still have a P200 air filter to use in stead of buying the venturi kit. I guess finding the right spark plug and main jet will be a manner of trial and error.

have you tried adjusting the throttle screw on the carb? if it stays running when you give it throttle with your hand on the bars, it might just need a bit more throttle at the carb. if that doesn't help, i would suggest pulling out all the jets and making sure they are 100% clean, clear, and clog free. i had a similar problem and i pulled the jets and took a safety pin to all the little holes to make sure they were clear and i blew some air into where the jets sit to make sure that was clear and it fixed my problem. also make sure all the bolts in the carb area are snugged up.

the throttle screw adjustments on the carb are amplified compared to the throttle on the bars so it shouldn't take too much. if you are getting a decent result, i'd stay with the 20/20. also, before you switch to a 24/24 double check to make sure your 20/20 jets are clear and clean.

i don't know... i think i'm out of suggestions. maybe you just have a bad carb.