Acceleration lag form sip pipe

Greetings everyone, I have a sip special pipe connected to a pinasco 177, reed valve on a 24 mm carb , I am experinceing acceleration lag ,I have to double pump the thorttle before the power kick in , is this usual to a sip pipe? previously the engine is connected to a sito plus and it did not have this problem, the only problem with sito is , it lack the top end power , my next problem with sip is at idle and low speed the engine sounds like its misfiring but when you open the throttle and the expansion chamber fill up WOW, YOU GET YOUR BUTT KICK. Is there a way to sovle this problem ? Many thanks . long live the wasp(vespa)!


It sounds like if that is a carb problem, you should look at your settings. Is that the standard SI 24 carb you’ve got.
Try playing with the needle and the air/fuel mix screw. Standard set up is 1 1/2 turn for the air/fuel screw from completely screwed in. The needle I am not sure if you can change the set up on it.

And you’ve checked the jets too???



you cant change the needle.chen if you are using a si 24 carbcan you tell me how u set it up? im runnin the same kit but with a simonini chrome pipe.ive tried both 24 mill carbs of a 200 and a t5 and cant get them set up!runs fine on the standard 125 carb.using a 118 u have any probs with pinking? im using super plus unleaded, tts oil,and octain booster!!!ive also put the timeing to 18 degrees as to 21 as specified. and still pinks its head off!any thing over about 5500 revs.which is about 55. no good!!!any ideas

did you seal the carb and base gasket when you put it together??? always an idea to give the gaskets a smear of non silicon sealer to make sure no air leakage which will cause pinking and overheating,also sip pipes need a lot of output from your motor to work efficiently to produce power hence your blipping the throttle to get it to go anywhere is filling the chambers of the pipe and giving it the build of pressure it needs to work,thats why upgeared scoots dont like the sip pipe and hills because it wont rev high enough to fill the chambers and push it on up.they need a pressure build inside to stop your fuel/air mix dissapearing straight out the exhaust port which is why the power drops off.simple when you know how[:drink:] [:smokin:] [:dance1:]

another way to stop the lag if it is exhaust is to have a power valve welded into the pipe this restricts the gas flow until a specific rev range is reached then opens to allow the pipe to operate as it should pulling you up any hill.

I have never seen a YPVS on a vespa, dont know if its possible. You maybe able to convert an EXUP but you need an ecu to control the servo. In theory an EXUP welded at the end of the downpipe would work but you would have to be a genius to figure out how to modify an ecu. On the Yamaha’s the EXUP stays closed up to around 4000 revs and is open fully at around 7000 revs. A highly tuned vespa will only rev to around 8000 so taking a yamaha ecu would not work, as their powerband is from 7000 to 14500 revs.

the powervalve was available on the mikeck pipe and made the rally 200 into a beast,torque from bottom to top of revs all day long.tried same valve on swift same result adjustable by setting bolt head on underside to pitch the revs req to open it