I have recently fitted a new SIP Road exhaust on my VNA 125 just to try and give it a little more torque. I read in the SIP literature that an uprated main jet should be fitted as well. At the moment it has the standard 72 main jet. Any suggestions as tyo what I should increase it to. Want to be able to climb hills especially with a pillion!
Still trying to get the bike to run okay. I experienced difficult starting from what seems like flooding of the engine. I reduced the main jet to 74 and the pilot jet to 42. I have also adjusted the mixture screw and replaced the float needle with a new one (hard to get hold of) It is still difficult to start and over runs on deceleration. Any ideas anyone?
Hey Peter,
I found a brief thread here that might give us each a starting point?
http://www.sip-scootershop.com/community/forums/p/422421/2382646.aspx#2382646
Here's the bit that sounds useful from Electricsun:
[quote user="ElectricSun"]To sort out your immediate problems, get a SIP road exhaust or a Sito plus, a main jet 2 or 4 up from what you've got...[/quote]
Better than nothing?
Hi Andy
Thanks for your imput. I have bought some larger jets. Existing jet is 72. I will try 74,76 & 78 to see what difference it makes. I will try 78 first and work downwards. Maybe I havn't gone high enough, I will experiment and post my results.
*BUMP*
I have the same question as Peter. I'm continuing to search for existing threads on this, but it seems most people who discuss jetting for the Sip Road also have some sort of kit installed. I have a stock all-original Cushman Vespa VNB. I want just a little boost for around-town scooting, so I'm hoping just to add the SIP pipe, up jet appropriately and leave it at that. Anyone able/willing to share advice?
Hi Andy,
Accelerates away okay in 1st but into 2nd I have this pause until the revs increase when the extra power then kicks in. maybe I have not gone high enough, will try larger main jet. Like you dont want to run it too lean.
Hi Andy,
I got hold of a 45 pilot jet to replace the 38 that was in there. I fittled a new Atomiser 260 (same value as the old one) and fitted a 78 main jet. I have also fitted an upgraded plug from a NGK H6 to an H7. At the moment it seems to have really lifted the performance. Hope you have luck with your 150.
[quote user="Peter"]
I have recently fitted a new SIP Road exhaust on my VNA 125 just to try and give it a little more torque. I read in the SIP literature that an uprated main jet should be fitted as well. At the moment it has the standard 72 main jet. Any suggestions as tyo what I should increase it to. Want to be able to climb hills especially with a pillion!
[/quote]
Any luck yet, Peter?
On my VNB, I had an 83 main to start with. I borrowed a handful of jets from a friend based on some recommendations. I put on the SIP Road and started with the biggest--a 103--thinking I'd probably be very rich and move back down to a 95 or so. As luck would have it, the bike ran great with the 103! What a huge difference the SIP Road pipe makes. The plug looks a little pale even with that jetting, so I may try going up higher just to see. I love how it runs right now though and no pinging.
My understanding is that you will want to upjet for sure to avoid running too lean and risking damage to the motor. Start high and work back down till you find the sweet spot. I don't know what differences there might be between your 125cc and mine, but hopefully this is helpful to you.
Cheers.