This may not apply to cars however I suppose some car knowledge can be applied. I have an Aprilia SR50R Carburettor model and since I bought I was very happy with the performance. Since I have added a Leovince zx exhaust because the old exhaust was rusty and I hoped to get some additional power. However, after I installed the exhaust, I was advised to rejet to a 65-69 jet and I chose a 69, but to my amazement the jet that was in there was a 78. I tried to run the bike with a 78 jet and new exhaust however the bike just revved and would hardly go past 10mph. I am now running the 69 jet and getting a max speed of 65 kmh and the spark plug is dark brown. What should I do!
Tuesday, October 2nd, 2012 AT 5:43 PM