I think your pipes is not the problem, your problem is the carb jetting and the pilot mixture screw setting. Do you know if the tech put in a bigger main jet? or pilot jet. but then he leaned it way down, that sounds like he may have adjusted the pilot mixture screw on the underside of the carb. Is your air intake stock or free flowing? If your air intake is stock, and you have V&H pipes, all that I needed is to adjust the pilot mixture screw out about 1 turn more from stock (counter-clockwise). Stock on an 800 is 1.75 turns out on the mixture screw, so you turn it to 2.75 for pipes. If you have an after-market free flowing air intake, maybe the pilot jet was changed, the pilot jet on an 800 is a 48, even if you have a free flowing air intake, keep the 48 pilot jet in there, if the tech guy put in a 50, change it back to a 48, and the carb setting (I don't know your air intake and needle so going to give you mine) carb setting for Vance & Hines Cruzers Thunder Mfg air intake K&N filter Dynojet needle DNO106 from kit #2147 e-clip on 2nd notch from top (don't use the main jets in the kit) 170MJ 48PJ 2.75 turns on mixture screw gold air valve under gas tank (EPA stuff) removed, reed valves air intake on inside of top of both cylinders blocked/capped/ I used heater hose between both nipples and stuffed a nut and bolt inside to block air flow inside the heater hose, oh just thought of something, if those reed valves is not blocked then fresh air will mix with exhaust and when fresh oxygen mixes with unburnt fuel mixture that causes the mixture to explode inside the exhaust pipe and that causes the pop, another reason for the pop in the pipes on deceleration is you close off the throttle to decelerate and hear a pop out the exhaust, that could be either unburnt fuel in the pipes exploding or too little, if too little you need to turn the pilot mixture screw out another turn to richen (add fuel) to the pilot idle circuit, you see the pilot circuit kicks in when the throttle is closed off like when you are decelerating, if the mixture screw is too lean that will cause a pop in exhaust because the fuel mixture in the combustion chamber misfires but does fire (explode) in the pipes cause it mixes with heat and oxygen
Last edited by btom; 07-15-2016 at 10:56 PM.