mechmanuk Posted December 15, 2017 Share Posted December 15, 2017 Hi guys, i bought myself a dragstar last year (first time ive had a bike in a while), she is a nice looker with a vance and hynes exhaust system and sounds superb. I noticed that at higher speed when i released the throttle she would pop back through the exhaust, but was very loud. I was told to get a manometer and set the carbs up which i have done. I ride up the street and she runs beautiful with no backfiring atall. But when shes ticking over and i rev her, she will give a loud pop and sometimes you can see flames in the back of the exhaust? i assume this isnt normal or am i wrong? Any help or advice appreciated Link to comment Share on other sites More sharing options...
slice Posted December 15, 2017 Share Posted December 15, 2017 Fraid it is what it is, you fit non-standard pipes then you will get pops and bangs, as you have already been told it's all to do with the fueling and on overrun or deceleration you have unburnt fuel in the pipes, you could fit baffles to the pipes that would reduce the sound with more back pressure in the pipes but also reduce the noise..! Another option is to fit a power commander to your bike, others know more about this than me but as I understand it it measures the fuel - air flow more accurately than the on-board ECU and can reduce the unburnt fuel to a level that is acceptable but it comes at a cost. Found this site https://www.sportsbikeshop.co.uk/motorcycle_parts/content_cat/177 cost seems to be around the £250/300 mark and they might not make one for your bike so you had best have a good look. Also it would be nice if you said "Hi" in the new members section, just a small intro would be good, folks like to think your not just here for info then fuck off never to be seen again..! Just sayin! Link to comment Share on other sites More sharing options...
Ttaskmaster Posted December 19, 2017 Share Posted December 19, 2017 While on the other hand, some people tune it to pop at the right moment so it sounds like a hot hatch hitting the rev limiter.... and then again, some people juggle geese! Link to comment Share on other sites More sharing options...
mechmanuk Posted December 22, 2017 Author Share Posted December 22, 2017 I have noticed the co's on both are low and hc's high on the rear cylinder is way high. I dont know what the emissions should be but i guess theres an issue with the plug or mixtures? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 22, 2017 Moderator Share Posted December 22, 2017 Wow, don't think going that far into how clean a custom burns is at the front of many who ride them. Generally the rear cyl runs hot because of its mate in front and share the same carb or settings so your dammed from the off. Their inefficient too given the hp for the cc. If you rev most bikes they will pop on the overrun on carbs. Think you have a choice, enjoy the noise, refit stock pipes like noise said. See what I did there..... Link to comment Share on other sites More sharing options...
mechmanuk Posted December 22, 2017 Author Share Posted December 22, 2017 i like the noise, but its the popping and coughing on overrun that i dont like, specially when the flames shoot thru? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 22, 2017 Moderator Share Posted December 22, 2017 That's because of the pipes, the lack of baffles allows enough air in the exhaust to allow it to ignite, then it goes bang. Link to comment Share on other sites More sharing options...
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