Dean_DT Posted May 21, 2012 Share Posted May 21, 2012 OK so my bike ( Yamaha Thundercat) been sat up for 3/4 weeks, yesterday i serviced her, and whacked in a Pipercross air filter and iridium plugs ( for longevity, not expecting a gain from the plugs!), Bike has a full system already on with race can. Went out today and bike was noticeably a touch quicker through gears 1-4 however when she hit 120mph, it was as if someone activated cruise control. it just would not go faster. In 5th it stopped revving at 11k rpm, which funnily enough is 120mph. nothing extra in 6th either. That was first thing this morning, temp prob around 5-7 Deg C. This afternoon, she went past 120 but slowed at 130 and stopped at 140. Temperature prob circa 12-14 Deg C. Normally pulls all way to 145/150 then slows getting to 160 ( clock speeds, not actual speeds, i have diff sprockets etc but they are the figures i can describe best with!) Been popping on overrun/throttling off way more than she used to too. Im thinking that the combination of can and filter is causing the bike to run lean which is affecting my performance at full load ( presuming that the engine is working harder at 140mph than it is at 70mph despite revs) and that because it was colder this morning, the air was denser, hence strangling it that bit more than it did this afternoon? So im thinking i need to re-Jet? anyone think of anything else that could be doing this? Link to comment Share on other sites More sharing options...
Noise Posted May 21, 2012 Share Posted May 21, 2012 Yup i think you are getting too much air going through the engine thus making her pop and splutter and higher speeds atc, get her to a garage and see if they can dyno run it to get the best out of her. re-jetting is easy but seeing that you have a sports bike you really want to get the best out of it and get it tuned properly. Hope this is of some help Link to comment Share on other sites More sharing options...
Dean_DT Posted May 21, 2012 Author Share Posted May 21, 2012 It does indeed. cheers mate. Just wanted someone to verify my theory! Problem is i binned the old filter, and i dont have the spare cash to get the bike Dyno tuned! Guess ill have to go easy on the old girl for a little while until i can get her on the rollers! Have seen Custom DynoJet kits from the US, where you give them your engine specs, modifications, altitude etc and they work out your optimum jet sizes for you, everything from pilots through to mains. May be worth a punt for £70? Link to comment Share on other sites More sharing options...
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