DarkWhisper441 Posted September 19, 2011 Share Posted September 19, 2011 Just done a oil/filter/plug change and found my plug to be white. so the bikes running lean. Had it on dyno and it was running air/fuel 14. How can i sort this out? bike running stock apart from a scorpion full system. has the stock ecu been mess around with by pre-owner? And could i reset it. if not how to i sort this problem out. All comments welcome. Link to comment Share on other sites More sharing options...
KirriePete Posted September 19, 2011 Share Posted September 19, 2011 Air/fuel ideal stochastic ratio is 14.7:1 so the dyno looks like it's running damn near spot-on. The only thing you say may be wrong is the plug colour - but is it white or light grey? Bear in mind that most modern engines are designed to run lean to cut down on the evil emissions that are killing all the cuddly-wuddly polar bears. Are you having any problems with it, like stuttering, poor pickup, stuff like that? If it's running OK, leave it alone would be my advice. Link to comment Share on other sites More sharing options...
DarkWhisper441 Posted September 19, 2011 Author Share Posted September 19, 2011 Pick up is a bit boggy. And when am crawling in traffic it's quite jerky. Link to comment Share on other sites More sharing options...
KirriePete Posted September 19, 2011 Share Posted September 19, 2011 Pick up is a bit boggy. It's a 125 that's tuned to be a wee bit more exciting than a plain vanilla commuter YBR or similar, the trade-off being less pulling lower down the rev range (not that there's much to play with on these in the first place). Whacking the throttle open before it comes on cam will result in more intake roar and .... errr .... not much else. Get a feel for where your engine is most responsive and use the gearbox to keep it there. And when am crawling in traffic it's quite jerky. Transmission snatch most likely, more evident on singles due to the bang pulse every other revolution. Select a lower gear, or slip the clutch if in 1st to keep it above the snatch zone (3000rpm?). Authors note - the above could well be a right load of old bolleaux. I haven't seen or heard this engine, so I'm guessing, but it's guesses based on 35 years of riding and fettling (I still f**k up every now and then, even after all that time!). Link to comment Share on other sites More sharing options...
pilninggas Posted September 22, 2011 Share Posted September 22, 2011 Just done a oil/filter/plug change and found my plug to be white. so the bikes running lean. Had it on dyno and it was running air/fuel 14. How can i sort this out? bike running stock apart from a scorpion full system. has the stock ecu been mess around with by pre-owner? And could i reset it. if not how to i sort this problem out. All comments welcome. Just seen this thread, 14:1 is not lean, it is rich! 14.7:1 is stoich as Pete has said, 1kg of fuel being burned for every 14.7kg of air (it is by mass). 14:1 is 1kg of fuel for 14kg of air. I'd like to know what sort of bike you have and what revs 14:1 was identified at. A bike will have a rnage of values; e.g. my FZR when it was last dynoed went rich, very rich, rich, with lean at part throttles. A car explanation, but still useful:http://autospeed.com/cms/title_Tuning-AirFuel-Ratios/A_1595/article.html Maybe the white spots are carbon deposits that have been 'bleached' by repeated exposure to combustion conditions (last saw this in old renault, years ago). Link to comment Share on other sites More sharing options...
DarkWhisper441 Posted September 25, 2011 Author Share Posted September 25, 2011 Here's my dyno test sheet Link to comment Share on other sites More sharing options...
KirriePete Posted September 28, 2011 Share Posted September 28, 2011 Not an expert on reading dyno sheets, but I'd say there's absolutely nothing wrong with that engine. Power curve is smooth, fuelling map is just about spot-bollock dead on, leanest it gets is at 35mph where it hits the stochastic 14.7:1 ratio - everywhere else it's just a wee bit richer. Peak power of 12.05 bhp is about what I'd expect from one of these - 14 at the crank, knock off a couple for transmission losses (most 'experts' reckon 15% or so) and there y'go. Would be nice to have rpm figures on the chart, but hey-ho. So - stop fretting that your engine is running badly, it isn't - it's actually in very good condition judging by that chart. Can I just ask how much experience you've got, both riding and fettling (and driving, maybe)? It's just that the low speed bogging down and jerkiness are hallmarks of a beginner not getting a feel for the 'sweet spot' - all those learner drivers 'kangaroo-ing' away from the lights spring to mind .... Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 28, 2011 Moderator Share Posted September 28, 2011 Cost me nigh on £600 + a full race system and a dynojet kit (total £1500 to get close to a power curve that smooth) on my old 600.....Took 28 dyno runs and ended up with different jets in the centre carbs due to temperature differences. Looks pretty good to me. Link to comment Share on other sites More sharing options...
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