sawtooth Posted December 28, 2009 Report Share Posted December 28, 2009 My bike (270cc) has a very popping banging note to the exhaust, is this normal? I know 2 other people with the same bike but 250cc's which both sound very smooth. My silencer packing looks no different to theirs. Not having another 270cc to compare to i don't know if mine sounds normal. The bike starts and runs fine and always has, the low down revs can be a bit jerky while doing slow manouvers but other than that it seems fine. Quote Link to comment Share on other sites More sharing options...
jezza Posted December 28, 2009 Report Share Posted December 28, 2009 Yes it's normal. Distinguishing feature of the 270. Quote Link to comment Share on other sites More sharing options...
sawtooth Posted December 28, 2009 Author Report Share Posted December 28, 2009 Good to hear, thanks! Quote Link to comment Share on other sites More sharing options...
2shock Posted December 28, 2009 Report Share Posted December 28, 2009 I thought the same when i changed from a 250 to a 270, but have realized since that 270's all sound 'poppy'. The 'jerkyness' in also another 270 trait (but not a particularly helpful one in my opinion!) In fact now wish i'd stuck the 250 because of it!! Quote Link to comment Share on other sites More sharing options...
sawtooth Posted December 29, 2009 Author Report Share Posted December 29, 2009 I know what you mean, i only got the 270cc because it came up at a good price. Its the only bike i've ever had though so its just something i've gotten used to. Quote Link to comment Share on other sites More sharing options...
nzralphy Posted December 29, 2009 Report Share Posted December 29, 2009 I toned mine down by retarding the ignition and machining a piece of alloy pipe and tapping it into the tail of the centre exhaust box. I can't remember the pipe diameters but the wall diameter was about 3mm. The plug was about 35mm long. It put a little more back pressure into the system and quitened things down (mostly the pop!) with little effect to low and mid range power, top end was effected only slightly. Quote Link to comment Share on other sites More sharing options...
dannybooth Posted December 30, 2009 Report Share Posted December 30, 2009 Its weird you mention that cos I started up my 250 yest after a week of very cold weather and mine was popping rather than ticking over... Quote Link to comment Share on other sites More sharing options...
sawtooth Posted December 30, 2009 Author Report Share Posted December 30, 2009 Its weird you mention that cos I started up my 250 yest after a week of very cold weather and mine was popping rather than ticking over... Mins always done it, rain, shine, summer or winter. I dont mind it though. Quote Link to comment Share on other sites More sharing options...
dan williams Posted December 30, 2009 Report Share Posted December 30, 2009 Love the bark of a healthy 270! Couple things you can do to tone it down. Go down one tooth on the counter shaft sprocket. Did that to my '05 and '08. Made a world of difference for me. Get carbon fiber reeds. Smooths out the bottom and adds wonderful grunt to the low end. Check your pilot jet. Stock Mikuni jetting is a bit on the rich side. Usual first mod around here is to replace the stock 30 pilot with a 27.5. On the 07-08 models the 250 got the primary side flywheel that the 270s had in previous years and the 270 lost the flywheel. This makes the 07-08 270 jerky and more prone to stalling at low RPM but makes for exciting acceleration when you whack the loud handle. Understand that the 270 has higher compression so each beat of its noble heart is a little stronger then the 250. You can drop the compression a bit with an extra base gasket. But why would you? Quote Link to comment Share on other sites More sharing options...
dan williams Posted December 30, 2009 Report Share Posted December 30, 2009 Its weird you mention that cos I started up my 250 yest after a week of very cold weather and mine was popping rather than ticking over... Cold air is denser so the effective cylinder pressure is higher. Basically like running a higher compression head. Bet it ran stronger then usual. Quote Link to comment Share on other sites More sharing options...
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