mojave Posted November 9, 2008 Report Share Posted November 9, 2008 (edited) OK, here's another knock related question (sorry). I'm not familar with Beta 2 strokes, or modern 2 strokes at all. So what I'm experiencing may be normal. Riding my Rev 3 like a trail bike there's an odd knock that occurs at very small throttle settings - like going up a mild hill in 3rd gear or steady speed level in 4th. The load is so low that the engine is hitting or missing - you know, ring-a-dinging. Some of the dings are more like DINGS. And I feel them through the handlebars. Under a decent load there is no pinging ever. Riding in a trials situation I don't notice anything either, just when I toddling along a trail. It definately increases in frequency when the engine is good and hot. I can also diminish the frequency by turning the air screw in, I'm running at 3/4 turn out now. And I'm running a better than premium gas at the moment. So, is this normal? If not, do you think it's benign considering the low load nature? It seems to me the idle and slow speed circuit is somewhat lean but this is where I have no experience - this 2 stroke ring-dinging, can jetting even cause pre-detonation in this mode? I can see ignition setting or glowing carbon in the combustion chamber causing it but jetting??? Edited November 9, 2008 by Mojave Quote Link to comment Share on other sites More sharing options...
neonsurge Posted November 9, 2008 Report Share Posted November 9, 2008 I was having a very similar problem a while back - going up one size on the pilot jet cured it completely. I have no idea what was ACTUALLY causing the problem since the bike was absolutely standard which suggests that increasing the jet size was just masking something else. Having said that, I'd already eliminated every other possibility within my (admittedly limited) mechanical capabilities including air leaks, timing, electrics etc. etc. and the bike never missed a beat afterwards so I stopped worrying about it. Quote Link to comment Share on other sites More sharing options...
mojave Posted November 10, 2008 Author Report Share Posted November 10, 2008 No pings in a one hour session today. I think maybe it's the gas. Today was about one third 100 octane and 2/3 premium 92. On the next fillup it should be 50/50. Eventually, it'll be all 100. Quote Link to comment Share on other sites More sharing options...
nzralphy Posted November 10, 2008 Report Share Posted November 10, 2008 Yes it could be petrol related. Someone, many moons ago, was saying Beta's were susceptible to needing good petrol..... remember that petrol has a manufacturing tolerance and the budget stuff varies a heck of a lot. FWIW i fitted a pilot jet one size smaller to get the bike to jet really well and it 'dings' like you say but only sometimes and mostly when hot. Ralphy Quote Link to comment Share on other sites More sharing options...
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