jimg Posted April 24, 2007 Report Share Posted April 24, 2007 My friend and I have recently purchased 2007 Sherco's. The jets in our bikes are a 36 pilot, 118 Main, needle clip position at 2nd from top. These are the sizes recommended by the importer and I agree they are correct for our elevation. But regardless of the jetting, both of our plugs are "burning" 1/2 dark brown and 1/2 very light to white on opposite sides of the plug. I was told this is do to improper or uneven combustion in the cylinder head. It doesn't seem to be any major concern, but I also know this is not optimum. I was told to add a spark plug spacer to reindex the plug in the cylinder (tighting to same ft.lbs) and it may help. I've owned 15 trials bikes and this is the first bike with this condition. Any suggestions or comments? I believe this condition plays a part as to why my 06 ran smoother. Quote Link to comment Share on other sites More sharing options...
paulthistle Posted April 24, 2007 Report Share Posted April 24, 2007 Generally speaking the porcelain at the tip reflects the low speed mixture, and deep inside is high speed. Plug heat range and compression all affect burn rates. Quote Link to comment Share on other sites More sharing options...
copemech Posted April 24, 2007 Report Share Posted April 24, 2007 Plug readings such as that are innacurate as things go. Not sure your altitude, but lean out(in) fuel screw as much as possible(floaty idle) and back out just a bit, try 2 1/2 turns out as a start. This smooths things out. I run a #35, but that is me, some like it richer. Plug gap at about .023-025 on the stocker. A VX or irridium plug run a bit cleaner off the bottom. Hope that helps. Quote Link to comment Share on other sites More sharing options...
chris Posted April 24, 2007 Report Share Posted April 24, 2007 Hi Mine also dose this, my theroy is Sherco have increased the crankcase compression for the 2007 bikes and also decreased the size of the transfer ports this increases the speed of the fresh mixture, perhapse causing it to flow more past the plug, cooling that side of the plug down so it can no longer self clean. Next time you look see which side is dark brown, mine is always on the inlet side. You can help this slightly by buying a new plug and tigtening it up so the electrode faces the back or using the correct size shim. I don't think it will make your bike run any smoother though but it will make your plug a slightly more even colour. Chris Quote Link to comment Share on other sites More sharing options...
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