| petrol oil mixture; plug fouling | |
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| Tweet Topic Started: Aug 25 2014, 07:10 PM (105 Views) | |
| jdj2 | Aug 25 2014, 07:10 PM Post #1 |
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Junior Fizzy Nut
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Hi please help, fitted a 60cc big bore kit, still on standard carb, petrol to oil was mixed at 20 1 as advised, bike smoked a lot oil dripping out of exhaust fouled plug, hotter plug B9es fitted same story fouled plug. Reduced oil mixture to 25 - 1 200ml of oil to five litres of petrol, bike started a lot better a lot less smoke, bike tested over three days now has fouled plug again, reluctant to reduce oil content anymore, many thanks |
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| chasthor | Aug 25 2014, 07:15 PM Post #2 |
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Spam Finder General
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I run at 30:1 using the current oils. Castrol Activo or something like that. Is your plug fouling during a run under load or on the stand? They don't like running on the stand! They don't get hot enough to clean the plug. |
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| mech73 | Aug 25 2014, 08:30 PM Post #3 |
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Fizzmeister Extrodinaire
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I run 20:1 and don't have a problem with plug fouling and it's what I'd advise if the bike is too be ridden hard, but like Chas says they do need to be properly ridden to keep the plug clean. If you ride mainly in urban areas or lots of short journeys it might be better with a little less oil. However I suspect the problem is elsewhere and if you want the capability of holding the bike flat out for a few miles with a tail wind, I'd definitely suggest the full amount of oil. Assuming it's an unmodified cylinder head, the plug should be a B7HS or B8HS. The B7HS is the hotter of the two and is the one originally specified by Yamaha. The B8HS is a cooler plug that lasts a bit better if the bike is ridden hard, but is more likely to foul. The B9 is a much cooler plug than standard and if the last two letters are 'ES' it's also too long. |
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