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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Exhaust reversion
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<blockquote data-quote="Howard" data-source="post: 48861" data-attributes="member: 271"><p>The last time exhaust reversion was mentioned here I spent some time reading up on it (because I hadn't a clue what it was (and I'm still not 100% sure - or even 50%), but as I understand it ....</p><p></p><p>Because of the valve overlap, at some revs there will always be some amount of blowback through the carb. The secret is to get the inlet tract of the correct length (or maybe volume) so that the fuel does not leave the inlet (Inlet length is tuned to suit the revs in the same way as exhaust). Apparently (and I have no proof) all air cleaners will have a mist inside, and this will reduce, as the revs increase. Putting the right bellmouth on in place of the filter creates a small "cloud" of fuel at the opening, which will expand and contract at various revs, but will stay within the influence of the engine.</p><p></p><p>If you take off the filter and don't replace with a bellmouth, you'll exagerate the problem.</p><p></p><p>If your problem is just one cylinder, it might need the valve timing tweaking, if it's both cylinders..... stop riding it so slowly!!! <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p>If I've misunderstood this concept, will someone please explain - it's good to know how these old beasts work.</p><p></p><p>H</p></blockquote><p></p>
[QUOTE="Howard, post: 48861, member: 271"] The last time exhaust reversion was mentioned here I spent some time reading up on it (because I hadn't a clue what it was (and I'm still not 100% sure - or even 50%), but as I understand it .... Because of the valve overlap, at some revs there will always be some amount of blowback through the carb. The secret is to get the inlet tract of the correct length (or maybe volume) so that the fuel does not leave the inlet (Inlet length is tuned to suit the revs in the same way as exhaust). Apparently (and I have no proof) all air cleaners will have a mist inside, and this will reduce, as the revs increase. Putting the right bellmouth on in place of the filter creates a small "cloud" of fuel at the opening, which will expand and contract at various revs, but will stay within the influence of the engine. If you take off the filter and don't replace with a bellmouth, you'll exagerate the problem. If your problem is just one cylinder, it might need the valve timing tweaking, if it's both cylinders..... stop riding it so slowly!!! :) If I've misunderstood this concept, will someone please explain - it's good to know how these old beasts work. H [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Exhaust reversion
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