Smoky exhaust when starting, or revving your CB500, SL125 and other similar Honda's, after a period of ticking over usually points to worn inlet or exhaust valves. Replacement should be as a matter of course when re-building your engine, or overhauling your cylinder head. Ideally matching to new genuine Honda valves at the same time. Genuine Honda items will ensure long term reliability, and save you the trouble of doing it all over again, because non Honda items may have been substituted!
Note: this part is superseded by 12023324405.
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