One of my (many) SVA fail points was the HC was at 1600ppm and it should be 1200ppm.

I had it MOT'd the week before and it passed the emissions with flying colours. In fact the garage owner even commented on how clean it was running.

The only thing I changed between the MOT and the SVA was instead of running with open carbs I've put on a massive Pipercross Foam Filter. Would this cause rich running?

Question is would it pass the SVA with the filter off or would he know that was a dodge?

Any other suggestions?

Cheers

Mike

Just to clear up a bit of a (seeming) misunderstanding - HC is not an indication of running rich. That is down to the CO reading.

HC is a measurement of hydrocarbons, which tends to be a reflection of unburnt fuel in the exhaust, for whatever reason.

This can be affected by so many things.
What was the CO reading? A mixture that is too weak can cause the hydrocarbons to soar, as the mixture in the cylinders has great difficulty in actually burning the full mix within the cylinder. Any unburnt fuel will show as excess hydrocarbons. The cure *might* be to actually richen it up!

Have you had any trouble with the carbs flooding during the build? Any unburnt fuel residing in the engine oil can show up on an emission test...

Igniton system in good order? Spark plug gaps not too wide?

Something else that can have a massive effect is igniton timing - especailly too far retarded. Trouble is, it is not something that is easily adjusted with the average bike motor.


HTH Stu.