Torini supermaxx backfire

Hi All
I have a Torini SUpermaxx and it is backfiring on throttle lift, is this normal? If not does anyone have any suggestions for fixing it?


After contacting Torini directly, this is what I received back,

Hi Stewart

I am assuming this is an exhaust backfire not an inlet backfire.

When a driver backs off the throttle, for some milliseconds the mixture is too Rich

Under normal conditions there would not be enough oxygen left in the exhaust gas to allow any unused fuel vapour to ignite. So somehow you also need to have enough oxygen in the exhaust system in order for the unburnt mixture to ignite.

There are multiple possibilities ranging from an inconsistent firing of the ignition system or a damaged spark plug, to an air leak in the inlet manifold causing too lean a mixture, an air leak / hole / damaged gasket in the exhaust system, running too lean could also mean that the mix has burnt too slowly allowing unburnt gasses into the muffler. Of a more mechanical nature, it could be incorrect valve clearance (not enough) / a leak past the exhaust valve / or a sticky exhaust valve / or the exhaust valve spring has lost tension, any such possibility that could allow unburnt gasses into the muffler.

Start by checking all gaskets are intact and no holes are present in the exhaust, ensure that the valve clearances are correct, replace the sparkplug and valve springs. As may be necessary, perform a leak down test to ascertain if the valves are sealing.


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The most common cause of this I’ve found is the idle air screw being too lean and/or there’s a leak like Torini mentioned. That said, it’s not super unusual or necessarily harmful.