Backfring can be caused by valves not closing properly (tuliped heads, worn
shims/cam lobes), burned valves/seats or exhaust leaks.
Had a Honda VT250 fitted with an XR500 engine (don't get me started on my
various repowers). It was popping on overrun, and proved to be a burned
valve. It was also a female dog to start, and prone to stalling, even doing
so twice when throttling-off in FIFTH gear (thereby locking the back wheel,
not fun).
A compression test can be used to show valve problems. Simple, cheap and easy.
Andrew Grebneff
Dunedin, New Zealand
VW & mollusc nut
1984 VW Caravelle (currently SVX engine; waiting for a Porsche trans)
1985 Mitsubishi Galant Sigma 2.0 (FWD), for sale
1986 CE80 Toyota Corolla 1.8DX diesel (extaxi)
1989 CE96 Toyota Corolla 1.8DX diesel wagon
1989 CT170 Toyota Corona Select 2.0 diesel (taxi)
