Forum

[ric]

Thankfully we're discussing sealing exhaust leaks on an old iron barrel model, because there have certainly been enough warnings in the last decade about the damage that the fumes released from curing Silicon sealant can do to Lambda sensors and Catalytic converters on modern vehicles.

[apparently lucky eddie]

In my early driving days and didn't know better I had a Mk1 Cortina and my daily commute took me past a bus stop outside a girls school. I would turn off the ignition and coast past the stop with the 'pedal to the metal' and then turn on the ignition again. This would result in a massive backfire, a 10 foot flame from the exhaust and screams and no doubt wet pants from the girls. I finally gave up when the front came off the manifold and the back box blew up the road.

[PeteF]

Yes Eddie, excellent way to blow a silencer off. Been there, done that.

[jefrs]

The fumes given off by curing silicone are mostly acetic acid (vinegar), it is an exothermic reaction, a thermo-setting plastic. The seal should be made around the outside and end face of the pipe not down the inside. If you are worried about the Lambda sensor on a later bike, it can be unscrewed. Once the silicone has cured there should be no more fumes.

[simon]

Could be a burnt valve if there isnt an exhaust leak.

[Gwilly]

Speaking of valves, could be a tight exhaust tappet needs readjusting.
Combination of little things to be checked really.

[NicoV]

And I did have an exhaust leak between the long bottle silencer and the exhaust pipe. It is fixed now.
Eddie, that story with the Cortina is hilarious. There is a guy on Youtube who has a sequence for having a Bullet produce flames, but not 10 ft flames