03-16-2021, 03:10 AM
Our Australian friend found the missing link ( o-ring ) i think.
Since the variable ticking sound disappeared when the combustion stopped ( sparkplug disconnected ) it is likely that the
exhaust reed valve seal is not working properly.
The pair valve system works on the principle of mixing air into the exhaust system by letting some air into the exhaust through a one way reed valve into the exhaust port using the "vacuum" that happens after the ex valves close and the shockwave makes it's way down the exhaust pipe, the resulting under pressure " sucks " some air past the reed valve and dilutes/ combusts the mixture resulting in cleaner exhaust emissions for the purpose of passing emission regulations.
The two openings to the exhaust channels can be seen in the picture between the spark plugs and the back of the rocker cover just outside of the tappet cover seal and will have an o-ring each in the tappet cover leading to the two reed valves bolted to the top of the valve tappet cover.
To test this you could use a plastic hose and listen to these openings for gas escaping here.
Second possibility is a faulty reed valve, this can be checked by inspecting the valves by removing the two bolts that hold the " flapper valve " housing to the tappet cover, these valves are meant to stop exhaust gas escaping through the air injection system, if a reed valve is not working it should be obvious by removing the rubber air hose to the flapper valve housing.
Question; has the tappet cover been removed in the past?
Very interesting find here GAVSP1, thanks for your help.
And thanks bflint for your update, appreciated.
Since the variable ticking sound disappeared when the combustion stopped ( sparkplug disconnected ) it is likely that the
exhaust reed valve seal is not working properly.
The pair valve system works on the principle of mixing air into the exhaust system by letting some air into the exhaust through a one way reed valve into the exhaust port using the "vacuum" that happens after the ex valves close and the shockwave makes it's way down the exhaust pipe, the resulting under pressure " sucks " some air past the reed valve and dilutes/ combusts the mixture resulting in cleaner exhaust emissions for the purpose of passing emission regulations.
The two openings to the exhaust channels can be seen in the picture between the spark plugs and the back of the rocker cover just outside of the tappet cover seal and will have an o-ring each in the tappet cover leading to the two reed valves bolted to the top of the valve tappet cover.
To test this you could use a plastic hose and listen to these openings for gas escaping here.
Second possibility is a faulty reed valve, this can be checked by inspecting the valves by removing the two bolts that hold the " flapper valve " housing to the tappet cover, these valves are meant to stop exhaust gas escaping through the air injection system, if a reed valve is not working it should be obvious by removing the rubber air hose to the flapper valve housing.
Question; has the tappet cover been removed in the past?
Very interesting find here GAVSP1, thanks for your help.
And thanks bflint for your update, appreciated.