Editor Bob Mack
Why are we interested in this subject? The sticking exhaust flap, particularly on twins seems to have been with us since they were first introduced on some of the range.
There’s some uncertainty about its actual purpose and whether it matters if it sticks wide open. Two things we do know for certain are that:-
- If it’s on a more recent model a warning appears on the dashboard.
- If it’s out of warranty there is a huge cost to replace the exhaust system.
Geoff Clough’s RT had a sticking valve so between us we decided to take a look to see if something simple could be done to unstick it.
It was relatively quite easy, to free it off and lube the moving parts. Geoff did a talk, with pictures, about it during a recent Zoom social. Our feeling was that it wasn’t a permanent solution and we didn’t fully understand why it sticks.
We decided that it would be helpful to find a scrapped, seized valve, try and free the mechanism as we did with Geoff’s and then may pull it apart to better understand why it seized up and how to prevent it from happening again.
Steve Moxey spoke to Barnstormers and they kindly gave us a scrap valve.
After treatment with solvents, diesel, and lube it was really free and sprung back very easily except from the fully closed position where it would sick.
It seemed that we had gone as far as we could with applying potions but still didn’t understand why it stuck in the first place, or in one position and why some do and some don’t.
At this point I started to take it apart and made a discovery which may provide the answer to our questions. More of that to come soon.