[Sammee3]

I start a ride yesterday, and the valve is in the 12 o'clock position, on. I happen to look at the valve today after cleaning the mountain of dust out of my air filter (routine maintenance here), and now it's facing 2 o'clock.

This isn't the first time this has happened, but it seems to be crawling more towards off over time. There's no way I'm hitting it with my knee (I don't party like that while riding), so the only thing I can think of is that the engine is vibrating it out of position.

Nothing urgent here, just a curious development over the last few months. Though at the rate it's going, I wouldn't be surprised if it turns itself completely off eventually.

 

[ramprat06]

I've never heard of that one. I can only imagine your answer to be the correct one. Start looking for a petcock. I'm sure there are many available that will suit the need. I can't remember which is which when it comes to the sizes, but I know there are a few differences.

 

[Sidecar Bob]

The petcock should need definite pressure to switch from one position to another. If it is loose enough to move on its own the seal is probably very worn and possibly leaking (off isn't really off again and/or you may not have a real reserve).

 

[ki4radiocom]

There should be a repair for that. I had to repair mine on my gl500c. It was not loose, it had a bad vacumm diapharm. Other wise it was tight.

 

[Sidecar Bob]

There are kits for the vacuum part but not for the main valve. I spent a lot of time experimenting with a few replacement seals for them but in the end I finally replaced it. Most on the forum recommend just changing to a non vacuum type and turning it off when you park but I'm experimenting with a separate vacuum valve too.

 

[Steve1]

I have had this one for a few years now ,it's a manual one works great and cheap.It's 18 x 1 mm.https://4into1.com/honda-motorcycle-fuel-valve-petcock-18-x-1-0mm-2/. Here is a repro vacuum one I know nothing about but would never have another stock one again after three failed. This one claims to replaces the stock one,16950-MC9-830.https://4into1.com/vacuum-petcock-18mm-x-1mm-honda-cmx450c-ft-vt500-gl500-650-cb450-550-650sc/