Hi, please help. My Haynes manual shows a one way check valve ,in 3.11  picture 7.26d.    Mine is missing so where should it be please?
Thanks very much.
Regards,
Reg.

Please have some patience.  Most people here aren't on the forum 24/7, there's no need to make more than one topic.

When the user that knows the answer comes along they'll be sure to post.

agreed. patience helps here. the answer will present itself before too long. or at least give you some idea where it is supposed to be. tbh, ive no idea. but im sufe someone else here does.
Aaron

where are you located ?

Better yet, can you post a picture of the page in the Haynes manual? It's pretty clear that nobody has any idea what you're talking about yet....

Having had 97 and 02 GSs myself I  had no idea what OP was talking about last night but it occured to me that it must be part of the  pollution mods made to the GSs starting in 04 in US.  Found it this morning on parts lists, part 6, 2nd air system has probably been removed by many GSers:

http://shop.shspowersports.com/fiche_section_detail.asp?section=300552&category=Motorcycles&make=SUZUKI&year=2004&fveh=7247

I think I know what you are talking about. I have a 2006 GS500f that I bought a few months ago. I took off almost all of the stuff from the vacuum line that comes from the right carb. I ran the line from the vacuum port on the carb through a "T" fitting that branches off to somewhere on the engine and then to the petcock. The motorcycle started running better, and the petcock worked properly for the first time.