Petcock issue ?

[tomo]

Been having a few running issues with my 1979 GS750, which I have sought advice about before but still have not sorted out. Usually she runs well, but every so often between 50-60mph she seems to intermittently lose power, but a few more revs and she picks up again. Last week-end though, I was cruising along at 60 when she started to bog down but this time the power faded right off and the engine cut out. I pulled over and tried to start, but while she span over ok would not start. Had a cig, then tried again a few times but same thing and the battery was starting to drain as she started to turn over slower. Had another cig, then tried to phone the AA, only to find my phone was dead too. Thinking what an idiot for not charging it, tried to start the bike again and this time she fired up. Hopped on to head home and she seemed fine until I got stuck behind some slow moving traffic when she started to hiccup again and cut out. This time, she fired up again on the third attempt and I was able to get back. I think I do need to give the carbs a good going over, but to me if it was a carb issue it would likely run rough but not cut out altogether, if say one of the carbs had a blocked jet or dodgy float. Ignition circuit seems fine but again I guess I really need to check everything. Thinking about it though, seems more like fuel starvation, so I am wondering whether it could be the petcock ?. Any thoughts/suggestions for how to check much appreciated.

[rphillips]

When you were having the problems did you move pet cock to PRI.? When on PRI. the fuel should flow wide open all the time.

[tomo]

I did try on both reserve (tank was low but don`t think low enough to need to turn to reserve) and prime, but did`nt seem to help.

[rphillips]

Did you read the thread in carb/fuel/exhaust section VM26SS issues, a day or so ago? seems kind'f similar.

[tomo]

I did read that thread, seems similar that is for sure, but with mine no popping and spitting, just feels like it is missing then power just fades away. Also ran fine up to and over 60mph, after it stopped the first time and when it finally started again, still ran great up to that speed until I got stuck behind traffic.

[unfocused]

First check - gas cap
2nd - pull the petcock and look at the screen
3rd - through the petcock away and get a new one