Possible fuel starvation?

[Destiny2191]

Evening all,

I have a problem with my GS500E 1994 (1999 engine in frame)

Basically the bike will rev fine up until about 6-7k up to 50-60mph, then just start lurching / spluttering.

I'm using standard carbs, rejetted to fit 2x K&N POD filters on them, any ideas on the problem?

Cheers

[mjj4]

Try running your bike on prime, old style petcocks are prone to the diaprham inside breaking down and causing vacuum leak, so you get fuel starvation typically on the highways. If that doesnt help try running it on choke as that will richen the mixture and if it improves the running then you know the bike is running lean. I'm not suggesting your bike is jetted wrong it could be a clogged jet causing it to be running lean. If running on choke makes it worse then that would suggest a rich mixture.

[Destiny2191]

Thanks for the reply, I'll give it a go.

PS The carbs are clean as a whistle

[Destiny2191]

Well paint me with the idiot brush and call me stupid, I left the hose dangling around near the rear shock, now seated behind battery... DOH!

[BockinBboy]

Not that this is the OPs problem, but just to provide some info toward the thread for future searchers.

The OPs symptoms do fall in line with that of the petcock which mjj4 mentions. Adidasguy has pointed out that the older model petcocks may not be able to handle the fuel flow needed for the larger jets placed in the carbs of bikes with lunchbox or pod air filters. Hence the reason for all of the threads bashing the petcocks for their fuel starvation problems and various folks goin to petcocks without a vacuum. If you have that air and jetting setup, you may benefit from a vacuum free Petcock or just run it on prime before you take off.  But if you haven't experienced the issue then don't  worry about it.

- Bboy