petcock mod

[John W]

My petcocks on my Gsx1100 and GS 850G are giving trouble again.After striping the 850,s for repair,I thought maybe I could modify it so that it did not require a vacuum to operate it by blocking off the prime channel inside the petcock and removing plunger and oring seal.This would mean the ON and RESERVE positions would deliver fuel when selected to either position and the PRIME position would then be the OFF position.Has anyone tried something like this and if so with what results??

John W

[Red_Phil]

I just did this with a GSX400 petcock,

The prime channel on this petcock is via a seperate channel with a bolt, the principle still applies though.
On the GSX400 petcock
6 o'clock is normal on,
9 o'clock is reserve &
3 o'clock is a blank bit with no hole.
The 3 o'clock position is not normally reachable, but I cut off the endstop that prevents this.

I modified the petcock by removing the diphragm and plunger and puting in a sheet of gasket card in it's place.
This meant that the petcock was no longer vacuum dependant but by turning the petcock to the 3 o'clock position you had an 'off' setting.

Your modification ought to be simpler as your already have a 3 position petcock.
If you replace the diaphragm and plunger with gasket card and block up the prime channel then you're laughing.

Remember to cap off the vacuum feed on the carb though or it'll run awfully lean on one cylinder.

[John W]

Petcock mod

Thanks for the info.I trust you have had no problems since you did the mod.
Regards
John W

[HiSPL]

Yes! Do it!

You'll never have trouble again with your petcock. I did that on both of my GS's and have not had a single problem since. The 750 has been this way since '02 and both have thousands of miles on them after the mod.

Do it!

P.S. You'll need to make a gasket (or use RTV) when you assemble the two halves of the petcock. Fuel will flood the entire vacuum side of the valve now and you need to seal it good. Also don't forget to block off the vacuum ports on the petcock AND #2 carb.

P.P.S. I used JBWeld to fill the prime hole and the vacuum port on the petcock, and used a vacuum plug on the #2 carb. I also used RTV to reassemble and it has not leaked.

Good Luck!
-=Tim=-

[Jim-H]

Newbee to Forum

I just got a 81 gsx-400-ex, a 2 cyl. 8 valve model. I'm having trouble starting it in cold weather. Rough idle also.

Seems to be a fuel system related problem.

I was wondering what problem were you experiencing before you decided to look at the fuel petcock ? And if the fuel petcock on my model is one that can be corrected. I have a very small leak at the fuel petcock and was wondering if the bike is experiencing the same fuel vacuum problem.

Fairly easy to fire the bike up by running and releasing the clutch.

[ron bayless]

blocking off the prime channel inside the petcock and removing plunger and oring seal.This would mean the ON and RESERVE positions would deliver fuel when selected to either position and the PRIME position would then be the OFF position.Has anyone tried something like this and if so with what results??

John W
JOHN W!!!!! YOU ARE MY BEST FRIEND!!!! I WILL DANCE AT YOUR NEXT WEDDING BROTHER!!! i READ YOUR POST,JUST DID THE MOD ON MY 1980 GS 1000L AND IT WORKED PERFECTLY!!! fOR WEEKS THE BIKE HAS EITHER BEEN SITTING OR WOULD NOT GO OVER 15 MILES WITHOUT STALLING ON ME.I JUST WENT 47 MILES AND SOME OF THE TIME WFO AND IT NEVER SPUTTERED ONE TIME.YOU ARE A GENIUS! GOT ANY SISTERS? I WOULD HAVE TO DIVORCE MY WIFE, BUT SHE WILL UNDERSTAND WHEN SHE SEES HOW GOOD THE BIKE RUNS NOW.