Motorcycle driveable only on PRI setting

chokne · June 15th, 2010, 07:27 AM

Hey everone, i need some of your expertise for my friends problem. He just bought a 98 gs500. The dude before didn't drive it for like 2 months. We went for a ride yesterday and found out he's only able to drive the bike in the PRI setting. If he puts the petcock at on, the bike has no power and eventually stalls. What cab cause that. We have thought about clogged fuel lines, or maybe something wrong with the manifold, not sucking in gas. Any other possible explanation?

Thanks peeps
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2WheelGuy · June 15th, 2010, 07:35 AM

The petcock is vacuum operated. Check the vacuum line connected to the petcock. It could be loose or cracked. If the hose is good check the petcock itself. With the petcock in the on or reserve position attach a hose to the vacuum port and suck on it (yeah I said suck on it). Gas should flow while you suck (yup you suck). If it doesn't you need to rebuild/replace the petcock.

Stuff could be clogged too but the fact that the bike runs fine on Prime leads me to think the problem is with the vacuum operated petcock.

chokne · June 15th, 2010, 10:37 AM

Nice, thanks for the advice!

I'll tell him to suck on it
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chokne · June 15th, 2010, 11:56 AM

Is it bad to run on prime?
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kkim · June 15th, 2010, 12:51 PM

yes. if the float fuel valve in side the carb sticks open, the gas will run from the tank into the carbs and out the overflow tube all over the bike/ground until the tank is empty. it's like having no "off" position at the petcock. the bike will run fine, however, if there is no problem with that float valve.

fix the petcock.

June 15th, 2010, 07:27 AM	#1
chokne I name everything Name: Michael Location: Montreal Join Date: Nov 2009 Motorcycle(s): Eva Posts: 68	Motorcycle driveable only on PRI setting Hey everone, i need some of your expertise for my friends problem. He just bought a 98 gs500. The dude before didn't drive it for like 2 months. We went for a ride yesterday and found out he's only able to drive the bike in the PRI setting. If he puts the petcock at on, the bike has no power and eventually stalls. What cab cause that. We have thought about clogged fuel lines, or maybe something wrong with the manifold, not sucking in gas. Any other possible explanation? Thanks peeps Posted via Mobile Device

June 15th, 2010, 07:35 AM	#2
2WheelGuy ninjette.org certified postwhore Name: Craig Location: Silicon Valley, CA USA Join Date: May 2009 Motorcycle(s): '98 EX250, '02 EX250, '08 250r, '03 SV650, '98 GSXR750 '03 Hayabusa, '87 YSR50, '84 ZX900, +MORE Posts: A lot.	The petcock is vacuum operated. Check the vacuum line connected to the petcock. It could be loose or cracked. If the hose is good check the petcock itself. With the petcock in the on or reserve position attach a hose to the vacuum port and suck on it (yeah I said suck on it). Gas should flow while you suck (yup you suck). If it doesn't you need to rebuild/replace the petcock. Stuff could be clogged too but the fact that the bike runs fine on Prime leads me to think the problem is with the vacuum operated petcock. __________________________________________________ CraigHarris.org Pacific Track Time CraigsWeb See you at 2014 MotoGP Laguna Seca! We'll be camping on Fox Hill. AFM #278

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June 15th, 2010, 10:37 AM	#3
chokne I name everything Name: Michael Location: Montreal Join Date: Nov 2009 Motorcycle(s): Eva Posts: 68	Nice, thanks for the advice! I'll tell him to suck on it Posted via Mobile Device

June 15th, 2010, 11:56 AM	#4
chokne I name everything Name: Michael Location: Montreal Join Date: Nov 2009 Motorcycle(s): Eva Posts: 68	Is it bad to run on prime? Posted via Mobile Device

June 15th, 2010, 12:51 PM	#5
kkim Join Date: Nov 2008 Posts: Too much.	yes. if the float fuel valve in side the carb sticks open, the gas will run from the tank into the carbs and out the overflow tube all over the bike/ground until the tank is empty. it's like having no "off" position at the petcock. the bike will run fine, however, if there is no problem with that float valve. fix the petcock.