new petcock, but stalls...

[Johnny K]

I have an 82' GS850. The carbs are clean and jetted. I have a V&H pipe. My old petcock did not have a connecting tube from the vent (small hole) on the petcock to the vent to the carbs. My mechanic just put a small hose at the end of each nipple and blocked it off with a screw and electrical tape. At that point, my bike ran awesome. However I could not shut my petcock on and off, it just was always on. So I bought a new vacummed petcock and put the gas line correctly with a see through fuel filter and then connected the other hose from the smaller nipple on the petcock to the small nipple on the carb. Well when I did this it ran for about 1 min, then stalled. The only way it would start is that the choke had to be on (full choke). But it wouldn't stay running and stalled and now can't get it to stay running. Since I hooked up that other tube to the vents, my engine makes a (train) noise like it is gasping for air quickly when it is running. Not a bad noise, just a different noise that I'm not used to. I thought it would be air related, but it sounds like it wants to start when it is full choke and not any other time. Stumped because im a newbie.
John.

[Nessism]

My guess is you have the vacuum line for the petcock hooked up wrong. Turn the petcock to the prime position and start the engine. Next pull the vacuum line off the carb port and see if there is vacuum there (engine will make a hissing sound and run poorly). Make sure the carb vent lines are open and the vacuum line is hooked up properly.

Good luck.

[Johnny K]

Okay.

You were right about the hissing noise. I think I had a thicker hose on the vent for the petcock to the carb. I got a smaller one today and when I connected it, the hissing stopped. When I took it for a ride it was hesitating at any RPM, when held there. Also, it sounded like little popping noises here and there throughout my 10 min ride to get gas. But when I accelerated, it had no problem. Just when held at any constant RPM. Well after that I cut and plugged with a screw and some electrical tape each nipple from the petcock and from the carb (a friend suggested it). Well that just made it worse. It idled fine, but when I went to go in 1st, it just bogged like it was getting too much fuel or not enough air. Hope that helps you solve prob a simple thing that I can't figure out. Dumb quest. The vent from the petcock is supposed to be connected to the vent off the carb right??? Thanks.

[Steve]

I think I found your problem. 8-[

... So I bought a new vacummed petcock and put the gas line correctly with a see through fuel filter ...

Many times, the in-line filter is to blame. Did you get yours at the auto store? They depend on having a pump forcing gas through them, so it does not really matter. The only "pump" our bikes have is gravity. If you try a fuel filter for a small lawn mower, it may resolve your problem. I dare say that most of us run without a filter and have very few, if any, problems.


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[Johnny K]

I purchased the inline fuel filter at a motorcycle shop. It costs $4. Its a nice one. All clear and a nice cylinder type filter inside of it. The gas is going through it no problem. What else???

[Nessism]

Your carbs have 4 hose nipples:

- Fuel inlet

- Two vent lines (which should have sections of hose installed and routed up and laying on top of the airbox)

- Vacuum port line which connects with your petcock

Make sure everything is hooked properly and report back.

[Johnny K]

Everything is working good. Took it out for a ride after I hooked up the right size hose to the vent off the petcock and carb. Thanks. I bought a new petcock and (left)=res, (down)=on, (right)=prime. The prime is considered off right? And if so, how long once you turn to prime should it stop the flow of fuel? When I was turning from on to prime, I saw in the fuel filter that it looked like it was filling up with fuel with little bubbles. Just wondering if thats normal and should I always switch it to prime when not riding at the end of the day?? Thanks again guys.

[onchiman]

No, "PRIME" is only to be used to fill the carb bowls just prior to starting if necessary .When running and parked leave it in the "ON" position. When the engine is running, the engine vacuum keeps the petcock open and fuel flowing. When the engine is stopped, there's no vacuum to keep the petcock open so fuel flow stops.

[Steve]

I bought a new petcock and (left)=res, (down)=on, (right)=prime.

Could be confusing here. Do you mean that the label is on the left or you turn the petcock to the left (counter-clockwise) for RES? What I have seen in most stock petcocks is the lever will point forward (requiring clockwise rotation) for RES, point down for ON, point backward (requiring counter-clockwise rotation) for PRIME.

The prime is considered off right? And if so, how long once you turn to prime should it stop the flow of fuel?

No, PRIME is not considered OFF. Quite the opposite. PRIME is the only position that does not require the engine to be running to allow fuel flow. When you stop riding, the petcock should be anywhere but PRIME. Generally, if you ride your bike at least every few days, you may never need to use the PRIME position. If it has been sitting for a couple of weeks (shame on you ) put it in PRIME for 20-30 seconds before turning on the key to start the bike. Apply full choke, do not touch the throttle, press the starter button. Adjust choke as necessary to keep rpm out of the stratosphere, put the petcock back into the ON position.

When I was turning from on to prime, I saw in the fuel filter that it looked like it was filling up with fuel with little bubbles. Just wondering if thats normal and should I always switch it to prime when not riding at the end of the day??

What happened just before this? If the carbs were dry and the engine not running, it would be normal to see fuel flow. If you had the engine running, I would not expect to see fuel flow, which would indicate that your petcock might not be working correctly.
As mentioned above, PRIME is the only position you don't want to leave the bike in overnight. :shock:


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[Johnny K]

Sorry for my confusing explaining but both of us are on the same page, just that I wrote it a little confusing. But I understand now how the vacumm works with the bike running and not running. I have noticed that since I do have the hose connected to the two vents off the petcock to the carb, when ever I let go of the throttle, my V&H exhaust makes backfire noises that doesn't sound that bad, but not a big deal. Should I worry about that?? Thanks again guys.