lil help fellas

i bough a new petcock for the tank to avoid the vacuum problem, the other one that had before was a regular one but I needed a new one because it was leaking a little bit and i bought a gas filter for the line, so when i changed the petcock and installed the filter on the line and tried to start the motorcycle for some reason now it feels like it needs more gas, it doesn't stay on, it goes off. so i repaired the old petcock and took off the filter, but still the problem remains like its asking for more gas, could it be that the carbs needs readjustment? or what could be the problem?

1982 yamaha xj750 maxim
Erik

 

Try running it with the fuel cap open, and see if your problem is resolved.

The fuel cap may not be venting properly.

 

ok, I will, any other thing that might help o that I should look into?

 

What fuel filter did you use? Many of the paper element filters for small engines will not flow enough fuel for a multi-carbed engine.

 

http://www.ebay.com/itm/YAMAHA-ATV-...50|Submodel:Maxim&hash=item3f275407bc&vxp=mtr

it was that one, but even now when i took it off, I need to keep the bike choked otherwise it will go off and it wasn't doing that before, I put some carb cleaner in the tank and changed the spark plugs, Im going to test it again today and see what happens.
Thanks for the help, I'll let you know how it goes

 

so it wasn't the fuel cap, I opened it and still, now its like struggling to run, its loosing power, really weird, i have to choke it to ride it, otherwise it would go off =/ I don't have a clue what it could be, since Im not mechanic wise

 

When you rebuilt the petcock, was it "zestfully clean" when you put it back together? Did you rebuild all of the petcock and replace all of the internal rubber?

There is a very tiny check-valve in the vacuum port. Did you make sure it was rattling freely?

Does fuel flow freely out of the petcock when you remove the tank from the bike, in both PRI and when vacuum is applied to the vacuum port when in the ON position?

 

i changed the petcock for another one, because when i put it back on it was leaking so had to install a new one with just fuel, res, the gas on the line flows good but when i start the bike it seems like it has no power, I was trying to ride it today and on 1st gear it looses power i have to really put some gas to make the engine go, I'm thinking its something with one of the carbs, but still dunno

 

Do I read this right? You have a new fuel control valve installed?

If so, since you changed to a non-vacuum petcock to a fuel control valve you did plug the vacuum line that was removed from the original petcock that goes to the carb manifold?

 

That too but let's back up a bit.

How many miles on this bike, what have you done to it, and what is your history with it so far?

Have the valve clearances been checked, the carbs serviced, the brakes rebuilt; what, if anything has been done since YOU got it?

I'm thinking you might be in for the "30 year old bike rude awakening." This doesn't sound like a petcock issue; bigger problems are in play here.

Give us some background (and your location) please.

 

seems to me that if you have to keep the choke on (it's call the enrichment circuit) on in order to run, then you're looking at a carb cleaning/rebuilding situation. If NOTHING else, the enrichment wells in the carbs bowls are probably getting clogged.

dave