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Running/idling problems, backfiring...old gas?
- Thread starter Bonsai
- Start date
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- Tags
- carburetors
Tomterrific
XS650 Junkie
Did you run a thin wire through the pilot jet? Plugged pilot jets are the number one reason why an old bike won't idle or idles on one cylinder.
If your engine was running fine and idleing on both cylinders you can spray carb cleaner into the mixture screw hole (after the screw is removed) to possibly blow the dirt off the idle jet back into the float bowl.
Your float may be sinking because it leaks and fills with gas. The gas flowing out the carb is indicative of this. Solder the hole or replace the float. Until then, you may be able to get away with riding if the leak isn't too bad because the gas used keeps the level from getting too high.......
That cylinder should have a fouled plug. Replace with a hotter heat range (like a BP6ES) so there is a chance the carbon burns off. Turn off the petcock before you stop the engine to lower the float level. Use premium with the hotter plug.
Tom
If your engine was running fine and idleing on both cylinders you can spray carb cleaner into the mixture screw hole (after the screw is removed) to possibly blow the dirt off the idle jet back into the float bowl.
Your float may be sinking because it leaks and fills with gas. The gas flowing out the carb is indicative of this. Solder the hole or replace the float. Until then, you may be able to get away with riding if the leak isn't too bad because the gas used keeps the level from getting too high.......
That cylinder should have a fouled plug. Replace with a hotter heat range (like a BP6ES) so there is a chance the carbon burns off. Turn off the petcock before you stop the engine to lower the float level. Use premium with the hotter plug.
Tom
No did not run a wire as at least one source said that potentially messes up the opening. Just cleaner and air...
It was running fine for a short time after purchase.
Floats seemed fine when I had it apart the first time- unless they developed a leak during reassembly.
Plugs (AL63s) are reading borderline okay- just not ideal. Running Shell Premium in it right now. The plug on the right side where the popping is going on is actually the better looking of the two.
It was running fine for a short time after purchase.
Floats seemed fine when I had it apart the first time- unless they developed a leak during reassembly.
Plugs (AL63s) are reading borderline okay- just not ideal. Running Shell Premium in it right now. The plug on the right side where the popping is going on is actually the better looking of the two.
Tomterrific
XS650 Junkie
You only need to poke through once to break teh bond of any jet plug. Never hog out the jet like a horny teenager. My method: Spray a bit of carb cleaner on the jet to soften the plug. Poke a little E guitar string through only once. Spray carb cleaner through the jet to remove the rest of any varnish. This is for carbs that sat for over a year and have extreme hard varnish.
Your plugs should run rather white on the tip with carbon building up deep inside the insulator. They are not black on the tip? Then they should be fine. If the plug is black, it is fouled.
Gas should not flow out the carb so there is something going on.
The needle and seat are not sealing? I think there is an o-ring around the BS34 N&S and it can leak round the outside if it isn't sealed.
Float leaking and getting heavy with gas? That will raise the float level.
Bent float tang when messing with carbs? Any time the carbs are torn into there is a chance to fat finger the internals. Limited disassembly is the best policy. Go to the carb guide and learn to set the float height.
Tom
Your plugs should run rather white on the tip with carbon building up deep inside the insulator. They are not black on the tip? Then they should be fine. If the plug is black, it is fouled.
Gas should not flow out the carb so there is something going on.
The needle and seat are not sealing? I think there is an o-ring around the BS34 N&S and it can leak round the outside if it isn't sealed.
Float leaking and getting heavy with gas? That will raise the float level.
Bent float tang when messing with carbs? Any time the carbs are torn into there is a chance to fat finger the internals. Limited disassembly is the best policy. Go to the carb guide and learn to set the float height.
Tom
Fresh plugs, raised the idle some, tweaked the mix screw on the right side a bit leaner and took it out and ran it on some back country roads. Seems to run okay all the way through the gears on up to 60+.
When I started itj it began "whumping" in the right pipe after a few minutes which increased in frequency as it continued to idle.
When running, it backfired on the right side, esp. on decel. Stalls unless you keep your hand on the throttle when moving into first and at stops.
Blowing gas out of the right filter- at least enough to spot up the rear fender and fake oil bag...So carb work is still in the plan.
Also noticed the chain is nicking the cover of the oil bag... joy... something else to fix. Found a horn bolted to the bottom- just ned to figure out if it is wired to some switch somewhere...
Noted some good smoking coming from the exhaust wrap on the left side- really starting to wonder what's hiding under there!
Pulled the plugs- they both look good - as compared to the first set that were pretty crudded up after two short runs up the block and back.
Also checked the battery- was good 12.46V after starting the bike at least a dozen times.
When I started itj it began "whumping" in the right pipe after a few minutes which increased in frequency as it continued to idle.
When running, it backfired on the right side, esp. on decel. Stalls unless you keep your hand on the throttle when moving into first and at stops.
Blowing gas out of the right filter- at least enough to spot up the rear fender and fake oil bag...So carb work is still in the plan.
Also noticed the chain is nicking the cover of the oil bag... joy... something else to fix. Found a horn bolted to the bottom- just ned to figure out if it is wired to some switch somewhere...
Noted some good smoking coming from the exhaust wrap on the left side- really starting to wonder what's hiding under there!
Pulled the plugs- they both look good - as compared to the first set that were pretty crudded up after two short runs up the block and back.
Also checked the battery- was good 12.46V after starting the bike at least a dozen times.
If you have gas going into the right air filter then you have a float or float needle and seat problem in that carb. It's over-filling and spilling into the air filter. You need to fix that 1st or the bike will never run right and you won't be able to tune the carb.
BS34s have O-rings that seal the float valve to the carb body, they are almost always brittle and no longer seal, the gas bypasses the float valve and overflows the bowl. Replace the o-rings.
Oh check compression, this wouldn't be the first time some loose carbon chunks got on a valve seat and dropped compression like a rock.
Oh check compression, this wouldn't be the first time some loose carbon chunks got on a valve seat and dropped compression like a rock.
Float stuck, float out of adjustment or trash in the needle and seat.
Previously you mentioned a trickle from the petcock when draining the tank. To properly drain the tank you need to remove the petcock from the tank and blow backwards through the petcock as there could be trash there as well.
PeePudSpud
Take It Easy!
Hey man i just had the same problem but check it out..
there is a little brass bleeder needle/nipple thing where the carb connects to the engine. a black rubble nipple covers it. check and make sure it's still covered. the black rubber nipple cover thing wore away on mine. if that thing isn't covered it caused too much air to get in the carb and will continually back fire unless that brass thing gets covered up.
there is a little brass bleeder needle/nipple thing where the carb connects to the engine. a black rubble nipple covers it. check and make sure it's still covered. the black rubber nipple cover thing wore away on mine. if that thing isn't covered it caused too much air to get in the carb and will continually back fire unless that brass thing gets covered up.
Those are vacuum ports. On a stock bike with two petcocks a hose runs from the back of each petcock to one of the vacuum ports. On a bike with one petcock, a hose comes from the left vacuum barb to the back of the petcock. The right side vacuum port gets a cap.
I think I posted a link earlier but here it is again. www.amckayltd.com/carbguide.pdf
Leo
I think I posted a link earlier but here it is again. www.amckayltd.com/carbguide.pdf
Leo
PeePudSpud
Take It Easy!
Leo,
hey thanks for clarifying my comment. i failed at getting the technical words right haha. I also didn't read EVERY comment before posting. But yeah mine rubber cap just fell apart and the second one is close too. ordering new ones from Mikesxs.
cheers
hey thanks for clarifying my comment. i failed at getting the technical words right haha. I also didn't read EVERY comment before posting. But yeah mine rubber cap just fell apart and the second one is close too. ordering new ones from Mikesxs.
cheers
