Ok. This is a stock 1980 XS650 Special. Stock air boxes and exhaust. It had been sitting for about 1 1/2 years that I know of. Super clean, but last ran who knows when. I changed the oil, Gentleman Jim rebuilt the carbs, installed High Output Replacement Coil Part #17-6803, Autolite 63 plugs, plug wires, and new NGK 5K Ohm Spark Plug Caps. Bike starts up after one kick or a bump of the starter, but only runs on the right cylinder. I have switched plugs, flip flopped the wires, and the problem does not change cylinders. Spark looks good at both plugs. Compression tested this morning and got 150 in the left, non firing cylinder and 155 in the RH cylinder. When I pull the LH plug after starting the bike up it is wet with fuel. To me it seems as though I have fuel, spark, and good compression. What am I missing? Thanks in advance.
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Running on One Cylinder. Why? Details inside.
- Thread starter Jerm
- Start date
cros36
thread killer
are sure you have spark on the non running cylinder? new coil does not mean your getting spark. what is your plug gap? when you flipfloped your plug wires did you flipflop your plug. and a fouled plug may not fire correctly.
Pulled both plugs and grounded them to the engine. The spark on each side looks the same. Plug gap is .035". When I flip flopped the wires and nothing changed I also put a different plug in the non firing cylinder. Still nothing changed. I should also mention that I removed the same coil, wire, and plug cap setup from another one of my bikes and installed it on this bike and got the same results. LH cylinder does not run. I think it is fuel related. Too much fuel?
cros36
thread killer
yeah, too much fuel. if you have compression, fuel, spark the only thing missing could be air. i bet someone will know the answer right away.
check this one out, you were apart of it, the answer may be later in the thread tho.
http://www.xs650.com/forum/showthread.php?t=11782
check this one out, you were apart of it, the answer may be later in the thread tho.
http://www.xs650.com/forum/showthread.php?t=11782
manofsteele
XS650 Addict
Not to be an ass but the same person rebuild my carbs and it wasn't done correctly. I had similar issues until I took the carbs apart and found they weren't jetted to what I was told that they were. I had 2 up on the mains and the pilots were left stock and not 1 up which they were supposed to be. After tearing them down and rejetting them to where they were supposed to be in the first place the bike runs fantastic now. Lesson learned, if you want something done right, do it yourself.
So I would check your carbs and jets and make sure they are what they are supposed to be at.
So I would check your carbs and jets and make sure they are what they are supposed to be at.
I am Carbon
shade tree mechanic
sounds like a carb if its not spark.I had the same problem too. Do you have the stock BS34s? The pilot circuit fuels the engine in low-speed operation, when the slide is lowered. In the back of the BS34 (80-83) you will find four round holes
The upper pair (below curved diaphragm chamber vent) vent the carb body above the
floats. Below those are the air jets. The pilot air jet is removable, and the main air jet is
fixed. In BS34 carbs the pilot jet is under a rubber plug at the end of the smaller vertical tubular casting in the carburetor body; the plug must seal correctly. Use a screwdriver or bit that completely fills the slot of the jet. If the jet
area is fairly clean and uncorroded, one sharp push-and-twist should free the jet. If jets
are fuel varnished, prep them for removal with solvent. In the BS34, spray-in solvent can be applied to the jet area and followed by compressed air until varnish breaks up--never immerse
carb bodies. Apply a bit of penetrating oil and allow it to soak in. Then seat the
workpiece firmly in a padded vise or clamp, and remove the jet. Use a sharp push-and
twist motion to break the jet loose. Light taps on the screwdriver will often break a
stubborn jet free. If the slot deforms, use a screwdriver with a thicker blade or regrind
the one you're using. Once the jets are removed, check to see that the correct series is in place. "Now this is where my problem was the oring was bad and it flooded the cylender out" The fuel screw in the BS34 carburetor is recessed in a vertical tubular casting on the
carb body toward the center line of each carb, forward of the slide tower. Unless it has been removed, the screw is covered with a thin brass cap, which
must be removed for cleaning and adjustment. Pierce the cap with a drill, being careful
not to damage the casting or the screw; just penetrate the cap. Sometimes a sheet
metal screw will hold firmly enough to grip the cap while pliers are used to extract it
(don't run the screw in deeply; avoid damage to the mixture screw beneath). Sometimes
it can be pried out after drilling. Remove the mixture screw, with the spring. A rubber Oring
is at the bottom of the mixture screw seat, with a metal washer on top of it. Remove
these with a probe. When new, the washer is somewhat flattened; this does not indicate
defect. Be sure that it's flexible and has no nicks or cracks.
If fuel screws show signs of damage, wear or corrosion pits, replace them.
CV Carbs - one of the best how-to manuals ive found for the original carbs
http://www.amckayltd.com/carbguide.pdf
you can download a keep on you computer the info that Igave you came from the carb guide, good luck
The upper pair (below curved diaphragm chamber vent) vent the carb body above the
floats. Below those are the air jets. The pilot air jet is removable, and the main air jet is
fixed. In BS34 carbs the pilot jet is under a rubber plug at the end of the smaller vertical tubular casting in the carburetor body; the plug must seal correctly. Use a screwdriver or bit that completely fills the slot of the jet. If the jet
area is fairly clean and uncorroded, one sharp push-and-twist should free the jet. If jets
are fuel varnished, prep them for removal with solvent. In the BS34, spray-in solvent can be applied to the jet area and followed by compressed air until varnish breaks up--never immerse
carb bodies. Apply a bit of penetrating oil and allow it to soak in. Then seat the
workpiece firmly in a padded vise or clamp, and remove the jet. Use a sharp push-and
twist motion to break the jet loose. Light taps on the screwdriver will often break a
stubborn jet free. If the slot deforms, use a screwdriver with a thicker blade or regrind
the one you're using. Once the jets are removed, check to see that the correct series is in place. "Now this is where my problem was the oring was bad and it flooded the cylender out" The fuel screw in the BS34 carburetor is recessed in a vertical tubular casting on the
carb body toward the center line of each carb, forward of the slide tower. Unless it has been removed, the screw is covered with a thin brass cap, which
must be removed for cleaning and adjustment. Pierce the cap with a drill, being careful
not to damage the casting or the screw; just penetrate the cap. Sometimes a sheet
metal screw will hold firmly enough to grip the cap while pliers are used to extract it
(don't run the screw in deeply; avoid damage to the mixture screw beneath). Sometimes
it can be pried out after drilling. Remove the mixture screw, with the spring. A rubber Oring
is at the bottom of the mixture screw seat, with a metal washer on top of it. Remove
these with a probe. When new, the washer is somewhat flattened; this does not indicate
defect. Be sure that it's flexible and has no nicks or cracks.
If fuel screws show signs of damage, wear or corrosion pits, replace them.
CV Carbs - one of the best how-to manuals ive found for the original carbs
http://www.amckayltd.com/carbguide.pdf
you can download a keep on you computer the info that Igave you came from the carb guide, good luck
I guess I should have taken care of the carbs myself, like everything else on my bikes. It seems like every time I pay someone to do something it ends up costing me twice as much in the long run. 
Thanks for the responses thus far. Looking forward to any other input members may have. Especially you, gentlemanjim.....
Thanks for the responses thus far. Looking forward to any other input members may have. Especially you, gentlemanjim.....
Wrong size jetting would not cause a bike to run on one cylinder. Lean, rich but not on one cylinder.
skrapper
XS650 Member
Sound like carbs out of sync. My '77' xs is doing the same thing. I had the carbs out and did the Fred Flintstone bench sync.
When I put them back in I had the same problem running on the left, dead on the right. I did some fiddling with the balance adjusted in between the carbs. All of a sudden the right side came to life, the revs went way up.
After I shut it down I adjusted the idle screw, now the right side runs and the left side is dead.
I guess it's time for a carb sync tool.
When I put them back in I had the same problem running on the left, dead on the right. I did some fiddling with the balance adjusted in between the carbs. All of a sudden the right side came to life, the revs went way up.
After I shut it down I adjusted the idle screw, now the right side runs and the left side is dead.
I guess it's time for a carb sync tool.
manofsteele
XS650 Addict
Really? That's weird. At least you got it working.
With no brushes, therefore no charging,the battery voltage was sinking lower and lower. These bikes run like crap when the voltage is low.
As RG said, low voltage makes them run poor, especially the 80 up bikes with the TCI. The TCI is very voltage sensitive.
Leo
Leo
