Sporadic backfires, running off 1 cylinder randomly, right side carb starve...

natek

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Any help appreciated;

I have a 1973 TX650 with...
-mid 70's linked BS38s w/Uni stage 2 foam pods rebuilt and jetted 1 up on mains and 4 up on pilots
-Stock headers cutoff about 3" behind mid controls with home made small baffles I've used on several bikes with no issues
-New peanut tank with halrey style petcock, rebuilt with better gasket
-Auto heat shield fuel line with new fuel filter
-Stock coils, stock points, NOS plug wires and stock recommended NGK plugs
-Stock charging system, tested and functional w/lithium Shoia battery and after market regulator and rectifier (both tested and functioning)
-Engine breather left side plugged, right side 6" tube with 90 degree angle valve aiming at right pod

About two months ago the bike was stolen and has had multiple issues ever since;

First it seemed something in the floats of the carbs wasn't seating and my petcock gasket had stopped allowing the petcock to turn off so the bowls would fill with gas and this caused there to be gas in the oil. Backfiring and odd coughs and gas from the pods incurred. Before realizing the issue, the bike would fire on the left cylinder, and ass it went through the first few revolutions on starting cold, would fire and idle eventually on the right. This eventually lead to on a ride home one day, the right side coughing, backfiring and the remaining 1/4 of a mile ride home on only the left cylinder. I changed the carbs with another set of sonic cleaned re-jetted and rebuilt BS38s I had waiting on another project as I didn't have time to investigate the current BS38s (this is my daily and my only running mode of transportation).
With the new carbs and oil change as well as new petcock, fuel like and fuel filter, the first few starts and test runs seemed to have fixed the issue. However, a few days of rain later (the bike sat) firing the bike lead to only running on the left cylinder unless at around 3k RPMs when the right would backfire and 'kick in' with a small puff of white smoke... upon idling back down the right side would again backfire, sputter and the bike would only run off the left cylinder. I went through the wiring and electrical system testing the coils, replacing the points condensers and rebuilding points from a 76 and replacing them on the 73 in question. I then checked the timing and cam chain tension just because I was there and had the time. The bike fired, ran well seemingly until about 6 miles in a test run... began to lose power and backfire/cut out of the right side as if it were running out of gas until eventually running, again, only on the left cylinder. I realized (and thought this was the problem) with the placement of the new larger fuel filter that there was little gas inside leading me to believe the 'kreme' job the PO of the peanut tank had done may have flaked off clogging the inner fuel filter on the petcock and starving the carbs of fuel leading to the right side running lean. I then replaced the entire tank with a new petcock and fuel line. Insert exact same scenario; seemingly fixed, 1 day later same issues.

to be noted: the carbs are running from 1 petcock without a "T" for the fuel instead the line runs into the left carb then links to the second (see pictures attached). I also assume there could be an issue with fuel transferring to the right side carb. Also to be noted upon riding the bike today all issues seemed to be fine... I rode the bike a solid 15 miles in stop and go traffic and as soon as I got on a strait away and hit 60 MPH and shifted from 4th to 5th the right side started it's song-and-dance and popped and sputtered and cut to only the left. I pulled over, tapped on the right side carb with a wrench to see if something had stuck and fired it up working fine again. About 2 more miles down the road; same issue. This time I pulled over and removed the right side carb bowl screw to see if there was fuel at all and it seemed there was little... upon replacing the screw, the bike fired up fine and got me almost home until the same issues happened again. I decided to ride it home the remaining 1 mile on the left side only and about 3/4 of a mile in it suddenly fired the right side and functioned normally the rest of the way. When I got home I looked at the carbs and it seems the right side engine breather valve spewed gas/oil all over my battery and wiring hidden under the seat.

HELP!!!!! :confused: :banghead: :wtf: Im going to throw this thing in the trash! Any advice would be greatly appreciated.

other notes: milage 20k, new clutch, rebuilt top end, new everything bolt on all 2k miles ago with no issues.
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:doh:
 
Three up on the pilots with one up on the mains, Sounds like you need to learn how to jet carbs. With what you have maybe two up on the pilots but I think just one up will work. Two or three up on the mains should work.
You also need to id the carbs closer than mid 70's. They made changes every two years. Some very major changes.
www.xs650.fi/pohja_files/fi/XS650carbs.htm will help id your carbs.
www.amckayltd.com/carbguide.pdf will help on tuning.
Leo
 
Leo, my apologies on the jetting quote as I'm sure I was inaccurate. The carbs were rebuilt and jetted by DogBunny whom as I'm sure you know, knows carbs well... I thought I had seen him mention those jetting specs in an email but looking back that was a recommendation to a buddy vith a V-star in a different situation. Anyhow, the carbs worked fantastically that had been on it, these are jetted the same. Also, they are 1976 carbs.
 
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