Considering melting my BS34's down into beer cans...

OdysseusXS

XS650 padawan
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OK, I am a newb, I have owned my XS (82' Yank delivered Heritage special) for almost 8 months, aside from some carb issues which the vendor sorted (both carbs ultrasonically cleaned, diaphragms checked, needles inspected). The left cylinder has always run a bit richer than the right. The vendor assured me that the carbs were synced, the valve clearances were checked and adjusted and the cam chain adjusted (not in this order of course). I checked the cam chain adjustment yesterday, plug leads pulled and cranking it over with the electric leg. Inner shaft is less than 1 mm proud. As I haven't played with the carbs sync screw I assume that they are still in sync. The left cylinder has always had a tendency to 'pop' on decel. So much so that I had to change the vac line to a tighter fit in the barb. I have also sealed around the perished entry point for the barb on the L/H intake boot. Could the L/H richness/history of popping be part of a deeper prob with the L/H carb? I have a Clymer's manual and have been trying to get my head around it. I am trying to nut this one out but I am not sure what to check next. I have also rebuilt both air filters so that they have a uniform level of resistance (PO had two different filters in it).

Any comments?:confused:
 

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Have attached pics of the L/H carb/intake boot, note the cracks on the carb end of the intake rubber, also attached some close ups of the butterfly shaft end thingy, just wondering if this sort of weeping of fuel is a sign of stuffed shaft seal...Third pic shows the vac barb that I had to hi-temp silicone back in place with permatex as the intake boot was so rotted that the barb just pulled straight out. No prize for reaching the conclusion that new intake boots are in order. Considering the JBM ones without vac barbs, the original vac-operated fuel tap is stuffed, it runs all the time, regardless of position, could this also be one of the probs with the L/H cylinder running rich?
 
My first action would be to replace the float valve o-rings. That is number one cause of a BS34 running rich, especially since you have the foam floats which pretty much never die. A leaking throttle shaft seal will cause a lean condition. It's pretty obvious those carbs still need more love. What exhaust does it have, what air filters? Your avatar makes it look mostly stock, are the mufflers drilled or rusted out?

Plug off the vacuum line, run the petcock on prime see if that changes anything. A ruptured petcock vacuum diaphragm can allow fuel straight into the intake.
 
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Once again gggary, you are a freakin Obi Wan Kenobi when it comes to advice. Thanks so much. I'm going outside and having a crack at some of those suggestions now. Yup, I had a feeling that the carbs need some money spent on bits. I don't want to mod the bike in any significant way, so I'll be keeping the '34's as long as I can resolve the rich L/H cylinder prob. Any benefits from just swapping the vac-fuel tap out with a bolt on manual setup?

The exhausts are stock originals which came with the bike, not drilled out (if you mean drilling out the internal baffles) they do have two tiny holes drilled (factory) beneath the main outlet on each pipe, I assumed this was some sort of breather setup. No rust anywhere on these pipes other than superficial stuff near mounting points, definitely not anything that could compromise the pipes. Why the suggestion of switching the fuel tap over to prime? How does this change anything?Just curious....

Also, had an event a while back where I was throwing the bike up onto the centre stand, was in a foul mood and used a bit too much force, bike came to a halt abruptly, few seconds later fuel started pouring (really pouring) out of the back of the l/h intake boot running back towards the air box, could this be a stuck float/rooted fuel tap combo? I took her off the centre stand, played with the fuel taps positions to no effect then rocked her back onto the centre stand with another light jolt just to see if I I could rattle a potentially stuck float free. It worked, fuel stopped immediately and has never done so again. Weird...
 
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Only when it's running, switch the tap to on (effectively off) every time you shut off the engine. It's just like a manual petcock IF the o-ring is still sealing the vacuum operated port, (not likely). But really the float valve o-rings are the likely problem.
 
is there a good manual pet cock to replace the vac one? I want to run one single manual petcock instead of my vacuum setup. Adds more unnecessary stuff.
 
Just blanked off the L/H vac barb, also resealed it in the rotten intake rubber with some hi-temp/fuel proof permatex, switched the vac-operated fuel tap over to prime and took her for a ride. Popping on decel gone. Pulling a bit harder down low, idle smoother. Not sure if this is wishful thinking but she seems a bit better. Won't know about the richness issue until the engine cools down so I can inspect the L/H plug. Thanks gggary!

I will rip the old intake boots off once I have a spare week to get her off the road and order the bits required.


Cheers,

ODSX
 
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