Too much vacuum???/Colortune issues

[KA1J]

I did find that 3 and 4 did not have the small washers and O-rings on the idle mixture screws, so I replaced them with some off of a parts bike. I then set all of the idle mixture screws at 1 1/4 turns out, which I read was the stock setting.

It is possible the O rings and washers remained behind when you pulled the mixture screws and now you have two layers of o rings & washers on the mixture jet? With my carbs the PO had tightened down #2&3 mixture screws 100% of the way down and with great force. I had to use a pick to get them out.

It sounds like you have done a thorough job of cleaning the carbs but perhaps along the way the carbs were exposed to carb cleaner and if so, the rubber components could have been damaged. There are O-rings on each side of each butterfly which will be damaged by carb cleaner and if they were never replaced, they're 30+ years old and may have become brittle and leaking or cracked. If so, your idle will never be controllable.

These O-rings are readily available but will require separating each carb body to get to them, at which point you will need to reattach & resync the carbs.

Something to do over the winter and something I neglected to do when rebuilding my carbs this year. Mine aren't leaking but I'm going to replace them anyway because everything else was replaced and these old O-rings will be the first parts to fail.

Also, if you get mercury in your engine, that's not good cause mercury and aluminum don't play nice.

[mr_misfit138]

It is possible the O rings and washers remained behind when you pulled the mixture screws and now you have two layers of o rings & washers on the mixture jet? With my carbs the PO had tightened down #2&3 mixture screws 100% of the way down and with great force. I had to use a pick to get them out.

It sounds like you have done a thorough job of cleaning the carbs but perhaps along the way the carbs were exposed to carb cleaner and if so, the rubber components could have been damaged. There are O-rings on each side of each butterfly which will be damaged by carb cleaner and if they were never replaced, they're 30+ years old and may have become brittle and leaking or cracked. If so, your idle will never be controllable.

These O-rings are readily available but will require separating each carb body to get to them, at which point you will need to reattach & resync the carbs.

Something to do over the winter and something I neglected to do when rebuilding my carbs this year. Mine aren't leaking but I'm going to replace them anyway because everything else was replaced and these old O-rings will be the first parts to fail.

Also, if you get mercury in your engine, that's not good cause mercury and aluminum don't play nice.

I'm certain that the o-rings nod washers on 3 and 4 were gone. I had to pull them out of 1 and 2 with a wire with a small hooked end. I replaced them with the ones from the parts bike and everything's working fine now. I opened the butterflies up to the bread tie diameter, and that got the bike idling at about 5000 rpm, so I scaled the thumb screw way back down to 1100 and re-synched, then Colortuning went fine, then I re-synched again, and the thing's running better than the day my dad bought it off the lot.

However, now I'm having similar with my own '80 SG. The Colortune ring is really faint, and doesn't change across the entire range, except for when it's all the way in only the spark is visible. It also sputters and backfires at idle a little. I had the same results both with 45 pilot jets in all 4 and pod filters, and 42.5 pilots and a drilled out airbox/K&N filter. All of the butterfly o-rings look to be in good shape, the idle mixture o-rings also look good, and I've always been careful not to get carb cleaner on rubber parts. Everything else with the carbs is in identical shape to my dad's bike, that's running perfectly now. The only difference is the airbox is drilled out. I was going to try swapping that out for a non-drilled bottom and stock filter, but that's the only obvious difference I could see. I'll double check the butterfly o-rings, though. Where did you get yours from?

Also, could the timing being slightly off cause these symptoms? My bike still has the sheared off bolts that came stock, so it's never been adjust before, but I'm guessing that it could be off a little. I've got a timing light, but I've read the the tach on the bike's not accurate enough, so an auxiliary tach should be used. Do you think that this is necessary?

Also, my vacuum gauges use a blue non-toxic liquid instead of mercury, so it shouldn't ruin anything, but I'm pretty sure I haven't let any get sucked in.

[KA1J]

Cool that your dad's bike is running well.

I bought mine from Len Chacal who has about everything ever made for the XJ series of bikes. He doesn't have everything XS11 but engine wise he seems to. He does have the carb parts. I'd send him a request at info @ xj4ever.com (removing the spaces) Here's the first page of his catalog: http://xjbikes.com/Forums/viewtopic/t=14561.html Also, Mikes XS at http://www.mikesxs.net/ probably has them too, just don't tell him it's for an XS11. You'll have to look for your carb parts & select wisely.

As to timing, someone with more knowledge about that will have to reply, I just don't know what the chances are your timing is off. I suspect it's OK...