Throwing in the towel

[Grimace]

Ok, the basics. 79 xs11standard. 4-1 exhaust and pod filters, carbs are jetted for both with 42.5 pilots and 140 mains.

I have done everything I can think of, including all of the tips and tricks on the carb faq. I can't get these carbs working.

I tore them down (completely) again the other day and replaced the throttle shaft seals. While they were apart, I blew carb cleaner through the bodies and all orifaces. I re-set the idle air screws to 2 turns out from lightly seated. I inspected the diaphram slides for holes. I put the carbs all back together, and did the pre-sync with a bread twist tie like in the faq. Then I inspected the adapter boots. Still no holes that I can see. I got the carbs re-installed on the bike, and synced the carbs with a mercury carb stick.

All 4 are at 18 inches, idles great, and set the air screws by ear per the carb tricks guide. Re-set the sync, and all is well. Got on to ride, and right out of the driveway, it starts stuttering and lean popping through the air filters. I am jetted for pod filters and 4-1 exhaust. 42.5 pilot jet and 140 mains. Ride it for about 25 miles (to work) and let it sit for a few hours, then I turn the air screws in a 1/4 turn and start it up. Sounds good. Leave work and it is rich popping and stuttering through the exhaust.

All of this popping (lean and rich) happens from just off idle to about 2500 then it picks up and runs fantastic.

Get home, and don't touch anything. Next day, get on it, and it is lean popping again through the intake. Ride to work, stop at a gas station and go inside for less than 5 minutes. Come back out and bike runs perfect with no low end issues at all.

Remember, all my problems are from idle (1000 or so) to 2500 or so. Take off from a stop light about 2 miles from gas station and it starts popping from intake and exhaust, bucking and stuttering and crapping out. Pin the throttle and it stutters a little more then hits hard and tries to pull the front end.

I am absolutely at a loss. I think there is something wrong with these carbs. Anyone have a set that I can re-build? Or is there a set of smooth bore performance carbs on the market for the xs11?

Thanks
Very Frustrated Grimace.

[Ken Talbot]

If you are 100% confident in the carbs, how about looking into the electrical side of things. Perhaps something is intermittently killing spark on one or more plugs, something vibration related. Perhaps something like pick-up coil wires, corrosion where the plug caps screw onto the end of the plug wires, loose wiring connections between the pick-ups and the ignition coils, etc.

[TopCatGr58]

Hey Grimace,

Sounds similar to a sticking float syndrome. I've had one that had a broken post repaired slightly crooked, and the float would stick flooding the carb and causing all sorts of low end sputter/coughing until I WOT'd it and got into the mains and then it would light on all 4s!

Sounds like you are very close, the one time it ran perfectly in the low and upper rpms. But otherwise, the float may be sticking either partially open one time=rich, and another time closed=lean?

Hate to say it, but another trip into the carbs may be in order, checking the float and pin movement. Also was a recent post with photos about sticking float, and tangs that need bending to prevent the float from dropping too far down causing the needle valve to get caught at an angle and sticking!?
T.C.

[Hammerhead1st]

Same type of problem here...

But mine was in the intake boots. used indian head gasket maker on em, ALL probs went away. It's ugly and messy, but boy howdy it works like crazy!! It actually sucks into the holes in the boots and seals instantly. I've had no issues since applying the stuff. Try some clear silicone covering every boot completely, including where the carbs go in.seal them right to the boots. At worst, you have water tight boots to ride with. At best your problem goes away and you can ride with a grin!

[Dragon Tamer]

Grimace,

Perhaps it is not the carbs themselves. Is your vacuum advance working? You can check that easily by removing the left cover and reving the engine a few times, watch the lever on the vacuum actuator to see if it moves.
Also what you are describing could be a vacuum leak (or several) check carefully, leaks are not usually in the boots themselves but show up where they attach to the heads or in the syncing nipple caps. It does not take much of a leak to make the pilot circuits in the carbs to malfunction and that is the rpm range where the problem will show up.

[eroellig]

Originally posted by TopCatGr58
Hey Grimace,

Sounds similar to a sticking float syndrome. [...]
T.C.

IF you are having sticking problems.....

When I rebuilt my carbs, I had one float that was "sticking". Turned out that the pin from the carb valve that touches the float tang had worn a small hole in the tang. I could feel it with a dental pick. I needed to polish that "hole" out of the tang. That cured my stickiness.

Eric

[Pat Kelly]

Popping is usually an air leak, but not always.

Check:
A- air leaks
B- pick-up coil wires
C- pilot jets (correct type, K&L won't work right)

[Dragon Tamer]

Hey Pat,

You are unusually inelequint this evening, something got you down?

[Pat Kelly]

Originally posted by Dragon Tamer
Hey Pat,

You are unusually inelequint this evening, something got you down?

Not really

[oseaghdha]

I vote for pickup coils.

[Grimace]

Lotta info to digest. Thanks for the responses guys.

I have already coated the intake boots with a two part epoxy we use at work to seal fuel tanks, and it seemed to work well, but I am gonna get a new set of boots very soon.

As far as the vacuum advance, I took the cover off and started the bike. The vacuum pot works, you can see it advance the timing as you twist the throttle. But it is very jittery. Should it be smooth or does it usually have a little bit of a nervous twitch to it until you get hard into the throttle?

As far as the plug wires go, I cut the sides of the coils and installed new wires (saw a write up on this a while back). I am fairly sure it has to be a carb problem since EVERY time I touch the carbs, the problem does something different. I will do some more work on these carbs, but does anyone have a lead on some aftermarket carbs or at least a good set of rebuildable cores?

Thanks again for so much advise,
Justin

[newmaac]

Jittery vac. advance? Are you hooking the vac hose to the proper source?
Vac advance goes to #2 carb.
Left petcock goes to #2 boot.

It makes a difference.

Good luck

[Grimace]

I have aftermarket petcocks that are manual. I have my vacuum advance going to the #2 carb port, not the boot.

[mrfiznix]

Originally posted by newmaac
Jittery vac. advance? Are you hooking the vac hose to the proper source?
Vac advance goes to #2 carb.
Left petcock goes to #2 boot.

It makes a difference.

Good luck

I thought the vac house went to #2 carb body, the #2 boot went to the octy, and the rear petcock tube went to the octy? Do I have my wires crossed?

[Ken Talbot]

In all cases, the cavuum advance hose goes to the brass nipple in the body of carb #2. Mrfiznix, your "wires aren't crossed", but because your bike is a Special, it has an octopus that needs a vacuum feed from any one of the boots, and #2 is probably as handy as any. Unmodified Standards have two vacuum-actuated petcocks, each of which needs a vacuum connection to work. Grimace is running with aftermarket manual petcocks that do not require a vauuum source.