BBBBBB Tune up troubles.... HELP please

[proctor1]

I recently (last weekend) did a carb sync and color tune to my 79 XS11 special. I have a studder "bbbbbbbbb" at almost every RPM range while accelerating, except arround 3,500-4,500.
What I've done:
I started with a carb teardown (very thourough cleaning)and rebuild .
After finally getting the %$#@&* octypus reconected she ran great from 1/4 throttle to wide open but didnt have the quick throttle response I know shes capable of.
I traveled to a fellow XSers to do a proper sync and color tune(thanks again Ross).
During the return trip home I had great idle and low RPM response but serious studder at RPM over 4K. Now I'm scratching my head.
During the return trip my clutch cable snapped so I replaced it. When I took the first ride with the new cable it felt like the clutch was slipping so I made an adjustment. OK... still studdering. What the #$%^.
I pulledthe plugs and discovered 1 and 2 are black as night 3 and 4 are the way they should look. So, 4 new plugs and she seems better but I still have the studder "bbbbbbb" when I accelerate.
O-yea I replaced all fuel lines with new and made sue to follow the routing diagram.

Is it possible my clutch is in need of serious repair or is it more likely that i need to colortune with the new plugs in, OR is it likely that my $%^&#@* octypus is not working properly.
Please help, I'm not sure what to check next. Thanks for any and all help.

[TopCatGr58]

Hey Proctor,

Aside from Ross, no body else here has seen it, so....although we know it's a 79SF, we don't know if you have done any other mods to it...Intake,ie. filters, vs. OEM box, and Exhaust...stock vs. aftermarket??

It ran okay before the carb teardown???? Are you new to this bike, or have had it a long time, has it sat a long time, etc.??

1-2 have fuel in common not electrical, and your clutch wouldn't cause this, so it's out of the equation for now.

IF you have the OEM air box, are the UPPER bowl vent tubes connected to the air box nipples, and are they OPEN...get clogged with oil, debris etc.!? Secondly are you sure you have the Octopus connected/routed correctly??? There is a diagram in the tech tips...front hose from Petcock goes to the line that has the "T" fitting because that's how it can bypass the Octy when you put the petcocks on PRIME. The rear spigots go to the Octy Valve assembly, and then it's routed BACK into the line that goes to the "T" fitting, and then down to the LOWER "T"s on the carb bodies!!

You say thorough cleaning....as in removing ALL jets, pilot screws, floats, valve needle seats, main jet needle/emulsion tube, vacuum slides, etc., and spritzed carb cleaner thru ALL orifices to ensure it flows thru the pilot jet tower, pilot jet screw tower, and out the small holes on the upper inside of the engine side of the carbs???

Black plugs usually indicates too rich, where did you end up Colortuning the pilot screws...what settings?? Finally, did you secure the sealing screw on top of the pilot jet tower....or did you have rubber plugs....both of which could have come loose allowing way too much fuel thru the pilot jet since it's coming directly from the bowl instead of thru the main jet tower and it's sharing tunnel!?
T.C.

[prometheus578]

"Man, that T.C. is thorough."

You may have several unrelated problems.
Ok, you have something going on that's making plugs 1 and 2 loopy.
As T.C. mentioned, it's not electrical... at least from a standpoint of pick-up coils or brain box. Only electrical left would be the individual plug wires or the two plug caps... firing intermittantly on those two cylinders, fouling the plugs.
Fouled plugs that fire when they feel about it would give you that stutter.
T.C. pretty much covered the carb issues.
Or.. you could be having clutch issues, and the fouled plugs are just incidental.
Clutch could be.. well, maybe not slipping, but grabbing, hence the stutter.
What kind o' oil are you running?

[proctor1]

bbbbbbb

Top Cat I did clen every orofice thoroughly. Dissasembly and reassembly was completed 1 carb at a time so each went back together the same way. As for mods I have a 4 to 1 exhaust with no baffel (yea its very loud but i like it like that) and I have a stock air box with a K&N filter. The The upper bowl vac tubes are clear (I think) but I will be double check along with cleaning the filter. I cant believe I didnt factor air flow into the basic equation.
I have about 50 miles on the new set of plugs and will inspect and report back before next run.
Prometheus why did you ask about my oil ? I did an oil change a couple hundred miles agoe right before fine tuning. I was fearful that gas had gotten into the oil from a sticky float . I went to get oil but the bikeshop was closed on sunday so I put in Penzoil SAE20W50. Please let me know if I have a big mistake or better yet please tell me I havent.
Thanks guys for your input, please respond back. Thanks Proctor

[prometheus578]

Well, the oil question.
Sometimes, a synthetic oil will allow clutch slippage.
Automotive oils are OK, such as Castrol 20w50... but stay away from any oil that has "added Friction Modifiers".
Too slippery for our wet clutches.

[mason79]

how do you know if oil has friction modifiers?

[TopCatGr58]

It'll say so in the lower half of the API/SAE label like this!!



Castrol GTX does NOT have anything written in the lower half of the circle!!
T.C.

[mason79]

it say's "energy conserving" is that what i'm looking for?

[prometheus578]

If it says "Energy Conserving", yes, that's what you're looking for... SO THAT YOU DON'T USE IT!
Too slippery.

[mason79]

okay, checked the bottle no word's like that thanks, prom

[proctor1]

bbbbbbb

Great news.

Changing the oil had a pronounced effect on preformance, thank you soooo much.
Plugs from 1st and 2nd cylinders are fowled again though. When I checked for clean nipples (they were clean) and put everything back I discovered that the vaccume line from carbs 1&2 to the airbox was way too short and may not have ben completely connected. Would this cause 1&2 pluggs to turn black ?

I remember that I the last thing I did after reassembling the carbs was to adjust the float level in 1&2 (made fuel level higher). If the replacement of the short vac line still produces black plugs on 1&2 I probably need to reset the floats dont I?

[prometheus578]

"Well, let's see..."

Interesting.
I don't think that the short vent line would be the problem.
Yes, having one vent line connected to the airbox(which causes a slight vacuum) and the other open would cause an imbalance in the carbs... allowing one set of floats to move just a little bit freer.. the difference would be infinitesimal. The carbs affected... would have an imperceiveably higher fuel level.
I think it just happenstance that the hose in question belongs to #'s 1+2 and the plug problem is also #'s 1+2.
I don't believe that this is the issue.
Now then... how does one adjust the float level... after reassembling the carbs?
Either way... this is probably then a float level issue.
How to demonstrate the importance of the float level?
I shall use, from personnal life, a quick story that demonstrates the technical aspect of things.

I finally got... after weeks of begging.... a date with that "Susie" from the Free Clinic (she who gives the shots)
Decided to take her out for a fancy dinner.
So... there we where... sitting, making small talk... gazing into each other's eyes.... only the two of us alone in our own little universe... (though there were other couples around us, also eating their Whoppers and fries)
Anyway...
I guess she was trying to impress me... seductively demonstrating, on the straw from her soda, her artful tongue techniques...
Anyway... what happened was... she blew across the top of her straw... and I got a faceful of sprayed diet Pepsi.
" Why... you cute little carburator...", thought I.
For me, being not only a chick magnet(maggot), am also an XS Guru Extraordinaire... and I know how carburators work.
Ya see... air rushing over that little tube that sticks up in the carburator.. draws up fuel from the float bowl which then also sprays out.
"Susie", well versed in all things carbonated, but not carburated, didn't realize that the higher the initial level of the soda... the easier it is to be drawn up.
The same with fuel levels in float bowls. The higher the fuel level(based upon the float setting), the easier it is to be drawn up by the vacuum of the air passing past it.
Long story short... (Yeah, like I ever do that)
A float level set too high... will cause a rich condition... and will foul plugs.

[proctor1]

Thanks for the analogy. I can relate to the date at the home of the whopper with the girl from the ....yea what ever.
Question (to which I will have my own answer tomorrow) if the vacuum line between the carbs and the air box were not connected would the imperceptible difference become more pronounced?

[prometheus578]

Nope.

Many people with pod filters just leave those lines open... or put little air filters on them to keep the bugs out.
The vent is just to allow for air changes, as the floats and fuel levels rise and fall.
Many older bikes just vented to atmosphere. The tube to the air filter is sort of a fuel vapor recovery system... emissions, ya know.
Infinitesimal... Imperceiveable...
From an engineering perspective, there would be a difference.
In the real world where people don't have "pocket protectors" and pointy heads... there would be no difference.
Now then... if you think you're clever'er than an engineer and just decide to plug those vent lines...
When the fuel level rises, the floats try to rise to shut off the flow, as things should be.
No vent... the air gets trapped... the floats move upward into the air pocket, but they can only move so far, that air becoming compressed.
One loses that nice give and take between shutting off the fuel and float bouyancy issues.
You'll soon have fuel running out of your airbox, as the floats can no longer rise enough to stop the flow.

[proctor1]

I see oh wise one. New tube on vacuume line, a quick 3-4 mile ride and I can see the black buildup beginning on #1 plug again. I'm sure #2 matches. I will pull carbs Sunday and re set float level and report back. Thanks for all the help.