XS11 Carb problem

[rchambliss]

To make a long story even longer, I have a 78 xs11, the bike had sat for at least a year. So when I started to get it back to health, I bought a new battery and etc. It ran so so but backfired and sputter. I found that the tank was rusty and proceeded to fix that first. I bought a tank liner kit and installed it. Then started on the carbs, there definetly was a lot of junk in it. I have triple cleaned it and probably have done it more than that. I adjusted the floats, more than a few times, as a note did find that one float was leaking, so I fixed that. So now to my problem, the bike runs terrible, it will idle ok, but when I give it gas it bogs down. This is when it is on the center stand not trying to drive it down the road. It seems like its not getting any gas. Also to let you know when I first got the bike it would get down the road pretty good, but would backfire and had hesitation, since I cleaned the carbs I am having more problems. Anybody have a suggestion?

[TopCatGr58]

Suggestions, suggestions!!

Hey there RChambliss,

First, to save you from reiterating your bike year and model # with any new thread, just edit your profile to include that info, since there ARE differences between the years and models!

Secondly, Welcome, and let's hope "we" can help you figure it out!


Okay, cleaned the tank and relined it! You did remove the petcocks and filter towers to do this....possibly a stupid question, but you never know!? Lots of the rust particles and gunk can get caught in the petcocks passages, so you might want to take them apart if you didn't ! Are the vacuum hoses to the petcocks good, no cracks, and have you tested your petcocks, putting them to ON and then applying suction to the vacuum hose to see if it allows fuel to flow?

Backfiring and sputtering could have been carb related, but could also be electrical....have you read the Pickup Coil FAQ and repair tip? Do you have the vacuum advance hose going to the proper outlet on the #2 carb, NOT the Intake Manifold outlet? Have you checked to make sure that the Carb Vent hoses are clear and not clogged up, they are the ones just above the fuel supply "T's"?!?!

Did you use a rebuild kit for the carbs, or did you go back with your original pilot jets? K & L kits are known to have the incorrect pilot jets, too rich!!!!

When cleaning the carbs, how did the rubber diaphragms look? Did you test them for leaks before taking the carbs apart? Sliding them up and putting your finger over the curved opening on the top air filter side of the inlet bell, they should not drop, or very slowly drop, if they slide quickly down, then you've got leaks!!!

Where did you set the pilot idle screws to? 1-1/4 turns out from gentle seat? Okay, this should get you started, check and or report what you have checked, and then we'll go from there!

[thumperjsa]

Speaking of filter towers, (I never knew what they were called before. Anyone got a spare. I have a petcock on my bike that is missing the set of pipes.

Thanx

[rchambliss]

Well there is no such thing as a dumb question...... But yeah I removed everything from the tank, blocked off all holes. Removed both Petcocks, Fuel Level, I know next time how to do that job better. Anyway it worked out ok. Cleaned the tank out well, including vent tube. Like I said before, I had a lot of trash in the carbs, but not anymore. I have cleaned the carbs at least 6 or 7 times, the carbs are definetly clean. I haven't looked at anything electrical, but I will. Yeah all the hoses are connected right, I didn't check to see if they are clogged or cracked, will do that also. I didn't put any new parts in, I got the bike from my dad, he told me the guy he got it from just had a lot of work done on the carbs, so I didn't feel it was necessary to change any parts. Yeah I checked the diaphrams, no leaks there. But tell me, does it matter how fast they come down, when they fall free? I haven't messed with the idle adjustment screw, its set to whatever the bike shop set it to before I got it. I will check that to see what its set to. However, today I took off the inline fuel filters and the bike seemed to run a lot better. I guess the next thing to buy may be some filters, but since I just lined the tank do you think it's necessary? I'll let you know what happens, Thanks

[rchambliss]

Oh yeah one other thing, I think this is a "E' Model, didn't see it marked on the bike anywhere, can you educate me?

[pathfinder]

If it is in fact a 78 model (built in 77 or 78) engine & frame # starts with 2H7.

[pathfinder]

Oh Yeh

I forgot USA = 2H7-000101, Canada = 2H8-000101, Europe = 2H9-000101

[rchambliss]

Yeah its definitely a '78 , 2H7-xxxxxx, Thanks.

[TopCatGr58]

I didn't put any new parts in, I got the bike from my dad, he told me the guy he got it from just had a lot of work done on the carbs, so I didn't feel it was necessary to change any parts. Yeah I checked the diaphrams, no leaks there. But tell me, does it matter how fast they come down, when they fall free?

Hey there again,

You'll still want to check the pilot jets, and count the # of holes in the sides of the jets! Above you stated that it had some carb work prior to you getting it, if they used K&L kits, they could have put in the wrong pilot screws(known bug in those kits!), and so you could be fighting already wrong pilot jets and not know it!

You will need to do a search for pilot jets, and look for threads with K&L, can't remember exactly how many holes there are, IIRC, 6 vs. the 8 or more on the K&L's!?

The slides do drop fairly quickly, like counting/saying "1000". You can also blow into that same curved slot and see how fast they rise as well! If they don't drop quickly when you're NOT holding that vent closed, then they could be hanging up!?

As for the filters, I don't have any on mine and it's going on the 4th year after my relining! I should get some on there, have to add it to my winter todo checklist!! Were you filters new? If so, then they may be too restrictive to flow properly!?

You stated you cleaned the Tank vent tube, but I was referring to the vent tubes on the carbs, and where they attach to the air box! If they get clogged, the carbs perform poorly no matter how clean the rest of it is!!

Sounds like you're on the way to finding out what's causing the problems, let us know what you find and how it behaves!!
T.C.

[wiredgeorge]

Question... How did you check the float levels? It sounds like they are set too low. Have you syncrhonized the carbs yet? If you have BS34 CV type carbs and the carbs are sync'd, then you may have some of the slides up high when the throttle is opened and thus the vacuum will be very low and you will just bog... It is more likely the fuel level in the bowl though... It is common for folks to set fuel level by inverting the carbs and measuring but this is kind of inaccurate on carbs that are older and the tangs have been bent up a zilliion times. You should use the service fuel level spec from your manual and meausure fuel level wet for most accurate work.

[pgg]

George, what is the wet level figure on a 78?

[rchambliss]

I syncrhonized the carbs today, they all checked good. As far as adjusting the float level, I did invert the carbs. So you think that my problem is the fuel level is to low? Can you go into more detail as far as adjusting them wet? And what should it be? I saw a thread on the forum where they built a device to adjust the floats. How do you suggest to do it?

[rchambliss]

Hey TopCat, I took a look at the pilot jets, there are 6 holes total. The pattern is 1 hole then 2 then 1 then 2, around the sides, Was this standard, or should I look for some original stuff? Haven't gotten very far this week, looks like the hurricane is going to bear down on us here on the East coast, and I've been busy around the house. I'll let you know what I find.

[rchambliss]

Well I spent some extra time on this tonight, I pulled the plugs and found 2 of them that were black. From what I read this means that the Air/Fuel mixture is too rich. So would that still point to the float level being wrong? Or would it be an idle screw adjustment problem? I think I'm the problem...haha, I've worked on cars a lot, but not much on bikes, so I need all the help I can get. Thanks,

[TopCatGr58]

Hey there Chambliss,

Well, I went searching thru the threads, I remember seeing someone posting a wonderful sized photo of the Pilot jets, but can't seem to find it! Here's a picture from the tech tips about jets, and the pilot jet is in the lower left corner, it only shows 1 hole in the side, but there are 2 more on each side if it was rotated a bit, and I just looked at a spare set of 78-79 carbs I had just gotten, and they also had 6 holes, so that appears to be the standard. I think the K&L's had 8, plus they also weren't the right size down the middle!


Which 2 plugs? It's important to mention which cylinders, 1-2-3-4. The electrical system links 1-4 and 2-3, and the fuel supply lines link 1-2 and 3-4, so knowing which ones can be a diagnostic clue!

If you were pretty sure that you had the float height set correctly, then it's probably more the pilot jets!? With a rich condition, the "Float" is rising too high when right side up before it shuts off the fuel supply, and the fuel level is too high. In inverted position, measure the float height(Stock is ~25.7mm), then adjust the tang so that the floats are sitting up(inverted) 1 mm higher than they were when 1st measured. This will cause the floats to rise quicker, and shut off the fuel supply sooner, so there will be less fuel in the bowl, reducing a possibly rich condition!

Could also be the pilot idle screws, how many turns out from a gentle seat are they set!? They're on top of the carbs, next to the intake manifold! Starting point is 1-1/4 turns out.

Hang in there, you'll get it working!! I know how those Hurricanes can be, Ex-Floridian myself! T.C.