sticking carb trouble

[HobbyMan]

79 XS1100F
I did a search for sticking carbs, but did not find anything. It seems that my number 1 carb is sticking. I synched them properly, but that does not help. When the engine is running lower than 900 rpm the vacuum drops to almost nothing. WHenever it is over 900rpm is skrockets way above (about 7 inches on the merc scale) all of the rest untill about 2500+ rpm when it becomes normal. When I try to rotate the shaft on the outside of the carb body, it will go down. What would cause this to happen? Could the butterfly be bent? If the shaft seals are worn, could the shaft be misaligned? Should I just get another carb set? Rock on guys and happy holdidays/ Chrismass

[Hired_Goon]

My first guess would be a leak in the intake boot. If your butterfly was bent it should allow fuel and air to still create a vacuum. Unless the carbs are way out of sync and number 1 is totally closed. SHould still have vacuum though.

Have you checked the valve clearances??

[trbig]

Something is wrong with that one carb. I doubt a butterfly is bent. You are supposed to synch them at 1100 rpm, but if you have something on the carb causing a lean condition, it will do that. I would check your carb holders first .(Spray carb cleaner around on it and see if the rpms change) You might even have a tear in the holder gasket you didn't know about. I know you guys have the carbs off quite a bit, do you leave the holders installed? It's alot of prying and twisting to get the carbs in with that stock airbox. You guys have several to play with.. if I were you, i would just take another holder off another bike.
I guess there's the possibility of some small piece of something might be holding the butterfly open.. but it doesn't seem like it would have synch'd well if there was. If you have to take them off again (The carbs) just look at them on the bench and make sure that #1 moves freely and not binding on the carb (Bent butterfly shaft.)

Anyway... just my 2 cents.


Tod

[skids]

If you soaked the carb in cleaning solution, the seals can swell and the butterfly plate motion can be sticky.

[HobbyMan]

well the carb boots are "almost new. My dad got them about 5-10 yrs ago when the bike was packed away. They were never used untill this last summer. They look brand new. It is probably the expanded shaft seals. I know they leak. Idiotically, before I knew what carb dip did to them, they got soaked for an hour this summer. Judging by vacuum, it is acting like it isn't closing all the way and not opening unitll sufficient force is applied to the shaft. Should I just replace all the shaft seals? I just cleaned the carbs and it did not fix the problem.

[skids]

If the seals are bad, yes, replacing them is best. I brought some back to life after a carb soak once, by soaking them in mineral spirits and working the action back and forth. The carb soak that I used (Berryman's?) does make nitril butyl rubber parts swell noticably! That is a lot of work on disassembly/reassembly. WD40 might get in there and perhaps displace the chemicals, but it might make a mess. Speaking from one of my experiences, removing the throttle plates to get the shaft seals out can lead to some real headaches...those little bugger screws are lock-tighted and you can lose threads or strip screwdriver holes. I would try a mineral bath first and leave the throttle bodies attached to the bracket, but just remove the tops and bottoms. Make sure you blow out all of the liquid from the passages (if you try it).

Originally posted by HobbyMan
Judging by vacuum, it is acting like it isn't closing all the way and not opening unitll sufficient force is applied to the shaft. Should I just replace all the shaft seals? I just cleaned the carbs and it did not fix the problem.

[skids]

PS, make sure that there is no interferrance with the motion of the linkages. Look for clearance with hose clamps, carb boots, tubing, etc.

[chopwatchagot]

wd40 may swell the seals also. It will swell the o-rings in air tools to twice their original size rendering them useless. Don't ask how I know.

[skids]

Oh boy! Scratch the WD40 and use mineral spirits. I know that worked for me.

Originally posted by chopwatchagot
wd40 may swell the seals also. It will swell the o-rings in air tools to twice their original size rendering them useless. Don't ask how I know.

[HobbyMan]

Gonna try that this weekend. What a pain. I just got them cleaned and put back in. Now to pull them out again. I think that I will just pick up another set on ebay, rebuild them, and in the mean time get these working 100%. Makes you think twice about owning 5 XSs

[trbig]

Makes you think twice about owning 5 XSs

I agree with you... because what a guy REALLY needs is at least 6 or 7 of them!

Tod

[walter1970]

Well if your having carb trouble hobbyman then I am the guy you want to ask since I am very, very experienced in this field. First off,Get a hammer, a few nails,,, Yeah, Like I know what Im doing,,LMAO!! I keep threatning my carbs to work right but they just laugh in my face! Hope you have a great Christmas!

[HobbyMan]

Yeah, that never seems to work I tried yelling at them to get them to work. No results. I feel like many other people do about their motorcycles, Have you seen Stephen King's Christine? Treat her nice, or you don't know what will happen next. "You know what happens to the sh**ers who don't." I think that is one of the all time best movies ever made. I wish that my motorcycle would fix itself. I am getting another set of carbs to clean up and put on from andreas. While the other carbs are on, I will have all the time to completely dissasemble the carbs in question. This will also give me some time to pull off my dad's fairing and polish it. While it is off, I will check/adjust the valves etc.., Anyway, Merry Christmass to you too.