Gas in airbox

[eddiev]

If you'r getting weak spark or none at all the fuel fill flow to the air-box.

How does that happen? I would think the unburnt mix would get pushed out the exhaust.

[don]

Thanks for the response and suggestions MG. I read all 6 pages of your post. I'll have to rule the choke deal out though, simply because the choke circuit outlet is behind (motor side) the throttle plates. I can see the gas comeing out of the needle hole. Also, if a needle was not seating properly, both needles would leak. They are hard against the slides. One would hold the other up. Besides, when you buy a set of jets or whatever, they don't come labeled to what cylinder they go to. You can buy just the needles and you can buy just the main jet.

I will check the air inlet to the main circuit for sure. That makes a lot of sense. But why would the same (1&2) carb do the same thing with a completely different set of carbs? Both have been dipped and ultrasonic cleaned. I have a feeling I'm doing something wrong.

[MacGyver]

Thanks for the response and suggestions MG. I read all 6 pages of your post. I'll have to rule the choke deal out though, simply because the choke circuit outlet is behind (motor side) the throttle plates. I can see the gas comeing out of the needle hole. Also, if a needle was not seating properly, both needles would leak. They are hard against the slides. One would hold the other up. Besides, when you buy a set of jets or whatever, they don't come labeled to what cylinder they go to. You can buy just the needles and you can buy just the main jet.

I will check the air inlet to the main circuit for sure. That makes a lot of sense. But why would the same (1&2) carb do the same thing with a completely different set of carbs? Both have been dipped and ultrasonic cleaned. I have a feeling I'm doing something wrong.

Yeah, I just threw the starter/choke out there. Yes, the needles should be all the same, the Main jets will be different - 1&4 #95, 2&3 #102.5 or outside/inside. Those were the only parts I made sure I had in the correct carb as the rest should be same.

OK, an idea here, have you checked the air box boots? If the problem does follow from set of carb to carb, it could be something as simple as part of the air box boot is completely or partially obstructing the Main air jet.

There should be a rubber spacer filling in the space in between the four air jets, there was on my two carbs. It was glued in place originally, but that had since worn out. Upon reassembly I siliconed them back in place. There are some good pictures of a disassembly of these carbs here:

http://forums.somethingawful.com/showthread.php?threadid=3017242&pagenumber=1#post352764314

Unfortunatly these carbs had been modified and don't have the spacers shown, so don't take the configuration as OEM. I am not sure if that spacer would make a difference, but someone put it there originally for a reason.

Finally, your float breather hoses for each carb, are they resting on the top of the airbox? I saw a picture of a set of these carbs recently where the previous user had connected the two breather outlets together with a single hose, hmmmm....

Hope that helps.

[don]

Hello again Tim,

I looked at the photos on the link you provided but they aren't the carbs we're talking about. Anyway, airbox boots are new (beginning of last season) and when I looked in the airbox with the mirror and mini-mag, the allignment of those " shark fins" is the first thing I checked. Everything looks symetrical. Yes, I have those rubber triangles installed as well. I'm sorry for the confusion about when we were talking about the main jets. Yes, the big ones go in the middle and the small ones outside. I was including the actual needle tube, (the part the mains screw into), with the main jets as an assembly. And finally, The vent tubes are indeed 2 different tubes routed over the airbox.

I do appreciate your thoughts and help. Thank you ........a lot. Open to more of it. Like I said, I think I'm just missing something silly.

[cyclefvr2]

im betting its a wore out needle and seat! thats what i have been through,take a look at it ,and turn carb upside down, blow through the fuel line and see if they leak air -hopefully the problem will be solved

[don]

Cyclefvr, new ones installed. Review post #29. that's where I am now.

Thanks for the input though.

[MacGyver]

Hello again Tim,

I looked at the photos on the link you provided but they aren't the carbs we're talking about.

The author tears apart three carbs (or more, there are three pages of posts and that was just page one) in that post, the BSW30SS is the second one, about half way down page 1 of the posts. If you don't have the BSW30SS, then I likely cannot be of much more help as this is all I have experience with on my 1983 GS550E.

Were you able to do a wet check of the fuel height? I would still be tempted to swap the needle tube and perhaps the needle and slider just to verify that the problem does or does not move with those components.

It is a puzzling problem.

[don]

Hi Tim,

My error. Ididn't scroll down enough. Yes those are the same carbs. I think I will look into the whole what needle works best in what hole thing. Thanks again.

[don]

OK. Did every combination of slide and needle with main jet possible and got the same result. #'s 1 and 3 suck gas up from between the needle and main jet. What next fellas.....????? This thing is giving me fits!!!!!!!! I'll try to get some sort of video of what I'm seeing for you guys if i can. Really, it looks just like a float needle being stuck open or the float hight is too high, but it isn't. I have the float hight set 1/8 inch leaner than the lean limit and it still does it. All of the jets are still submurged in fuel, but the floats are set supre lean and still looks like the floats are overflowing the bowls, but I am 100% positive the float needles are shutting the fuel off. WTFUDGE??????????????

[chef1366]

Your needle jets are worn out.

[don]

Hi chef,

The needles, or the needles, the jet tubes and the jets? And can you be sure? The bike ran great for like 1-1/2 seasons as is, then started running like crap over like a week or so then more rapidly. Don't mean to be a jerk, just wat to be sure. Made a lot of changes so far on the premmis, " what the heck else coud it be" to find out "none of the above".

Again, I really don't want to sound like a pin head. Just looking for some help with a problem that does not fall into the catagory of the usual cures. Both sets of carbs that I have are in pretty good shape from what I've seen. And I have access to ultrasonic cleaners etc. Just trying to get some help with an unusual problem from the experts.

[chef1366]

Hi chef,

The needles, or the needles, the jet tubes and the jets? And can you be sure? The bike ran great for like 1-1/2 seasons as is, then started running like crap over like a week or so then more rapidly. Don't mean to be a jerk, just wat to be sure. Made a lot of changes so far on the premmis, " what the heck else coud it be" to find out "none of the above".

Again, I really don't want to sound like a pin head. Just looking for some help with a problem that does not fall into the catagory of the usual cures. Both sets of carbs that I have are in pretty good shape from what I've seen. And I have access to ultrasonic cleaners etc. Just trying to get some help with an unusual problem from the experts.

The emulsion tubes (needle jets) can oval out and allow gas by the jet needle. The needle can also wear out but I haven't personally seen this.

[don]

I guess I'll try that, no other normal stuff has worked so far. Good thinking.

[don]

OK fellas, here we go,

First off I have to apologize to all I may have offended by contesting their suggestions. Second, I humbly bow to the GS gods of this site.

Now that that's over, the winning answer is ................. the valve on the tank. If someone had told me the following, I would have taken it with a grain of salt and went on my way. I wouldn't have believed it if I hadn't seen it myself.

I made sight glasses for the bowls so I could see what the fuel height was when the carbs were overflowing. If the fuel level was up when they were overflowing then I would know to look at the fuel delivery, if the fuel level was good when the carbs overflowed then I could eliminate the fuel delivery.

I started the bike and let it warm up. I hear it sounding a little ritch and the fuel level was indeed higher than when I started. I don't even know why I decided to do this, but I turned the fuel valve to PRI. When I did that, the fuel level returned to it's original height. I turned the valve back to the RUN position, and the fuel level started to rise again. To take what I had seen one step further, I removed the tank and put on my 1qt bottle that I use when I run the bike to tune it. I ran a whole quart of gas through it while monitoring the fuel height. The fuel level never changed. I pinched the fuel line off to stop the fuel flow and let the fuel level drop then let it go to see if the level returned to the same place of if it would "wander". It stopped at the same place every time.

I have taken a couple of short rides (40-50 miles) with the valve in the PRI position with no issues. I have put it in the RUN position a couple of times to see if it would act up, and sure enough, it does.


Once again, thank you all for all of the suggestions and help. I am truly grateful for it.

Don

[81gs1100]

I read earlier in you rposts that you turned the petcock on "pri" and the problem stopped, then rebuilt the petcock and the problem came back when on the "on" position? This is the first time reading the thread, but I thought you had it solved many posts ago about the petcock, but you seemed to have set it aside as not the problem?

Im just glad its working for you now, the question I have is what did you do to give yourself "site-glasses" to the floats?