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Carb issue and gas coming from the breather....

  • Thread starter Thread starter Anonymous
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Anonymous

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1981 GS 550T

I recently traded for this non running bike. I removed the carbs and went thru them following the instructions from the web site. After rebuilding and installing new kits I got the bike running. The problem im having with the bike is that the reference carb is fouling the plug and Im getting raw fuel coming from the breather vent tube. By reference carb I mean the carb that you use to sync the other three carbs too. Ive got a good light brown color on the other three spark plugs. First thing I thought was that the petcock was messed up. I plugged the vacume hose and set the petcock to prime. It made no difference. I pulled the carbs back off and verified that all floats were set to same level (24mm) and that the needle and seat was working as it should. Ive got new boots and o-rings and have verified that there are no intake leaks. Ive closed the air/fuel screw all the way closed and noticed a slight increase in idle. I know that something is screwy with the carb but not sure what to look for based on the symptoms. Any help would be greatly appreciated.

Mike
 
Could be a stuck float needle or possibly the enrichener (choke) isn't shutting down completely on that carb.
 
removed the carb again today. Completely dissasembled and soaked in bucket of carb cleaner again. Left it for 3hrs and blew out the passages and cleaned them with wire again. Reassembled everything and reset float level and verified that the needle and seat are working. Reinstalled carb and put fresh plugs in again. Cranked it up and saw smoke coming outta right side pipe. (same side as problem carb) Could smell fuel from that pipe. It fouled the plug again. Whatever is going on it seems to be happening from the second the bike starts running.....
 
Did you sinc' the carbs with a vacuum tool? If one carb is drawing too much vacuum, that carb will run richer. Try to get all the levels so the difference is no more than 1 cm from the highest to the lowest. I personally like to sinc' at 3,500rpm.
As for the mixture screws, did you count how far out each screw was? Did you replace them as they were? It is very common for these screws to be set at different points. If you did'nt count, then you may have that carb screw too far out. You can't just set all 4 the same and consider them done.
I assume you replaced every o-ring in that carb?
Have you checked the condition of that sparkplug lead and cap?
Are the valve clearances/compression in that cylinder good?
 
All the o-rings in the carb have been replaced. Did a compression test and all
the cylinder in question was in line with the other 3. After I did the sync I adjusted each screw till I got the highest idle and then adjust the main idle accordingly. As stated in previous post Ive got a light brown color to all the plugs except the second from the right. Yes the carbs were synced with a vacume gauge. Spark plug wires and coils are in good working order and the plugs are brand new. It fouls the second from the right in a matter of minutes just running. I dont even have to be riding it.
 
Just to try to eliminate possibilities, try swapping plug leads 2 and 3. See if the problem follows the swap. Clean the fouled plug first.
 
start the bike let it run for like 1 minute then carefully touch the header pipes, dpn'y let it run to long or heat from the motor will warm a cold pipe, see if all 4 header pipes are warm. that will mean all 4 are combusting.

look at the choke plunger is it stuck open, maybe your piolet jet is pluged, try spaying every orfice in the funcky carb with some carb spray and see if you can track where the spay comes from.

have you checked each spark plug in the dark to confirm spark?
-ryan
 
I have fire to all the plugs. I reverified this. Triple checked choke to ensure that it was closed. I swaped CV plunger from carb 1 to 3. Didnt make a difference. I can tell the plug is firing cause I get smoke till the plug fouls then I get nothing. Plug is dark and dry and very sooty which means it is fuel fouled.
 
To eliminate possibilities, I would swap the 2 and 3 leads first. There could be a difference in spark that your eye cannot see.
If you're positive the carbs were cleaned/adjusted and correctly assembled, and other factors we've already covered are OK such as compression, valve clearances, etc, then you may have to start swapping parts to see if the problem follows.
If it passes the plug lead swap, then it must be something in the carb. You're either getting too much fuel in the mixture due to a worn part or not enough air due to a dirty/blocked part.
I know you say you've rebuilt the carbs, adjusted floats, synched, etc.
Do you get any fuel overflow from that carbs overflow line? Any chance for a sticking/punctured float? Try a swap. Swap the floatvalve and its seat at the same time.
Did you take apart the jet needle and any washer(s) or spacer(s)? The jet needle could be worn on "one side" and disturbing it could result in a rich mixture. All spacer(s) must be put back in the same order.
 
When I removed the carb and went thru it again I tested the float to make sure it didnt have a hole in it. Also at no time have I ever gotten fuel outta any of the overflow tubes. Ill swap the plugs and give that a try. Also im wondering if a im proper sync could give this condition. Would having the sync incorrect for the main carb cause this sever rich condition?? If not then Im going to have to start looking at the actual carb parts (needle jet) perhaps as the culprit. Thanks for all the suggestions and please keep them coming. This is getting really frustrating. Esp since Ive had a little taste of how well it can run....
 
YES, a poor sinc' job can result in a rich running carb.
If you have a carb that's drawing more vacuum than the others, then that carb WILL run richer than the others at all rpm's. I always set the mercury levels so the difference is no more than 1 cm from the lowest to the highest level. I set mine at 3,500 rpm. From your previous posts I assumed you did a good sinc'.
 
I went back and resync the carbs. This time I had the other three purposely come on before carb 3. I got all the carbs to with in 1 cm then I turned each screw in one full turn in. My thought process in doing this was that id get carb 3 to not have so much vacume compared to the others. In doing this I had hoped to lessen the rich condition that i'm experiencing. Well after doing it two things happened. The bike actually ran better and carb 3 still fouled the new plug after bout 10 min. So its back to the drawing board. Im going to run some more with plug wire 2 and 3 swapped to see if that makes a difference. I'm assuming that 2 and 3 fire on the same stroke. Is that correct?
Ill keep posting what I find. I'm determined not to let the problem beat me!!!!
 
I remember going through something similar with an old Yamaha Virago I had. After pulling the carbs several times and finding nothing wrong I put a new set of plugs and the problem was solved.

The plugs in the bike while I was having problems were also new. It was a set of ND plugs and I got too looking at them after the fact and found that one of that set of plugs had a hairline crack in the insulator that you could make out with a magnifying glass. It seemed the plug would fire when I held it against the cylinder to check it but wouldn?t fire under compression.

In talking to a could of long time mechanics later they said it was a problem that they had seen numerous times in the past but hadn't seen it much in recent years as quality control had improved in general all over the industry.

I don't know if this is your problem but it's easy to check.

Mike
 
Yes, 2 and 3 are on the same coil.
Sometimes to find a problem, you just have to start eliminating possibilities. Something like switching plug leads and plugs is simple and might work. This will at least PROVE that it's not electrical. Swapping parts inside of 2 carbs is the next thing. However, you must be sure the problem is'nt being caused by incorrect re-assembly. If you swap parts and re-install them wrong you'll never pin-point the problem.
Everything else has to be right regarding that cylinder too. Compression, valve clearances, etc.
Try the plug leads and after that, try the plugs themselves. Let us know what it does and we'll go from there.
By the way, your petcock vacuum goes to #2 right?
 
yes that is correct. Vacume goes to 2.... Carb 3 is the problem child.
 
Okay, todays update,
I switched around plug wires 2 and 3. Road the bike and still fouled the plug on cylinder 3. Ive put new plug in cylinder 3 each time I try something different and still I get the same results. Ive switched to a hotter plug this time and will see if it helps along with the resync. Compression tested the cylinders and they were all pretty close to being equal. One thing im noticing again is the raw fuel coming from the breather and the front portion of the engine. Near the front valve assembly end caps. ( the chrome caps at the sides of the front top portion of the head). Im getting fuel outta both left and right front caps. Ive plugged off the vacume port from cylinder 2 just to make sure the fuel isnt coming from the petcock. It isnt a lot of fuel mind u. Cylinder 3 is the only one showing evidence of fouling. 1,2,4 all are showing a light tan to brown spark color. Also I can turn the air/fuel screw all the way in (lean it out) and still it will fuel foul the plug.
 
I would not try a hotter plug. This is just trying to compensate for the real problem.
Ok, let's go back a little. You say the bike was not running and you rebuilt the carbs. Everything is good except #3 is very rich. To this point it seems
certain the carb is the problem. Because you don't know the history of this bike's carbs, anything is possible. I'll try to mention as many idea's as I can, even if it's likely you've already checked it out. I don't have as much experience troubleshooting CV carbs but I'll do my best.
Is there any chance the carb is not stock? Does it look identical?
Did you replace anything regarding the jetting when you installed the rebuild kit? What parts did you replace? Are you sure every jet or part was identical to the other 3 kits? Are you certain all the parts that were NOT replaced are identical to each other and in similar condition? If all of this checks good, then you know you have all the right parts and all 4 are in good condition. O-rings should get special attention.
Next would involve adjustments and how things were re-assembled.
After cleaning the carbs, did you use compressed air to verify every passage is 100% clear? Even a partial blockage can cause problems. Give special attention to the pilot circuit. Are all jets tight? Is there any possibility you assembled the jet needle wrong? Are any spacer(s) or clips in the same order as the other carbs? Are the needles adjustable or fixed? Are all plates or springs in this area assembled the same as the other 3 carbs? Could you have put something back "upside down"? Is the rubber diaphragm in good shape and properly seated? I know you've set the floats and your float valve needles and seat sound like they're OK. You've also checked the choke plunger. Your mixture screw should be set similar to the others. Is this mixture screw IDENTICAL to the others? Your 2 float bowl vent lines should be clear. You say the carbs were synched well. On a bike that was not running, your rubber manifold o-rings should have been replaced and coated with hi-temp' bearing grease and torqued to 6 ft/lb.
You'll need to change that oil ASAP. If I can think of something else, I'll post it.
Good luck :) and let us know what you find.
 
Okay,
Whelp today has brought about some interesting developments. I pulled the carbs back off today and went thru them again. Again I didn't find anything messed up or outta place or missing. So I went back to looking at other possible causes. Well I decided to do the compression test again and went to grab my old tester. Thats when I noticed something funny. The needle on the tester was stuck at 118psi. After banging it around a bit I got it unstuck. So I went to Autozone and picked up a new one. Whelp cyl 1 was at 121 psi. Cyl 2
at 95 psi. Cyl 3 at 59 psi. Cyl 4 at 120 psi. I rechecked again and got same readings.Thoughs numbers are with the throttle closed. With the throttle open cyl 3 reads 89 psi instead of 60psi. So I guess we have found my rich condition on cyl 3 cause. This wasn't the answer I was hoping to find. I'm going to fill the cylinder with compressed air and try to listen for were the air is leaking out. I believe it to be a valve problem and not a compression ring . Keith thank you so much for your input, your time, and your patience. By the way bike has only 22,000 miles.
 
Well at least you'll find the problem and get it fixed soon. :)
Live and learn. :roll:
 
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