Finicky 86 GS550

[rtuite]

Well, I have been riding most of the summer, but not well. My bike needed some carb work, and I knew it. It was spitting large amounts of fuel from the back of the left hand (if sitting on it) carb body (where the airbox should hook up, but the boots are warped). There was a lot of backfiring and the bike would only run on 2 cylinders for several miles when cold, even when choking. Also, there was really not much power, even when it warmed up. It was also overflowing the bowl if I left it on the "prime" setting on the petcock.

Yesterday, I decided to pull the carbs and a friend and I spent about 4 hours cleaning, checking, and tuning the carbs. Several of the jets were clogged and there was a lot of varnish and crap in the bowls.

After everything was cleaned and back together, I was still having problems. The bike still ran weak, backfired a lot, stalled at idle, and various other problems. It was doing the same thing before, but a little differently. The fuel spitting seemed to be fixed, but I really did not run it long enough to really be sure.

Some questions were answered, some were not. I left a small gas tank (from a snowblower) hooked up overnight to see if the bowls were still overflowing, and found a puddle of gas on the garage floor this morning. Before, it would just run right out, but now it is better. Is this normal?

Also, I may have found the source of the running problems. The diaphragm in the petcock has several leaks, and was allowing fuel into the vacuum line that opens it. If I can fix the leaking when on "Prime" issue I can install an aftermarket Pingel petcock that is simply on/off instead of this silly on/reserve/prime thing Suzuki has going on here. Is this problematic, assuming the leaking fuel when on prime is not normal? I will have to mildly modify the tank, but I would rather do that instead of dealing with the diaphragm thing in the petcock, and I can install an out-of-tank fuel filter.

Lastly, I am open to suggestions for other reasons that may cause what I am experiencing. Ideas?

Thanks for any help,
Tony

[Calvin Blackmore]

Well, I have been riding most of the summer, but not well. My bike needed some carb work, and I knew it. It was spitting large amounts of fuel from the back of the left hand (if sitting on it) carb body (where the airbox should hook up, but the boots are warped). There was a lot of backfiring and the bike would only run on 2 cylinders for several miles when cold, even when choking. Also, there was really not much power, even when it warmed up. It was also overflowing the bowl if I left it on the "prime" setting on the petcock.

Yesterday, I decided to pull the carbs and a friend and I spent about 4 hours cleaning, checking, and tuning the carbs. Several of the jets were clogged and there was a lot of varnish and crap in the bowls.

After everything was cleaned and back together, I was still having problems. The bike still ran weak, backfired a lot, stalled at idle, and various other problems. It was doing the same thing before, but a little differently. The fuel spitting seemed to be fixed, but I really did not run it long enough to really be sure.

Some questions were answered, some were not. I left a small gas tank (from a snowblower) hooked up overnight to see if the bowls were still overflowing, and found a puddle of gas on the garage floor this morning. Before, it would just run right out, but now it is better. Is this normal?

Also, I may have found the source of the running problems. The diaphragm in the petcock has several leaks, and was allowing fuel into the vacuum line that opens it. If I can fix the leaking when on "Prime" issue I can install an aftermarket Pingel petcock that is simply on/off instead of this silly on/reserve/prime thing Suzuki has going on here. Is this problematic, assuming the leaking fuel when on prime is not normal? I will have to mildly modify the tank, but I would rather do that instead of dealing with the diaphragm thing in the petcock, and I can install an out-of-tank fuel filter.

Lastly, I am open to suggestions for other reasons that may cause what I am experiencing. Ideas?

Thanks for any help,
Tony

the fuel is ending up on the floor because the petcock does nto stop its flow and the needle valves are not seating fully ( or are worn---look for a groove)

If your carb boot is warped and not sealing you are alos gettign more air ot one carb than the other which would make things run god awful
they aint cheap but they are essential to proper running.

new oem petcock new oem boot new oem needle valves are in order.

[Texas Don]

You'll probably get many more informative responses than mine, but a couple of your problems sound familiar. Generally, it is thought that rebuilding a petcock with a new diaphragm is a waste of time and money. It will still leak. The petcock design is supposed to flow fuel continuously in the "prime" position. New petcocks are still available from Suzuki and should remedy the problem. If you opt to go with the Pingle version, you will just have to remember to shut it off each time that you stop the engine. Z1 sells an adapter plate that will prevent you having to modify your tank. Gas running out of the carbs is not normal. You can pretty much deduce that your float seats and needles are leaking. You really can't plan on getting by with the Zuke carbs by just giving them the once over. You have to totally tear them down, run them through a soak in carb cleaner, replace all the o-rings and intake boots, plus boot 0-rings that seal against the head, and carefully reinstall and sync them to stand a chance of getting it right.
Additionally, the valve clearance adjustment using the correct shims is critical on these bikes. Unless that has been done first, you're just spinning your wheels. It is a couple of days hard work to get all of this done properly, but when done correctly, all of those annoying problems go away and riding is fun again.
Texas Don

[Larry D]

Welcome !!

Sounds like you need a new petcock and new o-rings on the carbs. You can get the o-rings here.

http://www.cycleorings.com/

The carb rebuild series is on the homepage of this site. It should take about four days (not hours) to do it properly.

Good Luck !!

[seuadr]

make sure when you have the boots off, check all the o-rings in the boots/between the boots and the engine. 99% chance you will have to replace them. it's very cheap and very easy and that, combined with your boot sealing to your airbox properly will make a huge difference.

the other question is, when you had the carbs apart, did you clean the pilot circuits?

do you have a 2 carb setup? i have a friend that has an 85 and he was having lots of problems with it running, with what we believe is a factory 2 carb setup. he cleaned out the carbs, and replaced all those boots and orings and was in business.

[rtuite]

Sorry, I left out a ton of details on the bike. It is a 1986 with the dual factory Mikuni carbs. I believe I do need to go through the carbs again and install all new rubber and float seats. Last time we did it, we did strip all of the individual parts off the bodies, cleaned all the jets, pilot circuits, and everything. I think I did notice a little ring where the float needle seats, but I did not think it was severe enough to cause it to leak.

Assuming I rectify the issue causing the poor seal, should the carbs still overflow and leak fuel? I hope not, because no carb should ever leak fuel like that.

The other reason for using the Pingel petcock is because it is free. I cannot wrap a whole lot of money into this because I spent nearly $800 over the course of last fall to track down an ignition problem. If a problem arises that i need to spend a bunch of money on, I am going to have to sell the bike.

[Texas Don]

No, the carbs should definitely not overflow fuel. If the petcock and the carbs are working properly, you won't have any fuel flow when the bike is not running and you have the petcock in any position other than prime.
Texas Don

[rtuite]

No, the carbs should definitely not overflow fuel. If the petcock and the carbs are working properly, you won't have any fuel flow when the bike is not running and you have the petcock in any position other than prime.
Texas Don

Even if the petcock does not seal off, the carbs should never overflow, right?

[Texas Don]

Even if the petcock does not seal off, the carbs should never overflow, right?

Sorry, I could have made that clearer. The float needles should seal off the carbs and prevent fuel from flowing if they are working properly and the petcock isn't. Except, on 4 carb models that is. Fuel will evidently flow through carb 2 if the petcock diaphragm is leaking even if the float needle is sealing on that set-up. That little tiny ring that you observed on the needle point is what's causing your misery now. Replace them if they show any wear at all. Try thinking of it as a water hose with 2 faucets in series. If the first faucet (petcock) seals off the flow, you won't know that the second one (needle valve) is leaking until it causes other problems. The reverse is also true. If the second one (needle valve) is sealing off flow then you won't know that the first one (petcock) is leaking. What has probably happened in your case is that one or the other has been leaking for some time. You only observed the problem because the other one finally gave way. Clear as mud, eh?
Texas Don

[BassCliff]

Greetings and Salutations!!

Hi Mr. rtuite,

Dual-throated carbs? Sometimes I think those are more trouble than 4 regular carbs. Anyway, let me do my "welcome thang"...

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[LeeGS550E]

Its been a while for me, but I believe the float valve on the siamese mikuni's should shut off the fuel just the same as individual mikuni's. I'd recommend buying the correct replacement petcock and also replacing the float valves. Spend a few weeks making yourself avoid the trappings of our world like iced mocha's and Quizno's subs, and you'll have saved enough to get the proper petcock. Modifying for a pingel seems a pain in this case (just my opinion), and when everything's working right, the Prime/Vaccum settings on the stock petcock are kind of nice. Again, just my opinion.

As far as everything else goes, sounds like you've cleaned them well enough, but you definately want to replace the o-rings under the intake boots, and the o-ring around the float valve body. The only other o-ring in there is the mixing screw - better get that one too!