So where to go from here with the GS850 carbs.

[jlmoulto]

http://www.thegsresources.com/_forum/viewtopic.php?t=28146

Original Topic above moved to here where the discussion should be.


I'll try to summarize once more my problems and then any help you guys can give, would be appreciated. There are a few postings I have done previously trying to get this bike running. Some are irrelevant as a number of things have been done and redone since those postings.

I started this riding season discovering #3 cylinder was not firing. A compression check revealed low compression on this cylinder, which was ultimately cured by new rings and a valve adjustment.

Compression now sits at 150 even on all cylinders.

Bike will start and run on cylinders 2, 3, and 4. #1 will only start to run at higher revs (i.e. 4000 RPM) Bike sputters from a stop and doesn't even out until 60-70 km/hr

I took the bike to a second mechanic as the first guy was unable to fix the problem. (He was a friend and I worked with him to do all the work up to this point, mostly him, not me!)

We replaced the intake boots and the O-rings. The airbox has been sealed around the covers as a precaution to there being a leak there. I am reasonably cofident that I do not have an air leak. He took the carbs apart and cleaned them (although I am not 100% certain he did everything from the carb cleaning series on the homepage). The bike runs marginally better than when I brought it into him, however as mentioned the carbs cannot be synched at this point. When he tried to sync the carbs, he could not get them to be even. His response to me was that the carbs were no longer servicable. No specifics as to why just that they were worn out. He replaced a couple diaphragams from a junked set of carbs and also replaced the needles with new ones.

The question really is, do you think these carbs can be made servicable or am I better off trying another set? Is it worth spending the time to clean them myself? I certainly have limited mechanical abilities.

 

[argonsagas]

Go to the carb section on this site and read the part about cleaning the pilot jet.

You need a bristle from a wire brush and something to support it when used. an eraser, or an eraser on a pencil end, or a wine cork will do.

You also need a spray carb cleaner, with a tube nozzle.

With the pilot jet removed, grasp the jet with a pair of long-nosed pliers. Hold it firmly, but not tight, as you do want to take any chance of damaging it.

Start with the spray nozzle and blow it from the round end. A short blow should be all that is needed.

Look through it....if you see daylight clearly then you should be OK.
If not, blow it again.

Often tiny bits of junk get in there, and won't come out easily. The piece of junk may appear insignificant in size, perhaps barely visible, but it can make the difference between a carb that works and one that pretends.

If you see even a hint of shadow when looking through the ends, use the bristle and push it through carefully. Then spray it again.


While you are doing this, take advantage of the opportunity and blow out the other passages. Since your mechanic appears to have missed the pilot jets, it seems likely other cleaning issues may also have been missed.



Install a new in-line fuel filter.

 

[jlmoulto]

So a dirty pilot jet would cause my bike to behave like it currently is?

Has anyone heard of carbs that are no longer servicable?

 

[Anonymous]

From the Morgan Carbtune site:

"On older Suzuki models with CV carbs (except GSX400F) the two outside carbs are set about 2.5 - 3.0cmHg higher than the inside pair. For specific model details consult your workshop manual or the Suzuki importer. (If the airbox has been removed set all the carbs the same)."

If the fuel tank is removed during synching, make sure the vacuum hose is plugged (i.e. with a 6mm bolt); otherwise you will not be able to get any decent readings on the gauges!

Can't imagine that the carbs are no longer serviceable...

 

[SqDancerLynn1]

I would go back and start over with a mechanical sync of the carbs

 

[earlfor]

Carbs may no longer be servicable if jet needles are broken off and plugging the passages, but normally, no I havent heard of that. Did you see the original needeles that were replaced? Do you know if any of the points on the needles were missing? Why would the mechanic replace needles? Do the replacement needles have the same taper? If I am understanding correctly, three of the carbs work properly and only one does not? Do you know what the vacuum readings for the carbs were and at what rpm they were synched? did the Mech plug the petcock vacuum lead on the carb before doing the synch?

Depending on your answers, I would do my own synch to know exactly where things stood. Also, the running characteristics point to a dirt/clogged pilot, spraybar or faulty mixture setting. I dont think you need new carbs, but you DO need a new mechanic.

Earl

So a dirty pilot jet would cause my bike to behave like it currently is?

Has anyone heard of carbs that are no longer servicable?

 

[jlmoulto]

OK...here goes.

Tonight I decided I can't do anything worse than has already been done by the two mechanics that have worked on the bike before, so I took matters into my own hands and took the gas tank off, the airbox and finally the carbs. Couldn't find my manual (One of the mechanics still has it) but after about 15 minutes I had the carbs off. So I disconnected the choke, the gas line,a vacuum line to the petcock, loosened the screws on the intake rubbers and voila and the carbs came off. On the way from my sehd to the house, I managed to drop a screw on the ground. As I laid the carbs down in front of me to search for the screw, something popped into my vision (Those of you who are experts might already know what was missing from my description above). There appears to be two plastic T fittings on the carbs which had nothing attached to them. The carb series indiacted they are T vents, although as of yet I have no idea of their fuction or what they should be attached to, however I am willing to bet they are significant.

So would someone be so kind as to tell me what both mechanics overlooked and what I need to connect up?

If this is what kept me from riding all summer I will be extremely pissed.

 

[Anonymous]

Those are indeed vents, and are most likely NOT what are causing your problems.

All they do is allow air in or out of the carb bowls to make up for fuel going in or out as your engine runs.


Many folks, especially those with pod airfilters, just take the hoses off and leave it be, just like your carbs are.

If hoses are hooked up, they hook up to nothing- they just tuck in behind the airbox. (on my bike, the routing may be different on your machine)

Some folks like hoses hooked up that in the unlikely event that the bowls overflow to the point of reaching the vents, the overflowing fuel is routed away from the hot engine/transmission below.

 

[jlmoulto]

Thanks Condensr. At least I am relieved about that!!!!

So for those who said do it yourself, I am....You may entirely regret this as I have car #1 apart completely as per instructions and will be soaking in carb cleaner tomorrow.

Do I need to replace any parts while I am doing this?

How will I know if anything needs to be replaced?

You may be sorry you recommended me to take on this task myself as I will be asking for a lot of help!!!

 

[argonsagas]

You may be sorry you recommended me to take on this task myself as I will be asking for a lot of help!!!


No, we won't. Not a chance.

Many people believe in soaking carbs....in your case, I cannot think of any reason for doing so.

You have had two mechanics clean your carbs and spend some time and invest your money in parts to rebuild the carbs. Soaking them is the most likely thing for them to do, so it seems reasonable to believe they have been soaked almost to death.

Soaking, unfortunately, will NOT completely clean the pilot jets, as they are susceptible to debris of very small size. For that matter, so is the rest of the carburetor....times four.

When you disassemble the carbs be certain that all parts are kept not only secure, to prevent loss, but also separate.

Use small jars, bottles, cans, etc, to keep everything intact and separate. Mark them before doing any work so that you are sure which container belongs to which carb.

As regards the screw that fell when you moved the carbs, trying to identify it from available information would be no more than guess work.

There are small screws and bolts in several places. Check each carb carefully and be certain each has the identical parts. The most likely thing is a mixture screw, but it could be something else.

 

[bwringer]

You definitely need to replace all the o-rings.

I don't know of any other source for them besides our guru of o-rings:
http://cycleorings.com/

$12 for a complete set. Order some now!

Please, please, please be aware that many, if not most or all, aftermarket carb kits do NOT contain everything you need, often do NOT contain the correct parts, and always contain parts of very poor quality.

After struggling with incorrect jet sizes, poor quality needles, and the dozens of o-rings that simply aren't included (or are simply incorrect), I finally re-installed the original float needles, seats, and jets in my carbs after cleaning them thoroughly. The only usable parts I've found in carb kits so far are the bowl gaskets, and you can get these individually much cheaper. In fact, you can get OEM bowl gaskets for around $5 each, so why bother with aftermarket crap?

The ingredients of a successful carb rebuild are:
1. a set of o-rings from robert
2. Clean original or OEM jets, pilot screws, needles, and seats.
3. OEM or aftermarket bowl gaskets

Also note that "soaking" the carbs is only about 5% of the cleaning needed. You must ensure that every single air passage is open and clean, and the only way to do that is COMPLETE disassembly, a couple of cans of carb cleaner, and a few hours of time. Many people and shops also make the mistake of soaking carbs without removing all the plastic and rubber parts. This will destroy the o-rings or any other non-metal parts.

Can you get any of your original parts back from those idiot "mechanics"?

 

[jlmoulto]

Thanks again for the replies.

The screw I lost has been found and was merely one of the ones to hold on the airbox that I had been carrying in my hand along with the carb.

Good news, all of #1 carb is dissambled and I found nothing blocked. Is that unexpected given that the #1 cylinder I am having the most problems with?

Bad news. Disassembled #2 and everything was fine until I got to the pilot screw and discovered that someone had stripped the top of this one rendering it impossible for me to remove. Any ideas what to do or is this carb toast?

I'll leave #3 and #4 until tomorrow until I hopefully get some more direction from you guys.

 

[Anonymous]

Just a tip-

I'd been having lean mixture problems on my bike for a long time - after several carb disassembly and cleaning sessions.

Whilst I had paid great attention to cleaning all the FUEL passages in the carbs, what I neglected to pay attention to were the AIR passages, as bwringer mentioned above. The last time the carbs were off, I cleaned and cleaned and cleaned the air passages, which were in fact gummed up.

If you're a technical person, and dig theories, find yourself a factory service manual for your machine and read up on the carb theory. It'll show you exactly where the fuel and air passages are, where they go, and at what part of the throttle opening they function at. I believe there is actually a 1980 FSM circulating the net in PDF form.


Good luck! The carbs really aren't that bad, and you have the whole GSR here to support you in your efforts.

 

[Anonymous]

One more thing - you mentioned your problems started after a rebuild.

Is it possible that your valve timing is off? This might cause strange, fluctuating vacuum readings, but I'm not sure exactly. An even compression check across all cylinders, as you mentioned you have, might show that this is not possible.. One of the experts here might be able to comment further.

 

[jlmoulto]

I am assuming the timing is correct, of course I have no idea how to even begin to check that.

At high RPMs, the bike actually runs good with good pull, but nothing on the idle to mid of any sense. Seems to be flooding, not firing on cylinder #2 until high range.

I cleaned the carbs last night and two issues. Could not get out a pilot screw, but in all others it appearsed as if all air passages and jets were clear. I was expecting to find a problem, but none that I could tell.

 

[jlmoulto]

OK...advice please....I may have bad mouthed an honest mechanic (My first mechanic still sucks but just maybe I misunderstood this second guy.)

Tell me if what he is saying makes sense to you.

I went to have a chat with the guy out of frustration from the bike problems and to find out more information to share with you. He explained that in my carbs, the diaphrams won't seat. The rubber appears to be stretched. They are not smooth when they are inserted, but have "ribs" and creases in the rubber. He showed me a carb on his bench with the same problem and then showed me one that was seated "correctly". In looking at them, my diaphrams in all four carbs look like the ones he considered bad. He claimed that this would cause air leaks. His words of unservicable he said was because it would cost more to fix these then to buy a good used set. He also offered to sync and install another set for me for free if I get another set.

Does this make sense? Would the bad diaphrams cause this problem?

 

[UTgws]

I had the same problem with a pilot screw. I _CAREFULLY_ drilled a small hole in the _center_ of the pilot screw (1/8" bit i think) about half way through the threaded portion of the screw, then tapped a TORX bit into the hole in the pilot screw, and turned that sucker right out :lol: :lol:

 

[Anonymous]

I would not have suspected the carbs for a bad running condition after an engine rebuild, unless it took two years and I left them sitting around with the old gas in them. If you get a set of used carbs, they will probably need cleaning also. Try to get the best ones you can. Some or all the jets will be the wrong size. An often overlooked jet is the needle jet (your mains screw into it). They simply push up out after the mains are removed. Compare everything to the manual, not the old carbs, you probably didn't buy the bike new and they may not be the stock carbs.
The diaphrams always look bad, they have a very rough life, in a vacuum on one side with tornadic fuel and air storms on the other side. I can't really vision what they look like from your discription but the only way I see them not working is if they have a hole in them. The tops have a ridge and pretty much have to seat. The body is constantly stretched and colasped. Diaphrams are very expensive, think four of them would cost more than used carbs, so the guy was telling the truth there. Don't really know what the mechanic is saying about diaphrams, maybe Keith does if he's around? He's probably the best carb person on this site. You can purchase o-ring lube and try to straighten them out with that?

 

[opiewontaylor]

Diaphrams usually only become unusable when there is a hole or rip in them. They can usually be "cajoled" into seating with a little patience, even when old. I do agree that your best bet is to just get a used set of carbs off e-bay. After having these 2 "mechanics" work on them, it's entirely possible your carbs are now unservicable.

 

[KEITH KRAUSE]

The diaphragms should be fairly supple. No pin holes or larger cracks. We're talking possibly original parts here. A good shot of silicone spray can help.
Most often if a diaphragm is bad, the carb won't accept throttle above idle. With any cracks/holes, the compromised vacuum can't lift the piston and the throttle valves (plates) won't open.
You do have to make sure the spring/piston assembly is installed just right and the diaphragm "tab" is in the right spot.
Your problem could be a poor carb synch. Too little vacuum at that cylinder will cause your problem. At idle/slower speeds, the low vacuum is creating a very lean mixture compared to the others. Once the throttle opens up a little more there's enough fuel being drawn up to fire the cylinder correctly.
It could also be a clogged pilot circuit. If it's jetting related, it depends on what throttle position you're at when the bike acts up, not rpm's.