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1986 gs550ef twin carb problem

  • Thread starter Thread starter Grey600
  • Start date Start date
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Grey600

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I'm currently in the process of restoring a 1986 GS550EF (ES model full fairing) and the previous owner had put the bike away because it suddenly started running on two cylinders.
This bike is a 4 cylinder being fed by 2 mikuni carbs, and the fuel is drawn in from one carb and leads to the other. I've tested every option like ignitor coils and electrical leads but I've determined it is the carb. (The carbs were redone a year before it was put away)

The fuel leads into the right side carb and feeds to the left, but it is the right carb that isn't drawing any fuel, meaning cylinders 3 and 4 are not firing. I've opened the top and added a bit of fuel to see what would happen, it will fire once or twice but won't draw any new fuel.

This seems to be the only problem stopping the bike from running smoothly, as it will run on just two, but I'm wondering what the solution would be before I take apart the carb and have to replace gaskets. I'm thinking it is a stuck float in the float bowl but I'm hesitant about it.

Anyone have this much trouble with the twin carbs? Any suggestions? Thanks.

And just as a reference this model is the tscc engine built between 83-86 canadian version.
 
Hi I am going to read your post and make comments.
It is confusing but I think you have the hoses hooked up wrong.
 
Dismantling of carbs and cleaning them is the chief part of the mantra of these old bike.

I have never had a gasket tear on me so go ahead and carefully remove the bowls.

I found a pack of dead insects in one of my carbs once. They were dead but plugging the jets.

When you are in the carbs you cand replace all the internal o-rings with a kit from GSR member Robert Barr at http://www.cycleorings.com/

You should Also get the intake boot rings
 
Thanks for the link. I'm wondering now which hoses you're referring to, as I've only removed the fuel line from the gas tank to the carb. I'm not sure about any previous work.
 
You should be able to verify that fuel flows to both float bowls. By removing the drain screw on the one you suspect and putting the petcock on prime.

While these "siamesed carbs" scared me at first, they really aren't harder to work on than the regular carbs, other than the internal passages are more complicated and I'd hate to have to buy a new diaphragm for one.

Hang in there, you'll figure it out!
 
That bike wouldn't happen to be this one would it?
550sf.jpg


If it is , I almost snagged that one before you but the lack of an ownership put me off.......before i found out that it is easy enough to get one :(

Anyway, I just picked up an 83 the other day and it had sat for 3 years. The carbs were gummed ( as to be expected) and I changed them out today for a set from my "basket case from hell 550" that I had cleaned and rebuilt last year. The bike fired and run but it seems like only on 3 cylinders.

This is not uncommon and I suspect they got gummy again from sitting almost 9 months.....not withstanding stabilizer in the fuel. I've had this happen before and I'll bet that is what you are up against. Even though the PO may have cleaned them, you don't know how well they were done unless you do it yourself. Locally shops will charge around $300 for it so its always best to give it a try yourself if in doubt.

The first thing you can try is running Seafoam through them. Add about 1/3 to 1/2 a can in each full tank. It will smoke a bit and you may need a couple of tanks but it might sort you out.

Now as Jeep and the others are telling you a strip, dip and rebuild with fresh o-rings is the only real solution to carb issues and no, squirting carb cleaner through them does not work. Carb cleaning is easy, you can refer to the tutorial on the main page or go to the one on BassCliff's site http://members.dslextreme.com/users/bikecliff/

If you are not familiar with the 83 and up 550s, you should know that they are very prone to blowing ignitors. There are many of them rusting away for want of one as they are scarce as hen's teeth and pricey in the aftermarket. This is often as a result of overcharging and faulty R/Rs so once you get it running right you should make sure your charging system is operating properly. The Stator Papers is your consumate guide to this (main page).

Welcome aboard by the way. Cliff, our official greeter is on hiatus but someone will be along to give you the official greeting.

Feel free to PM me directly if you want any assistance.

Cheers,
Spyug
 
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spyug said:
If you are not familiar with the 83 and up 550s, you should know that they are very prone to blowing ignitors. There are many of them rusting away for want of one as they are scarce as hen's teeth and pricey in the aftermarket. This is often as a result of overcharging and faulty R/Rs so once you get it running right you should make sure your charging system is operating properly. The Stator Papers is your consumate guide to this (main page).
Click to expand...
Got that right. Mine was smoked when I bought it. Rick's Electric makes very high quality replacement regulators and alternator coils if you need them. http://www.ricksmotorsportelectrics.com/ You can find Ricks regulators maybe $10 cheaper on Ebay.

Also, good, modern batteries are hard to find for this model, at least I thought they were hard to find. We ended up getting a MotoBatt brand battery, which is a modern, sealed AGM type battery that fits perfectly and wasn't too expensive (maybe $60 - $65 shipped). It cranks like all get out and was a key component of getting this bike running right, given the amount of cranking we did to start the old girl and test those carbs!
 
Right !!!!! Same problem aswell, carbs have been ultrasonically cleaned, all jets have been blown out and checked amd poked and prodded, but still it fires on three at low revs, bought good s/hand genuine coils as the other were aftermarket ****e thinking it was electrical, i have sparks but still no 4 cylinder wail !! the floats did flood after refitting but a gentle tap sorted them out, but proved i have gas in both floats, can anybody advise what to do next as i have a mint gsx550ef sat here in my shed going nowhere and half stripped, thanks jon
 
i have sparks but still no 4 cylinder wail !!
Click to expand...

Are you sure you have spark at each plug? If so, did you pull and fire each plug outside the engine? You may have a duff plug. On my parts bike when I was playing with it for the "igniter interchange project" last year, I thought I had spark on all but actually had one intermittently missing (#2). Long story short, it turned out to be a bad plug cap. Changed that and fixed.

The next thing to do if you have spark across all four is to check which cylinder is not kicking in.This involves getting the bike to temperature and "feeling" each of the down pipes for the cold one. Be extremely careful or you can "brand" yourself. Obviously don't touch them just bring your hand close to each in turn. Better yet if you have access to a temperature probe or infrared thermometer you will be able to tell right away and more safely too. If it is the carb then you will be able to tell which one to work with.

Assuming it is a carb, you will need to strip, dip and rebuild again. Just because it was "professionally" cleaned, it doesn't mean that it was done right or you may have just picked up a piece of crud when you fired back up. It does happen and I think this may even be part of my problem at the moment too.

There is a saying, "to do is to know" which could be a mantra for living and working with GSs. Don't assume anything, always check and definitely don't assume that when something was done for you, it was done correctly.......unless it was by one of us :).

Good luck and let us know what you find out.

Cheers,
Spyug
 
I have got a temp probe , so yeh, good idea that, i,ll try that idea out, i,ll test the plugs again, then if no joy then i,ll pull the carbs down again, cheers jon
 
Yes, actually it is the same model, mine's got a smoked windscreen and stock black exhausts.
photo.php


Thanks for the float advice Ajay, I wanted to do the least "invasive" work because upon bringing the bike home and cleaning it the condition is near perfect apart from dust. It appeared the bike was "properly" cleaned out and put away, but yet again the reason it was put away in the first place was a sudden drop of 2 cylinders (the owner suggested igniter coils, which was not the case thankfully... man they're expensive), which apart from that the bike had been running perfectly. Even now only running on two the bike has good compression (both exhausts act more like air cannons in my garage) and the problem carb will still feed the combustion chamber if there's fuel in it.

I was hoping to get the carbs going without taking them apart completely, as I was trying to make this project as cost effective as possible. If the float bowls aren't stuck and the needle isn't clogged, the only other option is blockage so I'll be taking it apart anyways.
 
Thanks for all the help you guys, makes a nerd feel proud forums exist for damn near everything, including carbs for a bike that are older and more complex then me.

I'll hopefully have an answer to my problem soon and will have a nice vid and pics to go with the revival. Did I mention this is my first bike and first mechanical project? I'm already contemplating restoring this back to stock and trade/selling for another project... maybe cafe racer. Would love to be the only guy on the block with something other then a crotch rocket.

Ahh Browntown, how you love your repsols and gixxers.
 
Try tapping on carb fuel bowl w/object like screwdriver handle or such,the shock/vibes may free up possible stuck float valve needle and allow fuel to fill bowl again,do that w/fuel supply valve at gas tank turned to the Pri(prime position):crack open carb fuel bowl drain for evidence of gas filling bowl or just try to start engine after tapping. Just remember... to put fuel valve at gas tank back to "on" position to avoid gas/carb flooding problems .. .Does that carb have a proper operating enrichment plunger,sometimes called "choke".If it is stuck in closed position it will cause trouble.
 
Pic of "choke" or enrichment plunger on "siamese"carb,this brass piece was stuck in place,it's operating cable cable broken off also.It is seen attached to easyout bit.
 
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does anyone have a picture of where the rubber tubes go between each carb ? thanks
 
For Janner, pics of the carbs looking from front to back. The two tubes are the overflow tubes the big port to the backside on the lefthand carb (as you face it) is the gas in. The smaller tube is the vacuum port:
carb2.jpg


carb1.jpg


Hope that helps.

cheers,
spyug
 
Alright, alot of work has been done, haven't been on the site for a few months. I found the problem was a small piece of rust possibly from the fuel tank blocking the main jet screw in the carb. Cleaned out, rebuilt, started right up on four. Problem solved, of course a bigger problem arises.

With the engine running and carbs fully cleaned I moved on to taking the parts off to clean or repaint. While taking the exhaust off I noticed one of the bolts had broken off, and was stuck in the engine block. I tried welding another piece onto it but the bolt is completely deteriorated.

I bought the bike as a barebones project and can't afford the engine work as I don't have the tools to take apart and bore a new hole in the engine, so this project is on hold.

Moral of this rebuild was to check over EVERYTHING on the bike, especially bolts. I had the same problem with a bolt breaking off from the master cylinder, and if I had known the rebuild would cost more then a certifiable learner bike I would have saved up instead of buying a basket case.

Who needs a parts bike? I hear the EF model fairings and brackets are hard to come by.
 
Did you spray down any of the bolts with PB Blaster or other penetrating fluid? If not, get a can for future jobs; it will pay for itself very quickly.
 
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