GS650E Carb woes

[tom203]

Looking over parts fiches for these carbs, lots of different part numbers between g and e carbs and also different model years. Why so many ? unless it's just minor corrections to jet sizes after the first model year.My spare set of 81 carbs from a g looks like your 81- except mine are filthy!

[EZ_650]

Yeah, tom, I was hoping most of those part numbers were just namely a number the factory gave the assembly, with jets and all. After looking at the chart on BC's website, I saw that all the dimensions matched, even down to the bypass ports. But again, those were for 82-83 650s. And the spare carbs are from an 81 like yours.

Unfortunately I've decided not to tamper with trying to use these as I wouldn't have a clue what to do about jet sizing. My primary concern is with how the pilot jet path goes straight into the venturi and through the bypass, and pilot screw.

So, please! If anyone has an 82-83 650 (preferably E model) Mikuni BS32SS carb body, let me know. I want to ride this bike before winter gets here, and I just want to get this fixed...

Thanks,
Drew

[Force10]

Hopefully everything turns out good for ya. I'll keep my eyes open, see if I run across anything. The carbs for my 850 were only about 50% there, and I found a set of 650 carbs at a flea market for $5... Between the 2 set and a couple of parts from Steve (Thanks!) I now have a complete set. And I'm almost driving!
Once you get yours running we should go for a ride sometime. I'm in Clifton,OH. I don't mind helping you with working on it, I just don't know how much I have to offer...

[tom203]

If it was me, while you look for another carb- I'd try to carry on with your repair on your cracked post on your original carb. It might hold together long enough to keep riding- it might vibrate and snap off completely, but it's not under much stress, so as long as hinge pin stays secure, I'd wing it! I can't fathom the missing pilot jet hole stuff.

[EZ_650]

If it was me, while you look for another carb- I'd try to carry on with your repair on your cracked post on your original carb. It might hold together long enough to keep riding- it might vibrate and snap off completely, but it's not under much stress, so as long as hinge pin stays secure, I'd wing it! I can't fathom the missing pilot jet hole stuff.

I thought I would try to JB weld it, but a fellow mechanic at work said he'd tried JB weld for the same thing on one of his four wheelers, and it failed on him twice, after two different ways of securing it. I trust this guy, so I'm discouraged from trying it.

On your note, I will look at it again and try to maybe devise a solution that includes very small drill bits, taps, and fasteners.

Thanks Force10, certainly, I'd like to go for a ride if ever I get this going.

Thanks again guys for the responses! *thumbs up*

[EZ_650]

Well folks, she runs again! Thanks to chef1366 for supplying the needed carb body. I was able to get it cleaned up right, an installed the jets. I threw it all together, bench synced the set and adjusted the floats. I set the pilot screws at 2.5 out initially. I Installed them all and made sure everything was correct. I then installed the tank, and tried to start her up. It took quite some time of tinkering, and after adjusting the idle adjustment screw down some, she started up. She was idling around 1200, but when I revved, it hung. I figured I needed to just make some adjustments, and after scrounging around for a good replacement tank to use for gas, I went out to the store. I was just so fed up with spilling gas everywhere, lol. I ended up buying a nice container funnel and some vacuum caps for the petcock port.

So I went home, set up the funnel and gave a shot at adjusting the pilot screws. Before this though, I pulled the plugs, just to check them. Oddly enough, they were all BLACK. And this matched additional observations of a strong gas fume smell when it was running. But why the hang? I was sure there were no air leaks...

Well after tinkering a bit more, trying to get it to run less rich, I realized that I couldn't adjust the richness out with the pilot screws... In the mean time, I realized that the idle adjustment screw was a bit too far in then I realized. I adjusted it out, while holding the throttle open a bit at the grip. A few quick hang-free revs made me suspect that the hang was because the throttle wasn't closing all the way. But still, with the pilot screws were out 4.5-5 turns (can't remember exactly right now), and STILL, she was running rich. My eyes were burning, and I had the garage door open with the fan on!

I wish I had colortune and vacuum syncer... anyone?

So in a nutshell, she runs rich, stock jets, stock needle position, even with the pilot air screw full out. She'll idle but only with the idle adjustment screw in to the point that the revs hang. If you back it out, it revs good, albeit rich, but it won't idle.

[Suzuki_Don]

Check that your pilot air jets are correct. They should be #175s on the GS650E model.

[waterman]

Thanks for the experience and tips Merc!

Sadly, I am having a terrible experience putting this all back together... Let me start by going back few days.

Sometime in the middle of last week, I pulled the carbs and tore them down to re-dip them, in order to clear up an loctite and what not. So that all went well, and I even bought a second can of Barryman's to knock out two at a time. Well all went well with cleaning them and all passages looked great. So later on that night, I started assembling the carbs, and even replaced a few of the o-rings I had already replaced, but with the ones I got with my intake boot kit (i just bought them all).

Well I had everything installed on each carb, save for the floats... Yes, I'm sure most of you know what I'm going to say next, and you are right. I broke the top of one of the posts off. Actually, I cracked it though the hole, but I was not about to trust it cracked.

So, I jb-welded it that night, supposing that i'd get a head start on letting it cure, if that was even a viable option. At the same time, I began looking for a new carb body. Well that search brought me to kparkfan's FS thread. After not so carefully looking over this site I bought the carbs off his 81 650glx thinking they would work, somehow though it went over my head that he had an 81 and the specs on the carb chart were for 82-83s.
Well, upon quick inspection, they look the same, aside from a shorter brass choke tube on the bottom side. Mechanically, it didn't make sense to say this difference would produce discretions in how this carb and mine would perform.

Fast forward to today. Even though Rob dipped the one carb I needed before I bought it (thanks!) I decided to throw it in the chem-dip while I was at school. Anyway, I got home today and while spraying out the passages, I noticed something concerning... Yet another, bigger difference.

Just take note of the below pictures.

Notice how the '81 carbs' pilot jet housing has a hole that jets into the venturi. The original '82 carb does not have this... What does this mean as far as usability?

The bottom set of pictures shows what the 650 carbs I have look like. I think someone has drilled the hole that you are seeing. I would assume that this is what is causing your excessive richness and probably would not be able to be corrected without a new set of carbs.

I would think that turning your pilot screws in would make your idle mixture leaner not richer. After 3 or more turns out, I believe it is past the point of adjustment.

I happen to have set of stripped 650E carbs that I don't need anymore, I will have to check what condition they are in, but would get them to you for postage. I just shipped the air jets away and I am not sure if the diaphragms are with them yet. One of the posts may be broken off also. Likewise, I will have to check on what jets are with it yet. Let me check this afternoon to get you a list of what is there.

[Nessism]

A few comments, not sure if any of these are pertinent so disregard as appropriate.

- The pilot jets need to be set snug in the carb body - not adjustable.
- Pilot mixture screws should be somewhere in the 2.5 open range as a starting point
- The stock airbox/exhaust must be in place or the bike won't run properly without carb rejetting
- The intake pipe boot O-rings MUST be replaced if you haven't already done so or they WILL leak. The "spray" test to look for air leaks is unreliable.
- Using a fuel level gauge is the most reliable method to set your float height.
- All the carb O-rings should be changed if they are originals since they harden with age and don't seal properly
- A vacuum sync is necessary once you get the bike up and running
- Adjusting the valves is critical, both for the life of the engine, and to get the bike running properly.

Again, not sure how much of this applies but hope it helps.

[EZ_650]

A few comments, not sure if any of these are pertinent so disregard as appropriate.

- The pilot jets need to be set snug in the carb body - not adjustable.
- Pilot mixture screws should be somewhere in the 2.5 open range as a starting point
- The stock airbox/exhaust must be in place or the bike won't run properly without carb rejetting
- The intake pipe boot O-rings MUST be replaced if you haven't already done so or they WILL leak. The "spray" test to look for air leaks is unreliable.
- Using a fuel level gauge is the most reliable method to set your float height.
- All the carb O-rings should be changed if they are originals since they harden with age and don't seal properly
- A vacuum sync is necessary once you get the bike up and running
- Adjusting the valves is critical, both for the life of the engine, and to get the bike running properly.

Again, not sure how much of this applies but hope it helps.

Just to address these vital measures:
-Pilot jets are snug. I double checked.
-I started with the pilot mixture screws at 2.5. It ran way rich though (and even still.
-The stock airbox is in place. I have no intention to remove it nor an desire to.
-All o-rings in the carbs and intake boots have been replaced with ones from Rob Barr, and I installed his SS bolts too.
-I do not have a fuel level gauge...
-Again, O-rings have been replaced.
-I understand a vacuum sync is necessary, but I'm more trying to address the rich running condition first. Which is more important to get sorted out first?
-I have to adjust the valves, but with such low miles, it not an immediate priority. I will check them though.


Waterman:
The ones with the holes were ones that I bought, and came from an '81. In a previous post, I said that I was not using them. I have since found a correct carb body to replace the one I broke. That means that all 4 of the carbs on the bike currently do not have this hole. Thanks though!

Suzuki Don:
Thanks! I was clueless about what they should be, seeing how that info is missing from the table on BassCliff's site. I will check them and make sure that I didn't install the wrong ones! I am willing to bet this is my problem!

[Nessism]

How is the petcock? A failed petcock diaphragm will dump fuel down the vacuum line leading to a rich condition. Other than this the only thing I can think of is the float valves are leaking...that's where the fuel level gauge comes in. You can make one by taking an old carb floatbowl plug, drilling a hole though the bottom and epoxying a nipple on the bottom for a piece of clear tubing. Good stuff.

[EZ_650]

Ok, well, I just went and checked and sure enough, I put in the 160s that must have came in a rebuild kit I bought long ago. I was excited to have finally figured this out, until I went to my workbench to look for the stock 175s. I found 5 pilot air jets, one from each of my carbs (originals) and one the chef1366 forgot to remove from the carb I bought. Well, of the 5, I had four 160s and one 175...? I'm going to assume that the 175 came out of the carb I bought.

So what's going on here? Should I just find someone with 3 more 175s?

[EZ_650]

The petcock diaphragm is good, trust me lol. Besides, as I ran it last night, it was by use of a separate gas reservoir, with the petcock vacuum line capped off. The float valve points are in good condition, and the springs were still springy. I personally don't really see this as being the problem.

How then do I measure the fuel height in the tubing? Do I just bring the tubing up to the side of the carb and let gravity do it's trick with the gas?

[LarryA_Texas]

I think that hole came from the factory. It's just a slightly different style of carb.. But there was something that didn't make sense to me. Maybe I got it wrong or it's already been cleared up but: The pilot jets (under the rubber plug in the bowl) should be screwed in snug. Not overtight, but snug. Somewhere up there I read that you turned them out 3 turns. The "Out 3 turns" would be the mixture screws. These are the only screw adjustment you can make on a carb and they are on top of the throat where the carb is mounted to the engine. Every other setting is fixed by the size of the jet. To make changes you have to change jets.

Having said that here's my advice;
When you clean the carbs you have to follow step by step the cleanup series. It's very easy to miss one little thing and completely ruin your chances for a good running engine. It may not run at all. Some of the things I've run in to with these carbs that you may want to look for:

Make certain the boots are good. GS650 boots are part rubber and part aluminum and the bond between the two materials can break causing air leaks. A serious leak here will shut that cylinder down completely. And there are o-rings under those boots that have to be good to make the seal to the cylinder head. Bad o-rings won't usually make it not run at all, but it won't run well.

The air flow from the filter box to the carb is very important, too. Again, a problem here won't usually make it not run at all. But you'll never get it to run right.

Make sure the pilot jets are clean. There is a hole at the bottom of the jet that is easy to overlook. You should be able to spray cleaner into the top (where the screw threads are) and have it squirt out all the holes on the sides of the jet and a stream out the bottom. I think you said your's are new so that's not a problem...but be sure the new ones are the right size.

Another easy to overlook part is the choke tube and the hole it fits into at the bottom of the float bowl. Needles can be wrong and the needle jets can be a problem if they have debris in the small holes.

The mixture screws are sealing a very small hole...make sure it's clear. The tip of those screws sometimes break off into that little hole and can seal it completely. I've never heard of 5 turns out. that seems like it would never be necessary. And remember that as you screw them out the mixture is getting richer. Screw them in to lean it out. Yes, it's cutting off air, but the venturi affect of that air flow is what draws the fuel in. Try taking a look at the Mikuni website for more info on how carbs work and how to detect and correct problems. http://www.mikuni.com/fs-carburetor.html

Hope this helps and I haven't opened up a bunch of issues that have already been solved.

Larry

[Suzuki_Don]

Ok, well, I just went and checked and sure enough, I put in the 160s that must have came in a rebuild kit I bought long ago. I was excited to have finally figured this out, until I went to my workbench to look for the stock 175s. I found 5 pilot air jets, one from each of my carbs (originals) and one the chef1366 forgot to remove from the carb I bought. Well, of the 5, I had four 160s and one 175...? I'm going to assume that the 175 came out of the carb I bought.

So what's going on here? Should I just find someone with 3 more 175s?

OK from my searching of the Alpha-Sports microfiches I have come to the realisation that the #175 pilot air jets are no longer available. Maybe you can get them second hand or aftermarket. Personally I would not use anything in my carbs that was not made by Mikuni except "O" rings from Robert Barr. At present you are six sizes too small on the pilot air jet. The #170 air jet is still available as it is used on the '82 1100s and this jet would put you only two sizes out from stock.

Just a few ideas.