'83 GS550 Idle Going Crazy

[GS550ED]

So I spoke too soon in the thread I last posted saying that the bike ran fine. I recently installed some aftermarket Accel coils on my 1983 GS550ED and it ran fine except for running extremely lean and bogging bad. So I took the jets back out and upgraded them to one above stock (stock is 95 & 102.5 so I upgraded to 97 and 105) Strangely enough, the jets in the bike when I bought it were like 85's and 87's...

Anyways, after putting it back together, as well as replacing the idle jets with new ones of the same size and a new float valve seat and needle, and new O-rings all around, it started up after spraying in some carb cleaner. But after this the idle became extremely erratic even after it warmed up. It would leap up to 4-5k, and after I naturally turned down the idle, it would idle fine at 1200-1500 until I revved it, when it would then get stuck at 4-5k, or kill itself. I've played with the idle adjust for hours and I seem to find a sweet spot only for the bike to not like it 10 minutes later.

I cleaned the carbs very thoroughly and even tried using the stock number (95 and 102.5) jets just today, but with no luck. It won't stick with an idle. I'm at the end of my rope...I must have screwed up the carbs somehow.

 

[Turtleface]

http://www.thegsresources.com/_forum/showthread.php?t=175584

Do the things everyone is saying in this thread.

Buy a 1 gal can of Chem-Dip, or something comparable.

Buy these: http://www.cycleorings.com/#BS_Series_O-ring_Kit

Buy a Morgan Carbtune: http://www.carbtune.com/

Buy new spark plugs, can't have too many, you may foul a few while tuning.

Download and Print This: http://www.mtsac.edu/~cliff/storage/gs/mc_maint/GS_CV_Carb_Cleaning_Series.pdf

Download and Print This: http://members.dslextreme.com/users/cbsaunders/gs/carb-balance.pdf

Make sure you run them with the airbox installed, return the jetting and float levels to factory settings.

You HAVE to do all of those procedures listed above in the PDFs, or you'll spend a very large amount of time being frustrated while you attempt to tune your carbs. Once you get all that stuff done, then you can see where you stand, and then start adjusting things as needed. I would recommend that whenever you initiate a change, you only do one change at a time, to prevents mis-diagnosis of a problem.

 

[GS550ED]

http://www.thegsresources.com/_forum/showthread.php?t=175584

Do the things everyone is saying in this thread.

Buy a 1 gal can of Chem-Dip, or something comparable.

Buy these: http://www.cycleorings.com/#BS_Series_O-ring_Kit

Buy a Morgan Carbtune: http://www.carbtune.com/

Buy new spark plugs, can't have too many, you may foul a few while tuning.

Download and Print This: http://www.mtsac.edu/~cliff/storage/gs/mc_maint/GS_CV_Carb_Cleaning_Series.pdf

Download and Print This: http://members.dslextreme.com/users/cbsaunders/gs/carb-balance.pdf

Make sure you run them with the airbox installed, return the jetting and float levels to factory settings.

You HAVE to do all of those procedures listed above in the PDFs, or you'll spend a very large amount of time being frustrated while you attempt to tune your carbs. Once you get all that stuff done, then you can see where you stand, and then start adjusting things as needed. I would recommend that whenever you initiate a change, you only do one change at a time, to prevents mis-diagnosis of a problem.

I have dipped the carbs, thoroughly cleaned them (so much so that i removed all the paint and repainted them)

I have that O-ring kit, although since my bike has the twin siamese carbs I really only used 3 or 4 of the O-rings (don't have vent, fuel "T", etc)

Don't have the carbtune, but I'll see if I can get it.

Brand new spark plugs, gapped correctly.

That GS CV carb cleaning .pdf looks a bit alien to me. I only have two carbs and they look quite different from those pictured.

The jets are at factory settings as of today and as far as I know so are the floats.

Are there any guides tailored to the siamese carbs on the '83 GS550E?

 

[Nessism]

Is the airbox installed?

 

[GS550ED]

Is the airbox installed?

Airbox installed, little side cover installed (was absent when I bought the bike) and has brand new air filter.

 

[Turtleface]

How long did you dip the carbs for? I left mine in the goop for 12 hrs, per carb body. A quick bath won't get the worst of the gunk, and you have to make sure you clean out all the little tiny orifices in the jets and what have you, preferably with a single wire from a brass brush or something similar.

How are your carb boots? You said the motor hangs at a high rpm after blipping the throttle? I think that's a potential sign of an air leak, and maybe a lean condition to boot? Check your carb boots, make sure they're seated properly. New ones may be in your future. Even if they look perfect, if they're not soft and pliable, they're probably full of tiny, tiny fissures that let unwanted air into your carb's signal path. Also, you may have ports for a vacuum sync gauge on either the carb boot, or the intake side of the engine. Make sure those ports are good and blocked as well.

You also need to get a good caliper, and MEASURE the float level, as mentioned in your first thread. Even from the factory, they can be waaay off. Mine ranged anywhere from 18mm to 25mm, optimal level seems to be around 21 mm for my setup. Guessing on float levels won't work at all. Check out Nessism's sig line. "To measure is to know." Wiser words were never spoken.

 

[GS550ED]

How long did you dip the carbs for? I left mine in the goop for 12 hrs, per carb body. A quick bath won't get the worst of the gunk, and you have to make sure you clean out all the little tiny orifices in the jets and what have you, preferably with a single wire from a brass brush or something similar.

How are your carb boots? You said the motor hangs at a high rpm after blipping the throttle? I think that's a potential sign of an air leak, and maybe a lean condition to boot? Check your carb boots, make sure they're seated properly. New ones may be in your future. Even if they look perfect, if they're not soft and pliable, they're probably full of tiny, tiny fissures that let unwanted air into your carb's signal path. Also, you may have ports for a vacuum sync gauge on either the carb boot, or the intake side of the engine. Make sure those ports are good and blocked as well.

You also need to get a good caliper, and MEASURE the float level, as mentioned in your first thread. Even from the factory, they can be waaay off. Mine ranged anywhere from 18mm to 25mm, optimal level seems to be around 21 mm for my setup. Guessing on float levels won't work at all. Check out Nessism's sig line. "To measure is to know." Wiser words were never spoken.

They took a bath overnight, so I assume I got most of the gunk out. To be honest they weren't too hideously dirty when I opened them up (kind of made me think "why mess with 'em", but I wanted to learn how to work on them)

The boots may be an issue. They are pretty hard and brittle. I'll go out tomorrow with a can of carb cleaner and see if I have any leaks. Even if I don't, I'll probably replace them anyway. And my sync gauge ports are on the sides and have brand new washers and screws in them. (pretty much every little screw and washer and doohicky in the carbs is new, except for the jet needles/needle jets, no one sells them??)

I'll try and measure my float height tomorrow, although they were fine when I first bought the bike. I should emphasize that the bike idling erratically is most likely something I did to screw it up, because the bike ran adequately before I rebuilt the carbs.

 

[tom203]

They took a bath overnight, so I assume I got most of the gunk out. To be honest they weren't too hideously dirty when I opened them up (kind of made me think "why mess with 'em", but I wanted to learn how to work on them)

The boots may be an issue. They are pretty hard and brittle. I'll go out tomorrow with a can of carb cleaner and see if I have any leaks. .

Well, you pulled carbs out of their happy place in boots and if they seem hard, it's unlikely you now have a tight seal when you reinstalled them. What about the O-rings at boot/ head interface?

 

[TPL]

The symptoms sound like an air leak, manifold boots, maybe o rings seals.

good luck

 

[spyug]

What I see in a lot of these posts is that all the effort is focused on the carbs but the problem can be the source of the fuel, the tank, the petcock/filter and the hoses.

Very often squeaky clean carbs get put back on and they almost immediately go wonky. If grit, grunge, crappola or whatever is still lurking in the fuel system it will get into the carbs and all that good work is for naught.

I am not a big fan of inline filters so I'd recommend a good cleaning or even sealing of the tank. A cleaning or rebuilding of the petcock (maybe replacing) is also important and if the hoses are older, replacement would be best.

Don't beat yourself up over the carbs until you insure the fuel supply is clean.

Siamese carbs are no different than 4 seperates in the way they get tuned and work so no special worries there.

Good luck. Its a pest but you will sort it out.

Cheers,
Spyug

 

[GS550ED]

Well, you pulled carbs out of their happy place in boots and if they seem hard, it's unlikely you now have a tight seal when you reinstalled them. What about the O-rings at boot/ head interface?

Just replaced intake boots and intake boot O-rings.

 

[JEEPRUSTY]

If you tighten the clamps on the airbox to carb boots you can cause distortion and airleakage.

The plastic bends badly if you fully seat the screws. If this happens then you will suck air.

It is easy to do this as the boot rubber gets very hard with age.

 

[GS550ED]

If you tighten the clamps on the airbox to carb boots you can cause distortion and airleakage.

The plastic bends badly if you fully seat the screws. If this happens then you will suck air.

It is easy to do this as the boot rubber gets very hard with age.

It seems that the previous owner kept the boots overtightened, and with age, they have formed into that position permanently. I'm waiting for the replacements but in the meantime have made some progress.

I cleaned out the tank and put in some fresh 91 octane and it made a noticeable difference. I got the machine to behave when being ridden, and can rev it upwards of 7-8k even and have it drop back down to idle instead of stalling. I'm having a buddy synch the carbs just in case and will be putting new boots on sometime this week.

I really appreciate all the continuing help and suggestions. I'd be grumbling in my driveway with a dead Suzuki if it weren't for you guys!

 

[BigD_83]

What I see in a lot of these posts is that all the effort is focused on the carbs but the problem can be the source of the fuel, the tank, the petcock/filter and the hoses.

Very often squeaky clean carbs get put back on and they almost immediately go wonky. If grit, grunge, crappola or whatever is still lurking in the fuel system it will get into the carbs and all that good work is for naught.

I am not a big fan of inline filters so I'd recommend a good cleaning or even sealing of the tank. A cleaning or rebuilding of the petcock (maybe replacing) is also important and if the hoses are older, replacement would be best.

Don't beat yourself up over the carbs until you insure the fuel supply is clean.

Siamese carbs are no different than 4 seperates in the way they get tuned and work so no special worries there.

Good luck. Its a pest but you will sort it out.

Cheers,
Spyug

I agree about the inline filter, but I think it is a good idea to install one while trouble shooting, especially if you're trying to keep the bike on the road at the same time. Once the rust/debris from the fuel supply is sorted out, you can always replace the fuel line.

 

[GS550ED]

I agree about the inline filter, but I think it is a good idea to install one while trouble shooting, especially if you're trying to keep the bike on the road at the same time. Once the rust/debris from the fuel supply is sorted out, you can always replace the fuel line.

I have been looking into getting a small inline filter, but my bike (as well as a number of other GS models, I assume) is vacuum-fed, so won't it cause fuel feed problems?

Also, how small can the filters go? I don't have a lot of room directly under the tank. Thanks!

 

[BigD_83]

I have been looking into getting a small inline filter, but my bike (as well as a number of other GS models, I assume) is vacuum-fed, so won't it cause fuel feed problems?

Also, how small can the filters go? I don't have a lot of room directly under the tank. Thanks!

My understanding is that the petcock is vacuum actuated, but the fuel feed is gravity fed. PRI bypasses the vacuum and allows fuel to flow directly to the carbs. This meshes with my check of the system as when negative pressure is applied to the vacuum line I can hear the petcock opening and then closing once the vacuum is taken away.

I just had this discussion with the elder statesman at my local Suzuki shop, and his answer to whether the inline filter is affected by the vacuum was a resounding "No!" and that he had installed an inline filter on his 650GD and other bikes with no problems. The only pitfall is to make sure that the fuel isn't travelling uphill at any point in the system.

There is a discussion about this on the Kawasaki forum:

http://www.kawasakimotorcycle.org/forum/vintage-motorcyle-info/137434-line-fuel-filter.html

I ended up with the same fuel filter in the above discussion (the same as the ones from Z1 Enterprises). I suppose that placing it closer to the tank protects the fuel line from accumulating rust, but it might swing or bounce around a little more than if it is nestled amongst the carbs.

I think I'm going to mount it lower down, between the carbs rather than higher up, but I don't see much danger in it being in either location. I'll let you know how it goes for me once I get my 650 back together and have run it for a while.

 

[GS550ED]

My understanding is that the petcock is vacuum actuated, but the fuel feed is gravity fed. PRI bypasses the vacuum and allows fuel to flow directly to the carbs. This meshes with my check of the system as when negative pressure is applied to the vacuum line I can hear the petcock opening and then closing once the vacuum is taken away.

I just had this discussion with the elder statesman at my local Suzuki shop, and his answer to whether the inline filter is affected by the vacuum was a resounding "No!" and that he had installed an inline filter on his 650GD and other bikes with no problems. The only pitfall is to make sure that the fuel isn't travelling uphill at any point in the system.

There is a discussion about this on the Kawasaki forum:

http://www.kawasakimotorcycle.org/forum/vintage-motorcyle-info/137434-line-fuel-filter.html

I ended up with the same fuel filter in the above discussion (the same as the ones from Z1 Enterprises). I suppose that placing it closer to the tank protects the fuel line from accumulating rust, but it might swing or bounce around a little more than if it is nestled amongst the carbs.

I think I'm going to mount it lower down, between the carbs rather than higher up, but I don't see much danger in it being in either location. I'll let you know how it goes for me once I get my 650 back together and have run it for a while.

Well it's settled then. I'll be going in for a fuel filter as soon as I can. Thanks for clearing that up.

 

[BigD_83]

Well it's settled then. I'll be going in for a fuel filter as soon as I can. Thanks for clearing that up.

Of course, I'm open to other suggestions if someone with more experience lays out a good explanation. Been wrong before, and I'm sure I'll be wrong again in the future...

 

[skreemer]

Have you tried a vacuum synch of the carbs yet?

Are your fuel air mix screws drilled out? (if so what are they set to) IIRC they need to be between 3 and 3.5 turns out(check that with the haynes/chiltons/factory manual I'm getting this from memory). Lastly take a look at the knob between the carbs, it's the idle adjust and it just slightly tweaks the angles of the butterflies... if it's been over adjusted to have them open you'll be chasing the idle issue all over the place...


BTW in the 4 - 1 stage 3 dyno jet kit they never change the pilot jet size. They increase the fuel air mix slightly and up the main jets...

At idle though you should be on the fuel air mix screws/pilot jets and not much else...

 

[GS550ED]

Have you tried a vacuum synch of the carbs yet?

Are your fuel air mix screws drilled out? (if so what are they set to) IIRC they need to be between 3 and 3.5 turns out(check that with the haynes/chiltons/factory manual I'm getting this from memory). Lastly take a look at the knob between the carbs, it's the idle adjust and it just slightly tweaks the angles of the butterflies... if it's been over adjusted to have them open you'll be chasing the idle issue all over the place...


BTW in the 4 - 1 stage 3 dyno jet kit they never change the pilot jet size. They increase the fuel air mix slightly and up the main jets...

At idle though you should be on the fuel air mix screws/pilot jets and not much else...

I'm having a friend synch the carbs in a couple days. The fuel-air mixture screws are still untouched with their covers on them. I haven't changed the idle jet or main jet size, just replaced them with new ones.