Carb floats don't float? 81 GS850G

[Nate from Ogden]

Hello all. I think I am getting close to having my resurrected 81 GS850G with CV carbs working properly, except that I can't seem to prevent serious carb flooding.

To date, I've added a stock airbox w/ K&N filter, new rubber boots and carb manifolds, new needles and seats and o-rings, all from Suzuki, not aftermarket parts. I've also replaced the petcock with a new one. After putting everything together, it fires right up but it just runs 4 or 5 minutes and loads up so that it won't rev and eventually it won't keep running. By then the plugs are sooted up, wet and there is fuel leaking out of the airbox.

Is it possible that the floats aren't floating? They don't seem to be heavy or fuel soaked and I set the level per the manual but I have run out of ideas. Thanks for all the expert advice I've already found here.

 

[SAN]

flooding

flooding

Are your bowl vents blocked, any kinks in the vent hoses. why was the air box not on before.

 

[49er]

Hello all. I think I am getting close to having my resurrected 81 GS850G with CV carbs working properly, except that I can't seem to prevent serious carb flooding.

To date, I've added a stock airbox w/ K&N filter, new rubber boots and carb manifolds, new needles and seats and o-rings, all from Suzuki, not aftermarket parts. I've also replaced the petcock with a new one. After putting everything together, it fires right up but it just runs 4 or 5 minutes and loads up so that it won't rev and eventually it won't keep running. By then the plugs are sooted up, wet and there is fuel leaking out of the airbox.

Is it possible that the floats aren't floating? They don't seem to be heavy or fuel soaked and I set the level per the manual but I have run out of ideas. Thanks for all the expert advice I've already found here.

If you are getting fuel running out of your airbox, your carbs are flooding.
This will be caused by incorrect valve and seat height, incorrectly set float heights or a faulty/incorrectly plumbed petcock. The fact that all the plugs are fowling would suggest that it is not caused by sticking floats.
Did you replace the o rings on the main jets. I here that these can cause flooding on the CV carbs.
Has a PO run the bike with pods instead of the airbox. You said that you have just fitted an airbox to the bike. You may now be very rich in the jetting if it was previously tuned for pods.

 

[Nate from Ogden]

Carb flooding- further info

Carb flooding- further info

Thanks for the questions. The bike did have pod type filters in the past but I don't think that PO had run the bike that way. The bike was handed down between several POs, none who knew enough to get it working.

Main jets are 140s. Don't remember the pilot size. I did put in 4 new pilot jets and 4 new rubber plugs under them. The carbs have been cleaned thoroughly but not completely disassembled to the last nut and screw.

New needles and seats did get new o-rings as well. I checked float height by the Haynes manual I have and height is correct for all 4 carbs.

I did have a 70s vintage Mercury outboard that wowuld continually flood due to a carb float that didn't float and had missed the recall by the company years before. I just wondered if Suzukis suffered a similar problem.

 

[bwringer]

Hm, well, there's one problem -- the stock main jet size in a GS850 is 115.

 

[bwringer]

It is possible for foam floats to get damaged by various chemicals (like many carb cleaners) and soak up gas. I've run into this on cars and a few bikes. It's not a particular problem on GS Suzukis, but who knows what the POs sprayed in there.

You could try weighing the floats on a decently sensitive scale. They should all be the same within a few tenths of a gram. I used a cheapo electronic mailing scale we happened to have at work. Unfortunately, I don't remember what mine weighed. Make sure they don't have time to dry out if they've soaked up gas.

Another test is to toss the floats into a small container of gasoline (like a glass pickle jar with a metal lid) and see where the "waterline" is. Assuming they're not all damaged in exactly the same way, it should be easy to see if they are inconsistent. You should also leave them soaking in the gas (use a covered container) for a few hours, then see if any are riding lower or sinking. Obviously, this is something you want to do with good ventilation.

Yet another possible problem is low-quality needle valves. In the center of each needle, there's a spring-loaded nub that the float actually contacts. In some shoddy aftermarket parts, the spring under the nub is too weak to support the float when you turn the carbs upside-down to set float height. Basically, the nub should support the weight of the float without moving at all. If the spring is too weak, the float height setting will be off, and the float valve may not actually be able to close firmly.

Ask me how I know about that last one, and how long it took me to figure out what the %$#@! was happening. No, wait -- don't ask. It's too painful...

Lastly, I don't think this would be your particular problem since you're using a manual, but it's something I've encountered and may be useful info: last fall, I corrected the carbs on a friend's GS850 where the PO had set the float height incorrectly using the top of the floats (actually the bottom of the floats, since the carbs are upside-down when you make this measurement).

This measurement should be taken at the "step" or "notch" in the float. There's a clear diagram in all the shop manuals, but I note it because it's something that might happen.

I've also found that these bikes are remarkably sensitive to small adjustments in float height -- 0.5mm either way makes a significant difference in off-idle and midrange response.

 

[Nate from Ogden]

Well you've given me a task for tomorrow, that's for certain. I will have to double check those jets but I had to buy one and I'm close to positive it was a 140. So far I haven't been able to run it enough to know if things were going to be fine or too rich or whatever. The bike has a no-name, 4-1 pipe and it lives at 4500 ft ASL so there may be some jetting required to get it right. I did see somebody's jet decision tree here the other day, I better go back to that now since it has to come apart again anyway.

My needle & seats came from Suzuki and the springs were holding them up when I measured them. But I think I measured to the highest part- which would have been the bottom of the float. I will double check tomorrow.

 

[robertbarr]

I've never heard of a Mikuni float that lost its buoyancy, although I used to test them anyway by dropping each in a jar of gasoline. Unlike the hollow brass floats of yore, these appear to be made of buoyant material -- no air cavity to leak.

One test you could try: pull the filter cover (to observe) and switch the petcock to Reserve. Watch for fuel overflow. If there is none (which is what I expect, since you said it takes several minutes before you experience the overflow condition) then your floats are doing their jobs. That narrows your search to actual operating conditions, ie jet sizes and (maybe) float heights.

Since you know that your main jets are the wrong size, you'll be pulling them anyhow, so you might as well check the remaining jet sizes too. Someone along the way decided that bigger was better.

 

[Nightmare]

If you still have the original seats and needles try putting them back in and seeing if there's a large difference in the float height. I bought (ugh) keyster carb kits for my 850 and discovered that the seats were not exact replacements (amoung 70% of the entire kit). When i had these "new" seats in place and set the floats i had gas pouring into my engine

 

[bwringer]

If you still have the original seats and needles try putting them back in and seeing if there's a large difference in the float height. I bought (ugh) keyster carb kits for my 850 and discovered that the seats were not exact replacements (amoung 70% of the entire kit). When i had these "new" seats in place and set the floats i had gas pouring into my engine

My experience exactly. Oh, the agony... :evil: Why'd you have to remind me?

There's a guy in New Zealand who pops up on eBay every so often with high-quality needles and seats at reasonable prices. That's what's on my bike. I had to reset float height, but they work great. I don't know where to get these otherwise, but the links below might be a start. Of course, you can always order floats and needle valves from Suzuki for large $$$.

http://www.wgcarbs.com/ <== Forum member and THE Carb King!

http://www.motorcyclecarbs.com/


Keep after it, though -- there's nothing sweeter than a GS850 that starts instantly and runs perfectly.

Your best bet for a nice even powerband, even with the pipe, would be to retain the stock airbox and make sure it's sealed perfectly -- seal the sides with self-stick weatherstripping, and make sure the top of the air filter "cage" is also sealed with weatherstripping. The air filter foam should only have the lightest bare spritz of air filter oil -- it's common to find these have far too much oil in them, and won't flow enough air. These little things add up to make a big difference.

You might need to go up a size or two on the jets, maybe to 120 on the mains and a size or two on the pilots, but you shouldn't have to go too far. 140 mains are ridiculous.

 

[49er]

The air filter foam should only have the lightest bare spritz of air filter oil -- it's common to find these have far too much oil in them, and won't flow enough air. These little things add up to make a big difference.

You might need to go up a size or two on the jets, maybe to 120 on the mains and a size or two on the pilots, but you shouldn't have to go too far. 140 mains are ridiculous.[/quote]

I agree that most owners over oil their foam filters. All that is required is a thin film of oil to trap any fine dust particles. 2 stroke premix is the ideal ratio. Pour a small amount of 2 stoke mix into a bottle and spray onto your foam filter assy. Repeat and allow the fuel to evaporate before re-assembling the filter into the airbox. Rub your finger along the surface of the foam. There should be a fine trace of oil left on your skin.
Many a good tuning session is destroyed by over oiling foam filters.

 

[purplemotoman]

If you are looking for carb parts there is a place in southern Ontario Canada that sells parts. Here's the link:

http://www.siriusconinc.com

Just pick your make and type in your model.

 

[Nightmare]

Be careful about thoes keyster carb kits!! Your carbs are identical to mine, I bought 4 kits (trying to remember if it was from thoes guys or a local dealer, i think the local guy). Its easier to list what matched then what didn't (main jet, sort of (non-percision jet), air screw, gasket, pilot jet boot, and the air jet), EVERYTHING else didn't match up (circlips, etc). I was really cheesed off (after spending 120$) checked the part number for the carb kit on several differnet sources and they all said for a 1980 GS850G/GL...

See if you can get a list of what specific parts come in the kits (Main #115, Jet Needle 5D50, Needle Jet X-5, Pilot Jet #40, starter jet #32.5) The factory jets were high tolerance jets, but i doubt any replacements will be.

PS: SAVE YOUR OLD PARTS!!

 

[Nate from Ogden]

Thanks for all the help-

Thanks for all the help-

Ok, so the floats, float. I checked them in a tub of fuel.

I replaced the 132.5 mains that were in there for the stock 115s.

I set the float heights on the top of the round portion of the float instead of the step- the step was at the measured amount, so measuring to the main portion lowered the fuel height by that amount.

Its running and sounds much better. I haven't ridden it yet but that's my next post. I don't have a synch tool so I'm planning to take that to a buddy with a shop for that work.

It is much better than last week. Thanks for the expert advice.

 

[Nightmare]

If you want to double check the fuel level, an easy fuel valve can be built by clamping a 3/8th (i think) small piece of tubing OVER the bottom of the bowl drain, clamp the other part of the tube to a reducer and use a small diameter tube for the rest of the meter. After installing the 3/8th over the bottom of the bowl, run the bike and place the smaller diameter tube next the bowls, you should measure 4mm (+- 0.5mm ) from the split or mating surface of the carb body and the float bowls...

If needed I can post pictures of the ones i built, sounds kinda funny but they work really well, are cheap to build (like 10-15$) and easy to adapt (no stupid fittings to find and thread)

 

[Nate from Ogden]

Using hoses to measure fuel height

Using hoses to measure fuel height

I would like to see how some have done that because I can't see how to clamp a hose over the bowl drain. The spigot area on my bowls where the drain screw fits is pretty flat, nothing really to get a hose onto.

I read the post about drilling a spare set of drain screws and gluing in some tubing and I could do that without too much trouble.

Right now I am getting just a little bit (not enough to hit the floor) of fuel dripping out of the airbox after the engine is shut off.

I did however discover that there was fuel in the oil tonight. I've drained it and removed the filter and tomorrow I'll try reservicing it to the right level. I hope the excess was a result of the flooding caused by the over-high float levels that I have since lowered.