Need some help. GS450 Fuel Economy issues

[Guest]

I had a fuel economy drop a while back and you all told me that a valve adjustment was a must. So, I did it. Shes all in spec. And getting even worse fuel economy than before.

I did put on a new rear tire, but that should only cause a mile or two per gallon, and the valve adjustment should have gained me many miles to the gallon. Also, there is now a stronger vibration from about 3500 to 6000 rpm than before. It used to only really vibrate right near 5k's.

It used to have an air issue, I recall reading that if the bike's idle rises as it warms up there was some sort of airbox issue. I recall maybe it was leaking air in that it wasn't supposed to. That has gone nearly away. It rises a few hundred rpm, but that's just from when it first sits with a stable idle to when it's hot.

Also, when using the choke, it blows fuel out the left pipe. I haven't noticed it in the right one, but that could be that there's no leak to find. I don't use the choke any more than I have to because of that. Is there a particular reason for it dumping way too much fuel on choke? I know that's what choke is, but this seems like way way too much fuel.

I'm at a complete loss as to why a valve adjustment worsened my already bad fuel economy numbers. This bike got around 55 mpgs when I first bought it, and now the last time I filled up, I think I was in the <30 mpg range. which is bad. It's my daily driver, but I've been trying to stay off it. And I have taken it easy on the bike since I did the adjustment, I was definitely not romping on it.

So maybe I should ask, what are the chances, and what damage could I be doing by riding it? Or is it fine, it's just blowing fuel out the back?

Thanks

[tkent02]

I had a fuel economy drop a while back and you all told me that a valve adjustment was a must. So, I did it. Shes all in spec. And getting even worse fuel economy than before.

I did put on a new rear tire, but that should only cause a mile or two per gallon, and the valve adjustment should have gained me many miles to the gallon. Also, there is now a stronger vibration from about 3500 to 6000 rpm than before. It used to only really vibrate right near 5k's.

It used to have an air issue, I recall reading that if the bike's idle rises as it warms up there was some sort of airbox issue. I recall maybe it was leaking air in that it wasn't supposed to. That has gone nearly away. It rises a few hundred rpm, but that's just from when it first sits with a stable idle to when it's hot.

Also, when using the choke, it blows fuel out the left pipe. I haven't noticed it in the right one, but that could be that there's no leak to find. I don't use the choke any more than I have to because of that. Is there a particular reason for it dumping way too much fuel on choke? I know that's what choke is, but this seems like way way too much fuel.

I'm at a complete loss as to why a valve adjustment worsened my already bad fuel economy numbers. This bike got around 55 mpgs when I first bought it, and now the last time I filled up, I think I was in the <30 mpg range. which is bad. It's my daily driver, but I've been trying to stay off it. And I have taken it easy on the bike since I did the adjustment, I was definitely not romping on it.

So maybe I should ask, what are the chances, and what damage could I be doing by riding it? Or is it fine, it's just blowing fuel out the back?

Thanks

No that's not right and it's not doing the engine any good. What has been done to the carburetors?

[Bryce]

Carb work between the low 40 mpgs and the 30 mpg: 0. I didn't even take them off the bike when I did the valve adjustment.

I have torn them apart at least a half dozen times, and thoroughly soaked and sprayed and scrubbed and wiped them at least twice. I had a rust issue, so by the time that was all done, I had clean carbs, at least on the DIY scale they were very clean. They have been switched to pods, not the original airbox. I did forget to clean it, but that shouldn't create a sudden drop like that. Ill clean the pods and do a test tomorrow just for the fun. The jets have not been altered to my knowledge. The carbs have been bench synched, however they have not been synched dynamically since I did the valves first, and then found this big fuel problem.

I did get to borrow a scope to look in the plug holes while i was doing the valve adjustment, but I don't know what I was looking for. I did see that as much of the valves as I could see were still smooth and shiny edged, so I don't have any valve burn. If there is anything that I should have seen, good or bad, let me know I remember pretty much what I saw, I just don't know what any of it means.

Thanks,

[phydeauxmutt]

If you have added pods and not changed the jets, that could affect your fuel economy.

Because it can now breathe more air, you need to add more fuel to the mix. You then control how much of that mix goes into the engine by moving the throttle, but if you don't have enough gas to go with the extra air, you will have to keep adding throttle until you do. Adding more of that improper mix will NOT help your fuel economy.

As to why the fuel out the left pipe? Sounds like something has come loose inside a carb.

[hillsy]

All the carb cleaning in the world is pointless unless you blow out all the passages thoroughly with compressed air.

What sort of pods are they? No name / cheap pods are quite restrictive and can clog easily as opposed to K&N pods which are actually good.

[smilinbrad]

with the pods it seems possible to me (because I had a hydrocarbon emissions problem once) that you are running too lean to support combustion. To get enough fuel to ignite you have to twist the throttle far enough to lift the needle all the way out of the main jet. I still think your carbs are dirty and now definitely in need of proper jetting.
In my case I had a pilot screw fall out of one carb on my ZZR600 Kawasaki. The mix went so lean that the plug couldn't fire it and the mix went out the pipe un-burned. I couldn't pass an emissions test until my mechanic discovered the missing screw and replaced it. (Arizona had emissions tests for motorcycles)
Just saying........

[tkent02]

All the carb cleaning in the world is pointless unless you blow out all the passages thoroughly with compressed air.

That's not required. Compressed air can lodge things permanently in some passage, can be impossible to get it out after that. Picture a grain of sand an inch or two up some tiny passage and wedged in there tight. It's not coming out.
What's good is to shoot spray carb cleaner through all of the passages so you can see that the spray patterns are the same on all of the carbs, no clogs anywhere. Look at fuel coming out the choke fuel feeds, all if the transition ports, every single passage on the whole carb.

[Bryce]

So, it has been a while since I did anything with the carbs, but i shot spray carb cleaner through everywhere. I never thought to check that the patterns coming out each carb were the same, but there definitely were no noticeable restrictions of any sort.

The pods are (probably) no namers. Even if they had a name, the chance of finding it now is super slim. I did just remove them and attempt to clean them, but they are actually quite nasty. Thats my first thing tomorrow if the rain stops, to go see about getting a new set of filters. I was very wrong about what I thought the state of my filters were, so that is now a very real possibility. Although dirty filters should be a slow decline, not a stark 10 mpg drop from one tank to the next.

Is it tough to rejet? I pride myself on having done every bit of work on this bike (except for a tank rust soak). I did do some accessory electrical work on the bike, is there any chance I messed with the spark? I don't know where these bikes get their spark, if it's from a separate magnet, or just juice from the battery through points.

Thanks All,

[Nessism]

I'm surprised the bike ran at all after installing the pods because the airflow restriction was drastically altered. Your best bet is to purchase a Dynojet kit for the 450 and get some proper K&N pods (not cheapo junky Emgos). The Dynojet kit comes with new jets and needles, which have a more tapered shape. The needles are important since they affect the fuel mixture throughout the engines running range. Guys that simply throw bigger main jets in to compensate for pods are running lean at the low throttle settings which isn't good.

Another thing you should do is check fuel level on the bike using the clear tube test. Details are available in your service manual or review in older threads here. If the float needles are leaking fuel the fuel level in the carbs will be high and the bike will run rich. This is a very real possibialty and would explain why you have been able to run the bike with stock jetting and pods. One problem is masking another. Not the best way to go through life.

[Larry D]

Make sure both cylinders are firing. Sounds to me you're only running on one cylinder. With the bike idling, take an ice cube and touch the header, it should melt immediately.

[smilinbrad]

I had several problems with my carbs when I bought my 6,000 mile GS400. They had leaked long enough that the crankcase had about a quart of gas in it.
The bike sat so long that one side of one float developed a pin hole leak and filled itself with fuel. There's no way you can adjust anything on these carbs to compensate for that. I also bought a 2 gage vacuum set to balance them. I have it idling on both cylinders but I want to be sure. I had to make up my own air filter element from A Briggs and Stratton item! Too many mice!

[Bryce]

So I cleaned the pods as best I could, the two parts stores I ran to between classes yesterday didn't have anything even close. I'm going to have to go up to Iron Pony when I get a chance I guess.

I'm not super sure, but I feel like cleaning them did help the feel of the bike a bit. They are still fairly dirty, and I'm not real sure how much difference I notice. I keep forgetting to specifically check that both cylinders are firing, however, I know the other day I reached down to see if the bike was warming up yet (Cold out that morning) and it was starting to warm, and I know the right side is getting hot, as I have a small oil leak that drips and runs down of the exhaust pipe and starts to smoke after a while. So that one is working good for sure.

I don't see a procedure for rejetting on Bass Cliffs site, and I didn't find much in the carb section of forums. Does anyone have a link to a process to get them set right? I know that you can increase the jet size and that there are little clips to change the needle height, but how do you get all that to agree with the airflow? Is it just by feel of power through the range, that there is no flat spot, or do you just do a ton of plug chops or...?

Thanks all,

[tkent02]

When you cleaned the pods, did you oil them too?

OK, do these pods have gauze between the layers of screen, or paper, or just the layers of screen? And do they have a little rubber velocity stack inside, kind of a smooth bell mouth for the air to go in, or is it just a sharp edge inside, so that the air has to go around a sharp square corner?

Some pods hardly filter anything smaller than gravel, flow very little air and are damned near impossible to tune well. They just don't work.

In fact a picture of your pods would be helpful.

And don't buy any more pods until you know what kind to get!

[Bryce]

I am sure that even if they ever were decent at all, they are junk now. They are paper (maybe gauze) inside of mesh, and the air would go around the sharp corner. They are just a single ring around that slides over the outside of the intake on the carb, then clamp them down. That's it. Nothing else fancy to them at all. I know the bike ran at least fairly well on them for many years, PO told me he consistently got over 50 mpgs. And I think that there was often a rider. Neither of them are exceptionally small people either. So be it dumb luck or whatever, they must have done ok for a while.

I did not oil them, however, they still have plenty of dirt and oily grime in them I'm sure that it's probably about the same anyways. They just have to go: I fully intend to replace them, no matter what. What kind should I get? Apparently the type that have a piece that goes inside the carb to smooth the airflow. Anything else?

Thanks All,

[tkent02]

Look at K&N pods, which are expensive, and then look at APE pods, which are just about identical but about half price. I don't know of any others made anywhere near as well.

Also if you're not set on pods, look for a stock air box on ebay or a moto wrecking yard or wherever.. It will be cheaper in the long run, and the bike will run better and get better mileage unless you are a master tuner, which I doubt by the questions you have asked.