Idling too high...

[neptune]

Hi... I'm a new rider and new to the board...

Bought a '96 GS500 recently and very happy with it for the most part. Nice little bike, easy to ride and learn on.

My (first?) question is about idling... just had an oil change done few days ago (along with replacing front fork tubes) at a shop. Anyway, been riding for a couple days since and noticed today that the bike idles very high - at 3000 rpm (was fine last couple days). Any thoughts on why this is happening? Its weird because as I start to accelerate from a stop, the rpm's suddenly drop from 3000 and everything seems to be fine, until the next stop.

This is causing me to stall the bike sometimes since, at first, the rpm's climb from 3000 and then suddenly drop to around 1000 as I'm accelerating. Any help is much appreciated.


My second question is about backfiring... there's lots of it! Specially when letting off the throttle. From what I understand, this problem has always been there (from the previous owner). I'm not sure if its something to be overly concerned about, but its damn annoying to say the least! Any thoughts on this would be greatly appreciated as well.

These two issues may be related I'm told? Perhaps something with the carbuerator?

Thanks for your input!


- nep

[Black Snowman]

They are related, your bike is running lean. Either the fuel valve isn't giving it enough fuel (try running it in the Pri position and see if it helps) or there is something wrong with the carburators.

[The Antibody]

I've heard that the backfiring can come from fouled spark plugs. Maybe someone can back me up, or shoot me down. Either way. The high idle? Could be something with the carbs. I'll keep on the hush about that.

 -Anti

[Rashad]

Backfiring, might be a leak somehwere.. check the diaphragm caps to make sure the caps are still there, and check to make sure your vaccum hose is hooked up. Also, take off the caps and check the carb diaphragms for holes.

I do think its running lean. Idle hanging... etc.. sounds lean. But mine was backfiring and idling weird the other day because the caps on the diaphragms were leaking (vaccum ports had no caps).

Also, check and change the plugs.. they should be a nice tan color.

[KevinC]

Check for vacuum leaks as suggested, and then balance the carbs and adjust the idle mixtues.

[neptune]

Thanks for the input guys... I'm a complete 'n00b' however, so I don't realy understand all of what was said.

Checking leaks 'externally' I found there's a hole in the exhaust pipe... seems to be very small - I can't see it, but I can feel it when I put my hand around there while the bike is running. Not sure what that means.

I guess what I'm trying to say/ask is - should I take it in to a shop to have it looked at or, considering my newbie status, should I attempt to fix it on my own? I've already just spent about $750 replacing fork tubes, oil change, etc.


- nep

[The Buddha]

Is the hole right at the bottom. Just about at the lowest point in the pipe. That is there to get rid of water. Why did you replace the fork tubes...were they bent or did the shop "suggest" you replace them cos they were wore out. And $750 for that... Well lemme put it this way. My 3 500E's cost $800, $1000 and $550. And they all had good fork tubes....Dont do anything that shop tell you...ever again...I'll sell you 1/2 my bike for $750, or the whole thing if you pick it up and it has a good fork set.
Cool.
Srinath.

[The Buddha]

Oh sorry forgot to read your other problem...
Lean. $2.50 to $3.00 per pilot jet and you need 2 in the 40 size, and replace your stock 37.5 with it. Then/or fiddle with mixture screws. 1/2 turn at a time and open for richer mix at idle. Heck you may want to do this first before the pilots.
Cool.
Srinath.

[neptune]

Fork tubes had to be replaced because they were bent pretty bad (one even had a slight crease in it)... we actually tried to get a pair from various wreckers but no luck... ended up having to order a new set from Suzuki. Cost about $400 CDN for the pair.

About the hole - its maybe about a foot from the actual exhaust 'opening' at the end... don't think its for water?

[The Buddha]

Ok $750 canadian....That's about $35 USD right...Just kidding...I know y'all are very sensitive about the loonie... But anyway...
The hole is pretty small, on the under side of the pipe and is right about at the lowest point on the pipe. If so its a water drain hole. Look if another GS has it in neat the same spot. If so you are fine.
Cool.
Srinath.

[neptune]

Alright fair enough, I can check about the exhaust 'leak'...

Now, about the lean mixture. What can I do about that? Rather - HOW can I fix that? If you'd be so kind as to point me to a detailed How-To, I'd much appreciate it.

Thanks

[The Buddha]

OK I am sorry...Canadian bikes done have 37.5 pilots. They have 40's stock. So yoy are fine in that  So mixture screw is all that you eed to think about. Canadian bikes may not have that stoopid brass plug installed in it either so You may just be able to open the air screw 1/2 a turn and that should do it. The mix screw is on the front bottom sid of the carbs. So take a small mirror and hold it unde rthe carbs at and angle and see if you see a small aluminium round projection with a slotted screw under it. That on the right carb (as riding the bike) is partly obscured by the rubber hose thing that acts like the drain. You may have to dis connect it to adjust it. On the left carb the hose is not in the way. See it first. If it has a brass plug (the plug has a tiny hole in its middle) you have to get the carbs off and drill them out ,be very careful you dont run the drill into the screw head or break off the aluminum piece itself. Basically check it with a mirror and post back.
Cool.
Srinath.

[Kerry]

To see a picture of the brass plug Srinath is talking about, go to my web page (see link below).  In the Maintenance Tips and Tricks section, click on the Float Height Check link.  Now click on the first thumbnail picture in the series to see a larger version.

The brass plug (with the tiny hole in the center) is located between the two Phillip-head screws in the upper left corner of the photo.  This photo was taken from the left side of the bike.

EDIT: Changed link from sisna.com to bbburma.net

[Von Vester]

I don't want to be Mr. contridiction but I'm pretty sure afterfiring through the exhaust is caused by an overly rich mixture. This will cause a 'sneezing' sound coming from the exhaust exit.

The rich mixture dumps unburned fuel into the exhaust system. The fuel is at combustion temperature but cannot burn because there is insufficient oxygen, however, when it gets to the exhaust exit and gets fresh air it combusts and causes that 'sneezing' sound.

Check your sparkplugs. If one of them is covered with black dust then it is carbon fouled, which is caused by overly rich mixtures.[/u]

[The Buddha]

Lean mix also will misfire in the exhaust.
The mix goes through not ignited by the spark and will burn when it hits hot exhaust pipes. Rich mix usually will ignite in the cylinder but burn so slowly and poorly it will cause loss of power (very significant loss even for a slightly rich mix). It may burn in the exhaust as well but lean misfire is much more common.
Of course if you go richer than the soggy power loss state you will hit the drown out the spark stage but on the GS I have never hit that stage.
Cool.
Srinath.
PS...Near impossible to get this bike rich especially down low.

[neptune]

A friend mentioned it could also be the air filter causing backfiring? I guess it's under the gas tank right? Any idea how I can check it?

[scratch]

Take your seat off and you should be able to look straight into it, under the tank. If it's tha paper type, it should be pretty obvious if it's dirty. If it's the foam type, it should be...well that's pretty hard to describe...it's already a dark color. But, it should be covered in a light type of oil (air filter oil) and the foam shouldn't be hard or brittle.

[neptune]

Just an update on the two problems...

Turns out the high idle was because of the screw. My buddy and I were out riding on Friday and he thought about checking the idle screw. So anyway, that's been fixed (I hope)... the guys at the shop might've hit it by accident?

The backfiring has been fairly quiet too. Although, maybe I simply can't tell because its been so windy last couple weeks. It *sounds* quieter though. The only thing I can think of is fuel. Couple weekends ago, we went riding and my buddy filled up his bike with regular gas and mine as well. My GS did NOT like that one bit; coughing, backfiring and shutting off every chance it got. So we pulled into a Canadian Tire and bought a bottle of octane booster - fixed the problem right up!

I've always used premium grade fuel in my bike, but he doesn't on his (he's got a Seca II). I guess he figured mine didn't need it either, but it does. Just to top things off, couple days ago we bought some carb cleaner and dumped that into the gas tank as well. Bike's been running perfect since!

As for the air filter - its there and its only a touch dirty so I've left it in. Might change it at next oil change.

[scratch]

Good for you! Enjoy riding your motorcycle!

[neptune]

Thanks!

Now I just need to learn how to work on it... do oil changes, maintenance, etc.

I'm a total n00b when it comes to that stuff... any recommendations on where/how I can learn properly (and safely - both for me and the bike LOL)