Bike is running like poop. HELP!

[Copperhed51]

Alright, so I bought my bike a couple months ago (1993 GS500E with 8700 miles) and it was running pretty much perfectly when I got it.  A couple of weeks ago, I rode it home after it spent a night out in the rain and it was bogging down on the highway and I'd occasionally have to downshift to get the thing back up to around my 80mph cruising speed.  It wouldn't idle anymore and I had to hold it around 3k rpm to keep it from dieing at stop lights.  Shortly after this, I checked my oil and realized it was below the dipstick and I put almost 2 quarts to bring it up to the full line.  (I know, I'm retarded...I'd been checking it but hadn't been wiping off the dipstick because I'm used to my airplane and I don't have to on it)

So, lately I've been trying to tinker with things to fix it up.  I took the carbs off, noticed the O-ring was missing at the top so I put one in each carb.  The spark plugs were getting covered in soot because it was apparently running super rich.  When I pulled the carbs off, I turned the mixture screws back in about 1 turn so they are now 1 turn out.  I also replaced the main fuel supply hose to the carbs because it was cracked and leaking.  Before I did all this, the Prime position on the fuel selector wouldn't work and I'd always have to use starter fluid to start it if I ran the carbs dry.  Now, that problem is fixed.  I think the carbs have been re-jetted because the bike came with a ziplock bag with a couple of jets in it.

So right now, the bike won't really idle and runs pretty rough below 6k rpms.  Once it's above 6k, it runs pretty well but seems to run out of legs a thousand before red line or so.  It used to go up to red line and want to keep going.  When it tries to idle, black smoke comes out the exhaust and the plugs foul up.

The engine sounds fine and it doesn't seem to be burning much oil at this point.  The compressions are somewhat low, both cylinders are around 130psi, which I guess is below the limit if they're both that way.  So, what does everybody think?  Should I turn the mixture screws in another turn and see what happens?  When the bike is running at highway speeds, the plugs end up that nice brown color from what I can tell.  It seems it's just low rpm's, when it's chugging and coughing that is causing the plug fouling.  Do I need to do something inside the carbs?  Do I need to do a leakdown check to see if the rings or valves are leaking?  (My airplane mechanic has that equipment and I'm sure he'd let me borrow it)  Is there any simple solution to my problem?  Would it help to put a K&N air filter on to increase airflow and lean out the mixture some?  What do I do??

Oh yeah, forgot to mention, I've been running it on 100 octane leaded fuel lately.  It's what my airplane runs on and I don't think it's the problem but maybe it's contributing to the issue when combined with the low compression?

Thanks for any advice in advance,
Ryan

[kml.krk]

100 octane leaded fuel?? WOW! where did you get that!! I want some!! 
going back to your problems: you didn't mention your configuration (air filter, jetting, exhaust)

try going back to more regular fuel (regular, premium, super) I'm not sure if 100 leaded is right for GS, I know it is great for car but I  how it works in GS.

you also said that you took the carbs off?? did you clean them?? if not give them a proper wash and put em back together (you could try to use the sea foam carb cleaner) but it's best to clean 'em manually.
that's it for now, I ran out of ideas 
hope this help a little.

[Copperhed51]

I work at an airport and that's the fuel the planes run on.  I just use the fuel that we take every morning for fuel samples so I get 100 octane fuel for free!  It's a nice perk. 

I didn't do much cleaning of the carbs when I had them off because I didn't have much in the way of decent tools at home and I didn't want to strip the screws worse than they were already. 

As for my configuration, it's a stock air filter box thing, stock exhaust, and I'm not sure about the jetting.  I am fairly sure the carbs have been re-jetted but I have no idea what they have in them now.  I am the third owner of the bike so it's hard to say what the previous owners did.  All I know is I have a ziplock bag with some jets in it that are somehow related to this bike.  I guess I'll see how she runs over the next few days and try the seafoam to see if it gets me anywhere.  I just don't get why it's doing this though...it happened so suddenly.

[kml.krk]

free fuel  that sounds nice 

you said your bike sat in rain all night? it may caused the water to get to the ignition coil and you're not getting the right amount of current(electric) to the spark plugs.
if so take them off (ignition coils), and blow dry them with hair dryer or anything similar. just be carefull with electricity and fuel!! that's why it's better to take off the ignition coils and do it indoors.
good luck
(I hope this doesn't sound like I lost my mind) 

[GeeP]

Welcome to the board.

While it is nice to use the fuel drained from the sumps on the 100LL pumps, it isn't very good for your bike.  Ask a mechanic to show you a bottom plug from a O-235 during a 50-hour inspection to see why.  We used to run a CB550 on 100LL as a shop bike, and were constantly cleaning the plugs.  We finally went up about three heat ranges to keep them (somewhat) clean.

My guess is the plugs are lead fouled and your exhaust valves are coked up and sticking.  Do you treat your fuel with TCP?  If not, I would change out the plugs and run a tank of regular gas treated with the correct amount of TCP though the bike.  That should scavenge any lead left in the engine.

Also, be aware that automotive fuel hoses and seals designed to be compatible with alcohol additives are not compatible with the high levels of TEL and Benzene in aviation fuel. 

Running out of legs at 10k is normal.  The top of the torque curve is around 9k, which should be your shift point.

[TragicImage]

damn you aviation freaks!


Yea, GeeP is right, 100LL is nasty shite for an engine.... he also brought up a good point that Benzene can corrode the polymers in your fuel lines which goes into your carbs/engine and while its unlikely that it will effect it much in the short term, long term effects may be unpredictable......

[Copperhed51]

Yeah, I've seen some fine-wire plugs off an O-320 that had little balls of lead stuck in them.  My plugs definitely were fouled.  Even after I cleaned them up really well, it still ran like crap and fouled up in a hurry after starting the bike.  So, I decided to man up and go to the gas station and put some boring low octane fuel in the bike and after a couple of tanks of that, the bike is running pretty damn good.  Since I adjusted the mixture screws a little bit, I might have to go back and unscrew them slightly but I'm not sure.  It doesn't seem to be running lean but I'll just keep an eye on it. 

Thanks for all the help guys.  I guess the lesson is don't run straight 100LL in your bike if you know what's good for you/it.  I'll probably throw a little in the tank here and there but definitely no more tanks full of the stuff. 

Now that it's getting all cold and retarded here in KS, I think I'm gonna tear the bike down and paint the frame black, and probably do a black/silver or black/blue paint job on the whole bike.  As soon as I get an airline job, which should be soon, I'm gonna be moving up to an Aprilia RSV and will probably sell my GS, but who knows.  It has been a great first bike.

[mach1]

I didnt read everyone's posts but I did read your. Its your fuel, the Gs has low compression and a fuel with that octane wont get burned properly. I dont know much about leaded fule but I know its bad to use it on cars that require unleaded and even worse on a low output bike like the GS, I would say switch to 87oct.