1981 GS450L idle issues

[Guest]

I have a 1981 gs450l I got about a month ago, and have been working on the thing about every night scratching my head. I got the bike to run a few weeks ago, but it only runs when its at 4000rpms or higher (where I have the idle set to start the bike) and when I try to adjust the idle down, the bike will die and not start again for a little while, I pulled the plugs and they are black and dry, have orange/whitish spark on the plugs, and have yet to check the coils when the bike is cold, but I think the resistance goes up, and the coils get pretty hot after running for at most 5 minutes. I have dipped the carbs and sprayed them out twice, replaced the orings in the carbs, but think the pilot jet may be clogged and it is super hard to clean. I just checked for air leaks tonight and there are none, I know the needles and seats are not sticking because fuel will flow into the carbs when gravity fed through a fuel line.
that's a lot to take in, but I don't want to leave anything out.
I am thinking it may be either the pilot jet is clogged or too small, or the coils are bad and I need new ones, does anyone know the specs on coils for an 81 gs450l?
Posting this in fuel + carbs and also electrical forums, as it could be either

[Gorminrider]

You have to be sure the carbs are good. You have to poke and be able to blow through them with air coming out in all the right places...and Yes, the choke circuit and yes the idle circuit are obvious candidate because the bike more or less relies on it all the way to 5000 rpm albeit partially then when the main jet takes more on. So you know that already-get to it.
assuming everything is fixed there, if the symptom persists consider the ignition. One member puzzled for a month and finally discovered himself that the wire to the pulse coils was chafed and was arcing at higher rpm. I never would have guessed that.But there's a few other oddball ideas you can try if your imagination needs support.

Not saying they are good coils-old bikes who knows the trouble they have seen? not least is being dragged from slumber by every new owner....but pretend the coils can't be too bad or the bike wouldn't run on one or more sides...getting hot is not good though-something electrical comes to mind with your symptoms - be sure your Battery and charging system are ok. It's just possible your charging system is all alone running the bike and it will not run well at low rpm and especially not if the Regulator/Rectifier or stator is whacked. To test for all this now, a simple way is to run the bike from a car battery without the bikes charging system involved. You will need to know your way around Suzuki electrics so unplugging it and/or testing it will be a good start.

[Buddybud425]

(Bike is a 1981 GS450L with about 21000 miles)
So I haven't been able to get to work on the bike in almost two months, but plan to work on it in soon, I did a little research on this and just wanted to take I have tried dipping the carbs and spraying cleaner through all the circuits, but I was not able to get the needle jets out of the center of the carb, so the orings on those are the only things not replaced or new, I adjusted float height to whatever the Clymer manual said to do, the needles and seats are smooth and work good, I haven't adjusted the valves and I'm planning on taking the carbs apart and fully cleaning them and replacing the needle jet orings. I was also thinking if this doesn't work, could it be the valves even though the bike was running just before I picked it up (got it from a family friend whos a mechanic) otherwise I have no clue
Thanks for the reply Gorminrider, the one thing I haven't checked yet is the coils for resistance, but it does have spark right after it dies, just doesn't start up again, brand new plugs are black.
Thanks in advance for any help, this project is way trickier than I expected.

[Boba]

Did you follow the guide on bikecliff's website for the 450 twin carb rebuild?

Two things right off, the Clymer manual I believe says to set float height somewhere around 22mm?? I forget because I don't go by the Clymer manual for the carbs, I did a crap ton of research here on the board to get mine done and in another thread there was a discovery that the Clymer manual was wrong about Float height and it should be set closer to 26mm.

Secondly, do anything and everything to get those needle jets out and replace those o-rings. Don't damage them because I have no clue where you'd find an authentic Y-6 needle jet for these carbs.

Maybe soak them in PB blaster?

Also, what is your mixture screw set at? This one bit me. I set mine to what the previous person had set it to, which was one turn out, and it TURNED OUT that I needed it more like 3 turns out. I was running lean and couldn't figure out why. I was replacing gaskets, intake pipe o-rings, cleaning the carbs over and over, replacing the fuel petcock, and was considering messing with the needle height when Steve here on the board chimed in and told me my mixture screw was wrong (actually he corrected me first because I called it the air screw or something like that)

Anyway, some input that I hope helps you.

[Gorminrider]

yes, you need to get the main and idle jets out to clean them. See those tiny holes? Mine were so bad that I didn't know there were holes! I don't want you to destroy anything but keep trying various ways to get em out...tips abound online no doubt but careful patience is going to be the first tool if anything works...try acetone+ atf or add some to your favourite penetrating oil to get down past whatever corrossion is holding it....warm it cool it etc etc.

[Buddybud425]

Thanks for the help Boba and Gorminrider, I will try my best to get those needle jets out, and I will see where the floats are set at and adjust them to the correct height, I did look at the carb rebuild on bikecliff, and I also have cleaned many carbs before, including the ones on my 425 which are nearly(not completely) identical to this, I'll let you know how it goes, assuming I find the time to do it this next weekend. I have been thinking of maybe taking the carbs off of the 425 and putting them on the 450 just to see if it does work with good carbs, narrow down the problem, and maybe swap the intake boots too just to eliminate all possible problems.

[smilinbrad]

I have the Suzuki GS450A Service Manual and it has the float height at 23mm +- 1mm.
Let us know about the carb swap. I'm having carb issues with my 425 and 450. 425 cant find parts. 450 keeps flooding out at low speed, runs great higher up.