Fuel fouled plugs at idle, and a high rev.

[timebombprod]

Rebuilt the carbs and I must've done pretty good as the bike fired right up really quick, surprised me a bit. It reacts smoothly so no restriction anywhere it seems, but I have some issues.

1) when I rev it the bike does react nicely, but It likes to hang up high (2500ish) for a good while before going UNDER the idle speed, then I give a quick snap on the throttle and itll go back to 1150ish. I tested for vacuum leaks but they're atleast not on the intake boots or the part of the airbox that connects to the carbs. Should the pilot screw turns be at 3 or 2 and a half turns out? I have them at 3.


2) my plugs are covered in carbon buildup, they weren't before the initial fireup of the bike after I rebuilt the carbs. What causes this? All 4 headers steam strong.

The bike just sat at idle speed most of its runtime yesterday, except when i gave it a decent rev and it started sitting at 2500rpm.


What delivers fuel at above idle speed to 2500-3000ish?

[tom203]

Make sure your “choke” plungers are actually off...or you’ll get weird behavior .
lightly loaded, at 2500 rpm, your still running on idle circuit .

[timebombprod]

Make sure your “choke” plungers are actually off...or you’ll get weird behavior .
lightly loaded, at 2500 rpm, your still running on idle circuit .

Theres no cable attached to the choke so it automatically goes back into place when I let go of it, can it rest out of place? Pulls out and retracts fine.

[timebombprod]

What turns on after the idle circuit and at what rpm

[tom203]

Sooty plugs mean you’re running too rich. Are you running Suzuki mixture screws?

BDB9DE37-274B-4EFF-84C5-09E8D494BC1B.jpeg

[timebombprod]

Sooty plugs mean you’re running too rich. Are you running Suzuki mixture screws?

[ATTACH=CONFIG]62372[/ATTACH]

Yes I am, I did just rebuild them and do 3 turns out on the screws but I do have a pretty free flowing exhaust. <--- I just realised this would make it lean

I'm about to post two vids, might go back to testing out electrical components but it really doesnt seem like that should be the problem.

[timebombprod]

Vid 1 https://youtu.be/zRTRmFt6Afo

Vid 2, I forgot to save it...

Glad I took video 2 even though it wasnt saved, the bike didnt like staying on at first, it's got that choppy idle ofcourse, but in this one it raised to 3500rpm.

Things I've noticed

even though I'm pretty sure the choke sits correct, when the high idle happens, I can pull the choke and the idle will go back down to normal everytime.

It sounded better when I initially started it, almost a complete drone, but the longer it sat the lower the idle wanted to go, and the drone got inconsistent to a chop, and now it wants to not have a smooth rev.


The idle adjustment knob doesnt really work all that much, as in when adjusted, it doesnt really do much.


Nasty dirty black smoke came out at first but went away quick, maybe some buildup or something.

Can valves move around, I remember this one time when checking valve clearance I had one read .33 sometimes and when I'd spin the engine a few times around it eventually got back to a normal reading. The bike doesnt really make significant sounds that worry me, just sounds like crap right now.

[zed1015]

There's a very high chance that your old choke plungers could also be leaking even when fully closed and adding to if not fully causing your problems.
These should be the first thing to replace or renew to avoid replacing other parts needlessly.

MIKUNI Choke plunger seat replacement and Air corrector jets for GS fours VM's (thegsresources.com)

[timebombprod]

There's a very high chance that your old choke plungers could also be leaking even when fully closed and adding to if not fully causing your problems.
These should be the first thing to replace or renew to avoid replacing other parts needlessly.

MIKUNI Choke plunger seat replacement and Air corrector jets for GS fours VM's (thegsresources.com)

Any way to test before replacing? Not defying just wanna make sure before I have some possible extras laying around.


After reading, I wont test the choke plungers.

[timebombprod]

And with that idle rise after I give it a bit of gas, could that relate aswell?

My choke works okay, but when I pull it out all the way it will start to make the bike want to shut off. I'm guessing it is part of the problem

[timebombprod]

Where to order choke plunger? It's the brass pieces right?

[zed1015]

The engine dying under choke ( enrichener ) operation when warm is normal.
This floods the cylinders and bogs the engine.
Choke should be feathered off as the bike warms and fully closed of as soon as the engine is warm enough to idle without it and then left closed.
Light pressure from a fuel filled syringe with a tube attached and slipped snugly over the choke pick-up tube can detect plunger seat leakage but it's tricky to judge if you haven't done it before.
Leaking chokes can affect one or all plungers to a wide range of degrees and results in issues with erratic idle, uneven running, low mpg and more.
Any carbs i rebuild , especially over 10 years old automatically get new Viton plunger seats as i've barely come across any that are leaking to some degree.

[timebombprod]

The engine dying under choke ( enrichener ) operation when warm is normal.
This floods the cylinders and bogs the engine.
Choke should be feathered off as the bike warms and fully closed of as soon as the engine is warm enough to idle without it and then left closed.
Light pressure from a fuel filled syringe with a tube attached and slipped snugly over the choke pick-up tube can detect plunger seat leakage but it's tricky to judge if you haven't done it before.
Leaking chokes can affect one or all plungers to a wide range of degrees and results in issues with erratic idle, uneven running, low mpg and more.
Any carbs i rebuild , especially over 10 years old automatically get new Viton plunger seats as i've barely come across any that are leaking to some degree.

This is a tough one... I think I'd like to get them done though. What exactly am I gonna be taking off. The whole choke assembly attached to the carbs?

[zed1015]

Where to order choke plunger? It's the brass pieces right?

Yes! the brass plunger with the rubber seat in the tip.
Depending on model they may or may not be available which is why i developed the re-seating service for obsolete plungers.
Try Niche Cycles, CMSL, to see if they are still listed.

[zed1015]

This is a tough one... I think I'd like to get them done though. What exactly am I gonna be taking off. The whole choke assembly attached to the carbs?

To remove the plungers you disconnect/remove the lifter lever or bar depending on model.
Slacken the 14mm nut and unscrew the whole plunger assembly from each carb.
Once done the plunger and spring etc can be separated leaving the bare plunger free for repair or replacement.