5000 rpm idle!!!

[AustinPhoenix]

Ok everybody smarter than me...my bike went from idling at 3k after warming up to climbing to 5k after I tightened down the carb boots.

Here's what I know:
The throttle doesn't stick. I checked for slack and for routing to see if that was causing it.

I pre-synced it with a single strand of copper wire from a stranded 16 ga wire peice I had laying around...so it's not the butterflies. They open and close smoothly with enough resistance in the springs to keep them closed. The tension matches my 79 special's carbs.

My idle screws are 1.25 turns out across. And to clarify this, I turned the screw 360 degrees for a single turn.

I just installed fresh carb parts from z1 enterprises (jets, valves, etc...all the things that came in the rebuild kit).

I thought I set my float heights...can't find my notes on what I set them to, but I'll check this evening.

Questions about what I noticed and did and my plans to lower the rpm.

1. Should I count 180 degree rotation as a single turn on the idle screws?
2. The replacement springs for the idle screws are much smaller...what impact will this have? They're about 3/4 the size.
3. The butterflies are almost closed as it is...what impact will turning the main idle knob under the carbs to close the butterflies even more have on the idle? I read some on the forum about trying to make the engine sputter...then gradually opening it? Is that right?
4. By tightening the boots, why did the rmp jump 2k? If I had a vacuum leak because the carb boots weren't tight, wouldn't the rpms drop since more fuel is being pumped into the engine than air?

I plan on rechecking the float heights today. Pre-synching them again...maybe I screwed up somehow. Probably did. Then turning my tank around and raising the idle screws to 1.5 turns and slowly turning them in by 1/4 turn increments. Am I taking the correct approach?

[newc4]

Generally, I check the simple things first. You've suggested that the main idle knob is set correctly, but have you actually tried that adjustment? I believe that controls the buttlerflies. I've found that half a turn can make a big difference.

Darrell

[Dennyz]

This is usually caused by the idle mixture not being right and the idle speed set too high (to compensate for the idle mixture). If the throttle valves are open too much at idle (Idle Speed), enough air moves through the carbs to cause the diaphragms to activate.

This is where a ColourTune really helps out and you need to use a carb sync tool.

Rarely does each carb desire the same idle mixture setting as the others. Try turning the idle speed down to as low as it will go and still idle. Turn each mixture screw 1/4 turn in both direction looking for any rpm increase. You should notice a pattern of too lean or too rich. Continue the process at 1/8 turn until no more rpm increase can be found. It may be necessary to keep turning the idle down with each pass.

I like to leave my idle mixture just a bit to the rich side for smoother throttle response at low rpms.

[AustinPhoenix]

right track...

NewC4

When I synced the carbs, I was experimenting with knobs to see what was changed because I am a newbie. The way I set this was by having the 3rd butterfly barely open and then doing the twist tie pre-sync to the rest. I don't know if that was correct, but it made sense to me. I'll try a half turn and see what comes out of it.

Denny

Well that is definitely on the agenda for tonight. I'll set them in (LIGHTLY of course) and then turn them out 1.5 turns. Do you think changing the springs to the old ones will help or make a difference?

Color tuning and synching afterwards will definitley take place as well. Thanks!!

[oldnortonrider]

Pilot screw holes have probably been "wallowed out" to a larger size; mine all have. What this means~~is when pilot screw is backed out about 1/2 turn, it can be equivalant to much more~~possibly like 1 & half or two full turns. You can bet those "holes" have been "wallered out" on these 25-30 year old carburetors, by somebody overtightening the pilot screw. If that is the case~~see how it acts with the screws backed out only about half turn. Also, I do get better response, and low rpm adjustment with using the Super Premium fuel~~the higher octane stuff.

[randy]

Should I count 180 degree rotation as a single turn on the idle screws?

360 degrees is a full turn.

[HobbyMan]

The bread tie is just to get the butterflies in a ball park similar range. You should run the Idle stop screw down some. Also, once you get the rpm to drop, do a vacuum snyc

[Ken Talbot]

Once the carbs are properly sync'd, the butterflies will be closed at idle. The wire pre-sync will get all four butterflies close to the same opening, but they will all be open too much - hence the high idle.

Pilot screw is the term from the microfiche for the four screws on the inboard side of the carbs rather than idle screws. You adjust these screws at idle, but this is not how you set the idle.

The 'idle' screw is the single large one with a thumb wheel between #2 and #3 carb.

[AustinPhoenix]

coming together...

Oldnorton,

Ok, are you saying that I should start the pilot screws at the seated position and back them out half (180 degrees) turn and go from there? I counted the turns to a lightly seats position and made note of it (some were 1.25, one was 1.6 turns and the last was 1.75 turns out). That might explain the odd numbers...might have just been crud affecting them. Thanks for the tip!! I'll use it!!

Hobbyman

Thanks for clarifying. I thought that was right, but it never hurts to have a "meathead guru" back you up!

Ken

Thanks for the info. I thought they were supposed to be open slightly (<1mm).

Ok guru's, so let me get all of this straight.
I'll pre-synch again to get them all close to the same position.
Then I adjust the "idle" knob to close the butterflies.
Then adjust the pilot screws in about 1/2 turn from seated position and work my way back out at 1/4 turn increments.
Then vacuum sync and try to find a color tune.

Yes? No? I'm such a newbie.... And should I use the older longer/bigger springs for the pilot screws? Does that even matter?

[manshack_one]

When mine did that it was a vacuum leak. The caps on the sync ports were old and didn't seal it off. ran it high every time. new caps = correct idle for me anyways.

[oldnortonrider]

You've got a long way to go before you need to be concerned about Colortune or carb vacuum sync; get that idle rpm down from 5000 to about 1000. Should be able to do this with pilot screws being seated~~turn 'em about a half turn out. stop. leave 'em there (for now). Finish idle speed adjustment with "Idle Speed Adjustment Knob" .

When you do this, can you get the rpm down, to where it'll run "reasonable, low rpms"? On all 4 cylinders? If not, "Manshack" may have something there, regarding vacuum leak(s).

[manshack_one]

"If not, "Manshack" may have something there, regarding vacuum leak(s)."

you don't have to put manshack in quotes it's just my last name and I'm number one. i think there's a thread here somewhere where i explained my username. maybe it was a different forum? anyways, it's just my last name. It's just funny to me because it's my username and people always try to make it mean something when it doesn't. just poking fun at you ONR.


And yes, definitely check that your caps are capped off properly. It's an annoying thing to try and figure out and one of the last ones i looked at. remember the basics. Gas, Air and Fire. If it ain't running right it's got to be one of the three.

[AustinPhoenix]

Manshack...

OldNorton,

I know I have a long way...I just look at the finish line and try to figure out what I need to do to get there. I used to race and instead of splitting my time by laps, I would split it by quarter laps to make sure my pace was right. If I screw up one lap, I'm done. Screw up one split, no problem.

I'll follow your advice and set the screws at .5 turn out. Set the idle speed using the knob between carbs 2 & 3. I guess I'll hold off on checking the float heights for now. If it's still acting weird, I'll do the propane/carb cleaner test near the boots to see if idle increases through a vacuum leak.

Thanks Manshack and ONR! I'll HOPEFULLY be back later with a story about my first ride!

[AustinPhoenix]

SHE LIVES!!!

I had my FIRST ride on the XS tonight!!! I used the right procedure for the idle thanks to the XSive Guru's on here and had her baaaarely idling without any choke at about 800rpm. Then opened the idle enough to get her up to 1000rpm consistently.

All the gears shift easily!!! My brakes are a little squeaky up front, but I haven't even messed with them yet. From the looks of them, they're not difficult to take apart anyway.

Thank you for all the help!! Now to synch and color tune!!!

[XSPastor]

Congratulations and enjoy!