High RPM repost

[Tat2demon]

I asked about this problem in my carb rebuild thread but I wanted to re-post after today so all the info is in one post and there's no confusion.

Stock airbox with K+N filter, drilled 5 1/2 holes in the correct spot in the middle of the filter area on the box.

RC Performance Parts exhaust. I know nothing about it.

Installed jets are - 180, 140, 42.5. I was told in another post to leave these in. I also have all the jets that came with the Georgefix kits.

I cleaned the carbs and replaced the pilot screws with new ones from Georgefix rebuild kits.

Floats are all set at 24.9mm. I figured they should be a little lower with the airbox drilled.

I had a float with the sides crushed in but as of today that is replaced with a new one.

I re-synched today with freshly calibrated vacuum gauges.

I started at 1.25 turns out as is stated in my Haynes manual. At that point the RPMs stayed at 1k with the idle adjustment in just a bit. I popped in the Colortune and was very surprised at how many turns out I had to go for it to turn orange. After hitting orange I turned them back in about half a turn so it was blue again. Tuning each cylinder brought the idle higher and higher.

Now with all that done I am still idling at 2k with the idle adjustment all the way out.

I have sprayed carb cleaner around all the boots to make sure there's no leaks.

I think I have covered all the bases but no luck. Any ideas?

[James England]

Now with all that done I am still idling at 2k with the idle adjustment all the way out.

Are you referring to the throttle stop screw? The one with the black knob on the end?

[Tat2demon]

Yep. Thats not even touching the lever anymore.

[Tat2demon]

Oh and the throttle cable isnt hung up anywhere or stuck on the boot.

[bikerphil]

Probably have to re-sync after adjusting the mixture screws. You may also have a vacuum leak somewhere.

[CaptonZap]

Now with all that done I am still idling at 2k with the idle adjustment all the way out.


I think I have covered all the bases but no luck. Any ideas?

Yeah, but you won't like them.
It sounds like a mechanical problem, which will usually succumb to a good visual inspection.
Take the carbs off, you should be getting good at that, , and hold them up to a bright light source. Looking in the engine side of the bores, hook your finger in the cutaway of the slide on the other side, and push it up. You should see a SMALL sliver of light between the bore and the butterfly plate. All four should be about the same size.
Now take the idle set knob, the one hanging down in the center, where the cable hooks up, and give it a bit of an unscrew. (Counter clockwise when looking at it).
The sliver of light should get smaller, until the light is completely shut off in all four bores.
If that doesn't happen, start looking at all the linkage, and find out what is stopping the butterflies from closing.
Before going to all this trouble, you might want to disconnect the throttle cable and see if that cures it. CZ

[Tat2demon]

Probably have to re-sync after adjusting the mixture screws. You may also have a vacuum leak somewhere.

I left the gauges on during the whole process. When I was done they were all still synched.

Yeah, but you won't like them.
It sounds like a mechanical problem, which will usually succumb to a good visual inspection.
Take the carbs off, you should be getting good at that, , and hold them up to a bright light source. Looking in the engine side of the bores, hook your finger in the cutaway of the slide on the other side, and push it up. You should see a SMALL sliver of light between the bore and the butterfly plate. All four should be about the same size.
Now take the idle set knob, the one hanging down in the center, where the cable hooks up, and give it a bit of an unscrew. (Counter clockwise when looking at it).
The sliver of light should get smaller, until the light is completely shut off in all four bores.
If that doesn't happen, start looking at all the linkage, and find out what is stopping the butterflies from closing.
Before going to all this trouble, you might want to disconnect the throttle cable and see if that cures it. CZ

Yeah Ive gotten pretty damn good and popping them off and on. Ill head back out later tonight and take them off again.

[ViperRon]

Typically the butterflies in the carb will close enough to reduce airflow to the point the bike will idle to a stop. If you turn them all the way down they should shut to the point where you can not hardly see any light going arround the edges. If one of these butterflies was hanging open a little then when you sync you will open the others to balance to the one that is open so that all are open the same amount. If you are not getting air arround the butterfly then it must be comming from another source. You have checked the main sources like arround the intake boots at the carb and at the engine. I know some here have said they needed to replace butterfly seals before but I would think you would here air whistling in. I would first take and block off all ports on all four carb intake boots and the ignition advance tube on carb 2 and see if any of these drop the idle down. Then recheck and listen arround each carb retighten bolts holding boots to engine and clamps arround carbs.

For it to idle high it has to be getting extra air. These are the typical areas it gets in and most times I can find a vacume leak just listening for it.

[Tat2demon]

Hmm I never sprayed the butterfly seals. Everything else was hit with carb cleaner with no effect.

[Tat2demon]

I dont know if it helps but when the engine is cold it would Idle at 1k but once its warmed up its at 2k.

[CaptonZap]

I dont know if it helps but when the engine is cold it would Idle at 1k but once its warmed up its at 2k.

Mine did the same thing when I brought it out of hibernation. Turned out to be a bolt on the bottom of #3 carb boot was missing.
Like Ron said, tighten them all up. If you want to do it right, take them off, clean them up, apply some Gasgacinch and reinstall them. Then you will know that that potential leak is fixed. CZ

[Tat2demon]

Problem solved!

Seems that when I did the full tear down of the carbs, the butterfly in number 3 wasn't completely flush. I loosened the screws, flipped the arm a few times and it seated itself. Running beautifully now at 1k.

I'm a bit embarrassed that I couldn't figure out something that obvious on my own. I think that was the only thing I didn't check.

Thanks a lot for the help guys.

Now I was finally able to check my timing since I bought it 3 months ago. I was 10 off.

[skids]

Congrats! You are out of carb hell.

[ManagerMike]

Congrats! You are out of carb hell.

For now........

[Diskman01]

Hey Nate. You sprung for a colortune? What will an afternoon rental run me?