Unresponsive A/F mixture adjustments

[ninjaneer]

I thought I read once a post or a thread, but I can't, for the life of me, find it. I know if you tighten the mixture screws down until lightly sitted, the bike should start stumbling.
What would it mean if none of my mixture screws have this effect and how do you fix it?

 

[[email protected]]

I thought I read once a post or a thread, but I can't, for the life of me, find it. I know if you tighten the mixture screws down until lightly sitted, the bike should start stumbling.
What would it mean if none of my mixture screws have this effect and how do you fix it?

Try lowering your idle speed before adjusting the screws.

 

[ninjaneer]

mike, idle set to 1k. would going below that cause stumbling on its own?

 

[SpecOps13]

1,000 will retain some oil pressure. I'm not comfortble with it much lower. Are you running Ethanol???? If so and you're not
using a good conditioner,,,,There may be some trash in your idle circuits... If you pull a plug wire, does the idle drop?

 

[naughtyG]

I tried doing the AF screws adjustment like that and I too noticed I could go all the way in on any one of them without making any noticeable difference to the idling.

However, if you screw two or more of them all the way in it will stumble and die.

No idea how you can adjust AF without the proper equipment, i.e. an exhaust CO2 sniffer or at least an accurate laser thermometer to measure headers temp..

 

[ninjaneer]

i remember once, just effing around, that i could make the bike stumble on all but #3. this was some months back. but now, nothing. i shotgunned the carbs, before messing with the screws. could this have anything to do with it? i'd reckon only for the better, right? hmmmm.

 

[Rhoy Carter]

My a/f screws also do nothing when screwed all the way in and i know the carbs are super clean

 

[firefly]

I thought I read once a post or a thread, but I can't, for the life of me, find it. I know if you tighten the mixture screws down until lightly sitted, the bike should start stumbling.
What would it mean if none of my mixture screws have this effect and how do you fix it?

I had the same problem, this procedure fixed it, see first post.
http://www.vmaxforum.net/showthread.php?t=18908

 

[naughtyG]

I'm still stumped, as I tried my A/F screws after the full carbs cleanup procedure detailed in my How to's...

I know they were squeaky clean, I'd squeezed and sprayed and blown and sucked carb cleaner and compressed air into every hole in sight while they were apart, yet adjusting the A/F on idle amounted to zero, zilch, nada.

Hmm :ummm::confused2:

 

[sdt354]

My a/f screws also do nothing when screwed all the way in and i know the carbs are super clean

Bottomed out a/f screws should cause a stumble/ rpm drop. Same issue drove me nuts (now you know the cause) I had to actually use a tiny guitar string to run into the idle circuits then spray and shoot air in again a few tmes before the a/f screws responded. After a good,I thought, cleaning and rebuild too.
Just one not responding? I'd do a sync first then retry. A carb with the throttle plate open more than others will make idle a/f a pain to adjust. V-boost has to be off unless there's a way to adjust with boost open? wouldn't know if there is.Just my H.O.
Steve

 

[SpecOps13]

Just the other day. I had the #4 carb on my 89 doing nothing at IDLE. I could pull the plug wire and no difference. I could bottom the A/F Screw and no change. Pulled the Diaphragm and A/F Screw. Ran carb cleaner into all the openings without removing the air box, just the openings on the side. Then put about 120 pounds of pressure through the openings with an air hose.

Put all the parts back and adjusted the A/F Screw that then made a change. Re-Sync'd the carbs and went for a ride.. Idle was perfect, actually running on all 4 cylinders.

Prior to doing this, the bike idled like crap so I had to turn up the idle speed screw. reving the engine was very slow. Once off idle the bike ran like a Bat Outta Hell. After this work returning to idle and all stayed perfect. Reving the engine is now very quick. And, it still runs like ABOH...

 

[ninjaneer]

So I think, it might be the fact that I don't have an oring or a washer in any of the adjustment chambers. At least I don't think so. I stared into them with flash lights and felt around with a picker, but can't seem to find them. I looked for them when I shotgunned but they never showed, so I just figured eff it. Does anyone a have pic of what it looks like when the oring and washer are stuck in the chambers?

The carbs are clean, especially after the shotgun. I'll shotgun again. I'm thinking that I was able to cause the bike to stumble a while back because there was gunk built up allow a proper seal. Now that they are gunk free, I can no longer create a seal. Ya? Long shot? Possible? What do you think? It would seem this has some relevance, because now the bike is having a hard time starting. It now takes full choke and some coaxing to get 'im up, whereas before, only needed 1/4 choke and would fire up like a champ.

regards from my tapatalking android...

 

[SpecOps13]

I made some rubber plugs to go in on top of the screws after they're adjusted.. Provides an air and adjustment seal... Small rubber hose and a screw each.... Good Luck ninjaneer.. Spring, Washer, O-ring in that order on the Air Fuel Screw...

 

[ninjaneer]

I made some rubber plugs to go in on top of the screws after they're adjusted.. Provides an air and adjustment seal... Small rubber hose and a screw each.... Good Luck ninjaneer.. Spring, Washer, O-ring in that order on the Air Fuel Screw...

I remember you sharing this a while back. But I don't quite understand how your hose and screw "provides an air and adjustment seal" if they "go in on top of the screws after they're adjusted" :ummm:

 

[ninjaneer]

So I was trolling around the Net and came across a "generic" how to adjust afr mix writeup. As part of his procedures, he raises the idle to something like 3k prior to turning each adjustment screw and then lowering the idle back to factory spec after all is said and done. So I tried it out, but only raising the idle to 2k and lowering back to 1k. By doing this I was able to achieve the sought-after stumble.

My questions: Is there anything wrong or harmful in doing this? Does having to do this indicate that there is something else the matter?


Sent from my Tapatalking Hercules Android

 

[maleko89]

I suppose you could. I set the screws when engine is warm and then set idle to 2K after an adjustment to make sure no popping or whatever.