Carb nightmare.. Any help please?

I've replaced throttle shaft seals, thoroughly cleaned the crap outta them, even boiled them and ran 6 cans of carb cleaner through them, blasted 120psi of compressed air through every passage to ensure flow, followed the gospel completely and I'm still having an issue... 3 of my 4 carbs are functioning perfectly, but my #1 carb has been a royal pain. After shimming valves and synching, my #1 carb shows no combustion at idle during colortune unless I crack the throttle or back the pilot mix screw almost completely out. When I back it out far enough to see flame, its light blue and starts popping and missing like crazy. I'm at my wits end. If anyone has any ideas, please share. (P.s. ive already replaced carb boots and sprayed for vacuum leaks)
Thanks guys and gals...

 

Screw the #1 mixture screw back in to it's natural setting (about 3 turns out from a soft bottoming) and then use the colortune on that cylinder again..........and this time, bump the choke slightly on. If the cylinder comes alive, then that means that the pilot circuit on that carb is still clogged or some other issue (air jets reversed on that carb? No fuel in the fuel bowl In that carb?).

 

Did you wet set the float level? Another thought fill float bowls get a container that is marked in oz open drain screw on the float bowl see if all 4 floats are close in oz . You never know it could be this simple if bowl is not filling to proper level then it would be running lean .

 

Are the ports on the float bowl clean

 

Also check for an air leak at the carb to head manifold.
Fire the bike up and spray some sort of ignitable aerosol spray at the joint. If the engine revs rise at the same time as the spray then there's your problem.

 

did you wet set the carbs?
this is how to do it

Setting the fuel levels

also we recently had a few members who had a similar problem changed the mixture screw for a new one and the problem was solved.
photo of air jets proper placement


I see you have 81 xj650. what kind of airfilter are you running?

 

Thanks for the replies guys, I somehow wasnt getting notifications for replies and just saw these while re-reading In The Church Of Clean.
In response to your questions, I did in fact wet set all float levels, got them all within 2mm below the carb base
I did clean all passages in float bowls.
I gently and thoroughly cleaned and replaced the air and fuel jets and reinstalled them in their proper locations.
Ive replaced carb intake boots and throttle shaft seals, then checked again for leaks and found none.
And I'm running a factory replacement air filter with a completely stock air box setup.

When I first bought the bike, it had sat for a decade on the kickstand with fuel in it, so the #1 carb (the only one giving me problems) was by far the sludgiest, but as I stated earlier, I painstakingly cleaned all of them and blew air through all passages and nothing seems blocked up anymore. The one thing I didnt do is replace the mixture screws, which may be my next move.. So frustrating..

 

Also, when I apply the choke (cold start) or crack the throttle, I do get combustion at idle on my problem cylinder, just none at idle with the choke off if that helps in diagnosis

 

And Chacal, I missed your reply before replying. I might just have to pull them off yet again and give #1 yet another cleaning. I wish the pilot circuit was linear so I can poke a wire through the entire thing, but I figured after boiling, spraying and blasting with air multiple times, it would be cleared up by now...

 

Perhaps a compression test would be in order just to verify the condition of the number one cylinder.

It certainly sounds like you have done a thorough cleaning, but I like to do this to as a confidence check of clear passages after cleaning:

1. Drill an old pilot jet so that the straw from the carb cleaner fits snuggly in the hole.
2. Leave the pilot air jet in, but plug it with a wooden q-tip that is covered with a bit of heat shrink tubing.
3. Install the pilot screw without o-ring, set it to 2.5 turns from soft seat.
4. Blast the carb cleaner through the modified pilot jet and it should look something like this:

 

THANK YOU Rooster! I will definitely try that when I get out of work tonight. I Never found a video such as that, that clearly demonstrates a properly functioning pilot circuit. If I do not have an extra pilot jet, do you think id be able to seal the straw into the jet tube with something and get the same effect?

 

i didn't see anything about a running sync. dat will do dat

 

I assumed it was done there, but you know what they say about assuming.

You might could use some tubing if you have the right size. Just be sure to have those safety glasses on as carb cleaner in the eye is a bad thing. Also be sure to seal the air jet and pilot screw hole, otherwise most of the carb cleaner will just exit in those less restrictive areas.

 

Yep, did a bench sync then a running sync, was running rough still and then thats when I did the colortune and found my issue.
Ill pop them back off tonight and do the carb spray test and post my results.
And I agree with the safety glasses... Blasted myself good on my first go-through and cried like a little girl for 10 minutes. Learned my lesson real quick lol

Thanks for the help guys and wish me luck!

 

also when you follow the video . put your finger over the 2 holes and let the cleaner blast out where the pilot jet is screwed in

 

http://www.xj4ever.com/inside your carbs.pdf

 

That is why my bike would not start Toomanybikes. I cleaned out the jet in each bowl that the brass tube in the carburettor goes into. The bike started first time after that. I did not know about those tiny jets in the float bowls, all sorted now.

 

Did the pilot circuit check and everything is free and clear. Put everything back together, reset mix screw back to factory, did yet another running sync, colortuned.... Same f****ng problem.... I'm so frustrated I had to stop myself from kicking my bike over... I've ruled out the carbs being an issue. These damn things are completely rebuilt and cleaner than when the bike rolled off the factory floor... I back the mix screw all the way out and I get blue flame and white flashes accompanied by backfire that's blowing into my airbox and out of my brand new throttle shaft seals. Ugh... I hate this bike...

 

When you back the mixture screw all the way out you make the mix excessively lean (the o-rings lift and no longer seal the screws, which allows the screw holes to become new air intakes), which is why the flashes of white and the backfiring.

What does the colortune show when you are at 2 1/2 turns out?

 

Nothing but spark. But I believe I have found my problem.. One of my brand-new throttle shaft seals I bought from xjbikes a few weeks ago has expanded greatly since installing it. I once again hit everything with carb cleaner while running and rpms shot up when I hit my outside throttle shaft seal. Must've not hit it on my latest go-around. Hopefully its the only one, as it is the outermost seal on the #1 carb... I dont understand how that could have happened..

 

you got a puddle of carb cleaner in there and the seal sat in it for awhile
take it out and set it in the sum for a few hours, it might shrink back but it might be hard when it does.
go to your hardware store and get (2) #11 o-rings and squeeze them in there with some silicone grease and be fixed on the cheap

 

+1 on both of the above recommendations.

 

Thanks guys. I had a couple of my old seals set aside because they were still in good shape. Slapped one in and bam, combustion at idle. I just still dont understand how my one replacement seal went bad already. The only time any aerosol touched it was the last time I sprayed for leaks. All my other ones seem fine. Oh well, my blood pressure has dropped dramatically lol. Now I just have to do a running sync yet again, then colortune yet again then hopefully my nightmare has ended. I was just going crazy because I was doing EVERYTHING 100% properly and by the book so the rebuild would be a one-shot deal, now here I am putting the carbs back on for the 6th time since starting all because of one faulty brand-new seal lol. Oh well, I'm just glad it's not a dead cylinder I'm dealing with