What am I missing?!?!?!?run away rev hanging rev

Still getting the hanging revs!! Can get it to idle but have to play with her a bit, but hadnt started in a few weeks. Its always a pain to get started but after get going starts right up but still always all over the place keep having to play with idle screw to balance out. Will stay at idle unitl i start reving then it goes down and then proceeds to take back off alone.

Checked:
-new petcock, fuel filter, fuel line, fresh mid grade
-new throttle seals
-new exhaust gaskets
-new float needles/gaskets
-new spring clips and carb boot nipples
-vacuum leak test/passed, no increase in revs when sprayed any where
-clunk test passed, took apart to check polished some more and passed again
-float heights at 17.5mm on the money across the board
-new throttle cable, butterflys returning and throttle assembly not binding
-colortuned to a nice blue, couldnt do more then a bench sync because it would rev away with the carbtune hooked up even when not reving it

Any ideas where else to go? The bikes really starting to look the part, the solo seats on it now and even with the snow showers coming down here in baltimore Im dieing to get a little satisfaction on all the work ive been doing. I have all winter but def want to be riding first semi warm day!!

 

I would try a different set of carbs.
I just bought a second set of "beater" carbs just to have a set at hand in case I find a bike for sale that will not start and idle.
They are not yet rebuilt. If they were I would bring them up and give them a try with you.

 

Can you turn the idle set screw down enough to keep the idle down to about 1500 RPM? If you can get the idle to stay that low then I would try the carb sync again. If you colortuned with the idle above that then it won't be correct either. I also don't trust setting the floats other than reading the actual fuel level via clear tubing.

 

Half-appreciate the thought, might try that couldnt hurt to have a spare set of carbs around regardless.

Blue-I had it idle but if I touch anything it seems to go crazy, with the sticks in had trouble getting it to idle, and when it did the sticks seem too low to barely registering.
I colortuned at idle though mainly to check that the mixtures werent crazy out of wack one way or another and my mixture screws, washers, orings, springs are all new so that showed me nothing was binded up in there.
I did not do a fuel line test after setting the dry float height something I should probably check.

I feel like the carbs are so clean and completely rebuilt now I wouldnt have any problems, but got to be something obviously.

Def feel like once I fix this Im a sync and some plug chops away from being a happy xj rider.

 

Its the way I troubleshoot.

If the weather were nice I would ride up to your place and take my carbs out and try them in your bike.

 

Hi juan, have a look at the little caps on the 3 ports that don't have the vac' line on, I found that these looked good & sealed when cold, but when hot went soft & were leaking, I put extra cable ties on there, idle now a.o.k. Wiz.

 

I went and watched a few of the videos. It Looks like you got some rigging going on there. With that tank and all of the filters. The bikes bogging and then taking in air or fuel. Check all the vaccum lines. Its obvious that its a fuel/ air problem. I would Get a manual and go threw it. Make everything back to stock to do with the engine and carbs and go from there

 

wiz-I have a gravity fed petcock and new caps and spring clips on all 4 ports but ill try some zipties see if it will help

tyler-those vids are from when i pulled it out of the back yard of the po, I up jetted for the pods and short exhaust one of my first dozen times into the carbs...getting it back to stock would have been just as much as a pain since it came with no air box and the mufflers were rusted out, no going back now for me. Also I read the manual and this site like a bible these days lol.

Have a new 3/8 thread pingle style pet cock and fuel line though in the newly re done tank. I def like the clear line with a real petcock, the po had rigged up some hose vales and such b4 so just re did it all

 

A little trick with the carbtune on podded carbs is to turn it upside down. You will be able to read it with the lower vacuum that way. That is if the carbtune is the Morgan Carbtune II.

 

I would suspect a butterfly spring or springs is allowing the fly(s) to open.

You would have to remove the carbs to test that theory.

 

My xj550 does the same thing, idle rpms "floats" up and down. While it was running the butterfly brass end with the large C-clip "flutters" meaning the throttle bushings are probably worn. If you can push the throttle butterflys down to close tighter & the idle speed drops the spring tension is weak.

I backed out all Sync screws so the carb butterflys are almost closed - now it idles at 1,200 rpm +/- until it gets hot; then it idles a bit faster. Sometimes it dies at a light but starts right up again. Engine doesn't seem to mind being slightly out of perfect sync - still hauls.

You might try a "helper" accessory spring connected to the underside of the return arc / guide (half-moon shape) ... my next project.

 

You are blocking off the YICS when trying to synch aren't you?

 

Its fuel/air related for sure and an xj of course its the carbs lol

Yes Im using a YICS block off tool that I got from chacal.

I think its a spring butterfly issue as well, have to check in better detail cus they appeared fine b4 reinstalling the carbs this last time. I could put pressure on the sync screws which would bring it back down, although it didnt feel like they were moving really. The xtra spring sounds like a neat possible idea.

Im using a carbtune pro same company newer model so Ill try the upside down trick.

Thanks for the help as always.

 

It shouldn't need any extra springs, if the rack is lined up & the seals are ok.

 

I agree wiz,
Im sure its something Im over looking, I knew going into an old bike with mods there was going to be a lot of "gremlins" some probably self made. Hopefully Ill find out something when I go fiddle with it some more saturday.

 

Little update, I was able to get her all sync'd up using the carbtune. The idle seems a bit dif then b4 in a good way but not a huge difference. You can hear it and the reving away on the link to the mods forum in my sig.

I took the carbs off again none of the butterflys are sticking and Im def sync'd up now. I had the throttle cable off completely thats why I was using my hand in the video and still running away when throttled.

I want to get another set of carbs to try be working that after xmas either on here or ebay as soon as I can. But feel like I should be able to make these work with so many new parts on there already and sync'd, hate the feeling like Im being beat and these carbs are kicking my @$$!

Ideas? Ill be bored with time off and nothing to tinker with in the garage.