Idle problems

So I tried to balance the carbs today with the 2 bottle method.

This is coming after a bench sync and my fuel levels set. Valve clearances also taken care of. All mixture screws are set at 2.5 turns.

Started off with 1&2, everything seemed good, it was still idling at 1050 and I got em synced

Next to 3&4, again, got them balanced and it was still idling at 1050, great.

Onto the last, 2&3, get them balanced BUT rpm has shot up to like 2000 or so. I think, alright no problem. Just reach under and bring the idle down with the adjustment rod, keep turning it and no change.

So this brought me completely out of any bench synced setting I had for the rod and it was still idling at 2k.

Messed around with it for a while, screws turned all over and ended up with the same result, "synced" but still idling at 1500-2k so... Not synced.

Also, 2nd header still isn't as hot as the other 3.

Super frustrated coming from a winter of working on it lol

 

time to start messing with the pilot screws. you can do it by ear, but you really should have a color tune plug. don't forget to make sure the throttle cable has some slack in it.

FU

 

I assume you are using vacuum tubes to help in the balancing. I had similar issues with one cylinder running cold and after cleaning them. With the help of Chacal I did one more clean on the cold cylinder carb ...... that fixed it.

Yea, not being a mechanic, real frustrating. Hate taking carbs off-on-off-on-off etc ......

 

Cold header = dirty pilot circuit.

Warmish header = still too dirty pilot circuit.

If they aren't all clean you'll never get a good synch.

 

Alright so that's somewhere to start... If I do them by ear what am I looking for exactly?

Also I recall reading somewhere that the 2.5 turns apply differently to two different pilot screws, coarse and fine?

K-moe, the pilot circuit, is that the pilot mixture screws?

 

mixture screw is just part of the pilot circuit

 

So the pilot circuit is the hole where the screw goes in essentially?

Reckon I didn't clean them good enough.

 

The pilot circuit extends through a brass tube down into the enriching well in the bowl, it also has an air supply to the mixture screw as well as the fuel supply to the mixture screw as well as the enriching plunger. The mixture screw is just part of the Pilot circuit...

 

http://www.xjbikes.com/forums/index.php?threads/in-the-church-of-clean.14692/

http://www.xjbikes.com/forums/index.php?threads/the-secret-life-of-carburetors.14751/

And a clear view of what Hogfiddles is describing: http://www.xj4ever.com/inside your carbs.pdf

^^That^^ is why cleaning is really important (for any carb).

 

if you start from rich, turn them in till you just detect a drop in rpm. if you start from lean, go richer till the rpm's stop going up, then go leaner till you get that lean drop again. either way once you find the lean drop, go richer 1/8 turn. the lean drop off is kind of subtle, takes a good ear

fine thread, you can set then at 2 3/4 and go ride.

this is important.
you want to see light between the lifting fingers and the enrichment plungers too.

 

Can always count on you guys haha, going to start fresh tomorrow, was putting the grips and bar end mirrors on today.

Before I start tomorrow I'll throw in some extras.

Pretty sure it's a fine thread considering I've got them at 2.5 turns and I've been out riding/testing with no problems. Except of course the 2000-2500 rpm idle.

This puts me at rich I believe so I'll start turning them in tomorrow and see how that goes

The throttle cable has some slack to it, how much should it have? It looks pretty relaxed and only really engages once I pull it in. There's an initial pull that tightens it and then rolls open smoothly.

 

i've found 2.5 turns out is lean, 2.75 is in the ball park, 3 is kind of rich. this all depends on any mods, but for stock, it's close

 

that's what we're here for. you should just have some loose feel before feeling pull on the throttle at the grip. but when you are tuning you should put a bunch of slack in the throttle to be sure that the carbs are sitting on the idle stop screw, and not hanging on the throttle.

FU

 

I find that setting the mixture screws at 2.5 then give tweak of about 1/8 turn more puts the right on. Time after time, the colortune is right on. Once in a while there's one that may need a tweak, but not often.

I would be hard-pressed to call 2.5 turns rich. I turn them the extra 1/8 turn to richer them slightly. It keeps cyl temps down a touch, and will help keep you from burning up do to a lean condition

 

I ended up setting them at 2 3/4 as per Pollock and that seemed to work and then went back to syncing them and it was going pretty well until I got to the last step, balancing 2&3.

No matter what way I turned it was still emptying one of the bottles, 2 wasn't sucking enough.

I also think my throttle shaft seals are just done, I mean I'll blip the throttle and it sometimes seems to catch and I have to blip it a couple more times to get it to idle back down.

Ended up giving up then firing it back up and it rode alright for all of the 50 feet I tried it lol.

Then I tried to turn it on and it was struggling, finally turned on, idled super low and died out then wouldn't turn on unless I boosted it so I reckon my battery was out of juice after all this syncing.

We'll get there eventually.

 

Did you adjust the idle speed screw, as needed, to keep rpm's up? Did you blip the throttle and let it settle down after each small adjustment?

The 2/3 screw only balances left half to right half (1&2 with 3&4).

Dave

 

I did not blip the throttle since it would get stuck when I tried, but I started blipping it on the last set...

Going forward but slightly backward... It wasn't my battery that was low, the bike starts, but idles terribly low only when I pull the intake cap off of carb/intake #2, what does this mean?

Edit: gave all the adjustment screws one turn and it fired up no problem but idle shot to 3k. Seems that since I didn't blip the throttle after adjustments that I basically set it wayyy too low.

PROGRESS.

 

Well, I'm done for today and the near future since exams are almost here.

Ended up backing the idle adjustment screw's out a bit more on 1&4, no bottles attached or anything just trying to get that idle back down and it worked. Got it to 1050, but if I take it out for a ride it starts creeping up to 1500-2k range.

Oh well, it's a lack of precise tools like a colortune that make this whole process rather tedious but I'll make do.

Any suggestions as where to go from here are welcome, oh and the throttle isn't catching anymore, so that's nice.