Carb Adjustment Hell

[Prothec]

I'm learning a lot about my carbs on my XJ11, but unfortunately it seems like no amount of reading can set my mixture and sync my carbs for me.

I just popped the carbs back on the bike after cleaning again. I also swapped in the original jets that I found in a box from the PO. It has the stock airbox with kerker 4-1 and YICS Eliminator.

For the longest time I couldn't figure out why no adjustments to my mixture screws were making any difference. After a lot syncing, and a lot of turn this, turn that, do what sounds right, I had the bike really starting to sound great! Nice throttle response, no more pops, etc.

Then, I realized I forgot to attach the breather tube to the air box. Apparently that makes a pretty big difference....

Popping and backfiring like crazy now.. I checked the sync and it seems pretty close, and checked where I ended up with the mixture screws and they were around 5 1/2 turns out

Time to start over...

[DGXSER]

I honestly would not have thought the breather would change things that much. I wonder if you got something else loose while putting it on.

5-1/2 turns is really open.....typically that would signal a need to go up a jet size.

[Prothec]

I put 112.5 mains (had 120) / 47.5 (I think?) (had 50) pilot jets back in. The only reason I put them back in was not knowing any better. I should put the 120/50 jets back in, right?

I plan to spend a lot of time tomorrow trying to get things figured out. With no previous experience (aside from syncing my 650), this is a major learning experience

[Douglas Money]

Sounds like a vacuum leak.

[Ken Talbot]

For the longest time I couldn't figure out why no adjustments to my mixture screws were making any difference.

Often, this means the low-speed circuits are still dirty. If they're clean and working at all, you will get a difference as you adjust the screws.

[Prothec]

Okay, so I'm getting a difference on #1,3,4 carbs as I adjust the mixture, but #2 does not give me the change in idle speed that the rest do.

On 1,3, and 4, if I turn them a ways in, the idle speed drops dramatically and I can adjust them back out until the speed starts to pick up.

On #2, the only change I get is some popping in the exhaust as I turn the screw out. I turned it in about a quarter past the point the popping in the exhaust stops.

I do my best to get the idle speed to approximately 900 before I start adjusting and try to keep it there. I have the ESI 328 EZ-Tach+ and I never feel like it is reporting the right rpm.. I usually have it set on the 4 stroke/2cyl setting but it always jumps around a lot, so I pretty much go with the lower than normal sound of a slow idle.

[motoman]

112.5's are stock for that. Maybe 115 mains at the most with what you have exhausting. Not sure if you said or not whether the teeny o-rings around the idle mix screws were new or not. Also has to have the teeny washers in tact. If these are ALL not in tact and good cond., will be difficult to tune............

[Prothec]

The washers and orings looked good. Put them back on the screw - spring, washer, oring.

Been at this all day..still not quite right

[Prothec]

Should I stick with the stock jets I have in now?
It's hard to tell if it's my impatience or something else wrong at this point that I can't seem to get things adjusted.

I keep re-checking sync and they have stayed pretty close according to my dial gauge, BUT for the second time while trying to adjust mixture, I have adjusted myself down to where my idle screw isn't making contact with the plate and I'm over 1k rpm. At that point, I have tried resetting the mixture screws back to 2 turns out, getting the idle set again and starting over with sync, adjusting idle down, then trying to adjust mixture.

I have also considered pulling the carbs and bench syncing again...

[BA80]

The main jets won't have anything to do with the idle speed. Sounds like you have one or more throttle plates sticking. Or, a vacuum leak.

What do your sync readings look like?

[Prothec]

On my "Carburetor Synchronizer" dial gauge, it was around 5 - 6 inches.

It looks just like this one:
http://www.youtube.com/watch?v=gowRb...eature=related

The right gauge on mine is broken, so I'm turning 4 valves on and off to switch between carbs.


After reading this:

http://www.factorypro.com/tech/carbt...m_engines.html

and watching some not very useful youtube videos, I went back out to try again.

My charging system is hosed, so after a few stop/start attempts, I need to throw my battery on the charger and wait to get another go.

I think I need to get a feel for the RPM changes that the tech tip talks about. I have been looking for this rpm increase, then drop off it talk about, but I had only been seeing a rise. This time I reset the mixture screws and idle speed and started up. I dropped the idle speed real low and as I moved the screws I felt a slight rise in RPM, then slight drop off as I kept turning, so went back to that spot. The RPM would rise and when I left it there, the idle speed would drop back to where it was after a couple of seconds.

After I did this with all of the screws, the idle was starting to smooth out. I brought the idle speed back up around 1100 and checked the sync - it was pretty far off, so readjusted.

Battery's back on the charger, just waiting for another round in a bit.

[motoman]

Almost sounds like fuel level in bowl is too low and not picking up enough fuel through idle circuit, and trying to make up the difference with idle mix screws out so far.........JAT.

[Prothec]

Just checked where i'm at now and it's 4.25 - 4.5 per screw.

[BA80]

Almost sounds like fuel level in bowl is too low and not picking up enough fuel through idle circuit, and trying to make up the difference with idle mix screws out so far.........JAT.

The mixture screws on these carbs don't allow extra air, just fuel. If he can't get the idle down it's pulling air from somewhere. The fuel needs air to burn.

See what I'm sayin'?

[Woof]

Recently went through exactly what you are describing including the trashing of my battery.

First are you using the YICS tool to synch the carbs?

I may be able to help, sending you a PM with my number if you want to call.