Carbs, still kickin my butt! Ideas?

Bike back together and running but she's still teasing me. Carbs have been cleaned and used Chacal's Deluxe rebuild kit. All else done on the front end .... valves, vacuum, float bowls, etc.

Spark plug color is good on #2 and #4. Getting better on #3, but still remains rich on #1.

Hesitates out of first gear, was missing badly when i got above 3K when under a load. Turned idle mix screws in a bit on #1 & 3 and now missed up aroiund 4K rpm.

I really cannot tell which cylinder(s) are missing. I'm assuming either 1 or 3 or both.

Any way to detrmine where the problem is generated from? :?

 

Your float heights are set right?
Does it get better or worse as it warms up?

 

Has the running (vac) synch been performed?

 

Seems to get slightly worse when fully heated up. Running Vac sync done twice with 'carb tune vac tester' perfect and right on the money across all cylinders.

I do have one float bowl on the low side, number 3. It's at the lower limit (3mm +/- 2). it's at 4-5mm with bike on center stand (measured at center of float bowl) but on angle obviously as carb are not level. All others are perfect and on the nose.

the color tune tool did not work on either cylinder 1 or 3. only white, not blue, no yellow, no orange .... just white regardless of where the idle mix screw was turned to.

Again, on #3 it seems I've stopped the plug carbon up problem, but on #1 it still seems to carbon up the plug. for the time being I'm leaving #3 idle mix screw alone. I've just turned #1 idle mix screw to 1 turn above bottom so I'm runninmg out of room to fix carbon issue.

How many miles might it take to start burning off carbon if indeed I do get it set properly?

please continue with suggestions, snickers, and lol's for me even touching a carb.

 

FWIW - I had very similar problems recently on my 550 Seca. I could not determine the cause, and although all cylinders had carboned up plugs, I could tell at least one or two cylinders were either too lean or way too rich (showing incomplete combustion). This was after trying to set idle and vacuum sync within a reasonable range with little success.

Although I had already been through the cabs thoroughly, I ended up taking one more kick at it. I removed the carbs again and went through each and every single circuit (enrichment, idle, main, and floats). All removable jets, plungers, and emulsion tubes were checked and re-cleaned, all passages pressure cleaned, float pin seats cleaned and polished using the golf tee technique, clunk test done, etc. Then a bench float adjustment was done to get the float levels dead on (using gas tank and petcock on prime, several iterations). Then a butterfly valve bench sync was done (visual method with flashlight), then all mixture screws set to 2.75 turns out.

Put the carbs back in and replaced the spark plugs with clean new iridiums. Ensured all carb boots and airbox boots were secure and leak free. Fired up the bike and with some minor tweaking of the butterfly valve settings with an accurate vacuum gauge, the problem is completely gone and the bike runs and idles great. A road test through all RPM ranges confirmed success. I have not yet fine-tuned as I would need a colourtune and YICS cutoff tool to do so (don't have either), but the original problem (which sounds just like yours) is gone.

The lesson here is that the carbs are indeed the weak link on these XJ's, and sometimes you cannot find the problem, or there are several small problems, and tweaking either sync screws or mixture screws only worsens the situation and gets you further from where you actually need to be while doing nothing to solve the problem in the first place. That was my experience anyway.

I'd suggest you try the same approach - just assume you will never know or will not find the root problem with carbs installed, and therefore just do a carb re-removal and a thorough go-through of all 4 carb bodies. Reset your floats as close as possible to spec on all 4, bench sync, and use a reasonable starting point for mixture screw settings. At least you have the colourtune to fine tune once you are done - and you will have eliminated all possible carb-related problems.

 

+1 on 4nik8r, plus test vacuum leak

 

thanks for all the ideas .... remove the carbs and do what I've already done! WOW and all that after $2 grand invested.

 

dmlyster...about 2k sounds right.....I am approaching that dollar amount also....you are not alone.....you are doing it right...when you get it dialed in...you will be rewarded....

 

Get over the $2K.

You probably have a vacuum leak somewhere unless the carbs aren't as thoroughly done as you thought; and float valve specs are in the +/- MM ranges so they need to be as precise as possible.

From the sound of things, either you're fighting a vacuum leak (probably manifold-to-head) or a throttle shaft seal issue (didn't see a full teardown of the rack and butterfly removal to replace those listed) OR you're simply over-adjusting the carbs.

I strongly suspect a combination of any (pick 2) of the above.

Cubic dollars do not equate to success; you have to become a carburetor dentist. Right now it sounds like maybe you're still in chainsaw and hammer mode.

 

thanks for reply .... just want some fun for the cost and time. under it is not nearly as fun as on it!

I took the rack down to the nats petutie. Butterfly removal and all o-ring replacement. (Chacal deluxe carb kit used)

I'm able to vacuum adjust without problem, would I be able to do this if I had a vacuum leak?

I will need to remove the carbs again and should have all winter to screw with 'em as riding season is about over now.

Didn't seem to have vacuum leak prior to taking off carbs, as it ran good except for the float bowl leaking on #1. Could I have done something to create the leak?

 

When you installed the butterfly shaft seals, did you install them with silicone grease? it's very possible something didn't seal quite right or you split open a boot.

take an unlit propane torch and take it around the carb to manifold boots, throttle shaft seals, and vacuum caps....

And before Fitz asks... did you do your valve shim clearances????

 

yep, believe I used the silicone grease on butterfly seals too. But, I've been through this thing in my head so many times .... who knows what I may have missed.

Don't feel any boot cracks, and, vacuum matches real good on all cylinders.

Valves in spec ....... then rechecked and still in spec.

when the propane finds an air leak ..... what happens?

 

Engine revs higher.

 

Did you accurately WET-SET the float levels? With the rack off and held level in all directions? TO SPEC?

If not, you won't get a proper reaction to mixture adjustments.

Did you sync/ColorTune with the YICS blocked?

 

Yes .... Wet set floats (although # 3 moved some) but still at lower limit.
Yes ----- with the rack off and level in all directions
Yes ---- to spec
Yes .... used color tune with yics blocked (although, proper color achievable on #2 and #4 only. No color at all (only white) on #1 and #3. From previous posts no one seems to want to tackle that question.

thanks for continued curiosity.

 

I DID tackle that question.

If the YICS was actually blocked (depending on method) then it means either you have a vacuum leak or leaks somewhere or #1 and #3 still have plugged passages or their float levels are still off.

In answer to one of your previous questions, wrestling the carbs on and off could have broken a manifold loose at the head; plus it's really easy to "turn under" the lip on a manifold causing a leak even though the clamp is tight.

Other possibilities could be as simple as the little rubber caps on the vac spigots; they often look fine but are actually as hard as rocks and no longer sealing. I caught one "dancing in place" as I revved the engine looking for a phantom vac leak.

 

The carbs obviously need to come off anyway. I'll check your hints on vacuum leaks. Also for any plugged ports and re-adress #3 float bowl to bring the level up a bit.

YICS should have blocked prots ok. New tool purchased from Chacal and don't know how I could screw that up.

Still puzzled how I could get carbtune vacuum to be perfect across all cylinders if I have a leak somewhere.

No riding this year .... what a bummer.

 

Oh yea, also still trying to download SS brake line pic. I'll get it to you.

 

something here doesn't add up
1&3 plugs look rich. right? no matter what, you go to believe the plugs
2&4 look ok
1&3 color tune shows white, correct ? that says lean, right?, i ain't a color tune guy
slightly worse when fully heated up ? that says rich
#1 idle mix is 1 turn out that says your getting gas from someplace other than the idle mix screw

i'd say go back to home and start again
mix screws to 3.75 out
check the choke plungers real close on 1&3
check the needle in the slide on 1&3
check the air jets
do a running sync again with that blasted yics tool on the bench
see what you get

 

Yep, seems there is a bunch that doesn't add-up.

I will add your suggestions to my list for review.

All mix screws out to 3.75? #2 and #4 seem to be dialed in and don't want
to mess with em if I don't need to.

 

Polock's right about the symptoms though. One turn out and still rich (check the plugs) means you're getting fuel from somewhere besides the pilot screw.

Make a note of where #2 and #4 are now, then adjust as suggested. Or if the plugs bear witness, leave 2 and 4 alone for now.

And of course re-do the vac sync once you're close on mixtures. Any major mixture adjusting will throw it off.

 

big fitz- Plugs color and color tune confirm #2 and#4 and I know exactly how many turns out they are ..... it is definetly where I want them. So unless mucking with #1 & #3 changes these, this is where they stay.

So this leaves me with where else is fuel coming from? Only other thought is leaking vacuum cap(s) as I obviously have carb tune vacuum tester attached to them during calibration. I'll check these.

I'll be tearing it down and check all the items that Polock listed.

On another note ..... I reduced the pixels on my brake line pic. If your still interested you can view the SS brake line with banding by clicking my gallery tab. This is my second set ..... first one did the same thing.

I've observed no functionality issues with SS line and Chcal has indicated that pressure testing is good. It just gives me pause to observe this. Autoposy info from manufacturer has not yet been communicated.

 

I saw the brake sheath discoloration pic and have some questions:

Were they like that when you got them, and possibly didn't notice right away?

Did the discoloration develop over time, or quite suddenly, say within a day or two? Or over a couple of weeks, and more importantly how many miles?

When you say "second set" is the set in the pic the replacement set you got from Len and it looks like the first one you got from him?

Did that happen on both sides or just on the right as in the pic? In exactly the same place(s) both sets?

Based on the discoloration of the line in relation to the tire and the "gaps" in the fender/brace, I'm wondering if some road condition near you reacted with the sheathing. Do they use "tarmac" in your area (spray down a heavy coating of tar then sprinkle with stone chips?) How about fresh asphalt in your neighborhood? It appears heat or solvent-related. Is it on the inside or have you hit it with a mild solvent to see if it comes off?

My SS lines have black sheathing so I would never notice such a discoloration if it happened.

It doesn't appear to be anything more than cosmetic though.

 

check your air + fuel jets on 1 + 3 to see if they are in the right location? I had my jets swapped on 3 of my carbs accidentally and was having bizarre symptoms.....

 

will do. When I cleaned 'em I removed and replaced after cleaning one at a time to avoid a screw up, but, anything is possibility. Thanks.

 

Remember if you're using the Haynes manual they have them reversed...

 

SS brake lines ...... The pic is of the second set. No appearance of the band out of the box. The second set was nearly identical. It appeared on both left and right sides. Was not observed on MC to junction, but that one is coverd more with sheath for abrasion.

The band on the first set was withing a couple of inches on this set. As I recall a bit higher. Banding on both sides were not necessarily located in same are ...... a bit random yet on the lower side.

Showed up gradually within a week of installation and because of my carbs could not have had more than 10 miles on 'em. No cleaning solvents, no road coatings. It's on the inside of the clear sheath, so no possibility of cleaning.

Let me know if I missed one of your questions, and still waiting for Chacal report back from the supplier.

 

I did not know Haynes manual had them reversed. Air jets or fuel jets or both.

I'll definitly need to double check as during cleaning I just removed, cleaned and reset. Thanks

 

The ones in the top of the carb.

 

which one's are those ....... ha

 

Under the hat, diaphragm and slide out, there are two jets, possibly partially covered by a "deflector" plate (that nobody has quite figured out the reason for.)

From the sound of things, you never pulled those out either. When you do, don't mix them up or use the manual as a reference for re-installation. Just keep track.

 

I was being a smart-ass. That what the 'ha' was for. Yep, got those and one at at time to avoid mixing them up. However, guess its possible that Pprevious owner crossed them up, but then would not likely run as good as it did pre-crab cleaning.

Thanks for puttin up with me.