Carb problems again ......, and again ........, and

thanks hogf - still working these carbs over. With my luck I'll be reinstalling, finding it still doesn't run right then pulling and trying some new hint not yet tried.

I've no confidence but will not give in!

 

Len - oh yea, I've got this #1 completley broken down ....... unless I'm more clueless than I think (not impossible) there are no rubber seals, o-rings, or other rubber components left.

Please let me know if you believe I've missed something.

 

Not a chance.

 

Come on Len, some bailing wire, duct tape, a tube or two of rtv sealant, chunks of bicycle tire tubes and electrical tape...ought to be able to get er to idle.

Dmlyster, sounds like you are on the right trail. Just make sure that prior to reassemble, you insure that you can squirt cleaner through the enrichment circuit and the jets and then blow with hi pressure air.

After you have reassemble the carbs and did a bench set, set your carbs in your holder for doing a wet set to the floats and remove the bowl for carb # 1

Place a container underneath and run gasoline through the fuel line. If gas pours out, no line blockage. One less thing to worry about.

Wet set the floats to spec. Turn at a/f mixture screw out 2 3/4 turns from bottoming out.

With these carbs, they have to be exactly spot on. Like fishing, either the fish is on or it isn't....nothing in between..

Hope this helps
(smiling at the carbs while working on them seems to help karma)

 

That's it? then I got this!

 

I'm not sure the racks are the same width, or that the diameters are the same, or the jets are the same, or the airflow is the same, etc.........

Be interesting to fid out.........

Maybe one of those racks with a sets of pods would be the answer..... LOL


DAVE

 

Okay, Flushed with berryman's. Could not find a clogged port. Cleaner through every orafface followed by air. Kinda reminded me of my last colonoscopy prep, but I'm sure you didn't want to hear that.

It's now reassembled. Prior to putting it back on the rack I will try to wet set the float properly. Then install back on rack ..... only to wet set floats again.

I will be away from the bike for a few days so will work on setup when I get back ..... I'll pick up this thread at that time. Thanks for continued help.

 

"It's now reassembled. Prior to putting it back on the rack I will try to wet set the float properly. Then install back on rack ..... only to wet set floats again."

Wet setting the floats are done with the carbs off the bike on a level (left-right-front-back) carb holder. Once all 4 carbs are in spec then reinstall on bike. You do not have to anything to the floats once the carbs are back on the bike. The only adjustment is a running vacuum sync and then colortune the a/f mixture, and possibly a final adjustment to the running vacuum sync.

She should start, idle, run like a scared skink after that...

Hope this helps..

 

Okay, I'm reserecting my thread as I've got the carbs on and taken a few trial runs. It lives but still needs a pacemaker!

Plug condition: 1,2,4 seem to be too clean (lean). #3 carboned up (rich).
As I adjust the mix screw for #3 (clockwise - in) to try to lean the carb it seems to get worse (more carbon). Am I adjusting wrong way?

I cannot get 1,2,4 to that light brown color on the plugs. Still seems lean based on color.

Cold start / idle: When hot I adjust idle stop / bar for proper idle speed, idles fine at stops. After cooling and trying to start it is a no-go, regardless of enrichment circuit. I must increase Idle adjustment then she will lite up. And again after a few miles stop and reduce idle to avoid 2K to 2.5K idle at stops.

Engin seems slightly rough at low RPM around 3K. Near 4K I cannot feel that rough, slightly off condition.

Gas mileage is between 30 and 35 if not less.

I know there is a lot of stuff going on here, but any continued ideas will be more than welcome.

 

I don't recall the rest of the thread.... Did you check shims? Did you check for leaks? Did you check the enriched tube BOWL jet?

 

Yep, been following everyone's advice / suggestions for the past 2 years. Valves, vacuum tune, church of clean, float bowls set wet and dry, bench set butterflys, taken these carbs off and reinstalled 5 times now, carb rebuild from Chacal ...... and let me tell you, everyone has been real helpful not to mention patient with me.

It seems to me that I just cannot get a balance between air and fuel just the way it needs to be.

I can always check the vacuum balance again but how to get the fuel to match properly ..... cannot get the plug color where it should be.

 

Plug color isn't as good of an indicator of fuel mixture as it used to be. Gasoline formulations are quite different than they were even 10 years ago, and vary widely depending on your specific location. You can have the A/F ratio correct and still have a white-to-grey plug. Get a Gunson Colortune to set your A/F ratio with.

 

Check you mixture needles to see if they aren't bent or broken

Check your slide needle to make sure its not worn

Check your Emulsion tubes to make sure they are not worn where the slide needle goes down into them

Try that, then we'll come with another list like:

Check your TCI

 

Used the Gunnison colortune and it's all over the map. some hard to get pale blue color other adjust quite nicely into the recommended color. Runs crappy when set to recommended so adjusted until running good.

Needles are great when cleaned and re-assembled ...... unless I bent / broke them when putting them back together.

Clunk tested ...... clean and drops nicely.

How do I test the TCI?

thanks Hogfid and K-moe

 

Any leaks anywhere?

 

No leaks that I can find ..... use propane to look for engin rev. Bought new vacuum port covers from Chacal just in case .... all good

 

Humor me..... Check to make you have the right jets in the "airhorns" in the fronts of the carbs as well as the right positions under the diaphragms.

But I'm still curious about bent/ broken mixture tips--

 

Pull enrichment plunger #3 off the carb and inspect/polish it and the seat for it in the carb. One spec of anything holding the plunger open will create a rich situation and foul the plug.

Hope this helps.

 

checked and double checked jet locations under the diaphrame .... absolutly positive on that.

seriously doubt bent needle unless happened two weeks ago when reassembled.

I'll try the enricment plunger if I can get to it with carbs still installed on bike.

Thanks all.

 

Look at the mixture needles carefully........the reason I'm stressing that is simple; I'm rebuilding a rack for someone right now and one of the mix screws had a tip broken off...... not enough to be obvious, just enough that if it was turned all the way down it didn't protrude QUITE as much as the others did. It was just a tiny bit shorter that yo feel the difference but not see it. Maybe 1/64" difference. But that would really screw up the idle mix.......

Dave

 

Speaking of the mixture screws: were their tiny o-rings REPLACED or just deemed to be "OK?"

 

Yeah, good point. While on that--- Make sure that the order of the parts is correct too---
Spring
Washer
O-ring

I've seen many different incorrect stuff ranging from; wrong order, to wrong parts, to wrong thread( there's fine and coarse threads out there), to missing rings and/or washers, and recently did one where there wer two o-rings in the bore......

Dave

 

YEP .. Spring, washer, o-ring. O-rings all new and replaced from Chacal's rebuild kit.

 

Just took it for another test ride.

Getting low 30's gpm when riding mostly at 4k rpm and 55-60 mph.

?? riding at 5K rpm gets better milage ??

Prior to ride I tuned to my ear ... (instead of colortune). backed off mixture screw (counterclockwise) 3/4 turn, it sounded and ran much better but plug is still carboned up. But not as bad!

I'll try to pull mix screw (now on bike obviously). Those tiny pieces tough to remove without losing one when on bike.

 

Turning the mixture screws counterclockwise richens the mixture.

 

K-moe ---- Yea I know and this is part of what is baffling me. Plug cleaned up (at least some) and it ran a whole lot better.

but this is the position where it runs best.

Any thoughts on most efficient RPM's for best GPM?

 

Yup

 

Yup what? will you elaborate? please

 

Yup ..... thought the quote got in there, sorry.

 

If your mileage is still that bad, you're either

1. running way to rich yet
2.your Speedo is way off,
3. You're losing fuel through somewhere else.

Can you tell us what your rpm are AT STEADY 60MPH IN 5th gear?

Right now the best way to test the tci is to put in a known good one and take it for a ride, see if there is any change.

I may go back and re-read through the whole thread to see what else we may be missing.

Dzve

 

I'm definately RICH on NO. 3 cylinder as plug continues to carbon up.

The others 1,2, and 4 seem too lean as I cannot get color on the plugs, but that seems the least of my issues. I'm focusing on correcting No 3 right now.

My tac is registering about 4100 - 4200 (visual guess) in 5th gear giving me a speed reading of 60mph.

At this time I've decided to remove the mix screw (no. 3)and inspect / reset. I will be doing this with the carb in place ..... so most likely I will lose eithe the o-ring or washer and be ordering new ones from Chacal

Thanks for continued help.

 

RPM-to-speed seems about right.....

Let's see what you find with the needle----

Dave

 

Okay - got the mix needle and associated parts out. Have not lost anything yet. It seemed that the o-ring and washer were slightly stuck together but came apart easily ...... does that mean anything, like, not able to adjust properly?

Ordered as should be: o-ring,washer,spring, mix needle.

Under magnafing glass it looked good except for black speck at end of needle. Don't know if it was there while in place or not ... it just rubbed off. Seemed to be a few specs of (aluminum?) around threads. Under mag I see nothing bent and nothing appears to be broken, although I don't have comparison to ensure proper length.

Soaked pieces in Barryman's (except for o-ring) and cleaned. Shot some Barryman's down mix shaft and blew out with canned air. With my luck I've likely lodged something in that tiny ... tiny hole now. Oh well, needed to be done.

I'm now trying to remove the enrichment rod to get at that No. 3 plunger. I need a different 2.5 mm hex wrench to reach into and loosen from rod.

While at this point ..... any other hints of encourgment?

 

The ONLY way that I even found out that I had a broken enrichment screw was that I noticed that the tip of one didn't protrude quite as far as the others into the back bore of the carbs when they were all bottomed out. It's a TINY amount, and all I could tell was that it felt slightly different. When I looked close, I could see the tip just ever so slightly shorter...... as in " I could just feel and see the tips if three needles protruding slightly, but the fourth one was almost flush with the bore edge. If you just looked casually they look virtually the same til you look real close.... and feel them. Three would t" easily catch the skin of a finger lightly dragged over them, but one was just slightly more than barely perceptible.

Would be nice that's the issue!

Davee

 

Sounds like 2 options. Reinstall original and hope something changed or 2) buy a new one to make sure.

However, it was running fine prior to rebuilding the carb.

Decisions, Decisions.

I'll try to look at enrichment plunger and go from there.

 

Don't know if I can be of any help, but I had a similar problem with my mikunis, and could not resolve until I ordered a tap from len. None of mine were seating properly due to dirt and grime. Like daves previous post, I couldn't even tell the tips were not right until very close inspection. Good luck

 

Okay .... weekend project was to remove mix needle and enrichment plunger on number 3, without removing carbs from bike.
Pulled mix needle and components, cleaned again and reinstalled. And without loseing very small pieces ..... lucky I guess.
Pulled enrichment plunger and cleaned with finest 3M pad. Neither of these looked to be dirty or damaged so back in they went.

Took it for a ride and it seemed to be smother but not perfect. Number 3 plug still shows some soot but looks like it may be self cleaning. I'm going to take if for an extended ride to see if the plug self cleans and runs good.

So far I may have beat insanity 'Doing the same thing over and over and expecting a different result'. I should know in a few days if it's improved enough to consider a success.

Thanks for everyon's help, but I may not be done so I'll keep this thread going.

 

I may have found the reason the idle is rough on my '82 XJ750 w/ 13000 mi on it. When pulling the idle mixture screws I noticed 1 was missing the washer and ALL were missing the O-ring! Would this cause idle problems?

 

Yes, that is a problem!

 

Thanks for pulling up this thread again ....... I've been working on and testing the beast.

Got some great help from Chacal (Len). He has some seriouis patients with newbe's! He's helped a great deal by confirming via photos that potential problem parts are indeed still good. For a carb newbe that may not be able to recognize a bad component, a great help.

With Len's and forum help I got to the point of a smooth runner. And fuel mileage beyond belief. After ultra-sonic my #3 carb in carb cleaner I now got 46 mpg, quite an improvement from previous 27 mpg. Carboned up #3 plug now nice and clean.

Now, since this mpg is too good, Len and I agree I need to increase the lean condition to a more rich condition. I've been observing the plugs and am trying to get a slight brown tint to the plug. My approach is to begin moving the mix screw (counterclock wise) a 1/4 turn at a time then ride. Check again to see if I've attaind my light brown color. If not re-do the process. Then repeat until I get there.

Another other thoughts out there?

Thanks again Len and all on the forum that have helped!

 

1/4 turn is a WAY BIG adjustment when you're fine-tuning mixtures. Think maybe the thickness of a dime; what's that, 1/16 of a turn? 1/32?

 

Does that screw adjust more than just idle/low RPM mix?

 

Mixture screws don't adjust the idle. They adjust the amount of fuel that combine with the air/oil passing through the carbs to be ignited and compressed in the chamber. Adjusting the fuel amount is what raises or lowers the idle. The idle adjustment knob located at the rear of the carbs is used to adjust the idle. Make sense? Don't worry; it will.

Gary

 

Well, sorta. Mixture screws do adjust the IDLE mixture.

But they are not how you adjust the idle.

There are also adjusting screws on the throttle linkage that you use to synchronize the carbs. The big knob adjusts the overall idle.

Adjusting the sync and the mixtures are something we do AFTER the valves are in spec and the carbs serviced and their float levels set.

 

^^ what he said. And there had better not be any oil running through the carbs on an XJ.

 

Thanks, I'll be real soft on the pilot screw adjustment.

 

ordered one of these http://www.ebay.com.au/itm/26186140...48&var=560707333443&ssPageName=STRK:MEBIDX:IT
I will hopefully use the ultrasonic magic to fix the stuttering idle.
I like the concept thats for sure.
Good thread!

 

Would cost less than that to do a total rebuild

 

Been there... done that... bikes runs great just a bastard whenever I take off from a set of lights.
I DESPISE carb cleaner... and yes I did get that stuff in my eye more than once.
So, don't be too bloody quick with your barbs.

 

Wasn't a barb, dude......relax