Completely frustrated.

85 XJ700n--As I indicated in my previous post, everything has been done and now I am colortuning. Perfect blue on 2,3,&4, but I'm getting no combustion at idle on #1 with colortune plug in. Rev it a little and I get the blue color. I can see the plug firing at idle, and the bike will not run without the # 1 plug in and connected when I'm using the colortune on the other cylinders. What do I need to re-check?

 

Re: Colortune won't work on one cylinder

Pilot circuit is plugged. Take em off and clean #1 again Probably going to need some guitar string or a very small drill bit yo get though the passage under the pilot jet.

 

Re: Colortune won't work on one cylinder

Have you done a carb sync?
Have you turned the idle mixture screw out any more than your initial setting?

 

Re: Colortune won't work on one cylinder

When I cleaned the carbs I visually check each pilot circit and could see into the throat of the carb looking down. Is there another place I should check?

I did sync the carbs using the YICS tool.

 

Re: Colortune won't work on one cylinder

You need to remove the pilot jet and idle mixture screw in the carb. Clean the jet and blow the carb passage clean. The pilot jet has a very small orfice, make sure it is clear. A single wire strand from a toothbrush size wire brush is about the right size to clear the hole.
Seems like you did not totally dissamble the carbs to clean and there is some crud left in there.

 

Re: Colortune won't work on one cylinder

Take a look at this: http://www.xj4ever.com/inside%20your%20carbs.pdf

You've got a plugged passage somewhere.

 

--I ran a plastic wire through the pilot screw hole, and then used compressed air on the screw hole and actually blew gas out of the carb. Still can't get combustion using colortune plug. The bike runs with the regular plug, but screwing the pilot screw from closed to 5 makes no difference. Real bummer since all other carbs work perfectly. Hard to believe that I'm not getting gas with the hole clear and having used compressed air. So, when I remove the carbs to work on this carb, where should I be focusing my attention and what else can I do?

 

If you take out thge pilot jet and force carb cleaner in there , will it come out through the holes behind the butterfly?
Also there could be a vacuum leak on that cylinder.

 

Just finished re-cleaning this carb. Everything removed, flooded with carb cleaner, probed with small wire, blown out with compressed air, and now back together. Since I have them out, I'm going through the other three also, just to be double sure. Going back on tomorrow night and I'll report the results. Wish me luck.

 

You may have the little washer so fudged up that it is messing with you. Did you replace the washer?

 

washers were replaced. If there is still a problem it is not the screw, washer, or air hole into the carb throat.

 

what about the enrichment circuit in the bowl...zestfully clean?

 

Absolutely. Carb cleaner flows easily with and without compressed air. I didn't mention, but when I first re-installed the carbs and gassed up, the bike started on the first turn or so--with out any use of the enrichment -- or what I still call "choke". The bike starts, runs and idles so well I would have never thought there was a problem if I had not used the colortune.

 

Ok, I assume at this point that you have already done the valve adjustment, and they are in spec. So...for it not to show color on idle, on just one carb, then show color when you blip the throttle, it seems to me that the sync is off. So, the butterfly valve is closed on idle, and won't pull fuel, but when you blip the throttle, the valve opens, and voila.

Did you bench sync when the carbs were off? If so, have you done a running sync with YICS blocked?

 

You need to confirm that the Pilot Passages are clear.
You need to confirm that the AIR JETS are of the correct SIZE ... and are correctly PLACED!

You need to confirm that the PILOT FUEL JET is the right SIZE and is not clogged.

You must confirm that you do not have a MAJOR AIR LEAK on the Number-1 Carb Manifold.

Test for leaks:
Manifold Neck
Manifold Mating Surface to Head.
Possible Incision at Hose Clamp channel.
Wrong Hose Clamp.
NO Clamp.
Seal joint at Manifold to Head w/ RTV.

Major Leak --> NOT Shaft Seals leak.

 

Did a bench sync and running sync. When I blip the throttle I get a little backfire as if fuel was there all along.

 

Rick. Thanks for responding. I used your instructions to really clean the carbs after having them "cleaned" at a shop.

I confirmed the correct jets, size, and placement comparing them with the three that work and my original drawings.

Nothing that can be reached with a thin wire is not fully opened and very clean. I noticed on a schematic that the passage way to the pilot screw area -- apparently where gas flows -- has several small holes. These can't be seen or reached but I soaked the passages with carb cleaner and used compressed are--several times, so I think the carbs are very clean and clear.

I checked for leaks using propane with no change. Will do it again tonight. All the intake boots are in really good condition--no cracks at all.

Putting the carbs back on tonight and hopefully everything will work.

By the way, when I re-installed the carbs the first time, gassed them up, and hit the starter it fired up almost immediately and idled fine. Would have never known there was a problem except for the colortune issue.

 

Re: Completely frustrated.--

Got it working at last. Set all pilot screws at 2 1/2 and all cylinders except # 1 were firing and I closed the pilot screws to get the blue flame. Since # 1 wasn't firing, someone suggested opening the cold start system and see if I got combustion, which I did. Based on this I opened the pilot screw on the #1 cylinder about 4 turns to get combustion and blue flame. the others are less than two, so I guess this carb is just different. Thanks for everyone's help.

 

Re: Completely frustrated.--

Hmmm. This is most curious. I wonder if your #1 carb has different thread pitch on the pilot mixture screw than the other 3? If not, and they are all the same pitch, then there is still a passage plugged, or wrong/bad pilot mixture jetting in that carb.

 

Re: Completely frustrated.--

I wrote down all the jet numbers in each carb and they are all the same and installed the same. Like I indicated, all the passages have been cleaned, probed, and blasted with compressed air--several times. My understanding from a schematic I saw is that there are 2 or 3 small fuel holes in the passage running to the pilot screw, and perhaps they are partially or totally blocked. They can't be seen or probed. However, looking in the carb throat there is one hole where the butterfly closes (pilot screw hole) and two in back of it. I probed those also.

The bike cranks, idles, and runs beautifully, so I'm going to ride it for a while--with some Seafoam-- and see what happens.

 

follow-up to the above. Got carb specs and all jets are the original ones. Ran the bike about 25 miles and it ran well. Added some B-12 carb cleaner and some Star Tron Enzyme treatment and will check everything after a full tank.

 

If you take a 2-Inch length of Shrink-wrap and shrink 1-Inch onto the end of a Carb Cleaner red-tube, ... you will have a Tool you can use to Flush JETS and PASSAGES with Carb Cleaner.

The larger O-D fits into the AIR JET orifices and keeps the fluid from squirting-back at you.

Fits over the Siphon Tube for the Enrichment-well, ... too.

 

Thanks. Right now I have the pilot screw, spring, washer, and o-ring out and used a tooth pick to seal the bottom hole and have filled it with carb cleaner and will leave it for 24 hours. I'm then going to use compressed air and see if that clears it. If not, off they come again.

 

::: F-Y-I :::

The "Little Black Cones" that Doctors use on the Instrument that they use to examine your ears, ... make a great attachment to tape to an AIR CHUCK to be able to Blow-out the Passages.

Unscrew the Valve on the Air Chuck
Remove the Stopper that depresses the Schrader Stem.
Tape the "Little Black Cone" onto the Air Chuck with Duct Tape.
Place the Cone into the Carb Orifices for blowing-out passages.

 

these have to be the cleanest carbs in Georgia. All the passages are clear and everything is back together and on the bike. While I had them off I rechecked the valves and to my surprise found that I needed a new shim on the # 4 intake. All others are in spec. Chacal has it on the way, and once that's replaced I'll finished tuning the carbs, and report the results. By the way when I removed the plugs they looked really good, so I' close.

 

Re: Completely frustrated.--Success at last!

Installed the shim, re-installed the carbs, fired her up and still had a problem on #1. Had to open pilot screw about 4 1/2 turns to get combustion. Pulled out the propane and tried all the obvious locations around the carb with no success. Then turned the propane on full blast and finally got an increase in rpms near the intake boot. Finally found the vacuum leak between the block and intake boot. Removed the carbs and the intake boot and about 1/4 of the intake gasket was missing. Cut a gasket, re-installed, and all is well.

 

Vacuum leaks seem to be the culprit most of the time. Hanging rpms and a rich mixture throttle blades closed, air has to be getting in there somehow. Glad you found it.

MN