Finally back together, all cylinders fouling... TCI hot.

HI!

I've been working on a COMPLETELY REBUILD of my bike for the past several months. I had a transmission problem from a previous owner that I wanted to take care of so I had the bike stripped down to the frame, and did a complete bottom-up rebuild of the motor (aside from replacing a few transmission parts it was mostly just a disassemble/reassemble).

PROBLEM: The bike started right up, but it seems to be running REALLY rich. It runs rough, very "lumpy." It idles but eventually slowly dies. Choke makes it worse. dark-ish smoke out the tailpipe, and the big one, black spark plugs. Here's the deal though, ALL FOUR spark plugs are equally black. They weren't dripping wet, just black. These plugs were clean when I removed them from the engine a few months ago, and clean when I put them in, and were fouled in just a minute of running the engine.


THINGS I DID: Engine all together, timing should be right, checked all the valves and they're not perfect but they're not too far off (I'll be getting them perfect on final tuning).

I did a total rebuild of the carbs EXCEPT replacing the v-rings in the actual throttle shafts. Other than that I pulled them all apart and cleaned everything. They were actually not very dirty. There were no clogged jets, the needles were shiny and straight, and no resistance in the brass cylinders (clunk!). Regardless, I soaked all the non-rubber parts in carb parts cleaner and took carb cleaner spray to the rest. They're super clean. I also built myself a jig to test all the float levels and they seemed fine, only slightly adjusted one that was just a couple millimeters high. Right now they're 2-4mm below the bowl gasket, with the carbs levelled up.

I did not touch the mixture screws, but based on the condition of the carbs when I took them apart (a little very fine powder coating on everything but NO gunk or clogs anywhere) I highly doubt there's an issue there.

The enrichment circuit was nice and clean and all the rubber seems fine. It operates smoothly, closing fully... really considering the miles on the bike (60k!) the carbs were in remarkably good shape.

I also bench-synced the carbs before putting them on the bike.

I tried running it with and without the air cleaner, no difference.

I made one mistake and installed the manifolds upside down so the vacuum hose from the tank won't reach, so right now I'm just testing with all the manifold vacuum taps plugged, and the vacuum port on the tank plugged, with it set to "prime."

MY HYPOTHESIS: After scratching my head a bunch, I noted that one of the wiring harnesses under the seat was hot, and so was the TCI module on the side of the bike. This is with only running the bike for about a minute, maybe two. Could I have a bad connection or something that's causing problems with the TCI, resulting in a weak ignition?

If it was something as simple as a vacuum leak I would think it would affect one cylinder more than others, but the problem seems to be very even across all four cylinders, which is why I'm suspecting something global like ignition. However, I don't know how hot the TCI should be getting after a few minutes, so I have no basis of comparison. Is there a way to test this?

 

TCI problem is probably un-related to the fuel mixture situation......

Did you get the main and pilot fuel (or air) jets reversed. That would surely cause a very rich condition, as would have the choke not closing fully, or fuel level settings that are way too high.......

 

choke definitely closing fully. Main and pilot FUEL jets are definitely not swapped, I put the main (larger) jet in center tube that screws in to the brass jet tube thing, hard to describe but if you've built one you know what I mean The smaller fuel jet screws in the shorter tube directly to the carb body.

The Air jets I might have swapped but my logic on these is that they should match up with the fuel jets. You can see the "tube" that the air flows through in the side of the carb. The smaller air jet connects to the smaller fuel jet and same with the larger ones. I suppose I could whip up a visual aid...

by "fuel level" I assume you mean float level, and I checked all four carbs and they were all within 1mm (2 max) of specification.

 

Will a fouled plug tend to clear up if the mixture problem is resolved, or once the plug is fouled can it cause the problem to persist even if the original problem is resolved until the plugs are manually cleaned?

 

Oh, hey Chacal. I never made the connection that you were the xj4ever guy!

 

No, this is backwards, and that is most probably the cause of your fouling!

The plugs may come back to life after cleaning, but may not......

 

oh! WELL THEN! That would probably do it!

Thanks so much!

 

In the meantime, have a picture!

 

The Air Jets are OPPOSITE from FUEL Jets.



Main FUEL = O (Large)
Main AIR = o (Small)

Pilot FUEL = o (Small)
Pilot AIR = O (Large)

 

Okay, I swapped them (didn't even have to remove the carbs from the bike!) and HOO boy did that do the trick. Completely solved THAT issue.

Of course, now the thing is lean. WAY lean. Like, blip the throttle and the revs keep rising a bit even after you snap it closed, and then reaaaaaally slowly settles back down to idle, and giving a backfire or two.

Honestly it's a lot like it always ran BEFORE the teardown, just a lot worse.

I'm betting vacuum leak, but man, where? New caps on all the manifolds. Manifolds are cracked a bit on the outside but on the inside they're smooth. They're sealed to the block with RTV (for now, just got some gaskets for them). Everything seemed to seal up really well in the carbs... All I got left is the V-rings on the throttle shafts!

So I suppose that's my next step. Where else to look? There's also the valve adjustment issue. Would the valves being a bit on the tight side tend to make it run lean, since they're open a bit longer?

 

No.

Test for AIR Leaks.
Test for a tight Throttle Cable.

You should have Bench Synced with a FEELER that would allow the Throttles to CLOSE.

You need those Throttle Plates to Close.
Set the Idle Screws to Idle the Bike without the Throttles opened.

 

The next thing to do is fix this issue!:

Why, you ask?

Because:

NOTE: all intake manifolds differ between the left side and the right side versions in two critical manners:

* intake manifolds, when installed on the engines, "curve" inwards towards the centerline of the bike.

* they also curve "upwards" (as well as inwards).

This combination of both upward and inward curvatures of the intake manifolds is why it is not possible to simply swap left side (cylinders #1 and #2) and right side (cylinders #3 and #4) intake manifolds.....some people think that you can just "flip upside down" a right side manifold and it will become a left side manifold (or vice-versa). This would be true is there were only the "inward" curvature to the manifolds; however, the "upward" curvature prevents such swapping from occurring (as the swapped-side manifold would be curving "inwards and downward")...........and you'll never get the carbs to fit correctly into such mis-aligned manifolds, and on the slim chance that you do get them to fit, you'll end up with major vacuum leaks at that joint.

 

Throttle cable is nice and tight and snaps back closed really quick.

I did a bench sync procedure using a pair of paperclips... read the procedure on the everythingxj650 site. Curious about the idling with the throttles closed, though. Isn't the whole point of the idle set screw to keep the butterflies opened just the tiniest bit?

Of course, that said, one generally just sets the idle screw so that the bike idles at all. Kinda hard to tell if the butterfly is open or closed when it's on the bike and running!

I just read about spraying various connections with ether/starting fluid/etc to see if the engine revs up. Are there other tests I can do to look for leaks? Sorry I'm sure these questions have been asked a hundred times, I'm doing searches and reading through as many threads and learning as much as I possibly can!

 

This is good to know! Unfortunately I'm going on a trip this weekend and I won't have any more time to touch the bike until next week, but I'll let you guys know how it goes!

 

Just run the Vacuum Line to the No.-1 Carb.

There's nothing special about the Vacuum from No.-3!

 

Regarding your TCI, have you checked all of the associated ground connections for the ignition system? One for the coils, one below the voltage regulator, connections in general?
The TCI shouldn't get very hot.