Strange Mixture Problem XJ550

Hi guys, I've been riding my bike for a couple months (xj550 maxim), but the mixture was never that great. Around 4-5k RPM the bike would pop and not respond, which I understood meant that it was running lean. I never rode it for more than an hour at a time and not too often, as it was cold, so I didn't care about the problem too much. I tried spraying the carb boots with cleaner and found that one of the seals leaked. I bought a colortune, new mixture screw o-rings, float needles, needle seat o-rings, and throttle shaft seals. I had cleaned my carbs previously and had a fuel filter so all I needed to do was replace all the components. In addition I polished up the needle seats.

I put it all together, eyeballed a bench sync on the carbs, set the float levels, and put the carbs on the bike. I then did a running sync. My valve clearances are spot-on, I serviced them a couple hundred miles ago. Now it runs quite strangely. When cooler, the bike runs pretty well, sometimes even too rich (the engine would bog down when throttle applied from low rpm and there were pops when engine braking). When warm, it idles at 2000 rpm even with the idle screw completely unscrewed. I put the colortune on the first and second cylinders. They were running lean and I could not get them rich by unscrewing the mixture screws even all the way. I'm in Colorado at altitude so if anything I should be running rich, shouldn't I?

Any ideas you guys?

 

The pilot circuits are still plugged partially, they are TINY passages:

http://www.xj4ever.com/inside%20your%20carbs.pdf

 

How do I clean them? I broke the rack and soaked the carbs in cleaner for a while, then used Carb cleaner in a can and sprayed into all the jets. It seemed they were clear.

 

Did you remove the pilot mixture screws, replace their tiny o-rings and flush out those passages? If not, that's what chacal is referring to.

When you broke the rack and then soaked the carbs, did you also remove the butterflies and shafts and replace the throttle shaft seals? If not, then you may have "killed" the throttle shaft seals which will also cause a lean condition you can't "tune away." You shouldn't submerge a carb in anything unless it's FULLY stripped, which includes the throttle shafts and their hidden, trapped seals.

Were the float valve seats still installed when you soaked them? If so, there are o-rings on them that will also need to be replaced (although they will cause a different symptom when they fail.)

 

Hi Fitz, thanks for your input. In the first post of the thread I described what I had done in more detail. I didnt take out the pilot mixture screws when I soaked them, but other than that the rack was fully apart. After the soak I cleaned the carbs and replaced the shaft seals, needle seat o rings, needles, and pilot mixture screw o-rings. I did not get the cap off the pilot mixture screw till after that clean, so I did not flush the pilot circuit, but I did flush all the others. I guess I figured that the pilot circuit didnt need it because of the soak, but I guess I was wrong. Ill take the carbs off and flush the pilot circuit passages. Is there anything else I should double check while ive got the carbs off?

 

Another question-how can I tell when those passages are clean? When I spray with Carb cleaner I can see it coming out the other ports but I can't tell if they are fully clean or not.

 

I took my carbs off and cleaned the passageways and jets again, this time using a bristle from a metal brush to ensure the small openings by the butterfly valves were free and open. There was nothing visible that had been blocking up the passages. I checked and fixed my float levels, three of them are at 2.5mm and one is a tiny bit lower than that, a little less than 3mm (this is in spec, right?), then did a bench sync, threw my carbs on my bike and rode for around 40 min. It felt a little bit better than before, but I had not synced or mixture tuned the carbs yet.

I blocked the YICS port with the t-shirt method and synced my carbs. I then tried to mixture tune with my colortune. No matter what the sparks I see are blue. I kept enriching my bike (maybe 4 turns further out each) and there has been no change. The bike now runs really rich (if i throttle it up quickly from idle it will bog out). I noticed a couple of the plugs looked like they were rich, but for only one half of the plug. Is that relevant? I guess I am reading my colortune wrong or something? It definitely got worse from a richer mixture.

 

Did you replace the tiny o-rings on the pilot screws?

Are the enrichment plungers ALL "free" when the choke is off? What was the condition of the rubber seals inside the tips of the enrichment plungers? How about their little boots on top?

Put the mixture screws back at 2 1/2 ~ 3 turns out and get the bike fully warmed up again before you try to ColorTune.

If it continues to give you "rich" results, I'd suspect that you've got an erratic or incorrectly adjusted float or an enrichment plunger that isn't shutting off.

Oh, and 550 plugs do tend to "color" more on one side than the other. I think it's because of the relatively large YICS passages in relation to combustion chamber size.

 

The o-rings are new. The seals and boots of the plungers looked good when I last had the carbs apart a couple of months ago. I think I could tune the richness out, because I had one lean carb and three rich ones according to the plugs. Unscrewing the pilots definitely made the bike run a lot more rich, so they seem to be working right. I made extra sure my floats were operating right and set to the right levels.

Its just weird that I am seeing all lean (blue) colortune results while the bike seems to be running rich. My bike was around an hour warmed up, but I did it outside and maybe because of the light from the sun (even though I used the "periscope") I didn't see the combustion right. Is it pretty faint? I've never used a colortune before.

 

I think maybe we missed this:

If you've got a leaky intake, no amount of carb cleaning, or adusting will fix it. Gotta fix and or replace the intake boots.

Also, every YICS bike i've looked at has that one sided plug burn, i agree it's the yics doing something.

 

I replaced all seals.

 

it could be throttle shaft seals too...even though you sprayed the intake boots, it could still be sucked in around the throttle shaft. (carb dip nukes rubber) and check and make sure all your jets are in the right places!

also, isn't that idle a bit high?

 

You said you replaced the shaft seals, I thought you meant you sprayed the actual intake boots and had a rise in rpm.

 

No, I didn't replace the boots, but it wasn't them that leaked. It was the throttle shaft seals. My boots are in good shape and don't leak. I sprayed around that entire area but only got a rise from the throttle shaft seals on Carb one.