82 XJ550 Running Rough

Hey all, I posted here looking for help several months ago but ran out time to mess with the bike. I finally got around to it and it's still having the same issue: It'll only start with starting fluid and the throttle held open a bit but will stay running on gas. When it runs it runs really rough, doesn't want to rev freely it sputters and breaks up. Also, if the rpm's fall below 1.5-2k it will die.

I built the entire bike from parts, and it did run well for a few days before this started. Here's a list of the pertinent stuff that I did.

New Battery
Blade fuses
Tank cleaned and recoated
New Petcock
Had the carbs serviced by a shop. They wet set the float levels, synced, and cleaned them out a bit more.
Checked valves, in spec.
Replaced pick up coil. (I sprayed contact cleaner on the original)
New D8EA's gapped to .28

I've spent many hours reading the posts in this forum and from what I've read it seems that my problem is fuel related since I do have spark on all 4 and it runs but the carbs were just serviced which leads me to think that fuel would not be a problem. Needless to say I'm pretty confused about what to do with it next.

 

It sounds like your carbs weren't cleaned out thoroughly. Add an inline fuel filter if you haven't already. When you say you had the carbs serviced by s shop, did they disassemble the carbs to clean them? How was the bike running when you got it back from them?

 

Found your problem. Seriously. There is one shop in town that is hugely praised by our local townspeople, but one of the mechanics spent 10 mins trying to convince me that my bike was one of the early fuel injected bikes. Really.

Pull the carbs, clean em again, bench sync, wet set CORRECTLY. Not starting and holding low idles tells me it's either a plugged passage somewhere, or critically uncorrect float levels. Remember that the rack must be completely level for accurate measurement, this adjustment cannot be done on the bike. Then get a YICS tool and vac sync.

Does it start with choke? Run only with choke?

 

Petcock has a filter on it and is brand new. When I got the carbs back it ran exactly the same as it did before: very poorly. They did disassemble the carbs, but I'm not sure how far. The only reason I got a shop to look at them was to double check my cleaning, syncing, and wet setting because I thought maybe I screwed up. They said they were pretty clean, that my sync was good, and my float levels were a tiny bit off.

I tried choking it with no throttle and it wouldn't start. No choke and some throttle starts it, but only if I spray starting fluid into the carbs. Runs without choke and with it but still equally bad.

Today I went through the ignition troubleshooting guide, Tested the pickup coils, voltage at TCI on and cranking. Voltage to coils, and plug wire resistance all okay.

 

A video I took earlier. Not sure if it's helpful as the sound quality is not so good.

https://www.youtube.com/watch?v=btxRbLCwZ4Y

 

Sounds like you have an aftermarket exhaust or are running just the headpipes. Are you running pods filters too? Your problem might be your jetting. I would still put an inline fuel filter on the bike. The petcock filter lets garbage through.

 

I'll put an inline filter on my to-do list. It is running open headers with pod filters which I know require jetting but it ran well with that same setup during the first test rides after the rebuild. Between running good and running rough I didn't make any changes to the air filters, jets, or anything else for that matter.

 

How much "test riding" was done with the current intake and exhaust configuration?

The reason I ask is it doesn't take long to hurt a motor if it's running horribly lean.

Go back and re-check the valve clearances. If you find a couple that are suddenly inexplicably loose, those valves are no longer closing properly.

If all the valve clearances are still in spec (and match your notes from when you adjusted them) then do a compression test. Let's hope you didn't hole a piston.

 

About 7 miles of test riding. I checked the valve clearances twice already. Once before ever starting it, and again after I started having this problem. They were the same both times. I'll see if I can get my hands on something to test compression with tomorrow.

 

Was able to borrow my grandfathers compression tester today, here are the results:

C1: 165
C2: 155
C3: 175
C4: 165

 

Those numbers are way high. A healthy 550 makes 135 max.

If accurate, those results would indicate the cylinders are "wet" similar to when you put oil in to do a wet compression test.

The most likely cause for that would be that they're wet with fuel, indicating carb float level issues. Check your sump for gas (open the filler cap, stick your nose in and have a whiff.) It should smell like warm oil; if it smells like gas you're dumping fuel.

And then borrow a different compression gauge, and get a "second opinion."

 

I bought a cheap compression tester at autozone today and got similar results. 155,150,160,160. The oil smells like starting fluid and gas. Going to check the float levels again now. Edit: Checked float levels and they are all even with the heads of the screws that attach the float bowls.

 

You have (or had) a stuck float and leaky petcock. Don't run the engine until you get rid of the oil/gas mixture and add oil. And fix that petcock.

 

Plus the float levels don't sound right.

Check here: http://www.xj4ever.com/setting%20fuel%20levels.pdf and check the Mikuni BS28 specs. Should be 2.0mm +/-1.0mm from the carb body flange. MILLIMETERS are tiny.

You might also have a leaky enrichment plunger issue.

 

Also check the gas cap seal for cracks and broke/missing pieces.

Gary H.