Few questions about an XJ550 Maxim

Hello, last week I picked myself up an 82 Maxim 550 that has 15k miles.

Runs great, starts promptly, except for it doesn't want to idle without the choke or some throttle. If I leave it alone, the idle slowly dips lower and lower, then finally starts to sputter and kills. Spraying a bit of ether in the intake box can keep it running for a while. At first I thought it was just gummy carbs, but after riding for a bit at night I realized that the lights dim waaaay down below 2k~ rpm. The electrical output is so feeble at these low RPMs that the turn signals won't work.

I got to thinking, that perhaps the voltage regulator is hosed, or there is some other underlying electrical issue causing the bike to stall, such as a bad ground or two?

I checked thoroughly for air leaks, could not find any - at least that I could tell were leaks, since I had to manipulate the throttle myself while spraying ether on everything.

The plugs were something of an oddity. The insulators on all four were a rusty red color at the top, and a normal white-ish tan the rest of the way down. The lip of the threaded body was covered in a thin layer of soot, and the anode was a dark grey. I noticed there was actually a thin layer of what visibly was rust on all the electrodes of all four plugs, towards the body where the arc wasn't being produced.

Away from the engine itself, did these bikes come standard with roller or o-ring chains? And is there an easy way to tell the difference?

I noticed this bike has no fuel gauge/low fuel warning light of any kind. How big of a pain is it to install one? Such as getting a tank from a similiar bike that did come equipped with a sending unit of some sorts, then rigging up a light or gauge?

With all those out of the way - is a good carb cleaning in order, or are there other gremlins that could be getting in the way of a proper idle? Carburetion is still something of a mystery to me, most of my engine knowledge lies in the realm of fuel injection.
I read up on the great carb guides on this forum and figured out how they work (mostly), and think I can tackle cleaning them without bad things happening. I believe I have Mikuni BS28s?

Any advice will be well appreciated.

 

All very valid questions;

The battery most likely is weak. These bikes depend heavily upon the battery below 2K; a good, strong and properly charged battery will support the turn signals while sitting at a stoplight. Wait until you discover the other phenomenon: the battery with enough "juice" to spin the motor but nothing left over to fire the plugs.

The fusebox in these bikes is an Achilles' heel. The fuse clips crystallize and will just break for no reason or if you so much as look at them. You can replace just the clips with similar bits from Radio Shack; or rid yourself of the hard-to-find glass fuses altogether and upgrade to a modern fusebox. The latter is preferred.

If your plugs really ARE rusty (and it's possible) I'd put a new set in there right away before you try to "read" those.

Standard 530 chain. If your bike has sat for a long period and the chain is the least bit rusty you might just replace it. My 7K-mile bike had sat for a long time and the chain was rusted internally. Once I started riding the bike, the chain wouldjn't hold adjustment, and kept bleeding red every time I lubed it. Replace both sprockets too.

The SECA 550 has a fuel gauge but due to styling constraints the tanks won't swap. A whole bunch of the same era bikes have at least low-fuel warning lights, it would be easy enough to retrofit a sending unit.

At 15K miles it's very likely you need a valve adjustment unless you have documented proof it's actually been done. Due to the perceived difficulty of the procedure, this was often simply ignored by the original owner(s) of these bikes. Valve clearances in need of attention will also affect the way the bike idles. You also need to check compression and check and adjust the valves before beginning any carb tuning or you'll drive yourself crazy.

Check your rear brake shoes for delamination. This is a very common occurance with these bikes especially if they've sat. Do it right away; it can have disastrous results-- it can cause an unexpected rear wheel lockup.

Once again, if it sat for any period of time, you probably DO need a good carb cleaning; and install an inline fuel filter so you don't have to keep doing them.

Welcome aboard; the 550s are suhweet-- ask a man who owns one (or two...)

 

These xj's tend to be really cold blooded. I have an 82 550 and mine isnt really warm and runing good until i ride a good 5 to 7 miles. You might want to try adjusting your idle screw. That is located on the back side of your engine. There should be a space between the engine and the rest of the bike right around teh area where your foot brake is. The idle screw is above that but in teh middle back of the engine.

http://pdftown.com/Yamaha-XJ-550-Service-Manual.html

The link above this paragraph is a service manual that i found at a site called pdftown. It should have all teh information you need to tear your bike down to pieces and put it all back together.

Hope everything works out for ya bud. That bike will run like a rapped ape when its working right.

 

The previous owner of the bike had it for a year, but didn't ride it a whole lot. Since the title was mileage exempt, I had no idea what the exact mileage he put on was, but I'm assuming it wasn't a whole lot. The trip-meter was about 230 or so.

I forgot about the valve clearances. I will have to give those a look; changing valve shims isn't the most complex work from what I saw in the guide on this forum... but I lack the tool needed to change out the shims.

Two weeks ago there was a yamaha dealer near me, but they closed up. Next closest yamaha shop is a good hour drive away. I'm not really sure where I can acquire this tool.


Chain isn't rusty, it's one of the first things I looked over when I got it. I just now looked at one of your previous posts about chains, and I looked it over carefully. The gap between teeth on the sprockets is a nice, smooth stretched U, there is about 1 3/4" of play on the chain in the center of its span, and I can only nudge a link just barely at the 3 o'clock position on the rear sprocket.
There is one point of concern, though. On (what I assume to be) the wheel/chain adjuster bolt, the one that points back on the sprocket side of the wheel, held in place by a locknut, is bent. The bike was obviously dropped, as it has some damage on its left side, including that bolt. I can back it out, I think, assuming I get the lock nut loose, but there is no way I am going to be able to turn it in more.

I looked up the fusebox mod, and it seems easy enough to do. I'll put that on my 'to-do' list.

I'll also check out the rear brakes, assuming I just need to detach the brake lever and drive out the axle?



I fiddled with the idle adjustment knob, but that didn't work out so well. Sure I could get it to maintain a 2k idle from startup, but if I gave it any throttle, it didn't want to come back down from 5k. Backing it out again dropped the RPMs, but then it'd conk out again. I am considering messing with the idle air screws on each of the carbs themselves, but I'm a bit worried about messing with those.

The idle problem actually gets worse the warmer the bike is. When it's overnight cold, it'll start and hum along at a third choke. As it warms up, I actually have to give it a touch more choke to keep it alive if I don't want to hold the throttle when stopped.

It already pulls very well when I hit 6-7k rpm; goes from naught to sixty in no time at all. If I can get this idle problem squared away so I can actually relax when I'm at a light or stop sign, I'll be a happy motorcyclist. This is my first bike, by the way.
Also thanks for the pdf - it'll come in handy!

 

PM chacal, he has the wares to do the job.
he also has shims. get your readings and send him what you got. he will make sure you get the parts and tools... for a nominal fee of course

 

The "tool" is commonly available and should run you less than $20.

The rear axle will slide right out (no driving necessary,) however you can also pull the blocks off the ends of the swingarm, drop the adjusters and slide the whole shooting match out the back then disassemble it. Don't forget to undo the torque rod too, and use a new cotter pin upon reassembly.

You can replace the bent chain puller bolt with a standard metric bolt. It will have a 13mm head instead of the 10mm of the original, and you'll need to grind the tip to a slight taper but it will work fine.

Don't start fiddling with the carbs until you've checked the valves and are ready to do a real sync, otherwise unless you're real lucky you'll just make matters worse.

 

Do you have the Clymer manual for the bike? I would check to make sure you are getting proper voltages and then check to make sure your resistance readings aren't too high at the connector under the seat that goes to the regulator rectifier. I had the same problem with the idle dropping lower and lower until the bike died, and I swore up and down it was the carbs even though I had cleaned and adjusted them several times over.

It turns out, that the battery wasn't charging properly at idle and that was causing the battery to drain little by little with the bike running at idle. My problem turned out to be the alternator brushes were registering extremely high resistance through the brown and green wires at the connector I mentioned. So even though they were well within spec lengthwise, they were causing my charging problem and also my eventual dying at idle.

 

BTW -- welcome! I have an xj 550 and I love it.
Really follow fitz's advice about replacing the rear brake shoes. Had the delamination 'event' on my xj750 and it was shocking!
Consider putting your bike and location in your signature

 

Finally got those valve clearances checked! All four of the screws on the ignition cover stripped... even an extractor didn't work. Managed to get two off by slotting them and using a flathead, the other two I had to cut the heads off. Anyone know offhand what thread pitch these are so I can buy some replacements?

On to the valves -
Intake 1 .005" .127mm
Intake 2 .006" .152mm
Intake 3 .004" .102mm
Intake 4 .005" .127mm
Exhaust 1 .004" 102mm
Exhaust 2 .006" .152mm
Exhaust 3 .006" .152mm
Exhaust 4 .006" .152mm

Measurements were based on the thickest feeler gauge that would slide between the lobe and the shim, with the lobe point 180 degrees away from the shim, so the center of the heel would be facing the shim. The engine was slightly warm, probably no hotter than 90 degrees.

Next up I'll be taking some basic electrical measurements. While I was poking around the valves, the battery reads 12.5v standing, 10.9v cranking. Didn't measure voltage drops, though.

 

Take one of the ones you got out with ya to Ace hardware or the like.

Valve clearances are close with the exception of intake 3 and exhaust 1.
I'd recheck them when it's cold to be sure.

 

They are standard pitch M6 bolts/screws. I had to retap mine because in the three or four days that I had my cover off, some hornets decided to lay their young in the threads and seal em up real good. I couldn't believe how hard that stuff was. I had to chisel it out with a scribe, then I had to retap the threads because the mud was packed so hard in the threads.

 

Rechecked the valves, they're the same as my previous measurements.

Today I went for a short ride, about 20 miles, after putting a cup of B12 Chemtool in the tank with a gallon of fuel. Ran terrible smoke everywhere, all kinds of good fun. Then topped it off with fresh fuel and went for a hundred mile ride.

After I came home, it'd almost idle without choke. Almost. Might give the chemtool another go or two and see how things end up down the road. I'm really hesitant to get into the carbs, if you can't tell.

The other thing I noticed is that right around 6k rpm at load, it gets a really noticeable vibration that lasts until 8k, then subsides into 'normal' vibration. Obviously this is most noticeable when I'm cruising at 55-60mph, right at 6k rpm.
Is this normal for a 550, or is there something going on?

 

i have a 550 thats the same year and it doesnt vibrate at all. You should probably try to figure that out. Maybe something loose.

 

Installed new spark plugs yesterday and went for a short ride, about 15 miles.

Pulled the plugs and I have the same red coloration on the insulation nose. It's a cherry red color.

From what I can find, it indicates a fuel additive, but I've not put anything extra in the fuel. Could it just be the blending of the gasoline where I live? (SE wisconsin)

 

You just posted that you had run a cup of Chemtool thru the gas tank. Isn't that "putting something extra in the fuel?"

The 550 does have a "resonance range" like any of the other XJs. However, if the bike is properly tuned and carbs sync'ed, it's not very noticeable. My 24K bike has a bit more of a buzz than my 9K bike; neither are very bad.

If you're running the stock exhaust, check the mount for your collector box (under the back of it) and check all the headpipe-collector clamps and the muffler-collector clamps. Anything loose in the exhaust system will set up one heck of a "harmonic" vibration.

rpgoerlich is right though; re-check those valve clearances COLD. As in sat overnight stone cold.

And quit fiddling with the carbs before you get it waay out of tune before you're ready to do a real sync.

 

I haven't touched the carbs I'm waiting until I can get all the tools, like the YICS tool and a proper manometer, before I even think of tearing them down. No reason to go into things half-cocked. I'd also like to prepare to buy new boots in case the old head-to-carb boots crack or otherwise fail to seal after I remove the carb rack. They don't look that old, but I like to be prepared.

I should've elaborated a bit more - I ran the chemtool through before I got the new plugs. Puttered around until I was well into the reserve, then emptied the tank and got fresh gas. The older plugs had that rusty color on them, which I assume to be the red getting deposited on top of a normal tan color.

I double checked the valves when it was overnight cold, and got the same numbers. When I order all the other stuff, perhaps in my next cheque or two, I'll likely get the shim tool and a pair of shims.

This chacal guy is gonna love me.

 

+1. (A "real" manometer makes the job too easy.)

Your intake manifolds are likely not cracked all the way through, the easiest way to tell is to flex them from the inside while the carbs are off. Any cracks that don't go through can be packed with black high-temp RTV.

The reason everyone advocates repair over replacement for the intake manifolds is because it's way too easy to break a mounting screw and then you end up having a screw extraction nightmare which may include pulling the head and taking it somewhere to be professionally attended to.

My point was to not prematurely fiddle with mixture screws and ESPECIALLY not the "air" screws (actually the throttle stop screws on #1, #2 and #4) as those are the ones that are used for sync.