Drained the Magneto Oil Last Night '83 XT550

What's that? You didn't know the XT550 has magneto oil? Neither did I. This is how I found out.

I've been trying to track down a problem with my XT550 and I'm bald, so now I'm pulling my eye brows out.

The bike runs, sometimes it's a little hard to start, but it runs. Now it runs consistently like it's not firing on all cylinders for the first 15 minutes. Being a single this makes it even more interesting. It pops on decelleration. Above 1/2 throttle, it just doesn't want to go and will actually slow down. As it starts to "wake up", it surges, backs off, surges, backs off, surges for a bit and then out of now where, full power! It will run normal from then on as long as it's warm. It will restart and be normal. Let it cool off and it goes back to it's groggy state.

This started about a week ago. The only thing that has been done to it is a valve adjustment. The day I picked it up, it was fine. Then it rained for a week, and I accidentally left the gas on. When it ran this way, cleaned the carb, thinking it was running lean due to varnish.

Since then, I've pulled the carb joint boots, inspected them, replaced the o-ring behind the boots and replaced Yamaha's stock clamps with ordinary hose clamps. I've sprayed it with carb cleaner and there's no change in idle, so I no longer suspect a carb leak anywhere.

I've replaced the spark plug.

The PO had taped up the plug wire and boot with electrical tape. I removed it, inspected the boot and wire. I have no idea why he covered it in electrical tape, but I re-covered it in electrical tape again.

I've pulled all the panels, scrubbed every ground, even though they look OK with a wire brush. I've cleaned every electrical contact I could find that was related to the CDI, magneto, spark plug coil.

None of this helped.

So, I decided I should check the timing.

I pull the left side engine cover to look at the magneto, since the tiny hole yamaha provides for checking the timing doesn't let you see much. Plus, I broke my screw driver trying to take it off, so I wanted to see if there was a reason it broke a 1/2" wide flat head screw driver.

I figure this way, I can see what timing marks are available. The bottom two cover bolts are oily, but this is no surprise. I've had several bikes that get a bit of oil in this cavity.

I crack the cover, more oil comes out, a lot more. I grab and oil pan too late and about a 1/2 quart or so of oil drains out.

I think to myself "$h*t, this is one of the bikes that has the clutch on the left. Oh, well. I got in this deep, I may as well take a look at the clutch." As I pull the cover off, there's the flywheel and stator covered in oil. Great. Well, it is a 27 year old bike...

So I examine the available markings on the flywheel, remove the timing cap and reinstall.

Then I fire up the bike and in no time at all, I see how all this oil got in there, it's spitting oil out the timing light hole! Worse, it covered my girlfriend's cars' rear fender and tire with oil. So I can't check the timing. There is a steady pulsing air/oil stream coming out of this hole.

So, I need some help here. First, can you replace this crank seal without splitting the cases? (please say yes, please say yes).

Second, am I going to need a flywheel puller?

Third, this thing is huge! Is it possible to use a stator and flywheel and CDI pick-up from a different bike on the XT550?

Most importantly, do you think this could be the source of my runs like crap problem?

My word, you learn something new every day...

I can understand that it has oil in there; mine has it too and must be a a helluva pressure since it seeps past the little timing hole plug a bit. Oil doesn't conduct electricity, so it's safe in there. Helps with the cooling, from what I've heard. I think to check the timing you have to don a rain suit or good MX goggles to do it. I have a manual for the 550, I'll check it out for you and get back to you. Good luck and hope the gf's car ain't too dirty :thumbsup:

She had to wash it immediately upon discovery. I had already wiped it off with a rag, but that wasn't good enough. She washed it. Right now it's raining, so it would have been washed one way or the other.

I had one other thing I tried as far as the runs like a retarded orangatan for 15 minutes, since I had the valves adjusted, I loosened the auto-decompression cable, just to make sure that wasn't it. Tonight, I'm going to loosen it all the way (adjusted all the way in) so I'll have no decomp action and see if that makes a difference.

I hope so. Hair is gone, eyebrows are gone, up next is the mustache and goatee. I'm gonna look really funny if I don't get a solution soon.

I feel a little better about the magneto oil if your bike is this way too.

I also dread the ghosts of CDI's past may have possessed my bike. It's too damn weird.

I've looked at the XT550 service manual, it provides no answers on if this can be replaced without splitting the cases. It does mention a flywheel puller in the "special tools" section, but I didn't see if they mention it in the disassembly process.

I'll have to sponsor you a wig pretty soon^_^. I checked through the manual, but no mention of the seal anywhere. BTW, play on the decomp lever pivot on the head must be 0.02in, or so they say. I've always been wondering...what stops a person from using the XT600 CDI on our 550's? If a 550 can be bored out to 600 spec and still run, surely the 600CDI will work with the 550. Just my 2 cents, anyway. There is a small possibility that the oil could be contaminated with something (water, fuel, metal shavings, dead bugs) that could cause arcing inside the stator causing the crap running. The odds are very small though. Check the wires from the stator to the CDI, as mine are mostly buggered and because of that my XT stranded me 2km from home the other day...weird little bikes hey

hmm... that makes sense, but after I drained it, it should have hopefully got the crap out before it refilled again.

Oh, to answer my own question re: different flywheel.

Ok, this is a process and I figure I'll list my thinking to make sure if someone else trys it, they know how I got to this crazyness.

I think the XT/TT600 flywheel and stator will fit. I don't know if it's physically smaller or weighs less, but it looks like it.

In 1983, Yammaha made the XT550 and the TT600.

The LH case cover, which holds the stator, is the same for 1982 XT550 all the way to 1989 XT600.

The flywheel for the 1984 TT600 is the same as the 1983. The crank is the same for 1987 down to 1984.

The nut and washer that holds the flywheel on is the same for tons of Yamahas, including the XT600 and XT550, so the flywheel *PROBABLY* has the same shaft diameter. If the shaft diameter is the same and the stator connections and pick up are the same and it's swapped as a complete unit (flywheel, pick up and stator), it should work, since the XT550 and XT600 use the same CDI. (you asked, here it is.)

There's one big unknown, that is is the woodruff key in the correct location so the pickup sees the signal at 12* BTDC? That I don't know and the solution could only be found by taking it to a machine shop if I'm wrong.

So after I get all this straightened out, I'm going to go ride my little beast and not think about this for a while. If I change the oil seal, I'll be sure to weigh and measure the XT550 flywheel. When I think about it again, I'll see if I can get some nice, unsuspecting ebay seller to weigh and measure the flywheel and if I'm right, I'll buy it and try it.

But that still doesn't solve the runs like a dog with peanut butter stuck on the roof of his mouth.

Answered yet another of my questions:

There is no oil seal over the crankshaft bearing.

It's normal to have the generator stator and rotor bathed in engine oil.

So it's supposed to be this way.

Having adjusted the auto-decompression lever all the way in, in effect making it not work, it does not change anything.

It did start first kick, but I can't claim that's different because sometimes it did start first kick before.

One thing that does appear different is the exhaust pipes are now even hotter than before, but perhaps that's cause I took a 25 mph run instead of a 40 mph run.

So I fear it's CDI time. Anyone have one I can borrow to check?

I really hope it's just a carb issue and not the CDI. Holding thumbs

The more I think about it, the more convinced I am that it's running retarded. Not as in special ed either. I think instead of firing at 12-36 degrees BTDC, it's firing at best at TDC or perhaps even ATDC by a degree or two.

I bet the fuel is still burning as it moves past the valves and into the exhaust.

I've eliminated everything else, grounds, bad plug (the plug was shot), dirty carb, random air leak making it super lean. I've checked the voltage off the coil and that seems more than sufficient. I tried to check the continuity, but was having a brain fart, so I never thought to reverse the leads. I kept getting unlimited ohms because there's a diode in the line somewhere according to the wiring diagram. So I'm 90% sure that's good.

All that's left is valves because that's the last thing that was changed... although maybe it's the rear tire? I got a new rear tire too, must be bad rubber.

I can't check the timing to verify it because of the outright dumb design of the crank case (why put a timing mark on something you can't check without getting an oil bath? At least put the plug on the top and marks on the side of the flywheel to limit the oil blow-through as much as possible, or how about a sight glass or something?)

Nothing else makes sense except random variable ignition timing due to a bad CDI. There's either a capacitor that doesn't cooperate without 15 minutes of persuasion or another component that's failed inside the CDI, but works after 15 minutes or so.

Well, now I have an excuse to try the DIY CDI someone posted.

I too lost a quart of oil onto the garage floor the first time I took the stator cover off an XT550. I think every XT550 owner probably has. Fortunately, you don't have to lean the bike very far to the side for all the oil to stay in there.

You could lean the bike over and pull the stator cover off again the make sure there isn't any metal filings stuck to the magnets on the flywheel. You don't have to pull the flywheel to do this, so it's only a 5-10 minute job.

Also, checking the timing isn't all that bad, but it takes a few minutes. Loosen the air box and pull it back, loosen the carb and slide it out the stator side of the bike. Remove the upper motor mount. Disconnect the auto decomp cable. remove the valve cover by lifting it and sliding it backward until you can slide it out the stator side of the bike. Remember that there are two "hidden" allen bolts holding the valve cover on besides those you can see, one under the motor mount and one behind the intake valve access plate.

Then, simply throw a 19mm socket on the crank and rotate it until the slash next to the "t" is lined up with the mark in the bottom inspection hole. The two dash marks on the timing gear should be parallel to the top of the head. If they're way off, rotate the crank 360 degrees and check again.

My guess is that the timing is fine. The design of the timing chain and gear on the XT550 is such that the timing chain would probably break before it would jump a tooth. So if it was right to begin with, it's most likely still right and you have something else wrong.

When I say timing, I mean ignition timing.

If you can tell me how to do that without getting soaked in oil, I'd much appreciate it. But like I said, I'm betting I have retarded ignition timing because of the other symptoms and the only permanent fix is replacing the CDI.

Of course, my efforts to check the timing weren't totally in vain, the gasket isn't sealing any more, so I gotta replace that. too.

Thanks though. I'm feeling a whole lot better that I'm not the only one. When I had the cover off, it did not appear to have any filings or other contamination on the flywheel magnet.

So I'm currently working on a DIY CDI circuit, a friend thinks he's got a better, cheaper and easier idea than the ones listed in the other thread.

But he wants to know, the stator pickup is this a normally open or normally closed circuit? Or does it go high or low (assuming it produces current instead of connecting a circuit). If somebody knows, I'd be very appreciative.

Sorry, I should have paid better attention to your first post.

If your going to replace the CDI, maybe it would be worth a try to cut your existing CDI open and see what's what?

I seem to recall a post where someone took their CDI apart off an XT550 and found corrosion. Once they cleaned it up and resealed it, the bike ran fine.

I saw that too, and I'm really, really tempted to do it.

After next weekend (as in starting eight days from now, not tomorrow) I would.

I've got a ride planned and while I think it's a not so great idea, I'd rather take the bike with the misfiring CDI and ride it around in circles for 20 minutes until it decides to behave, and be able to ride it the rest of the time than take the CDI apart and find out I have no bike at all.

My next available option is my kid's DRZ-125, or have my girlfriend ride the DRZ and I ride her KE.

But after I get some sort or resolution, even if it's only a 12 degree without any advance analog CDI replacement, I'll crack open the current CDI and see what I can find.

I'm fairly certain it's only one component that can probably be purchased at Radio Shack that has failed this time.

I've got a ride planned and while I think it's a not so great idea, I'd rather take the bike with the misfiring CDI and ride it around in circles for 20 minutes until it decides to behave, and be able to ride it the rest of the time than take the CDI apart and find out I have no bike at all.

I hear that. I have a ride planned for this Wednesday and even though my XT is running okay, I'm commuting today on my scooter just to keep the XT safe and sound in my garage.

I have no backup bike for the ride, so I can't take a chance on a mishap between now and then (knock on wood).

I have a dead CDI that I've been meaning to open up, but I haven't got around to it yet. This one didn't give any warning before failure, it just stopped working completely. I replaced it with one of Wayne Gum's CDI's. One of these days I'm going to try and repair so I have a spare.

So, if you do attempt surgery on yours, maybe you could take a few photos

to show what you find and what you do to fix it?

First I gotta figure out how you get that acrylic/epoxy stuff out without destroying it. Maybe soak it in napalm? I mean acetone?

I hope it doesn't crap out on me on the trails, that's why I'm frantically trying to get everything I need for the DIY CDI. I figure pop that in if it works, keep the misbehaving one in the tool sack just in case the replacement isn't so hot.

My XT550 is my back up bike, for the street. My street bike took a dump earlier in the year and I haven't gotten to fixing it yet.

Can somebody do me a huge huge favor?

Can you take the seat or air cleaner side cover off your bike, fire it up and give me a reading on both red and brown wires? The other side of the probe will go to ground, any exposed metal on the frame or engine will work.

Should be AC. I'm getting 62V~ on one and 7-9~ on the other. For some reason, I think this should be higher? But since the bike runs, even if it's crappy I think it's ok.

You'll need to stick the probe under the water proof jacket to get a reading.

I haven't forgotten 'bout ya, Smac... but I've been trying to track down my multimeter. I'm pretty sure my brother has it. He works nights, so I won't be able to get it back from him till Saturday sometime.

I actually have two XT550's in my garage at the moment, mine and one that belongs to a guy I ride with. I'll test 'em both.

Well, better late than never, I suppose.

I only had time at noon to test the bike with the factory CDI. I got a steady 65~ off the red wire and only 2.5-2.6~ off the brown? That was at idle, I didn't have enough hands to blip the throttle.

Let me know if you want me to test my bike too.

That's pretty close to the numbers I got, so I'm reasonably sure my bike is putting out the correct voltage then.

I presume this bike is running normal.

I didn't have enough hands to do all that and work the throttle either.

Thanks so much.

Ok, so I'm back on the task again.

I (well actually a friend) built a small (an I mean small - a half dozen components) circuit that hopefully will replace the CDI.

But it runs on DC. I have no idea if it will work. I have no idea what it's supposed to do. My hardware skills have completely rusted apart. I can do really simple stuff, but more complicated I'm lost.

He looked over the diagrams, looked over some other circuits and came up with this. He thinks it will work, it connects to the battery for power, the 36 degree timing lead and the spark plug coil.

The high voltage side of the stator is completely left out.

Is there any harm in running the bike with the high voltage side of the coil empty?

I'm going to try it tonight, so we'll see if it works.

Tried the DIY CDI my friend put together, got nothing.

He was under the impression the CDI grounds the coil, but it doesn't. So there will be a take two which I hope will work.

Also, if you're reading this, check the XT550 ignition info thread, if you know the answer, I'll be very appreciative, if you don't, well just bump the Views count.

I found something else interesting out, I'm letting you all know at the risk of letting thieves know how to steal our bikes, so hopefully you can do something to keep theives from stealing your bike. The bike will run, sans key, kill switch in the off position and every other potential method to keep someone from stealing the bike by disconnecting the black wire from the CDI to the coil.

I may drill a hole in the frame by the CDI and up to just before the oil tank to run a separate wire between these two points just to make it harder to steal. It obviously won't prevent every theft, but it should help as a deterrent. I may also try the dual wire speaker wire in the correct diameter and use that instead run through the frame, cutting one wire also cuts the coil's power - so it won't run.

That's quite scary, to see how easily these oldies can be stolen. 2 weeks ago a buddy of mine had his 2009 Suzuki Boulevard carried away just a few blocks away from where I stay. Scary stuff...oh well, he bought the ZX-12 we had in our shop today so he's happy again. It's sad what the economy is doing to people...it's like a civil war here

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