My Yamaha 1982 xj550j keeps flooding everytime it idles.

My friend had the bike for a long time and he never winterized it, and you can guess what happened. After rebuilding the carb and cleaning it out with carb cleaner the bike would start, and then just choke it self from the fuel. I had taken apart the carb 4 times and it looks like the float needles and move freely and the float height is correct. I even synced my carbs with a home made manometer, even tho I didn't have the YICS tool. I honestly have no idea why it's flooding!!! I even changed the fuel filter I litterly tried everything. Please help!

The Petcock isn't on prime!!
and the carbs are Mikuni BS34.

 

Update:

Took the carb out again and removed the float bowls, I did a little test to see if it's the float needles are leaking. I plugged up the fuel tank took off the floats and just put the needles in the seats by then selfs, turned on gas nothing, took the them out and surly there is gas squirting out. So that rules out if the needles and the little brass thing the needles goes it are bad.

I also measured the float when it's upright as I push it with my finger which is 18 mm, isn't it supposed to be 20-21 mm?


I also saw a video of this guy saying that the float drop might cause an issue if its hanging too low so I'm going to try that now.

 

Another update:

So I thought if that the reason to why this was happening is because the floats were being held by the rubber gasket so before putting the carbs back I violently shook it till I could hear all the floats move freely and then to make sure I bench synced the carbs and raised the idle speed by about a full turn up.

And boom! the bike started and the idle sounded really good, I got about quarter of a mile on it! I got into 4th gear and then started to down shift to first and then the bike just starter revving uncontrollably like crazy when I was at the stop sign. So I had to kill switch it and bring all the way home.

I took the carb out and set the idle full turn back because I thought that's the reason it was reving like crazy and guess what! it started leaking again!!!!

Mind that to adjust the idle speed I have to take off the whole carb because some genius decided to put the screw in the bottom.

 

It's a tight fit for the hand to get to the idle screw. You should be able to reach it with fingertips.

 

It's impossible to turn the idle with your hand, anyways I turned up the idle half way in the screw and nothing changed still flooding

 

turned the screw up by a half still flood, then turned it up by a fourth and it started to do the mega acceleration in neutral, im guessing I put on and took off the carb so much I damaged the rubber gasket seals and now it's a vacuum leak problem.

 

Not sure what you are doing here. You should never take any measurements while putting any pressure on the floats. You also should be performing a wet set of the float levels. That is the ONLY way to determine how high your fuel level will be in the bowl.
Are you sure you have the right carbs?
Mikuni BS28 (all XJ550 except 1984 XJ550L):

-Fuel level measured via the clear-tube gauge: 2mm +/- 1mm (.08 +/- .039 inches)

-Float height: 21.5 +/- 1.0mm

As you can see the fuel level is supposed to be 2mm +/- 1mm with the BS-28 Mikuni carbs.

Here is some forum info on the BS-28's:
https://www.xjbikes.com/forums/threads/mikuni-carbs-part-1-exploded-view-with-pics.31061/

 

Ah, I see! hmmm I always thought I had BS34 because the BS28 had some weird tubes coming out of them and my carbs don't have that.

I'll check the float height again when I get home, also what do you mean by "perform a wet set" is there a guide on how to perform it?

 

https://www.xjbikes.com/forums/threads/hanging-float.58701/#post-449657

 

Update again:

The floats are all correct height of 21-22 mm and the fuel level is correct aswell.

I discovered that the fuel also leaks when the engine is off! So maybe somehow the fuel tank is just forcing fuel into the carb and pushing out the needle? I have no idea how to test this or what to do next

Also the mega rev was because the idle was up too high but the carb is still leaking specifically out of the 4th carb the right most. and the engine overflow tube.

 

Final update!

Holy shit! I found out why all of this was happening!!!! So there is this rubber gasket on the float bowl and when you screw in the float bowl it expands! and guess what! the float was getting stuck on it . I just took all of them out and stretched them, so far no leaks and no mega rpm problems!

 

So ummmmm

I hoped on the bike and went crazy on it, when I came back home there was smoke/vapor and a smell of sunflower oil. it wasn't like black smoke burning it was like water boiling vapor smoke, then I saw that there was oil splattering out of the air box, my whole air filter is now coffee brown color!

Tomorrow I'll check the engine oil level on the stand leveled and see if the there is some issue with the crankshaft (preying to god it's not)

This has never happened before and I'm guessing this is caused by me going 80 mph for the first time in like 10 years.

 

The oil level looks fine, I'm honestly stumbled at what could cause this. Has anyone had this issue before? maybe some line is clogged in the crankshaft and caused alot of pressure when the bike was going 80 mph?

 

Maybe when your bowls were overflowing, the gas went into the oil and overfilled the crankcase. The while riding the extra fluid flowed into your airbox. Better check your oil for contamination.

 

That's probably what it is. I'm gonna change the oil see if that fixes the issue. the oil is black anyways

 

Try to never ride with gas mixed in the oil, it should go without saying.

 

Yeah, I lowkey didn't know that it was even connected to the airbox like that. I thought the oil was coming out from the carbs until some research

 

Just changed the oil, it's really dark and smells like fuel. it was also sparkly I think because of metal bits. I'll take it for a ride right now see how it feels.

 

Alright, the first drive after the oil change seemed magnificent! The next ride the bike seemed to be a little sputurly under load. there was a little bit of vapor coming out of the air box every time it's running.

Currently no filter because it's soaked in oil

 

Update: Bad luck,

The engine was always running with a dead cylinder and had random misfires and had what sounded like lifter tick i believe was due to a broken spark plug cap which i thought i fixed with electrical tape. Today i found out what prolonged misfires do, i was driving on a low rpm when the engine cries and came to hault with a loud screech. Back home I took off the cylinder I found out this bike never had lifters and as i came to the cylinder i discovered it broke. The exhaust valve snapped clean off right into the piston and i know you know what happened. See videos and a photo below.

Rip Yamaha Xj550j 1982

1982- October 21 2024


Trigger Warning!!!!





Im gonna get a new cylinder head, pistons and a piston ring. Hopefully it will come back to life.

 

Bad luck indeed, but as @Huntchuks said, never ride with fuel contaminated oil....
Reading back quickly over your history I think you had numerous issues that caused this.
1. Your petcock - the carbs were flooding when not running? Petcock not in prime? This means your petcock is leaking, and,
2. One or more of your float valves was leaking, or not set correctly. If I recall, the Mikuni valves are held in with small clamps, and sealed with a rubber o ring - did you change these? Always assuming that the issue with the floats hanging up on the gasket wasn't the only issue, and bench set and wet set were carried out.
3. Riding with oil contaminated - I would hazzard a guess either the lifter or the valve stuck, got twatted by the piston a few times then cried enough. Feel and your ears should have told you something wasn't right, but experience is everything...

So, to fix it - new (used!) barrels, pistons and head might be ok, if you can get them cheap, otherwise look out for an engine, a good one of course.
It's a tough life sometimes, you think you've found Nirvana, only to have you kick you in the bollocks. If it's any consolation, I estimate 80% of issues with the xj is carb related...

 

Just finished reading the thread. I would guess no matter the oil contamination, the piston was already done or close to dead. When starting new project bikes, one of the first things I do is pull the plugs and take a look at each piston top with a good light. I can get an idea of what might need to be done. Rust, carbon, piston wall issues and worst of all what you have.

If you are up to it, rebuild that top end. If you have the time, tools and funding, go for it. You will gain knowledge, skill and many other mental disciplines as you move forward with the project.

Best of luck.

 

I know for a fact the leak wasn't there anymore and i put brand new oil in it! it didn't even have 20 miles on it when my blew up.

After long thought I do believe that piston was a close to death and yesterday decided to end its live and it got locked up somehow and i think the engine then skipped timing and set the valve right into the piston delivering a final blow right in the liver.

Unless the timing was right when i opened it up it looked off to me if you look at the photo below you can see that both of valves would be open at the same time, maybe it is supposed to be like that idk i can't tell until i find a service manual

I am gonna try to revive it so i'm buying the following:

Used cylinder head off ebay
New piston or used of ebay too
New set of piston rings for all the cylinders
New Head Gasket
New Spark Plug
And a new Oil filter


I really need to find a service manual please tell me if you have a pdf of one ‍‍‍

Hopefully i'll get her running back on the road again, i appreciate everyone who helped me.

 

I found a fully working 650 motor, maybe i can put it instead of the 550? but the only issue is it's probably not gonna fit or the biggest issue is that it's a shaft driven vs the chain driven, but i think i can just swap the transmission? This project is getting really interesting!!!

 

Forget the 650, nothing works.
This theory that the piston just died - it's nonsense, they don't fail unless something causes them to, and even if it did, do you think the head of the exh valve committed harri Kari in sympathy? And if the cam timing mysteriously decided to jump some teeth, all the other valves would be bent (which they might we'll be actually, depending if the motor stopped quickly or ran on for a while).
Service manuals are cheap as chips on ebay?
I would be inspecting the barrel for serious scoring, so you'll need some barrel gasket o rings as well, need to lift it to get that piston off - and drop the sump to retrieve some of the carnage...

 

I just scrapped all of that and order a new 550 motor + gasket kit. Will arrive Friday we'll see what happens then!

 

Alright so i ended just getting a old motor of ebay, it came had no compression had to take off the head and lap the valves and put some oil in the cylinder try to fire it up get them unstuck and boom perfect compression, now the rubber boots are absolutely cooked on it so you can already imagine what happens, also the clutch makes a really weird sound does anyone know what it is? or could it just be that there wasn't sufficient oil in the engine so the clutch is isn't lubricated at all

https://youtube.com/shorts/Br_tBslpM9E?si=8rIFVYUwliPyczS0

 

The noise sounds like the clutch actuating rod shaking. I would not have ran the engine with the clutch cover off. The gears surely sound noisy because they are not spash lubricated by engine oil. Is the oil pump pickup submerged in oil? How long did you have it running like that, just for the video?

 

It's not the actuating rod i held it with a screw driver and it was freely spinning, I'm not sure where the oil pump pickup is, and it was running like that only for the video

 

oh i took the clutch pack out and it didn't make any noise with all the friction plates out, i'm gonna get the clutch hub holding tool so i can take it off and inspect what's behind it

 

Can you move the clutch hub side to side?

 

No, i want to take it off see what's behind it
maybe it's tbis

https://xjbikes.com/forums/threads/clutch-rattle-fix-xj550.117514/

 

Have you got a Haynes manual for your bike?

 

Yes

 

or wait no it's this one Clymer

https://imgur.com/a/3Uub4ql

 

That should give you details of the clutch and oil pump. The latter will be in the oil pan. On the shaft driven bikes the pump is driven by chain off the rear of the clutch backet, 550 might be the same?

 

Alright. so i have finally solved the issue with that noise, the bike was low on oil. matter of fact it only had a quart in it when i drained it. The engine runs perfectly right now but as there always is (with this bike) there is another issue. The clutch seems to not want to engage at all, every time i go into first gear the bike stalls. The lever has very little free play and is firm not loose. the other end of the cable the little metal thing that the cable attaches to on the clutch cover is right on the mark aswell. I did soak my friction plates in oil before installing them and the friction plate is torqued to 8 lbs. I'm so confused on why it's having this issue now as the friction plates are in order according to the service manual and few videos i've watched. If anyone has any advice on this i'm happy to take it!

 

Try this.
Bike on centre stand, put in 1st gear, foot on brake, pull clutch lever in, start it.
If it's just a grabby clutch it should free up and let the engine run with a slight lurch.
The centre stand is to make sure you don't drop it if it gets fruity with you.

The above procedure is one I had to do a lot when my plates were old and grabby when cold.

 

so uhh rear brake snapped instantly

 

it's like the clutch doesn't engage at all

 

@Vany, "the rear bake snapped instantly" What does that mean? With the bike on the center stand, you can find neutral and the rear wheel will spin freely? If not, look for a locked up rear brake or the brake is stuck.

Once you are sure the wheel is free, then you can do as @Dave in Ireland has mentioned. Start the bike on the center stand with the bike in neutral, pull in the clutch and slap the bike into 1st gear. If you had very little oil in the bike, it might take a bit of running the bike to get them clutch plates to free up and have the clutch act the way it should.

Let us know how the troubleshooting is going.

 

Sorry i meant that the rear brake instantly snapped as i shifted into first on the center stand with the clutch in. it snapped the rod that connect the pedal to the brake.

 

As in the brake adjustment rod? Did you have the tension bar item 35 attached and secured?

And just for further discussion when the clutch is "engaged" the plates are together and the bike moves. When the clutch is disengaged (lever pulled in) the plates are apart and the bike should not move.

 

I'll send videos of the rear brake, trying to shift and the clutch, lever etc.

And yes i meant that the clutch doesn't disengage (the bike still moves when the lever is pulled in)

 

No Master cylinder on the 550 clutch side. How is the play in the cable for the clutch? It sounds like you might not have had the bike road ready when you started to troubleshoot the clutch issue. Having it road ready with all the brake items connected will have to be done. Hope you didn't harm any parts if the tension arm was not in place. If it was all connected and it still happened, you may have a brake shoe that has come apart in the back brake area. It does happen. If that is the case, consider yourself lucky it happened when you were troubleshooting the bike on the center stand.

 

Here are some videos, i will start it tommorow and show what it does as it's currently night and my neighbors won't be happy

https://youtube.com/shorts/OGTYfAMrLDE?si=ZT5DT328c55wzrYx

https://youtube.com/shorts/sYdWE1bckdI?si=7FGpqv41UZpDA7Hn

 

It sure looks like the bolt is missing from the tension bar? Normally, that causes the brake adjusting rod to get severely bent, but I guess in your case it just snapped the spline.

The bike looks to have accumulated some rust and been outdoors quite a bit, so even more reason to look at those rear brake shoes - or better yet just replace them before you get any real riding in. You can visit that once you get it to move.


There is also the possibility that you have a safety circuit issue with the ignition cutoff, although that seems less likely with the snapped spline. However, for troubleshooting purposes you can disconnect the bullet connector (B/W wire) near the TCI to disable the safety ignition cutoff. The ignition cutoff will activate any time the bike is put in gear and the side stand is not up. Or, if the side stand switch, wiring, or side stand relay are not working properly the bike will stall when placed in gear.

 

No the issue is definitely in the clutch, the bike won't even roll with the clutch in (in gear) I'm gonna try to bump start it tomorrow and just hold the clutch in

the brake snapped because i activated it while the bike was on the center stand in gear and the engine is much stronger than the brake

 

https://imgur.com/a/wX8VM7t

Image of the clutch pack

https://youtube.com/shorts/cMEYkRHdj9c?si=u6HwcOP9xfFCDIK4

Shifting while started and on center stand

 

so this whole time my service manual lied to me... Turns out there are 8 friction plates and one of the is like special or something and the spring goes on the inside of it, after i did that the clutch started working perfectly, and carb 2 decided to start leaking gas out into the airbox through the jet so i'm guessing it's a stuck float, and i need to pull the carbs out and fix it