Smoke out the tail pipes

Riding home from work today and was hearing some strange noises at higher RPM's. Almost like valves were floating or perhaps an internal chain of some sort was loose.
Got home and shut down the bike and noticed smoke coming from the tail pipes.
Saying to myself " Self, that does not look good".
Did not smell of strong burnt oil, but what else could it be.
I checked and adjusted the valves about 1000km ago at most.
Must look again.
Parking the bike until I can investigate and hopefully fix.
Any other thoughts from you wizards out there?
The summer has been so nice up in the Great White North, really would like to continue to ride.
Thanks in advance.

 

Pulling your plug and checking them is where I'd start. But... It could a lot of different things. There smart people here that will help out soon.

 

What model xj are you riding??

 

83-XJ750 M. Maxim.

 

Could overheating cause this smoke to appear? Traffic was the absolute shits yesterday. Way too much idling and waiting trying to get home.

 

Did you check the oil level? Make sure the oil is not contaminated with gas, remove filler cap and get a good whiff. If it smells of gas you likely have a sticking / leaking float valve in one of the carbs overfilling the crankcase and causing it to pump out the breather into the air box.

If you find gas in the oil, don't run the bike until doing an oil and filter change.

 

Thanks Rooster 53,
Checked the oil level and smelled it and no gas smell. Confident that there is no carberator problems related to overflow issues.
Bike starts immediatley upon pushing starter.
However, there is popping which I attribute to a vaccuum leak caused most likely by throttle shaft seals or perhaps some other rubber bit leaking.
A hanging idle.
I will be tearing apart the carbs in the winter to address those "rubber bits" issues.
The problem at hand.
I took the spark plugs out to look at them.
I have no idea how to post these photos I took. I'll do some research on how to post.
They look ok to me, not totally tan in color, but I think probably slightly rich.
Could this smoke from the tail pipe( not a lot. Can see it slightly puffing under idle, and wisps after I shut it down) be just a result of the viscosity of the oil during a long slooowww drive home over 1 hour in rush hour traffic, and
Oil getting past the valve seals.
I am using Dino fluid 10/40
( Km's unknown, but odometer says 94k. Drive gear in odometer worn and not functioning).
Engine is probably tired and has worn parts internally.
Looking at the cost to rebuild or maybe find another mill with known Km's.
Winter might just get really interesting with this one.
Maybe I should find a compression test kit, and see if this is worth rebuilding.

 

What color is the smoke? Is it black, white or blue?

 

Definately not black black, looked to me more pale grey blue.
I smelled it but it did not really have a strong burnt smell.
I even opened the throttle and sniffed at the air box.
Don't know why, just do shit like that.
Thought it might help.

 

Could be just tired valve seals, rings and Pistons

 

I suppose a compression and leak down test would confirm?

 

Posting pictures of the plugs for review. They are very similiar in color etc. Do they look ok?

 

Plug looks actually pretty good. If it was burning oil bad enough I would expect to see black and may be wet sooty plugs.
Leak down test would confirm a weak cylinder or two. Too thin of oil could be an issue. I have been using Shell Rotella 15/40 diesel oil and it has been working fine with my clutch and I have no oil control issues.
Worn valve guides and seals maybe if the leak down test numbers are acceptable.

 

Thanks MN-Maxims.
Appreciate the feedback.
Thinking the same for the oil, once these plugs were pulled.
I'll switch oils at the next change.
Looking at more than a carb rebuild this winter now.

 

Looks a tad lean to me. I see what looks like a fleck of melted aluminum at the 5-o-clock position of the ring, and a few more at the 11 o-clock position inside of the electrode well.

 

k-moe,
What you are seeing means there is a smelter happening within the cylinder?
If this continues, will the piston will eventually get a hole?

 

Here is what the rest of them look like.

 

Yep. they all look a tad lean. Bump the idle mixture screw out 1/4 turn and recheck after a good ride.

 

Completed a compression test today.
Did a valve check.
All valves were in spec.
Intakes- 1,3,4 -.11mm, 2 - .13mm
Exhaust- 1,2 -.18mm, 3- .19mm, 4-.17mm

Compression.
1-120
2-110-115
3-105
4-115
Will try round 2 after battery charges up again.
Was getting slow with the cranking.

If these numbers hold or improve, looks like the top end may just be tired and will get a rebuild this winter during the cold.

 

Finally had time to complete round 2 compression test on a full battery
This time started at #4.
4-125
3-120
2-120
1-122
Haynes states that the Standard compression should be 156#'s
Minimum is 128#'s
With 100+k on the motor I would think this is on the bottom end, but will it need a rebuild?
This was cold readings. I did not warm it up first.

If I rebuild the top end with new guides, seals, and lapping valves, will this put more syress on the bottom end and hasten its demise?
I want to split the cases this winter and rebuild the starter and primary chain assembly.
Install a new chain guide, new clutch, new wheel bearings- both front and rear, middle gear assessment, rebuild the master cylinder and install new brake lines and pads.
Rebuild the carbs.
Big project for the winter.
Would be a great project.
So, is the compression decent enough to put all of this time and effort into it?

 

You have 100,000 K on that motor that is about 60,000 miles.
I would say that is pretty good and maybe could use a freshen up but there are bikes out there with more miles that are still running strong.
Think I would change oil and adjust your mixture screws out a tad and see how it runs. How much oil are you having to add between changes?

 

Previously, Adding very little oil between changes.
This smoking, at least when I noticed it, was really only after a very hot and slow ride.
I have not ridden it since, because of the chain noise that I have.
Very confident that the primary chain will need a new guide, at the very least, and probably a new chain also.
Along with the oil nozzle.
Did not want to destroy anything else if I could help it.
I have adjusted out the mixture screws tonight a 1/4 turn to 2 1/2.
I may sneak out for a short ride tomorrow am, before anyone else is awake.
Under k-moes advice also, I will pull the plugs after and see if they change color.
I read in a thread on this site, that if the valves seals are faulty, you will not see this on your plugs.
As the exhaust side gets cooked pretty good due to the heat, and the oil dropping thru the seals gets burnt in the exhaust gases and expelled thru the pipes, and never reach the cylinders.

 

If your chain guide is smoked, you are right to stop riding it and pull the motor. Rebuilding is pretty expensive. I always suggest to look for a low mile bike that is getting parted out. I have a spare motor with 21,000 miles on it from a shop that the owner bailed on the repairs it needed. When a bike gets parted out the last thing to sell is the engine and they don't go for much because the guy parting it out just wants to get rid of it. Worth a look to see if anything is around.

 

Thanks for the advice.
I'll be cruising the CL and Ebay ads and making inquiries.