250-500cc Spitting oil from silencer at connection

So I just got my 04 wr250 it’s in pristine condition great power I love it! Only issue is it’s spitting oil from the connection of the silencer to the exhaust. A little coming out the silencer as well. Now I know this could be a number of issues but I’m going to check the connection and try and tighten it up but the oil coming out the end of the silencer I’m thinking could be from the way it’s jetted? I haven’t Rode it much just around the block a few times as I just got it and it runs amazing except it doesn’t idle that well it’ll stall out if not revved. I’m running motul 800 synthetic at 45:1 that’s what the previous owner used. Could it be the oil as well? I tried using the jetting thread to get a handle on how I should jet my bike but it only shows up as a spreadsheet and impossible for me to read it. If anyone has any jetting tips for this bike would be greatly appreciated as I think that is the issue here along with a lose connection. Attached is a pic of the connection. And this was from maybe 10 minutes worth of street riding.

if your idle is off as in sputters out
start with the engine fully warmed up
screw in your idle mixture screw then out and find your best idle
it is an air bypass so if you need to turn it in to get a good idle you are removing air from the mixture , as in richen it up
a good idle if your pilot jet is correct should be somewhere around 1 1/2 turn out on the mixture screw
the next step is the needle height adjustment for mid range
do one at a time

You need to change to a lower grade oil . You are not running the bike hard enough to burn off motul 800 .
If you don't mind splooge then leave it .
Try an oil one step down the ladder

Thanks guys and yeah I was thinking the oil needs to be changed. This is just what he was running and gave me the left over from a quart he had. Any recommendations on an oil? I’m just trail riding with some connecting streets trails are pretty open though.

Yea don't go to a leaner oil mix . As then there is less oil to lubricate but it still won't be hot enough to burn it off .
My my gas gas ec300 used to smoke on Castro tts . But on 2t it's fine . That thing did 6 years on a piston .
I mostly ran the maxima semi synthetic stuff at 40 to 1 . Because thats what my guy at thw shop ran /sold
That went in all my huskys too .
Honestly I'd find a bike shop u like and someone who rides local to you and a similar bike and see what he runs /sells .

I would also repack the muffler, it could be saturated with oil causing the condition. It is also cheap to do.

try motul 710. I like it much better than 800

What pilot, main, and needle are in your carb now?

Heath

I have no idea! I’ll ask the previous owner I just got the bike I plan to mess around this weekend with it. Again it runs absolutely mint except for the idle which I’m Guessing I can fix with the air screw. After reading a lot about the motul 800 I’m hoping that alone will change a lot

I’m gonna ask my local shop what they recommend running oil wise and at what ratio. Again I ride some pretty open trails some street riding too so I do open it up quite a bit so I think a rich setting would work good. The previous owner said he had it jetted a little leaner because he rode it slow. I have to find out the exact jetting. Does anyone have a basic setting for something a little rich that’s worked for them? TIA

No clue on the basic setting for jetting but in the past and currently, I have the same issue with the spitting oil and ~never had too much luck stopping it with oil\gas mixing ratios; Myself, I'm not going any less than a 50:1 mixing ratio.

Once, I merely changed oil types to something that burned at a ~lower temp, or something like that, and lots of the spooging stopped with that single change.

Repacking the stinger might be a symptom of something else, but this has ~cured my spooging issues in the past; Since I'm back to picture-taking of my 2t, I should dress it up for the masses and fix some minor issues like this.

--
And that is one clean looking, ~14 yr old bike.

Haha isn’t it! You could eat off this thing!

I drained the gas today and switched oils and mixed at 40:1 and it seems the spitting has stopped! I guess it was the combo of old gas/oil and the oil I was using in comparison to the riding I was doing. Thanks for the help guys!

First thing I'd do. A muffler full of spooge will affect carb tuning
And, if you can get Amsoil Dominator it has a low flash point and produces less spooge.

The muffler was just repacked. I think it was the old gas and the racing oil. Seems to be fine now. Thanks everyone