Odd oil appearing in carb.

[Guest]

so a very good friend of mine has an 81' yamaha 850 special...(i know its not a suzuki but im lost on this one...)

he got the bike a few months ago, it appeared to run well but we broke the carbs down and cleaned em just in case...

after getting them back together and on the bike it ran no differently, after a spin around town and popping the airbox off there was some oily residue in the far right carb... i was hoping it was some sort of residual goo left somewhere in the carb or intake that just found its way into the carb... after cleaning it up 100% and putting it back together he took it for another spin... afterwards, we took the airbox off and it was the same situation...

he took it out twice more, (total of 4) and after every ride it was the same thing... after cleaning it and riding around town, we take the airbox off and there is oily residue in the far right carb... im assuming its engine oil because what else could it be?? but im concerned as to what could be causing it...

im including an image of the carb, if you have any idea of what could be causing this i would greatly appreciate it, even an idea of where to start would be great.

thanks again everybody!
Sincerely,
~Nate

[Cdnpt1]

Did you pull the plugs? I would be interested to see what that one looks like vs the others. How is compression across all cylinders? Have you done a leak down test to check rings? Have you pulled the valve cover to check out valve seals? Does it smoke at all?

[Nessism]

Engine blow-by mixed with gasoline? Is the float height in spec?

[Bustedknuckles]

unfortunately replaced the plugs a couple days ago and i dont remember seeing anything too out of wack... neither of us have a compression gauge so im not sure about that either, apparently there was some lite smoking coming from the air pod on that carb... i havent checked the seals on the valves yet, thats soon on the list... and i have NO idea what a leak down test is... im assuming though that it may be very helpful in determining whats wrong... right now im really just looking for a "most likely this" response, which you have given me a great start on... i"ll pop the valve cover off and check out the valve seals, and i really need to get a compression gauge...

thanks again though fellas

[7981GS]

Intake valve stuck open and getting the blow-by shoved back to the carb on the compression stroke?

Daniel

[BassCliff]

Hi,

Is the oil over-filled? Is there too much oil vapor making its way back into the carbs via the crankcase breather? Is the air filter over-oiled or need to be cleaned?


Thank you for your indulgence,

BassCliff

[oohsam]

uhmm...are you sure its oil? Might just be fuel mixed with some funk...Seen something like that before.

[Cdnpt1]

Leak down test info

http://www.thegsresources.com/_forum/showthread.php?t=186558

[7981GS]

after getting them back together and on the bike it ran no differently, after a spin around town and popping the airbox off there was some oily residue in the far right carb...
i was hoping it was some sort of residual goo left somewhere in the carb or intake that just found its way into the carb...
after cleaning it up 100% and putting it back together he took it for another spin... afterwards, we took the airbox off and it was the same situation...

he took it out twice more, (total of 4) and after every ride it was the same thing... after cleaning it and riding around town, we take the airbox off and there is oily residue in the far right carb....
im assuming its engine oil because what else could it be?? but im concerned as to what could be causing it...

thanks again everybody!
Sincerely,
~Nate

The key words here are that it is ONLY happening in the one far right carb.


Daniel

[Bustedknuckles]

alright, so i think ive narrowed it down to the intake valve seal being bad on the far right cylinder, due to the fact that its only that carb with the issue and also because the oil is leaking out of the carb not exhaust, i HAVENT checked the cylinder compression or done a leak down test yet but the tools to do so are IN THE MAIL. i figured the valve seals need replaced anyways so i'll go ahead and do it. hopefully this is the issue...

i am going to attempt the valve job WITHOUT removing the head, i heard it can be done with compressed air or by stuffing the cylinder with some sort of cord or rope... i know its not by the book but thats what im trying first... if it doesnt work or if a part falls into the cylinder then obviously i'll pull the head but i REALLY dont wanna have to unhook everything and pull the motor...

so here's the question... do i need any specialty tools? i know they make valve spring compressors, but ive also heard of people doing this without them... and does anyone have any advice or suggestions on how to approach this?

Thanks again everybody,
Sincerely,
~Nate

[7981GS]

I use a motorcycle valve spring compressor myself as they can be had for under $60.00
If you received BassCliff's welcome, it should contain a way to modify a piece of PCV pipe to help with the task for cheap in it.

Daniel

[Bustedknuckles]

im not opposed to getting a valve spring compressor, i AM opposed to removing the motor in order to get the head off... if i get the tool it can only be used if the head is off right??? it compresses the spring from both ends...

what im really wanting to know is does anyone have any adivice on performing this repair WITHOUT pulling the head? AND does anyone have a good DIY that i can refer to?

[7981GS]

With automotive engines, you can usually turn the engine over until the piston is down, fill the cylinder with rope and turn the engine until it holds the valves in place.
Then you would use a tool that is mounted to a rocker stud and depress the valve top seat down to remove the keepers and go from there.
On these engines, I don't know/haven't heard of anyone making a tool to depress the valve retainer with the engine together.
Perhaps someone who knows of such a tool might chime in?

Daniel

[Nessism]

You don't have to pull the engine to pull the head.

I've never known of anyone removing the valve springs with the head attached. If you succeed please take lots of photos and share.

[gearhead13]

I had a tool that I used to remove the valve springs on my V8 351C with the head in place. Lots of room in there to fit it. I never saw a Yamaha head so I dont know what kind of room there is in there.
Kind of like this one here: