Oil & fuel coming out of air filter

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marineviper

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Hello guys, helping a friend out with his 80 xs400. This is the first time with a yamaha (I ride and tinker with a 96 Suzuki Intruder 1400) so please bear with me.

He told me that it looked like oil was getting into the carbs originally and making it smoke pretty bad, he wheeled it over to my garage and I was able to get it started pretty quickly, it ran for a good 2 minutes on medium choke. I dechoked it fully and it was running pretty strong in the garage for 30 sec until it just plain died. I looked down and to my surprise there was oil under the right side exhaust pipe. and a good size puddle. (i was on it and had the bike straight up)

Checked the oil and it was within range.

Got on it today, and left the bike on the kickstand; she started right up, was running normal and than died 30sec and I finally noticed it came from the air box.

Got it started again with the airpod off and just as it died I watched a frothy oil/fuel mix come rushing out of the carb...

I really don't know where to start.

Thanks to anyone who has seen this
 
self lubricating carb!
is the crank case breather tube connected to the airbox still?

sounds like you have a lot of trial and error ahead of you... too high compression or too much oil causing some blow by? worn rings? but im no expert
 
Well after searching the forum a little bit I decided to due more research on the bike...turns out oil was not in spec, i didnt see the sight glass on the side and figured it just shouldn't be over the kickstand gear, well thats where it was, draining the oil right now, going to run two oil changes in it real quick as it was way way over...and while i'm at it going to do a quick compression check, what should be a good compression range be on this motor?

Also it does have an inline fuel filter and i don't think its leaking by the petcock, so my quess is that it was left in prime for a couple of moons back in the day.
 
I would start with reading the manual first and make sure it has the proper amount of oil in it. Always check the oil with the bike on it's center stand. You can download it for free in the tech section. How about some pics so we can see what you have.
 
i think around 140psi but not higher than 170psi and no more than 15% difference between R and L.

and as chris alluded too, it should all be in the manual
 
120-155 dry is the range of these. Make sure to use oil for wet clutches.
 
okay, got new oil in her and checked compression hot, got 110 on left and 120 on right. Granted I do have a cheap compression gauge to.

added some seafoam and ran it for 15 minutes and than she shut off on me, wasn't easy to restart but it did without giving throttle...I'm hoping its the seafoam causing that or that it didn't get to hot.
 
So the manual says no less than 118 and that 142 is recommended at sealevel...I looked up the conversion for altitude and 118=104psi and 142=125....So basically I am looking at 125psi left and 136psi right at sealevel.

And the guy I'm working on this for bobbed this bike out and custom did some things...I'll try getting a pic sometime tomorrow...definately different than my kind of tea of bike. Granted I do like different, hence why i ride an Intruder 1400
 
Compression at sea level? I have heard of combustion changes at different altitudes but not compression.
 
I think I'd try another compression test with some oil in the holes. 110 sounds pretty low more like my old worn out garden tractor. As for the oil if it's over filled you'd get it sloshing out the breather like you mentioned. And it'd be magnified with bad rings and blow by. I've rebuilt enough small engines to know over filling the oil will likely lead to blown seals eventually as well. Personally I think I'd spend a bit more time to get it running reliably as possible and take it for a ride. There are times when a good ride may loosen up the rings and get them to seal. But a rebuild will be on the horizon.
 
xschris said:
Compression at sea level? I have heard of combustion changes at different altitudes but not compression.
Click to expand...

Makes sense though, the air is less dense at higher altitudes, so compressing the same volume of air means compressing less molecules per volume. Hence there are less molecules to stuff together, which means that they build up less pressure.
 
I live at 1000' above and get 150psi If I go down to sea level it would go up to 155.
 
Idk, I was told by a local machinest/9sec drag racer and was told at our elevation 120 is quite normal for our location. It's definitely not a concern for blowby. The bike runs pretty darn good as long as I get the carbs cleaned
 
i wouldnt classify a bike that runs for only 15 mins before dying as running pretty good lol

but thats just me:shrug:
 

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