oil explosion - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 13 (permalink) Old 06-24-2014, 01:00 PM Thread Starter
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oil explosion

ok so here's the problem, when i'm riding my bike, drops of oil spit out of the breather hose on the front of the engine. it didnt seem like a big deal at the time. but the other day when i rode my bike to the waffle house, i pulled away from a stop light quite exuberantly and maybe a half a cup of hot oil spat out of the hose and onto my leg and all over the side of the bike. i was talking to a local mechanic about it and he looked very sad and told be that i had blown a hole in the piston. is he right? it seemed like a sensible explanation for what happened but i figured i'd ask you wise ones before doing any major work on it.

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post #2 of 13 (permalink) Old 06-24-2014, 01:18 PM
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well, if you had blown a hole in a piston, you would know it.. it would probably only be running on 1 cylinder, and you would know it.

you may have a large amount of blow by tho.

another possibility is that its overfull... check on center stand, oil level should be just below the top of the sight glass.. any more and it may be over full.

How is your crank case vent connected? stock they go from the front cylinder up to the bottom of the surge tank (air box). if you have ear shaved, then it should go to a breather filter mounted someplace... in other words, it don't sound like its properly connected (you shouldn't get oil on ya).

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post #3 of 13 (permalink) Old 06-24-2014, 06:36 PM Thread Starter
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the wierd thing is it runs on two cylinders most of the time, but sometimes one cuts out. its hard to tell which one while riding tho. i also had trouble with oil coming into the spark plug sleeve on the front cylinder a while back, but i fixed that.

i dont think overfill is the culprit either tho, i had about half of the oil i was supposed to at the end of the ride.

my crank case vent isnt connected to anything really. i did an ear shave and didnt put a filter on it. but would a filter solve the problem? it'd certainly stop a good deal of oil from squirting on me. but i figure there's something wrong inside my motor that's causing this. what is blow by? that sounds like it could be it
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post #4 of 13 (permalink) Old 06-24-2014, 06:39 PM
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I believe "blow by" is oil gushing from the case vent from having too much oil/pressure, somebody will correct me if I'm wrong.


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post #5 of 13 (permalink) Old 06-24-2014, 07:04 PM Thread Starter
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thats makes sense. is there a way to fix it?
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post #6 of 13 (permalink) Old 06-24-2014, 07:34 PM
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Blow by is normally combustion gasses that get past the rings. It can cause high pressure in the crankcase that can cause oil to be pushed out of the breather in some cases

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post #7 of 13 (permalink) Old 06-24-2014, 08:12 PM Thread Starter
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hmmmm rings ... that sounds like a very plausible culprit. but that also sounds i get to rebuild an engine! woo hoo! do yall have any free advice to give before i get my hands dirty?
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post #8 of 13 (permalink) Old 06-24-2014, 11:22 PM
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I would guess it is probably just not vented properly.

Route the crankcase vent vertical for some distance. Liquid oil does not go 'up' well and will drain back into the sump. Vapor/pressure will be able to escape. Arrange something to keep debris out of the vent hose.
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post #9 of 13 (permalink) Old 06-25-2014, 03:50 PM Thread Starter
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alright i'm confused now, should i replace my rings or should i fix my vent hose or both?

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post #10 of 13 (permalink) Old 06-25-2014, 04:42 PM
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Quote:
Originally Posted by oriontheblacksmith View Post
alright i'm confused now, should i replace my rings or should i fix my vent hose or both?
I would route the vent first, liquid oil can collect in a low spot over time and then 'blow' out.

I would not be in a hurry to do a ring job if the bike runs ok. Always time off season if necessary, as long as it is serviceable.
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