Uh OH.... I think I lost a piston ring?

[Jedz123]

Hey guys...
Unfortunately my little 400 did something horrible today. I was on a nice back road ride when I noticed my bike started to loose power. I pulled over and noticed the cylinder on the left side was puffing white smoke... I got back on the bike and rushed it home... When I got home I also noticed oil was coming out of the air box drain. I took the air box off inspected and realized that the oil was coming from the cam breather hose. I Installed a set of pods just to see what was going on and as soon as I gave it throttle it would gush out oil... I noticed that the compression in the crank case was abnormally high.
I unfortunately foresee a rebuild, I haven't had a chance to do a compression test but I know it can't be good. the Plug was oily so I can only assume the worse...
Worth rebuilding? get a new motor? Whats your insight?
It's very sad for it's such an awesome little bike I hate to throw it away...
Thanks guys
-Jedz

[sedelen]

Hey guys...
Unfortunately my little 400 did something horrible today. I was on a nice back road ride when I noticed my bike started to loose power. I pulled over and noticed the cylinder on the left side was puffing white smoke... I got back on the bike and rushed it home... When I got home I also noticed oil was coming out of the air box drain. I took the air box off inspected and realized that the oil was coming from the cam breather hose. I Installed a set of pods just to see what was going on and as soon as I gave it throttle it would gush out oil... I noticed that the compression in the crank case was abnormally high.
I unfortunately foresee a rebuild, I haven't had a chance to do a compression test but I know it can't be good. the Plug was oily so I can only assume the worse...
Worth rebuilding? get a new motor? Whats your insight?
It's very sad for it's such an awesome little bike I hate to throw it away...
Thanks guys
-Jedz

I don't understand that if you lost a ring how that would increase oil flow from the breather. You might've burned a hole in the piston.
What does your plug look like? That might yield a clue. White smoke, lets see, blue is oil, black is gas, white is ?
I don't think I'd run it until you looked at it, look at that plug first, if that don't look good, check the compression. The other things it could be would be a blown valve seal, which I'm inclined to believe and may be the cheapest way out.

[chef1366]

Are you sure your petcock isn't sucking fuel into the crankcase?

[tom203]

Are you sure your petcock isn't sucking fuel into the crankcase?

Yes, this makes more sense than a "lost piston ring".

[Jedz123]

Oil on the spark plug. Now that I'm looking at it more its looking like a blown Head gasket? I plugged the cam breather and there is an exceptional amount of pressure building in the crank case. Can't be the petcock for it isn't a vacuum style petcock, just a simple on off reserve switch.

[tom203]

Oil on the spark plug. Now that I'm looking at it more its looking like a blown Head gasket? I plugged the cam breather and there is an exceptional amount of pressure building in the crank case. Can't be the petcock for it isn't a vacuum style petcock, just a simple on off reserve switch.

Ok, simple petcock it is ! How about that leftside carb has stuck open float valve allowing excess fuel to flood cylinder, foul plug, and every compression stroke forces fuel pass rings into crankcase causing pressure buildup?

[Jedz123]

Double checked and the carb is definitely not the issue. I just serviced them 2 weeks ago and before installation I installed an inline fuel filter to prevent any debris from getting back into the carbs. Bike was running great until the smoke and lack of power. The carb is not overflowing fuel nor is my slide stuck. Replaced the plug and the new one has motor oil on it too now. Bike holds an idle just fine and runs ok, but it goes no where if you try to rev it out... Waiting for my buddy to give back my compression tester so I can better diagnose.

[cowboyup3371]

Get rid of that inline fuel filter...you don't need it as the petcock does the same thing.

[Jedz123]

??? Ive run fuel filters in all my bikes. After a season (15-20k miles) you see how much crap that thing actually filters out and saves your carbs from that extra cleaning... I've run fuel filters in all my bikes and ATVs and they have never been a source of an issue. My Bandit has nearly 50k miles on it and have always ran a fuel filter, runs great always starts, carbs are always clean, never runs lean...

Just baffled by that statement...

[cowboyup3371]

The petcocks feed gas to the carbs through a gravity system that yes, is controlled by the vacuum. However, fuel doesn't flow fast enough to warrant the fuel filters most people try to put on. You'll find many threads on here that discuss this issue and recommend you do away with them; once people do they don't tend to have problems again. If you do use one, get one designed for a lawn tractor or something like that.

[GabrielGoes]

check your oil level

[Jedz123]

Oil level is Right on.

[Jedz123]

Updater...
Just went out to the garage to move out the bikes and quad for we are moving up north and I was curious if the 400 would start and come out of the garage on her own steam.. First kick she jumped right over and idled just fine like it usually did. I ran it for about a half hour and nothing seemed to be wrong. She pulled hard to redline and ran happy. I pulled it back into the house and let it idle as I moved out the B-12 and the quadrunner. After moving them back out I came back to it and it started to do what it did before. Blue-ish White smoke on the left side wouldent rev properly, etc. The bike runs great cold but after a warm up she then starts to eat oil and blow exhuast into the crank case . This looks like a head gasket to me. After the move I plan on pulling the motor and having the head rebuilt and worked. Head gasket will be replaced at that time but I didn't know if it gave anyone else any new ideas.
Thanks

[tom203]

It seems to me that a mechanical problem like blown headgasket, etc. would show up at startup- yet, you say bike ran well -up to redline- for half hour, but then fell back to the dark side. Did this problem start when you "serviced the carbs" a few weeks back, or was it happenning before? You say it's "eating oil" -are you actually putting oil in ? Gas that finds it way to crankcase would cause pressure build up forcing oil everywhere- I'd drain some oil soon after one of these episodes and give it a good smell.

[Jedz123]

Tom
I ran it again today and shut it down before it had a chance to become problematic again. I noticed that the oil level was higher than when i checked a week prior. So i took off the oil filler cap and smelled... The whole crank case is contaminated with GAS!!! What the!?!?! Thanks for advising I've never even though of that! The problem never happened prior the carb service and what baffles me is that It ran fine for a few weeks before this issue arose... I'm greatly concerned now! So I'm guessing this is a carb issue... to much fuel flowing into the bike? Any idea on how i could cure this issue? ugh.
Thanks!