valve cover vent hose blowing all oil out at wot By godfeast (Read 2,909 times)

[godfeast]

Thought I'd open a new thread for the other issue I am having just to see what kind of insight you guys might have into this.

Scooter runs after sitting a little while, but is hard to start and after just a few minutes of wot it will shutdown ( likely from overheating as its super hot) and all the oil will have blown out the vent cover hose.

I have the vent setup to a 2' long hose with a fuel filter on the end and tied up near the back gas tank.

I recently had problems with the valves being burnt by the bike constantly loosening up the exhaust to downpipe header bolts.

I replaced the head with a new one (valves already installed on new unit), checked the timing several times, then set the valve clearances.

I found out after this had happened that the stator and pickup sensor had gone bad as well ( stator readings off and the heat had effected the pickup enough to kill it - both were several years and many thousands of miles old).

The drama of the stator situation is in another thread.

What I would like to know is, what issues can cause such a massive amount of blowby?

I've already ordered a new piston and ring set (assuming I can just hone the cylinder a bit, I hope) since I know sometimes bad rings can cause some blowby (not sure this much though).

So, other than the rings, what can cause this to happen?

[alleyoop]

Rings are not sealing and the pistion can also get out of round they sometimes get oval shape in which case the rings are not sealing.
Alleyoop

[godfeast]

So basically just rings then? Thanks for the input.

I kinda figured that would be the go to issue. Thankfully the rings and new piston wont take long to get here and I can knock this issue down.

I'm also hoping that the overheating couldn't have cause too much damage, but we will see I suppose.

[imnts2]

There are a lot of things that can cause excessive blow buy. I for one am not a big fan of hard break-ins. I like a little babying for a few miles.It is easy to scuff a piston skirt. The stock emission system pumps the blow by and some exhaust gasses back into an engine that is not as well cooled as I think it should be. top all that off with a carb system that tends to run on the lean side means it is really easy to overheat these engines often built with darn near pot metal.

I am a bit embarrassed how long it took me to realize that the 150cc version of this engine built to the cheapest standards is probable a bit bigger than can be cooled properly.

So what to do. 1. be careful to change oil at the first sign of color change. Any sign of tan or brown. 2. read the plug frequently. I want to see signs it is a little rich. 3. If it bogs down, let it. slow down and let it cool a little. 4. consider getting a high end Taiwanese head, cylinder,piston and rings instead of the cheapest EBay Chinese stuff.

[godfeast]

WOW!

I just finished the top end swap and man was it a mess. The bottom ring and the lower oil ring had both frozen into the piston, the spark plug was welded/corroded badly at the tip, and the piston itself was scarred along its side.

It runs fine now, so its off to hunt down the electrical problem I have for my headlights tomorrow.

[alleyoop]

Good Job Godfeast,
Great to hear it is up and running. Now take it easy on it for the first several hundred miles Ok. Otherwise you will become a PRO and sqapping the top ends all within 30 minutes
Alleyoop

[imnts2]

The real question is what caused the rings to "freeze". Overheating? Not frequent enough oil changes? Water?

Do you have all the cooling ducts in place?

Glad the fix was easy.

Cheers'
lefty2

[nulldevice]

Note the rings farthest from the combustion chamber were welded to the piston. The way there can be that kind of damage is to run it until it is out of oil.

Break it in hard so the rings seat well but don't flog it, and watch the oil level more carefully. Don't flog it after break in either.

[tvnacman]

Null , Please define flog .

John

[tvnacman]

May 10, 2012 17:39:28 GMT -6 godfeast said:

WOW!

I just finished the top end swap and man was it a mess. The bottom ring and the lower oil ring had both frozen into the piston, the spark plug was welded/corroded badly at the tip, and the piston itself was scarred along its side.

It runs fine now, so its off to hunt down the electrical problem I have for my headlights tomorrow.

scored on the side ? how was the cylinder wall where the piston was scored , was the cylinder wall scored or worn away ?

John

[alleyoop]

FLOG= BEAT THE SHIT OUT OF IT
Alleyoop

[tvnacman]

thanks Al

John

[godfeast]

Back to square one...

I had idled it and ran it around the house for a few following the repair, then today I had to get to work asap and I rode it at WOT for 25 minutes.

the oil all shot out again and it started stalling, then after my 11 hour shift, it wouldnt start at all but acted like it wanted to.

It had spark, had gas, ... meh.

No idea what to do at this point. Thinking about pushing the damn thing into a ditch.

[tvnacman]

did you check the cylinder walls ? If it was lean you cooked the piston 25 min at wot , that almost sounds like you asked for it . I would put a larger main jet in the carb and get it to run as rich as you can without proformance problems .

John

[godfeast]

the original issue was a loose exhaust connection that I ended up overheating the engine from; valves didnt burn before piston gave out.

The sleeve i put in was from a pull and I honed the inside to remove the glaze.

Is there any other thing that could cause this or is it only a ring job gone wrong now?

and I have a larger jet in than needed. i run slightly rich because im always afraid of running lean.