tomkirkman : Lots of Smoke, Oh no.

Lots of Smoke, Oh no.
Post by tomkirkman on May 31, 2006, 10:06pm

For the first time since I corrected the carburetor problems, I drove the M715 I bought last year. Went about 2 miles and when I stopped and turned off the ignition, smoke was pouring from under the hood - I thought it was on fire! Honestly.

But, all it was was smoke coming up out of the carburetor/breather. I have a grave suspicion what this means, but thought I'd toss it out here in case anyone had any other ideas. I hope I'm wrong, but I've seen this before.

Re: Lots of Smoke, Oh no.
Post by amphi on May 31, 2006, 11:25pm

May be serious --- maybe not.

If the smoke is coming from the crankcase breather tube (the one below the carb) it could be blow-by from a bad compression ring or worse a blown piston. Maybe it just needs to be run for a while – if it has been sitting – cylinder walls could be rusted.

You can do a quick compression check, without tools, by cranking the engine with the ignition OFF or disconnected. You don't want it to run.

With even compression the starter motor will give a smooth cranking sound as all pistons come up against equal pressure.

If you have low compression on one or more cylinders the starter motor will speed-up as the weak one comes to the top.

I don't know how to put this sound into words but you can definitely hear this uneven cranking if it exists.

Let us know what you hear.

Re: Lots of Smoke, Oh no.
Post by tomkirkman on Jun 2, 2006, 7:37pm

In the roughly 1-year in which I've had this particular vehicle, I've run it for about 20 or 30 minutes each month just to keep the batteries charged and everything internally lubricated. It had never smoked before yesterday when I drove it about 2 miles.

I wouldn't expect a compression ring to go out all of a sudden, although I could see a piston going out. These were also my thoughts when I saw all that smoke.

I'll try your test tomorrow and see what happens.

By the way, we're not talking about a little smoke or vapor weaping up out of the breather - it looks like something is on fire or with the hose shut, like the raditor has blown out. LOTS of smoke. Not blue, not white, just light neutral colored smoke, but tons of it.

..............

Re: Lots of Smoke, Oh no.
Post by wrecker on Jun 3, 2006, 7:51am

That much smoke sounds like something has to be getting into the combustion chamber or compression from a cylinder is getting into the intake system. Since it's coming out of the carb, that means intake system which sounds like a stuck intake valve. You should have noticed the backfire through the carb though if a stuck valve was the problem. If an exhaust valve is stuck shut, you might get the symptom as the intake opens, the excess exhaust gas will enter the intake, but the piston is on the way down at that point. I'd run the compression test, and before assuming a cracked piston, look at the valve springs, as one of them might be broken. Also, make sure your exhaust pipe doesn't have a rat's nest in it from sitting around too long. Hope you get it figured out.

Re: Lots of Smoke, Oh no.
Post by jeepistdougiowa on Jun 3, 2006, 12:00pm

I've burnt a whole thru a 230 piton before, it acts as any other engine would, blatantly obvious there's a major malfunction...LOL

If you've never heard it before, it sounds much like a blown headgasket(when it blows to atmosphere)

Re: Lots of Smoke, Oh no.
Post by tomkirkman on Jun 6, 2006, 8:55pm

Nothing seems or sounds out of the ordinary. The starter spins the motor over evenly and sounds the same as always. The truck idles good, once its warmed up and seems to run fine. I'm baffled. No backfire through the carburetor.

Will have to do a compression check and see what's up.

Re: Lots of Smoke, Oh no.
Post by hiker on Jun 6, 2006, 9:21pm

Check your oil level. Sometimes the diaphram leaks on the fuel pump and allows gas to get into the crankcase, thus thinning the engine oil. This thinned oil mixture gets past the rings and gets burned causing smoke. Just a long shot but easy to check.
Robert