gas blowing past rings?

[bxd20]

I have a Tecumseh powered mower that wasn't needed for a few years and sat.

Pulled it out, cleaned it up, and eventually got it started, ran poor so I removed the lower bowl on the carb and cleaned things out and it seemed to run well. Checked the oil and it looked like it was diluting with gas. Next time I tried to start it gas was pouring out of the muffler.

From the online research I've done, it sounds like the piston ring was stuck and this caused gasoline to wash the oil off the cylinder walls and also gas blow past the rings into the oil? Is that correct?

What I'm reading as a suggestion is to remove the plug and pull the cord a few times to dry the top side out. Then drain oil (gas contaminated) from crankcase and refill. Maybe squirt some oil into spark plug hole and pull a few times to aid in lubrication/compression? Should I try a heavier weight oil? It will be used infrequently, but in Florida heat.

Should I run it a couple minutes and change oil a second time?

I'm guessing if the piston ring was stuck it shouldn't be any longer, since the gasoline would have cleaned it. Hopefully the engine hasn't suffered damage from running a short while in this state but compression still feels good subjectively speaking.

 

[hounddog]

It would take a HECK of a lot fuel to get by rings to fill the crankcase. If rings that bad I'm surprised it would run as the compression would be nil. All that fuel in he crankcase sounds like a carb. flooding issue to me. What little fuel is in the oil if and when it runs correctly will evaporate after engine temp gets high enough. I wouldn't waste a quick second oil change on a lawnmower.

 

[Chris142]

2nd the carb flooding

 

[Quest]

before you casually jump into conclusions, always consider pulling the carb and check (I mean overhaul, inspect, re-build). Ring doesn't get stuck that easily and if it does, it usually comes and bite you in ways that are typical of very hard starts due to low compression), but not necessary immediately associate to heavy dilution of oil (smells like gas).

Q.

 

[Propflux01]

+3 on the carb flood.

 

[440Magnum]

Its the carb, absolutely no question. If fuel "pours out the muffler," then the carb float valve is leaking. There's no other way for that much fuel to get in the cylinder in order to come out the muffler.

 

[bxd20]

Thanks for the replies. With the carb float valve leaking, is there any chance something is sticking that I can disassemble and clean with carb cleaner? Frankly this is a low end mower and sinking even $25 into a rebuild kit isn't worth it.

Still starts easily and runs with power.

 

[Brons2]

I bought a carb rebuild kit for my snapper with B&S a while back and it only cost around $7.

That being said, I think you should get some 20w50 and just run it until it's hot. If there was so much gas in the cylinder that it poured out the exhaust, it's hard to imagine that it would actually start. Run it through a couple of usage cycles and see where you are with it.

 

[bxd20]

It started and ran, a couple times. Then the next time I went to start it, it was spewing gas out the muffler and obviously didn't start. I pulled plug, pulled cord, installed plug and got it started just long enough to confirm it still runs well. And then I shut it off on purpose. By now the crankcase was filled to overflowing and the oil was severely diluted and watery.

 

[bepperb]

" is there any chance something is sticking that I can disassemble and clean with carb cleaner? "


I would assume that there is a float in the bowl. When the bowl has enough fuel that moves a cone up against a seat. In a rebuild the cone and seat are replaced but they probably have a varnish you can clean.

Your other alternative would be to buy a cheap fuel shutoff valve.

It's also possible the float is stuck and/or not floating anymore (corroded brass float or disintegrated cork float).

 

[apwillard1986]

We had a similiar problem with one of our garden tractors... We installed a fuel shutoff and have not had the issue since.

 

[bxd20]

I finally found an hour to look at this.

Removed carb from mower. Took apart the bowl / float / jet area and cleaned everything with B12. Was very hard to get started, had to keep spraying a little bit of starting fluid into air intake to keep it running for the first two minutes. Then it finally caught by itself and started smoothing out. For the next two minutes it ran like a champ on its own, and then it started sputtering and slowing down. As it died the muffler was obviously spitting gasoline again.

So what parts should I replace? The inlet needle and seat? Which I believe is Tecumseh part 631021B. Here's a blow up for this carb:

http://www.partstree.com/parts/?lc=tecumseh&mn=CA-632795&dn=CA021632795-CA

Thanks guys.

 

[Quest]

Ummm...seems like your carb is still somewhat clogged/dirty..

The only way to service these carbs properly is (a) perform a rebuild using carb kit;

(b) you need some brass wires, etc. to poke/clear any holes, orfices, tiny air-passageways, etc.

(c) you definitely need compressed air to clear it.

(d) if it's varnish-related clogs, you need to dunk your carb in carb cleaning (dunking soln) for 15mins approx. before you take it out and blow clear/dry it.

(e) just like those Walbro/LMS side-draft carbs in newer B&S, which a mesh fuel filter is highly recommended (to keep dirt from getting into the carb bowl, etc.) I suspect that your Tecumseh may be of similar settings, so it is highly recommended to install an inline mesh fuel filter (150 or 75microns is ok) to keep the dirt at bay.

Q.

 

[gman2304]

If you cleaned it with B-12 the odds are good you now have damaged the O rings and gaskets in the carb. That stuff is rough on gaskets and o rings.

 

[bxd20]

You learn something new everyday. B12 can said it was for carburetor and choke cleaning. I only sprayed, did not soak. The float was kinda dirty and the bowl had a little bit of dirt in it.

An original replacement brand new genuine Temcumseh carb is about $38 incl shipping on EBay. At this point, if $38 and 15 min of my time to bolt it on takes away all my issues, I'm ready to cough up the money. Any concerns that I will get it installed and it will need tuning to run right?

Otherwise I guess I will break it all down again, put the parts into a soaking bath (what do you recommend??), and then "rebuild" the carb. I am still unclear on which parts to replace during the rebuild. They sell a Tecumseh 'rebuilt kit' for this engine that is only about $6, I can't find any details on what's included. The needle and seat are another $6-7, then there's shipping.... by the time I'm done disassembling, soaking, cleaning, I've spent well into the $20+ range and it still may not work.

$38 is sounding better.

Recommendations?

 

[Quest]

buying a new carb makes good sense in your case.

Q.

 

[bxd20]

I contacted the EBay seller to confirm it was an original Tecumseh carb, and it's not. Very deceptive ad, he only listed Tecumseh and the tecumseh part number, not saying it wasn't original! He says it will work with my engine and at worst I would have to "fine tune the high adjuster".

1. Do you guys think an aftermarket carb (I think it's an Oregon brand) is OK?
2. Is tuning the high adjuster a big deal?

 

[Quest]

Originally Posted By: bxd20


1. Do you guys think an aftermarket carb (I think it's an Oregon brand) is OK?
2. Is tuning the high adjuster a big deal?


In my case RE: working on B&S 675 series (125K or 127K) with sidedraft walbro clones, Oregon version is actually the same the OE B&S as far as construction, material, etc. concerned. since most of these LMS series walbro china made carb(for B&S, in my case) are pretty much the same "sheet", with no adjustments and parts are basically interchangeable and functionally the same, I have no doubt that they may be sourced from the same OE manufacturer no doubt.

In your case I would give it a try with the Oregon version, you got nothing to loose afterall.

Q.

 

[anonobomber]

You may just need to replace your float. Take out the float and shake it next to your ear. If you can hear fluid sloshing around in there then your float needs to be replaced. I've seen it happen on a couple of Tecumseh motors. Once you replace that and run a wire through your jets (the holes in the brass bolt holding the bowl in) there's one in the center and another running through the side you should be golden.

 

[bxd20]

Originally Posted By: anonobomber
You may just need to replace your float. Take out the float and shake it next to your ear. If you can hear fluid sloshing around in there then your float needs to be replaced. I've seen it happen on a couple of Tecumseh motors. Once you replace that and run a wire through your jets (the holes in the brass bolt holding the bowl in) there's one in the center and another running through the side you should be golden.


Thanks for that tip! I took the float out again and shook it and sure enough, it was gas logged. I just ordered the new OEM Tecumseh version of the float, made of white plastic, will update when it arrives. Valve and seat look good to my eyes. Hopefully this does it.