1980 TXT fuel coming out the exhaust

jonzeman · 11-20-2016, 11:43 AM

I have a 1980 TXT with a robin 244 cc motor that I just rebuilt the top end. Put everything back together, and the cart will barely pull itself. There's raw fuel coming out of the muffler. I mixed the fuel a little strong i.e. 40:1 so it smokes a bit. The compression is 110, not great, but thought new rings aren't seated yet, so not bad. Took carb apart and cleaned. Looking for suggestions.

cart around · 11-20-2016, 12:01 PM

What were the symptoms that caused you to rebuild it?

After the rebuild these are the things that come to mind.

Piston in backwards: The square hole in the side of the piston should be facing the intake. If you can see it through the exhaust, it's in backwards.

Rings on upside down: These are known as keystone rings. They have a bevel that goes on top. There are alignment pins in the ring grooves. The ring ends surround those pins.
Did you check the ring end gap before installing?

Gas in the exhaust could also mean a ruptured lower diaphragm in the fuel pump. That is why I asked what the original problem was.

jonzeman · 11-20-2016, 12:42 PM

The reason I rebuilt it was there was no compression, one of the rings were totally gone, the other was stuck. Piston charred as well, so I just bought a new piston and rings, and honed the jug, which surprisingly looked real good, no scars. The new piston and rings had no directions with them, so I just winged it, did figure out the pin in the ring groves (love youtube). As far as the rings being upside down, there was a small mark on one side, I assumed that was the top side. I did put the piston in the correct way, I double checked that.
I don't know what caused the meltown originally, I thought the oil injector stopped working, but now know it works fine, and I unhooked it and sealed it off because I added oil directly to the gas. I haven't taken the fuel pump off to check that part out, although that sounds like my next move, as in other threads I've read, sounds like a backfire will take out the diaphragm, and it did backfire quite a bit before the rebuild.
Thanks for the advice, was just trying to get a cheap fix, not a show cart by any means, just entertainment for the grandkids!

jonzeman · 11-20-2016, 02:44 PM

Pretty sure I found the culprit! Took the fuel pump off, didn't see anything on the bottom diaphragm except some small black marks, but switched the top to the bottom, and now it doesn't pump at all. So I ordered a new one, I'll let you know in a few days if that fixed everything!
Thanks for the help! Awesome forum, I've learned a bunch here!

cart around · 11-20-2016, 02:54 PM

This thread shows what my diaphragm looked like. http://www.buggiesgonewild.com/gas-e...fuel-pump.html

11-20-2016, 11:43 AM	#1
jonzeman Not Yet Wild Join Date: Jun 2015 Posts: 11	1980 TXT fuel coming out the exhaust I have a 1980 TXT with a robin 244 cc motor that I just rebuilt the top end. Put everything back together, and the cart will barely pull itself. There's raw fuel coming out of the muffler. I mixed the fuel a little strong i.e. 40:1 so it smokes a bit. The compression is 110, not great, but thought new rings aren't seated yet, so not bad. Took carb apart and cleaned. Looking for suggestions.
jonzeman Not Yet Wild Join Date: Jun 2015 Posts: 11

11-20-2016, 12:01 PM	#2
cart around Test before replacing Join Date: Aug 2013 Location: Ohio side of the Pennsylvania border. Posts: 3,496	Re: 1980 TXT fuel coming out the exhaust What were the symptoms that caused you to rebuild it? After the rebuild these are the things that come to mind. Piston in backwards: The square hole in the side of the piston should be facing the intake. If you can see it through the exhaust, it's in backwards. Rings on upside down: These are known as keystone rings. They have a bevel that goes on top. There are alignment pins in the ring grooves. The ring ends surround those pins. Did you check the ring end gap before installing? Gas in the exhaust could also mean a ruptured lower diaphragm in the fuel pump. That is why I asked what the original problem was.

11-20-2016, 12:42 PM	#3
jonzeman Not Yet Wild Join Date: Jun 2015 Posts: 11	Re: 1980 TXT fuel coming out the exhaust The reason I rebuilt it was there was no compression, one of the rings were totally gone, the other was stuck. Piston charred as well, so I just bought a new piston and rings, and honed the jug, which surprisingly looked real good, no scars. The new piston and rings had no directions with them, so I just winged it, did figure out the pin in the ring groves (love youtube). As far as the rings being upside down, there was a small mark on one side, I assumed that was the top side. I did put the piston in the correct way, I double checked that. I don't know what caused the meltown originally, I thought the oil injector stopped working, but now know it works fine, and I unhooked it and sealed it off because I added oil directly to the gas. I haven't taken the fuel pump off to check that part out, although that sounds like my next move, as in other threads I've read, sounds like a backfire will take out the diaphragm, and it did backfire quite a bit before the rebuild. Thanks for the advice, was just trying to get a cheap fix, not a show cart by any means, just entertainment for the grandkids!
jonzeman Not Yet Wild Join Date: Jun 2015 Posts: 11

11-20-2016, 02:44 PM	#4
jonzeman Not Yet Wild Join Date: Jun 2015 Posts: 11	Re: 1980 TXT fuel coming out the exhaust Pretty sure I found the culprit! Took the fuel pump off, didn't see anything on the bottom diaphragm except some small black marks, but switched the top to the bottom, and now it doesn't pump at all. So I ordered a new one, I'll let you know in a few days if that fixed everything! Thanks for the help! Awesome forum, I've learned a bunch here!
jonzeman Not Yet Wild Join Date: Jun 2015 Posts: 11

11-20-2016, 02:54 PM	#5
cart around Test before replacing Join Date: Aug 2013 Location: Ohio side of the Pennsylvania border. Posts: 3,496	Re: 1980 TXT fuel coming out the exhaust This thread shows what my diaphragm looked like. http://www.buggiesgonewild.com/gas-e...fuel-pump.html

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