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Discussion Starter #1
It's a Roper 8-26 with a Tecumseh engine. Early 80's. Bought it from a family friend who hadn't run it in a few years, but he did take care of it really well.

First time I put gas in it it leaked out. Needed a carburator rebuild. I took the carb off, and gave it to my stepfather who rebuilt it (he works for a small engine shop). Then I put the carb back on.

It has a fresh oil change, and a new spark plug.

It starts up and runs like a champion. After about 20 minutes or so almost suddenly it starts gasping and stalls, or comes close to stalling. It almost seems to do it more while it's not under load? if I let it sit for a minute and start it it'll run fine for about 5 minutes then do it again. I've adjusted the carb the best I could but had no luck fixing it.


Brought it out to my stepdads. He adjusted the carb settings and gave it back and said it should be all set. Said it was running too rich.

Just fired it up and ran it and it's doing the exact same thing. It's driving me nuts. Anyone have any ideas?
 

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Sounds like a gas cap that went bad. :eek: Unscrew the cap enough so it can vent, if that fixes it replace the cap. They go bad, it's a known issue. :cool:
 

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It's a Roper 8-26 with a Tecumseh engine. Early 80's. Bought it from a family friend who hadn't run it in a few years, but he did take care of it really well.

First time I put gas in it it leaked out. Needed a carburator rebuild. I took the carb off, and gave it to my stepfather who rebuilt it (he works for a small engine shop). Then I put the carb back on.

It has a fresh oil change, and a new spark plug.

It starts up and runs like a champion. After about 20 minutes or so almost suddenly it starts gasping and stalls, or comes close to stalling. It almost seems to do it more while it's not under load? if I let it sit for a minute and start it it'll run fine for about 5 minutes then do it again. I've adjusted the carb the best I could but had no luck fixing it.


Brought it out to my stepdads. He adjusted the carb settings and gave it back and said it should be all set. Said it was running too rich.

Just fired it up and ran it and it's doing the exact same thing. It's driving me nuts. Anyone have any ideas?
When your stepfather had it, did he say that he ran it for longer than 5 minutes? Does adjusting the choke make a difference in performance ie: better with choke or better without choke.
 

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My exact words
Yep, I was multitasking :eek: and we were probably typing the reply at the same exact time with almost the same exact words. Great minds think alike. I've been throught this bad gas cap thing the replacement cap is an updated design without the little metal upside down cone. Cheers ! :cool:
 

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Did loosening the gas cap fix it? Once in awhile it can be due to an exhaust valve sticking when the engine is warm. Another area that may be acting up as the ignition coil may be failing.
 

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if the engine has a lot of hours on it, it is quite possible that the exhaust valve has become recessed in the valve seat and the valve gap/lash may have closed up some. When the engine gets hot the valve will grow in length leaving the exhaust valve up off the valve seat causing a loss of compression/power. There only two ways i know of the check this. First you can do a leakdown test on the engine. Second pull the carb then the breather which sits behind the carb and that will give you access to the valve stems. At that point you need to check the lash on the valves.

using a leakdown will only tell you if the valve is not seating properly but removing the breather will give you a good visual on the lash.
 

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I'm still thinking it's a rich running problem...should it turn out not to be gas cap venting.....Ask your step dad what he found the problem to be first time [said it's rich running]..Perhaps the needle seat is poor shape, or the float may be the metal type and filling with gas, or lastly, the fuel line is inside flaking and sending slivers thru to the needle seat..holding it partially open..IMO..
 

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Discussion Starter #12
Thanks for all of the replies. When I went to start it this morning, instantly started acting up. I would get it to run fine for a minute or two, then back to stalling (when I say stalling, rpm's up and down, few pops, etc) .. Stepdad thinks he missed something on the carb rebuild.
 

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Thanks for all of the replies. When I went to start it this morning, instantly started acting up. I would get it to run fine for a minute or two, then back to stalling (when I say stalling, rpm's up and down, few pops, etc) .. Stepdad thinks he missed something on the carb rebuild.
Did you try adjusting the mixture screws? I had a similar problem recently on an HM80...leaned-out the main mixture screw by 1/2 turn and ran like a champ. A threw in a new plug as well since the old one was coked-up from running rich.
 

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Discussion Starter #14
It's a Roper 8-26 with a Tecumseh engine. Early 80's. Bought it from a family friend who hadn't run it in a few years, but he did take care of it really well.

First time I put gas in it it leaked out. Needed a carburator rebuild. I took the carb off, and gave it to my stepfather who rebuilt it (he works for a small engine shop). Then I put the carb back on.

It has a fresh oil change, and a new spark plug.

It starts up and runs like a champion. After about 20 minutes or so almost suddenly it starts gasping and stalls, or comes close to stalling. It almost seems to do it more while it's not under load? if I let it sit for a minute and start it it'll run fine for about 5 minutes then do it again. I've adjusted the carb the best I could but had no luck fixing it.


Brought it out to my stepdads. He adjusted the carb settings and gave it back and said it should be all set. Said it was running too rich.

Just fired it up and ran it and it's doing the exact same thing. It's driving me nuts. Anyone have any ideas?
When your stepfather had it, did he say that he ran it for longer than 5 minutes? Does adjusting the choke make a difference in performance ie: better with choke or better without choke.

It runs terribly when I choke it. Even when I first start it up.

I'm not sure how long he ran it for, enough to get it hot.
 

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Discussion Starter #15
Thanks for all of the replies. When I went to start it this morning, instantly started acting up. I would get it to run fine for a minute or two, then back to stalling (when I say stalling, rpm's up and down, few pops, etc) .. Stepdad thinks he missed something on the carb rebuild.
Did you try adjusting the mixture screws? I had a similar problem recently on an HM80...leaned-out the main mixture screw by 1/2 turn and ran like a champ. A threw in a new plug as well since the old one was coked-up from running rich.


Plug was replaced when my stepdad adjusted the carb the other day because it was fouled up from running rich. I've adjusted both screws while it's running like that with no success.
 

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Discussion Starter #16
I'm still thinking it's a rich running problem...should it turn out not to be gas cap venting.....Ask your step dad what he found the problem to be first time [said it's rich running]..Perhaps the needle seat is poor shape, or the float may be the metal type and filling with gas, or lastly, the fuel line is inside flaking and sending slivers thru to the needle seat..holding it partially open..IMO..
That was the problem. Gas line was bad and a piece flaked off into the carb. 10 points!

Thought I would post the solution if anyone was curious.
 
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