91 300 Not running right

[Leed1315 0]

My brother got a 91 300 Honda 4wd from the original owner. The man had only used it around the farm since he had it and had put it up and ended up nearly giving it to my brother. It will start right up with no motor noise or ticking. I don't feel like its revs a quick and strong as it should be but it usually runs fairly well for a few minutes and then starts to sputter and act like its not getting fuel. I think he had someone put a cheap carb on it then brought it back to the Honda shop and had the original one put back on it and acts like no change. I have seen similar stuff on others before so I checked the voltage and its good and watched the spark with an inline spark tester and never seen it go away. The petcock is giving a steady stream of fuel. At this point I don't believe it is not spark related. I'm leaning towards carb even though the Honda shop had it. I also remember that the choke needle is different lengths on some years and it crossed my mind that if it was the wrong one and not sealing like it should it could cause similar issues. Other than that the possibility of a valve issue. I I've seen a few carbs over the years that you just couldn't get right. Something was stuck in there and no matter how much it was cleaned it just wouldn't do right. I do ATV salvage so I've messed with a lot of stuff and probably have  a carb I can clean and put on it. I'm not an expert on the older Hondas though and I know there are some common things on certain machines that can be machine specific and very simple but overlooked when you aren't familiar with them. Other than going into the carb is there anything that you might recommend?

[shadetree 5,869]

6 hours ago, Leed1315 said:

My brother got a 91 300 Honda 4wd from the original owner. The man had only used it around the farm since he had it and had put it up and ended up nearly giving it to my brother. It will start right up with no motor noise or ticking. I don't feel like its revs a quick and strong as it should be but it usually runs fairly well for a few minutes and then starts to sputter and act like its not getting fuel. I think he had someone put a cheap carb on it then brought it back to the Honda shop and had the original one put back on it and acts like no change. I have seen similar stuff on others before so I checked the voltage and its good and watched the spark with an inline spark tester and never seen it go away. The petcock is giving a steady stream of fuel. At this point I don't believe it is not spark related. I'm leaning towards carb even though the Honda shop had it. I also remember that the choke needle is different lengths on some years and it crossed my mind that if it was the wrong one and not sealing like it should it could cause similar issues. Other than that the possibility of a valve issue. I I've seen a few carbs over the years that you just couldn't get right. Something was stuck in there and no matter how much it was cleaned it just wouldn't do right. I do ATV salvage so I've messed with a lot of stuff and probably have  a carb I can clean and put on it. I'm not an expert on the older Hondas though and I know there are some common things on certain machines that can be machine specific and very simple but overlooked when you aren't familiar with them. Other than going into the carb is there anything that you might recommend?

won't hurt to check the gas cap ?!..lol...lots of folks leave the knob on top of the gas cap in the off position. if its off ?..fuel won't vent to the carb. if ya get the old oem carb back ?, pull the top off (4 screws ) check the rubber piece under it for any holes/tears ?. if ya can get it to idle ?, take a can of propane ( DO NOT LIGHT IT ! )..just get some gas around the intake boot...if it idles up when you do this ?..you have a cracked, or not sealing intake boot. dirty air filter ?, clogged oem snorkel ?.