Will only run when warm

[Apollos7]

Hello,
I’ve searched, but haven’t found a similar problem to what I’m having. I picked up a Craftsman Easy Start 917.378890 with a B&S 6.25 hp: these are the numbers I found on it 123K05-0344-E1. It didn’t run, so this is what I’ve done. Cleaned gas tank, new plug and air filter, cleaned carb and installed repair kit. I put the coil on an ohm meter, but the numbers were all over the place. The guy at the local parts shop did a bench test. He said it had good spark, and suggested no replacing it. Currently, it will start right up, and run a couple of seconds. After about 10 times, it will keep running, and slowly climb until it runs smooth and steady. It operates great and will start right back up , as long as it’s warm. The compression is around 60 psi, if that means anything on these. I put a little oil in the cylinder, but the compression didn’t go up any. I’ve removed the head, decarbed, and checked valve movement. It all looks pretty good. The gasket is in good shape. The valves seam to be tight ( they don’t turn when seated). All that seams to be left is that coil, but it doesn’t make sense to me. Can anyone make sense of this? Thanks!
P.S. I addressed that primer issue with a washer bolted down over that flimsy plastic housing.

 

[Scrubcadet10]

did you check the float level of the carb after you installed the repair kit? (assuming you replaced the needle and seat)

 

[artemjemmy]

This is a primer bulb model, right? Keep priming it to keep it from dying and yeah, it will smooth out after it gets hot and air density drops somewhat. Did you check that the plastic intake manifold is tightly bolted to the the block? That is a potential leak point, but doesn't seem likely with those symptoms. Since you did a carb clean and it still does this, I would suggest try drilling out the main jet roughly 1 or 2 thousands assuming the rest of the carb is good. Fairly confident that it is a carb problem.

 

[Rivets]

First thing to do is what Scrub said, check the float level, I’m willing to bet from your description that you will find that the float is lower on the side opposite of the pin, creating a lean starting and running condition.

 

[Apollos7]

did you check the float level of the carb after you installed the repair kit? (assuming you replaced the needle and seat)

Yes and yes

 

[Apollos7]

This is a primer bulb model, right? Keep priming it to keep it from dying and yeah, it will smooth out after it gets hot and air density drops somewhat. Did you check that the plastic intake manifold is tightly bolted to the the block? That is a potential leak point, but doesn't seem likely with those symptoms. Since you did a carb clean and it still does this, I would suggest try drilling out the main jet roughly 1 or 2 thousands assuming the rest of the carb is good. Fairly confident that it is a carb problem.

I might try opening up the main jet. The plastic intake was cracked. I snapped it off the rest of the way and epoxied it back together.

 

[Apollos7]

First thing to do is what Scrub said, check the float level, I’m willing to bet from your description that you will find that the float is lower on the side opposite of the pin, creating a lean starting and running condition.

Yes, that was the condition before I put in the new valve seat, but it currently sits level.

 

[Rivets]

If the float is level, you then have a partially plugged jet in the carb. This would lead me to cleaning the carb again and checking all openings you can find and spraying through them with carb cleaner. Also double check that intake manifold for other cracks or leaking manifold to block gasket. I would not recommend trying to enlarging a jet by a couple of thousands unless you know exactly what you are going and have access to micro drills. Very easy to ruin the jet and then you will need to replace the carb.

 

[Apollos7]

I might try opening up the main jet. The plastic intake was cracked. I snapped it off the rest of the way and epoxied it back together.

You don’t happen to know what the main jet size is, do you?

 

[Apollos7]

If the float is level, you then have a partially plugged jet in the carb. This would lead me to cleaning the carb again and checking all openings you can find and spraying through them with carb cleaner. Also double check that intake manifold for other cracks or leaking manifold to block gasket. I would not recommend trying to enlarging a jet by a couple of thousands unless you know exactly what you are going and have access to micro drills. Very easy to ruin the jet and then you will need to replace the carb.

I’m currently cleaning the carb again. It was very dirty when I started, but I’ve cleaned multiple times now.