Lawn Boy problem

[dodge man]

Ive got a Lawn Boy two stroke that doesn’t start well. It’s a little over 20 years old. I installed a new carburetor last year and put a new primer bulb on it several years ago. I suspect something is wrong with the priming system. If I shoot a little low pressure air in the hole in the primer bulb it starts normal. If I just pump the primer bulb it won’t start. The choke closes correctly, it’s a manual choke part of the throttle. Ive looked at the exhaust port it seems clear. I’ve tried a new spark plug. It doesn’t get used a lot, just for trimming but it’s an aluminum deck and is a nice mower. It starts fine after it’s warm and runs well. Any ideas?

 

[oldnslo]

Have you tried replacing the primer bulb? They get old and crack allowing them to leak.

 

[dodge man]

Yes. In my original post I had said I replaced it. I do wonder though it never seems to spring back up immediately, I wonder if it’s a cheap aftermarket?

 

[sea2summit]

What is the compression at?

 

[oldnslo]

I would pull the primer hose off the carb and place in small container of gas to see if you get air movement when pushing the bulb. Since works with light air pressure points towards volume loss or inability to build any pressure.

They are a simple circuit that can be frustrating

 

[AWSubie]

Reed valve sticky?

 

[dodge man]

Since it starts easy when warm and runs and makes good power I assume compression is good and not a sticking reed valve but don’t know for sure.

I also think the primer just isn’t moving enough air but don’t know why.

 

[LS Tractor Owner]

My guess is the primer bulb. I used to have one of those ---- best mower ever! Finally gave up the ghost after 25 years. Wish I still had it!

 

[dstig1]

Yes. In my original post I had said I replaced it. I do wonder though it never seems to spring back up immediately, I wonder if it’s a cheap aftermarket?

But you said you replaced the primer bulb "several years ago"... Did you also do it again recently? Seems likely the culprit

ETA: and replace any hoses too. Sometime they crack and it isn't obvious and it can cause problems.

 

[dodge man]

I ordered a new primer build just now off of Amazon, $7. It also comes with a hose and the plastic base the bulb goes on. I looked at the hose today and it looked ok but there isn’t much else it could be. I’ll post an update when I get the parts and install them. Thanks for all the suggestions.