Don't forget the spring!

[Merkava_4]

Briggs & Stratton 10M902 0489 E2 05101754
Craftsman Push Mower 917388920

I forgot the spring. I got a little push mower off craigslist and I installed a new carburetor on it yesterday. Couldn't get the engine started, so I took the starter housing back off to hook my electric drill up to the flywheel to check for spark. Had plenty of spark. Then I pulled the spark plug out to see if it was wet with fuel. Dry as a bone. Then I took the air cleaner off to look inside while I push the primer bulb. Primer bulb was working fine. I kept thinking, "This engine needs a choke, but it doesn't have a choke because it's a Pulsa-Prime carburetor." Put the spark plug back in and pulled the rope some more. Still not starting. Pushed the primer bulb a few more times until I saw a stream of fuel squirting into the venturi.

Pulled the rope and the engine fired up and ran smoothly. I'm thinking to myself, "If the engine runs fine now, why didn't it fire up earlier?" So I decided to take the mower to the front yard and try it out. Engine ran fine the whole time and the mower cut great. Emptied the bag that was full of leaves and grass and put the bag back on. Pulled the rope and the engine fired right up and ran smoothly. Finished mowing the lawn.

Put the mower away and went inside the house. Laying right smack in the middle of the kitchen table was a little spring. I recognized the spring immediately; it was the spring that SHOULD HAVE BEEN on the carburetor before I installed it. I was curious what the official name of the spring was, so I brought up the IPL to take a look. Reference # 390, "Spring, Choke-Diaphragm." I thought to myself, "That's exactly what I need; a choke!!"

This morning when the mower was nice and cold, I took the fuel tank back off and installed the little spring. Pulled the rope and it fired up on the first pull.

[bobodu]

I found a packet with a spring on my dining room table and an e-clip.....I must have used the old ones.

[RoyM]

I remember doing that, got the engine reassembled and was tidying up the bench before going outside to run 'er up. There were the new parts. OH DRAT!!! Started all over, didn't tell the boss. I wasn't on a clock and the shop was slow so got away with it.

[KE4AVB]

And here I was thought it was the fuel pump diaphragm spring.

I think we all had cases leaving parts out or putting the old one back in because we were distracted. It is so frustrating sometimes.

I remember one time after spending 3 hours re-assembling a Friden rotary calculator back together that one very first parts that was to assembled was left out. I ended up spending another 4 1/2 hours taking it back apart and reassembling it.

I would rather find that I was at fault instead what a co-worker would do to me sometimes while I was out to lunch. He would remove a part from my work desk and I would be looking all over it for the part that was NLA just for him to walk in a couple hours later and tell me what he did. I nearly floored him one time and he quit doing it.

[rogerf]

Hallo folks,

I had thought that it was the fuel pump diaphragm spring as well. Just shows that it pays to read the parts list sometimes!

Can anyone explain how the spring works as a choke?

Beats me and it would be interesting to know!

Cheers from Oz, Roger

[KE4AVB]

I think is just an example no one paying attention at Briggs proofreading department. Here one from carburetor kit I have here calling a fuel pump spring. Form No. MS-2541-08/06

[bgsengine]

I think is just an example no one paying attention at Briggs proofreading department. Here one from carburetor kit I have here calling a fuel pump spring. Form No. MS-2541-08/06

In parts lists in some places they just re-use part names - same spring was also a diaphragm choke spring on the choke-a-matic carbs (391681,299637) - it pushed up on the diaphragm and attached choke link to close the choke plate in the carb, and vacuum developed by the intake air on the low pressure side of the venturi worked to pull it open as the engine came up to speed. (Which is where the 391813 repair kits originated - roll pin and teflon washer to correct warp that allowed vacuum to leak away and not open choke fully)

[Mek-a-nik]

I thought it was the fuel pump spring. The primer does the "choking"?

[KE4AVB]

Explaination sounds good and makes sense.

But Hmm on the kit number. Must have re-number the kit as the 391813 comes up here as a pickup tube.

[bgsengine]

Explaination sounds good and makes sense.

But Hmm on the kit number. Must have re-number the kit as the 391813 comes up here as a pickup tube.

My mistake - I was just quoting the part numbers from memory I meant 391413 and too many times when I go to type that out (including in the shop management system) I keep putting 391813 for some reason that is beyond me.