[rtw_travel]

I bought this about 24 years ago and it has had this problem since day 1... its just getting worse and I am getting older and less willing to put up with it.

It is a 3.5hp, 'Eager 1', 4 stroke engine. The blade is ~20". I clean the plug, change the oil and sharpen the blade every year. There are a few paint chips, but no sign of serious rust anywhere - they knew how to build decks in the good old days! I think I blew out the innards on the muffler but otherwise the mower is in good shape.


The problem is starting when cold. Here is how I have to do it.
1) prime the engine 5-10 times by pushing the primer button.
2) Pull starter.
3) The engine immediately starts and runs up to operating speed for a few seconds, then dies.
4) Start again at step one. If you don't prime, it won't catch at all.
5) After 5 or 6 starts in this manner, the engine will run up to full speed, cough a bit, seem like its going to die, and then settle out at normal operating speed. Then I cut the lawn.

It has been doing this consistently for years. It will never start any other way.

It'll never stall once it has been running for more than about 10 seconds. If I turn it off, it starts with one pull and no priming when warm.

The carburator is auto-everything. There is no manual throttle or manual choke. Engine speed is regulated by the engine itself using a (vacuum?) control arm on the throttle input. I have never dissassembled the carb to see what is what, but its like it has no choke.

Any suggestions on what to look for & how to fix the starting problem?

[21boat]

I didn't see anywhere about changing a fuel filter here anywhere which can easily cause this problem. Look in the gas tank or an in line filter or where fuel line attachés to carb,

Also a fuel line that is cracked or a bad connection to let a tad of air in until the line gets completely full with fuel then it runs

A weak fuel pump on the carb can also cause the same problem.

Check fuel line and filter first and then fuel pump next.

[KISS]

I know of a briggs engine that has that sort of problem. I have 3 of them. A really stupid design. Once the mechanism that rotates with the throttle position gets worn, it fails to activate the choke.

The choke is designed to "blow off" once the engine starts. The problem is it usually never sets.

In my case if I remove the air cleaner, the choke is visible.

Full on (highest speed) is supposed to set the choke. If it doesn't, I just manually move it into position.

First start of the season, I use carb cleaner to start it. Never use starting fluid.

I know what part is defective, but I don't use these mowers much.

Adjusting the linkage hold down plate so that the choke closes when in choke is one place to start. Look for a choke with the air cleaner off.

There is another potential area, but I doubt this is a problem unless there is a speed regulating problem.
Speed is regulated by the relative tensions of some springs and the relative position of the throttle and the governor. The throttle plates must be free to move, otherwise the engine will have lots of trouble starting and will have poor speed regulation.

The blower (fins on the flywheel) are used for cooling and also exert pressure on the governor plate. This is how speed is regulated.

So, the suggestion to you is remove the air cleaner and look for a choke plate and see if it closes in the start position.

As I said, this particular design tried to get the choke to pull off automatically. The mechanics are flimsy because it's based on a rivet. A bevel washer, an aircraft nut combined with a thrust washer would have made it work.

[rtw_travel]

Thanks for the info - very useful. I did not have anytime to look at it this weekend, so I did a test instead.

I took the air filter off and covered the air inlet with flat piece of metal as if the choke was on. The mower started first pull and kept running... so it really is the choke.

I'll take the carburettor apart and see what has happened... or maybe find a cup that fits over the round air filter than will act like a choke. I think one of the old plastic sippy cups we had for our kids might fit... as long as my wife doesn't notice.

[KISS]

Progress, anyway.