Briggs 9L602 help please

[Tarheel 77]

Hi all, Hope everyone is well. I have a problem I hope some of you can maybe help me with.

My brother brought me a walk behind mower with a B&S 9L602-1611-F1 engine. Would not run. Upon having a look, I found the primer bulb not working. Bought a replacement along with a diaphragm and gasket.

Installed these and the engine started right off but ran rough like an old points engine with a condenser going bad. I might smooth out for a second, but most of the time it is rough. Put the spark tester on it and it has fire. Replaced the plug 4 times. no change.

Ordered a new factory carb, installed it and no change. Pulled the head, removed and cleaned up the valves. No change. Got a donor engine that was running.

Exchanged the carb, no change. Exchanged the magneto/coil, no change.

I have about ran out of ideas. I will pull the starter clutch and check the flywheel key later but that's about all I've got.

Anyone seen something like this before ? Any ideas ?

Thanks for any help.

[PGL 438]

Have you checked gas flow from the tank to the carb? Maybe restriction in outlet, filter, line

[Tarheel 77]

Thanks for the reply PLG, This is a Briggs with a primer carb that mounts on the tank. But it isn't starving for fuel as best I can tell, its running rich. Like the ignition is breaking down or some such.

From the time of my first post I have checked the flywheel key, replaced the flywheel, exchanged the muffler and checked to make sure the intake was clear.

I have ran it with the kill switch wire removed etc etc. I'm just about out of ideas.

The one last thought that has come to me is the fuel. Its only a week old and in a metal can. No water and it runs fine in my BGB tractor but as long as I grasping at straws-----

Thanks again.

[simple_stan 0]

Check the intake tube for damage. I have seen a number of the smaller engines with a loose intake tube at the cylinder block.

[Tarheel 77]

Thanks for the reply Stan, sorry for the delay in getting back to you. Here is where I'm at as of now.

Talked to B&S, they had no wish what so ever to be of any help. 20 times or more they asked that I take the machine to a B&S repair shop. Told them I had been the repair shop for years but they weren't impressed.

Told me it was because I used the wrong spark plug. Knew that was hogwash off the bat and it turned out to be just that. Also told me that the factory turns out bad plastic carbs all the time. Go figure.

From that time until now I have replaced the carb 5 times and the tank 3. One of the carbs was new but all the tanks were used. When checking the tanks with a straight edge and very thin feeler gauges, I can't find any warp-age and can't see light.

I have changed to pure gasoline, no help. So I'm still at a loss. Brother now has a human powered reel mower and that is a good thing for him, but I'm not quite able to let this thing beat me.

I'm looking for an old style Pulsa Jet automatic choke carb and tank to give a try on it. (if it will fit) And if that fails, I'll be looking for an old Tillotson H series diaphragm carb to make fit.

It still may not run, but it won't be because of flooding (and that is the problem as it clears up and runs smooth 30 to 45 seconds before running out of fuel)

I'm still open for input. I know this forum is about tractors but I didn't know of anywhere else to turn. Thanks.

[PGL 438]

If it's a problem with fuel and you have tried so many tanks, carbs, plugs, etc. it's hard to believe they were all bad. What about the fuel lines blocked, kinked, air leak, filter plug? Tried a clean tank with new clear line held up for direct gravity flow to the carb?

[Kenzen 1]

Bad carb float (level)?

[MrSteele 492]

For Sh**s and giggles. Have you checked the governor? Especially the linkages to the blade governor. Are they bent or stuck in any way. I keep an older carb than the automatic choke, cause I hate the automatic chokes, and cannot abide by the bulbs. When I want an engine to start, I want it to start. Using the older carbs usually requires playing with the governor and linkages, might also be your problem, too

[Tarheel 77]

This is a mated tank and carb. Can't run one without the other. It is a diaphragm carb so no float.

The diaphragm is both the fuel pump and the constant level valve and takes the place of a float.

This engine is a 3 or 4 horse power but uses more fuel than any of the engines on my BGB tractors.

MrSteele, The linkage is free and this engine has an internal governor.

PLG, I agree. It is hard to believe all of the carbs and tanks are bad. But your saying so caused me to realize something I had overlooked because of the Briggs Tech saying they sold bad carbs.

The carb & tank from the running engine was no longer any good after being installed on the problem engine. It had run through my mind that this was wrong, but as I said, I didmissed it because of the Tech.

The one thing they all have in common is the problem engine. The one thing I can think of that I have yet to check is crankcase pressure/pulse (this is what works the diaphragm) If the engine is somehow pushing to much pressure and pushing fuel past the diaphragm ?

That would explain the flooding and the extreme fuel use. Blow by is the only thing I can think off right off that would cause such.

I'm grasping at straws here and I know it. This engine had plenty of compression but hey, something has to be wrong.

BTW, a friend told me how to fix it. He said to remove the fuel cap and put a new mower under it. Haha.

Here is a link to the parts manual in case anyone would care to see it.

https://www.briggsandstratton.com/na/en_us/support/manuals/results.enginemanuals.html?searchrequested=09l602-1611

Thanks again for the input. My first order of business will be to purchase yet another diaphragm kit and see if one of the failed carbs will then run on the donor engine. It it does, its a pretty good bet that pulling the piston and cleaning or replacing the rings is needed.

Still open for any input and thanks again.

[MrSteele 492]

If that is that useless plastic carb, there is no need to remove one and attempt using even a good known carb. check to see if the engine is one of the chinese engines. If it is, take your friend's advice, remove the gas tank cap and put another engine under it. I have had zero luck repairing any of them. Whatever you do, do not attempt a set of rings in the engine. They are special order for your shop, less than half as thick as for American made engines, and putting the shimmed from the factory engine halves back together is near impossible. You will find spacers in the cam shaft placement that need to be put back in. Apparently, the Chinese worry about looks, definitely not how long anything lasts. Their motto must be, no repairs, only replacements

[Tarheel 77]

Yes, It is the plastic. Thanks for the input MrSteel. I am thinking you've hit the nail on the head about this engine.

Someone needs to put a video on Youtube about these.

[fishnwiz 3,290]

I spent 1 month messing around with a Chinese engine only to end up pulling it and tossing it out in the end. That being said, a few guys here have had pretty good luck with some of the Harbor Freight engines.

Best of luck on your swap.

[MrSteele 492]

I used to save known good carburetors from American made engines. They work well on another American made engine. Saving the Chinese carb is a useless endeavor, most likely, it will not work on another Chinese engine. That particular carb, Chinese or American, is the worst excuse Briggs has ever made or had made, for a carburetor. But, it serves the purpose of " do not repair....but replace"