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MLM 08-13-2019 06:07 PM

Briggs carburator
18.5 hp Twin II Briggs and Stratton
model 42D707
Type 2280 E1
Code 9901125B

Made the fatal mistake of buying an Ariens with a 21hp Briggs Intek from home Depot. I could write a book on it but I ended up replacing engine with the above Twin II last spring.
Had the carborator rebuilt and it has ran great, but now, after about an hour's worth of mowing, it wants to die unless I choke it.

Dirt in the carb or what?

Changed fuel filter and blew out fuel lines...



dougand3 08-13-2019 09:29 PM

Re: Briggs carburator
When was carb rebuilt - 1.5 yrs ago? Do you use ethanol gas? I'm thinking fuel pump diaphragm is slightly stiff, not moving as much fuel with full air. Could be partially clogged jet, tho.

38racing 08-14-2019 09:57 AM

Re: Briggs carburator
Check gas cap for venting.

JimC_Vt 08-14-2019 11:07 AM

Re: Briggs carburator
Probably a plugged jet , look for the obvious, water dirt ethanol goo .if one of the two jets is plugged, you got a single cylinder motor, that WILL NOT power a load.

My 2 cents, Jim

MLM 08-15-2019 05:12 PM

dougand3 , carb rebuilt spring 2018. I try to avoid ethanol as much as I can, but can't rule out that some may have been ran through it. I don't understand why it runs great for the first 45 to 60 minutes, and then starves for gas. Yes I the tank is vented as the original 21hp Intek had a hose running from carb to gas tank that is not needed with this older Twin II Briggs. So it is open ...

It got so bad that it wouldn't run at all with out choke fully engaged.

Next day, I ran it for about half an hour and it seemed to run pretty good. I have no doubt that it wouldn't have been the case if I kept on running it ...

Guess I'll tear it apart ... Joy!

MLM 08-15-2019 05:18 PM

JimC_Vt , yeah, something must be blocking fuel ...

It's been a really good engine. Came off a ranch king I wore out... 18.5 hp is stronger than that 21hp Intek ever was.

I'll never buy another single cylinder riding mower tractor again.

MLM 08-15-2019 05:18 PM

Thanks to all for your input!

Cannon51 08-16-2019 04:13 AM

Re: Briggs carburator
Taryl has a video on cleaning the opposed twin carbs. I've worked on a few of them that were dirty or had water in them. On one of them there was a small passage from the top down to the main jet that was clogged up. I had to use a bread tie wire to get it clean. More info Disassembly, Cleaning and Repair of Briggs and Stratton Opposed Twin-Cylinder Carburetor - Part 1

wayne50 08-16-2019 11:25 AM

Re: Briggs carburator
I tried changing the fuel pump diaphragms on a Briggs Twin carb, which I had previously done 4 years earlier, but this time I sprayed some carb cleaner into the holes where the pump housing mounted to the front of the carb. Evidently,that carb cleaner was just enough to finish stopping up the passage that Cannon referred to above the main jet, and afterwards the engine would no longer run. After repeated attempts to clean the carb, I finally unscrewed the main jet (took an Allen wrench) and then I was able to get the passage above the main jet open.

TobyU 08-17-2019 06:48 PM

Re: Briggs carburator
If not fuel starvation getting to carb then I would suspect something floating around in carb bowl. I always pull plug our of side and remove jet and clean and take top off of carb.

I like the single briggs.
They are not power match for a twin (of any hp rating or style)but they are easy to fix and parts and cheap and plentiful. Hardy no catastrophic engine failures, unlike the intek twins that will snap a rod in a heartbeat if low on oil, slip valve guides on right cyl and ingest pushrod. Plus parts are more for them and carbs are outrageous still.

dougand3 08-17-2019 07:08 PM

Re: Briggs carburator
Briggs & Stratton 693480. Formerly, you could only buy an OEM carb for $100+. Recently, I saw an AM carb for $31.

Joe Naab 08-17-2019 08:34 PM

Re: Briggs carburator
When I read threads like this one it makes me glad that I stick to the old stuff. May the L head Kohler twins be around forever! Just sayin... :praying:

MLM 08-31-2019 09:20 AM

Well, I finally tore into it and somehow the plastic fuel pump body onto which the diaphragm mounts had a hairline crack in it.

Have no idea why after running fine for over a year, it could develop a crack.
Just old I guess.
Like me.

Again, thanks for all your help.

Love this forum!

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