Surging idle and fuel filter..possible problem?

[rpm90001]

Hello everyone. I have a cub cadet 1018 with a 18 hp Briggs that sat under 15 feet water for a few days. I have gone through the whole machine but having a problem with it surging the first 3/4 of the throttle. Full throttle seems ok. One thing I noticed is the fuel filter. I had a new fram in line filter that was a little bigger than the oem filter, original filter was about as round as a quarter and the new one the size of a half dollar, mabey a little smaller. I noticed the the filter is always empty, just a tiny bit in the bottom. I would say its less that 10% filled with fuel. Could this cause my surging problem? I did clean the carb, it was pretty bad, but cleaned up well. Should the filter have more fuel in it? Could it be over sized? Everything else works great.

Thanks for any help.

Geo

[JandL1701]

I hope this helps,

The fuel is delivered to the fuel filter and is routed to the outside of the filter element, then drawn through the filtering element and ported to the outflow hose. So, the fuel in the visible part of the filter is not that important, just that there is some there. If your engine runs at full throttle and surges in the mid-range I don't think its a fuel problem from a fuel filter view anyway. Maybe the problem is the carb in the midrange metering, sitting underwater may have warped some internal channels or done some damage which can not be seen or fixed. However, with that said, as long as it cuts grass and does the job, the RPM surge at mid-range should not be an issue. I would use it as is and be thankfull it runs at all.

[Mek-a-nik]

You say it runs good under full throttle. Is that under load, cutting, or just no-load? If it smooths out under load, I'd put some Seafoam or similar mechanic-in-a-can in it and see if that helps.
As JandL1701 says, there may be permanent damage to the carb. A full disassembly and cleaning in an ultrasonic cleaner may help, if that's not what you did when you cleaned the carb.

[RedGoat]

Try checking the jets in your carb. There's some tiny holes that usually run perpendicular to the jet which require something really small (like a snipped piece of wire brush) to clean. Poke a piece of wire brush in there and make sure they're clear.

[rpm90001]

Thank you, I replaced the filter before reading this post. I replaced it with oem filter. But glad it is normal, but the new filter did fill almost to full.

When I cleaned the carb I did not do a good job. At that point I did not even know it it would fire, so I just cleaned the rust out, sprayed it, and hit it with compressed air. The jets would not budge. I may replace the carb with new.

One thing I would like to add.. Mower will not run with throttle between 0 and 1/4 throttle. I have to keep it above 1/4. Close it all the way and it dies. Also while it is surging, if I hold the governor steady it will die. Also will get a little spit and sputter while surging. I'm going now to find out what a new carb cost.

Briggs 18 hp
31q-777 0305e1 040317ze. Anyone know the year?

Thank you for the help.

Geo

[rpm90001]

Well I guess you can not buy a replacement walbro carb, the replacement is a Nikki part number 794572. I found a few places to order, but I have to find out if it would come with the selanoid (sp) at the bottom of the bowl. Would this be normal that this is included? I don't believe the one from the walbro carb would fit. $68

[38racing]

engine is an 2004 . The surge below full throttle and dieing at 1/4 cold just be the idle mixture. some carbs still have an adjustment for that. There is also an idle speed adjustment and you could just use it to increase the rpm at 1/4 throttle to keep it running.

[rpm90001]

Thank you, I don't remember seeing any adjustments on the walbro carb. I ordered the replacement Nikki carb. One thing I don't understand is it looks like it has a lever for the choke that attaches to the carb, does this mean I can't use the original choke lever on the dash? Or just added in case you need it. Here is a link to a picture with the lever.
http://www.smallenginesuppliers.com/sho ... s3217.html


Everything I see,is this carb is a direct replacement for the walbro. I think replacing it was the best way to go. About $20 more than the rebuild kit.

Geo

[38racing]

in your picture there is a needle screw with a spring on it near top left. The walbro has a similar one and it's the idle mixture adjusting screw. Normally it has a plastic limiter cap on it. But you (or Briggs) have me confused. The IPL for your engine of type 0305 shows that Nikki carb that you have in the picture so why does it have a walbro on it now?

[bgsengine]

in your picture there is a needle screw with a spring on it near top left. The walbro has a similar one and it's the idle mixture adjusting screw. Normally it has a plastic limiter cap on it. But you (or Briggs) have me confused. The IPL for your engine of type 0305 shows that Nikki carb that you have in the picture so why does it have a walbro on it now?

IPL is showing Nikki because that's the *replacement* for the Walbro carbs. Engines came originally with both but I am guessing Briggs is trying to trim their inventory list, so they'll go for what gives them most profit - and Nikki parts are hard to find from anywhere but Briggs, if you know what I mean..... Walbro carbs are mostly all NLA from Briggs anymore, so if you want Walbro, it'll be N.O.S. or Used.