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View Full Version : New Zero Turn mower problem, need help!



radkins
07-19-2016, 11:50 PM
Ok I have a new Poulan Pro ZTR mower, 24 H Briggs with 32 hours on it and suddenly it's running rough, barely at all in fact. I am sure it's a fuel problem since it's running extremely lean as evidenced by the exhaust smell, blistered spark plugs and extremely hot exhaust. It was running fine when we shut it off for a break and then 15 minutes later I fired it up and the problem started then, so far I have verified clean fuel in the tank, new fuel filter and the fuel pump is maintaining a good fuel flow to the carburetor. The darn thing is under warranty but I cant wait the two to three weeks or even longer to get it back so even if it means voiding the warranty I am going to attempt to fix this thing myself. I partially disassembled the carburetor looking for dirt or water in the fuel bowl but it was spotless without a trace of contamination of any kind, I verified 12 volts to the anti-backfire solenoid and the solenoid itself APPEARS to be working properly, basically I can't see a darn thing wrong but the mixture is obviously way too lean.

Any suggestions on what to look for from here would be greatly appreciated.

dave_r
07-20-2016, 12:37 AM
Can you see if the solenoid actually works (as in, remove the solenoid from the carb and then just turn the key on? And seems to have a full range of motion?
The float bowl is full of fuel when you take it off?

And nothing is blocking the air intake?

Boostinjdm
07-20-2016, 12:47 AM
You can just turn the key on and plug/unplug that solenoid a few times to check it. It will make a solid click when opening/closing.

Willy
07-20-2016, 12:49 AM
I've had about 5 of these engines with the 2 bbl Nikki sidedraft carb that exhibited similar issues under high speed low load conditions. I'm assuming you have this carb, if not, disregard the rest of my response.
Idle operation was good as was full load operation, only low load high speed operation was affected. In other words, normal grass cutting conditions.

In all of these cases everything looked good and clean as in your case. The issue I found was located under the cover plate, photos #11-13, low speed air/fuel delivery circuits as shown in link #2 of the two links below. In all cases a squirt or two of varsol thru the those circuits from both ends of the passage followed by with blast of air both ways in the passages rectified the issue.
I did not actually see debris in these passageways but I have no doubt that small pieces of foreign matter were blown out since engine operation was back to normal afterward.

Remember that the low speed circuit has a major effect on A/F mixture even at high speed low load operating conditions as the throttle's butterfly position is actually not open all that far under those conditions.

Part #1 (http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb.asp)


Part #2 (http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb2.asp)

goose
07-20-2016, 07:38 AM
Can you just get the carb replaced under warranty? If they let you keep the old part, you'll have a backup carb for the future.
Might take a couple weeks wait for warranty work, but might take a couple weeks messing around with the mower by yourself.

DocRock
07-20-2016, 07:53 AM
Can you just get the carb replaced under warranty? If they let you keep the old part, you'll have a backup carb for the future.
Might take a couple weeks wait for warranty work, but might take a couple weeks messing around with the mower by yourself.
Usually the warranty excludes "bad" gas. That is IF contaminated fuel is the source of the problem.

lynnl
07-20-2016, 09:21 AM
The last several years it has seemed like most of my awake time is spent messing with carburetors ...chainsaws, lawn mowers, string trimmers, outboard motors, etc.

I've spent the last four or five weeks refurbishing my fishing boat, which had sat unused for the last 3 or 4 years. I must've taken those carbs on and off a dozen times. ...and they're a pain in the ass.

I was consulting with a guy who really knows what he's doing, and does part time evening and Saturday boat work for a shop nearby. One of the carbs was being particularly troublesome so I took it and new parts to him to rebuild and run it through an ultra sonic cleaning. I was surprised that they were using a Harbor Freight ultra sonic cleaner.
He said it does a great job at cleaning, far better than solvent soakings. Theirs had been in regular use for several years.

So at $60 some dollars (with the ubiquitous 20% coupon) I got one the other day. If it fixes one carburetor issue for me I'll be happy.

radkins
07-20-2016, 09:45 AM
I've had about 5 of these engines with the 2 bbl Nikki sidedraft carb that exhibited similar issues under high speed low load conditions. I'm assuming you have this carb, if not, disregard the rest of my response.
Idle operation was good as was full load operation, only low load high speed operation was affected. In other words, normal grass cutting conditions.

In all of these cases everything looked good and clean as in your case. The issue I found was located under the cover plate, photos #11-13, low speed air/fuel delivery circuits as shown in link #2 of the two links below. In all cases a squirt or two of varsol thru the those circuits from both ends of the passage followed by with blast of air both ways in the passages rectified the issue.
I did not actually see debris in these passageways but I have no doubt that small pieces of foreign matter were blown out since engine operation was back to normal afterward.

Remember that the low speed circuit has a major effect on A/F mixture even at high speed low load operating conditions as the throttle's butterfly position is actually not open all that far under those conditions.

Part #1 (http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb.asp)


Part #2 (http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb2.asp)



Yep that's it and you described the problem perfectly, that's exactly how it's acting!


Thanks a LOT for the links! I am just now going over the info there and printing out some notes, armed with this detailed instruction I feel much better about my chances of correctly solving this problem. I am no stranger to engine repair and carburetors but this one is a new one for me and while basically it's just a carburetor the little differences can be a puzzle.

radkins
07-20-2016, 01:35 PM
Got it! :D

After twice disassembling what is essentially a brand new carburetor, thoroughly cleaning all passages but finding nothing in the way of gunk or any type of buildup anyway I was almost ready to give up. The first time it was disassembled I cleaned everything as suggested and again checked the backfire solenoid for proper operation then reassembled and reinstalled to no avail, it still did the same thing. I removed the darn thing again and after disassembly I decided to take it to my ammo reloading bench which has a large lighted magnifier, the intention was to look for possible cracks in the carburetor body but while examining the area around the main jets I noticed what looked to be a very tiny string-like piece of something just barely sticking up out of one of the jets. Thinking it was just a tiny piece of cat fur from my vicious watch cat who spends most of his life sleeping on that bench I gripped it with a pair of tweezers to pull it out but it seemed stuck, what it turned out to be was a threadlike piece of plastic that was attached to a bigger piece that was all but completely blocking that jet! It was stuck so tight that the cleaner I blew through it from the spray can did not dislodge it but under pressure enough of the cleaner got past it to make it appear that the jet was open, I dug it out and after reassembly and installation it not only runs REALLY good now but it honestly has more power than when I brought it home new, this leads me to believe that piece of plastic has been partially blocking that jet since the darn thing was new. I assume it finally got sucked into that jet and blocked the flow enough to cause me to have to repair it, this has been a real pain in the rump but in the end I was rewarded with a better running mower than I had when I first got it.

Willy
07-20-2016, 02:33 PM
Great news to see you got to the crux of the matter, who would have guessed finding something like that!?
Like you say, probably installed at the Nikki factory.
Good diagnosis and execution on your part, most guys would have given up on the first try.
You can now proudly stick another feather in your cap.:)