# Help with Predator 3500 invert/generator fouling spark plugs



## Mike Louthan

This is my 6th brand new Harbor freight Generator in the last 6 weeks. I currently have 2 of them, one is broke down only spitting and sputtering with 0 load applied and now the other will not handle even a coffee pot without going into AC overload. I will be taking these back Monday and getting new ones AGAIN! THE LONGEST I HAVE HAD ONE RUN IS 130 HOURS BEFORE THIS PROBLEM. Everytime the spark plugs are charred black with carbon. I take them out, replace with a new one and runs good for 10 seconds and turns the new plug black from carbon. First couple times I thought it was a fluke but this many times with the same problem says otherwise. Harbor freight tell me I am the only person they know of that has this issue. I have followed their break in procedure, use seafoam in the gas, changed oil at 30 hours and still keep having these issues. Once the generators start this I have not been able to get any of them to recover..even after changing and cleaning the plugs numerous times. If I remove the air filter COMPLETELY, the generator will run but only without a load applied. If I put the filter back on, the vacuum sucks it right it and starts spitting and sputtering. I noticed on this last one that the air filter is soaked in gas and you can see it spitting gas out while running. Any help would be greatly appreciated as this is getting very old considering the closest store is an hour and a half from me.


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## Brian Esberner

Did you buy the extra warranty at Harbor Freight? I am having issues with my 2500 predator and it's just over two years old so I think I might be screwed


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## diferg

Mike Louthan said:


> This is my 6th brand new Harbor freight Generator in the last 6 weeks. I currently have 2 of them, one is broke down only spitting and sputtering with 0 load applied and now the other will not handle even a coffee pot without going into AC overload. I will be taking these back Monday and getting new ones AGAIN! THE LONGEST I HAVE HAD ONE RUN IS 130 HOURS BEFORE THIS PROBLEM. Everytime the spark plugs are charred black with carbon. I take them out, replace with a new one and runs good for 10 seconds and turns the new plug black from carbon. First couple times I thought it was a fluke but this many times with the same problem says otherwise. Harbor freight tell me I am the only person they know of that has this issue. I have followed their break in procedure, use seafoam in the gas, changed oil at 30 hours and still keep having these issues. Once the generators start this I have not been able to get any of them to recover..even after changing and cleaning the plugs numerous times. If I remove the air filter COMPLETELY, the generator will run but only without a load applied. If I put the filter back on, the vacuum sucks it right it and starts spitting and sputtering. I noticed on this last one that the air filter is soaked in gas and you can see it spitting gas out while running. Any help would be greatly appreciated as this is getting very old considering the closest store is an hour and a half from me.


Try Leaving gas cap loose when running.

I had very similar episode with predator 3500 today. unit was running the air conditioner on my rv. was a hot day about 98 deg F, ran about 4 hours sitting in direct sun light on concrete slab with no breeze at all. I heard the generator start to run kind of ragged then air conditioner stopped working. generator was still running but badly! the overload light was on, I unplugged the rv and turned off the generator and let it sit had vert strong smell of gasoline. an hour later it would not start, checked the oil level (it has a low oil cut off switch) oil was fine. removed spark plug, (could still smell gasoline) plug was covered in black soot and definitely fouled out. spun generator over without plug to clear cylinder of excess gasoline. cleaned plug and reinstalled. tried generator again. started right up. left gas cap loose and reconnected to rv ran great for another 4 hours until I turned it off. 


I believe the heat of day and heat of generator caused gas tank to pressurize and flood carburetor with gasoline. I am going to buy replacement gas cap and drill 3 1/16" holes in it. will only use this cap when running In safe location install original for transport.


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## mlevinson

Maybe this?

https://www.powerequipmentforum.com...tor-3500-inverter-generatore-5.html#post63176


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## diferg

makes sense to me! possibly a combination of both scenarios. please post your solution to spark arrestor replacement.


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## Sburcham

*Spark arrestor*

Clean the spark arrestor of the exhaust


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## RedOctobyr

In addition to the spark arrestor, there was some recent discussion of a charcoal canister in these units causing problems with fouling plugs. Some discussion starting here, of how the person fixed theirs: 



https://www.powerequipmentforum.com...tor-3500-inverter-generatore-5.html#post63228


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## ddecarr

Mine did the same thing after <100 hrs. Are you also removing the spark arrestor? Behind the spark arrestor is another fine wire screen that is inserted into the generator exhaust port. You need to use a small screwdriver at the lip to pry it loose and pull it straight out. When my plug fouled, this screen was also loaded with fouling, not letting exhaust out of the cylinder. Cleaned screen, replaced plug, runs great. Don't know why it fouled to begin with.


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## pjohnson1970

Mine did the same thing and I was really unsure what to do, I rang the guys at http://bellwoodrewinds.co.uk where i bought it from and they advised me to clean the spark arrestor.


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## Wîll Kīng

Mine ran rough within a few minutes of running right out of the box. Yanked the carbon canister out, cleaned the spark plug and spark arrestor. Ran the little generator for 45 at 2700 watts without any issues. Also had no more gas dripping out of the overflow tubes in the bottom of the enclosure. Also closed the spark plug gap a bit, was a little too much for my liking.


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## Robh

OK necro thread, but this is still worth stating...

The price difference between a Predator and a Honda may be twice as much, if not more. But the price difference between a Predator and a Champion or similar may only be 20% or so. I really don't understand why one doesn't just pay a little bit more for something better than to deal with SIX returns!!

That being said, there is a long thread on this forum about Predator 3500 fixes if you are willing to perform some minor surgery. It'll fix all your issues.


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## Handirifle

I know this is an old thread, but thought I would update it a bit.

The predator 3500 comes jetted rich, for some off reason. In addition, it's not uncommon to have a partially clogged idle jet. There are numerous youtube videos of correcting this. The idle jet is a remove an clean, but most everyone changes the main jet to a smaller one. 

Cleaning the idle jet helps stop the surging they often do, and replacing the main jet cures it for good.

The main in mine was a #77, while most report a number#76. I ordered a #68 thru this link. Main Jets & Pilot Jets.

Total cost ends up around $12 shipped. I installed mine yesterday. The difference in running is amazing. Purrs like a kitten. Just for the record, mine is a new gen, with less than 4 hours on it, but I could see the plug was burning black, and soot already building up on the spark arrestor. Rejetting should pretty well eliminate both problems.

Yes, you should not have to do this to a new gen, but for less than $20 it runs like a champ. Also, from what I have seen, and read, DO NOT DRILL HOLES IN THE COVERS. There is a youtube where the guy shows, that the intake air is drawn in through the bottom front of the generator, and travels up across the electronics, to cool them, before getting to the engine. Opening up holes in the outer case, reduces airflow across the electronics and could cause heat failure. He drilled holes in his air filter housing, but I am betting, based on how mine now runs, that is not needed either.

I can only assume, these engines are jetted before getting into the generator housing, and it causes issues, it does not cause when used in other applications. The engine is their same 6.5 hp, 212cc engine they sell, and use throughout their lineup. Heck my Sears rototiller, has one in it. In fact I pulled the idle jet out of it, and put it into my gen.

Check youtube for these things before taking the next one back. Do, however, recheck the spark plug, to make sure it does not run too lean, based on your elevation, where you use it most. Something inbetween a 68-76 might be called for if that is the case. I have seen some guys order a jet kit, with several sizes in it, to make it easier to swap. 

Doing all the above takes about an hour, or less, and you do not need to remove the carb to do it. DO be careful, not to lose the idle jet. Mine snapped out of my pliers. I hear it rattle around in the plastic floor of the gen. After 1.5hrs looking I still did not find it, so that was why I pulled mine from my tiller. Hopefully you do not need to.


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