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rich_kildow

Predator 670 bogging, smoking, and popping

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rich_kildow

I'm banging my head against the wall a bit with this one.  My Predator 22hp repower has worked great up until today.  It started and began mowing just fine until about 10 minutes in when it started bogging down every 15-30 seconds, releasing a quick burp of dark smoke when it did so, then returning to normal WOT.  This went on for a few minutes and I started to question if the oil was overfilled.  By the time I was back to the garage the bogging interval was closer together.  Turning the fuel cutoff off stabilized everything.  When I got the covers off I noticed fuel in the carb intake area.

I'm guessing it's getting too much fuel, which makes me think bad float(s).  I fiddled with it a bit more and then it started popping constantly.  I have 2 videos showing it below.

If it helps at all, it is 85+ and humid today, but it certainly isn't the first time it's been run on a warm summer day.  I haven't touched anything on this motor other than installing it, so there shouldn't be any jetting or carb adjustment issues.  Any ideas?

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GardenTrACtorguy

I have heard the coils and ignition on these 670’s are terriable.  I would start by testing the coils if it was my machine.

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rich_kildow

Would that cause a dead cylinder or these kinds of symptoms?  I was trying to think of a way to describe how it sounded overall, and it's just anemic.  Like a 6 or 8 cup with one dead cylinder.  You can't quite pinpoint it, but something is off.

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GardenTrACtorguy

If you test the coils and they are bad aftermarket ones are much better than the original ones.  I have also heard about the magnets in the flywheel can loose magnesium, but I’m unsure about how true it is.  More research may be in order.

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SimpleOrange

Ok we know the engine runs like sheet after a 10 minute work out on a hot day, the popping sounds like its an ignition problem. 

I believe the insulation on the internal coil wires has broken down, some one should research what class of insulation was used to manufacture these ignition coils.

As you can see from the chart below class A and B combined with engine heat on a hot day would not have fared well.

Now that the day has cooled go out and start your mower, if it's going to bother the neighbours cut some grass we want to see how long it takes for the coil to act up.

Onan in order to keep the ignition coil healthy mounted it at the coolest spot on the engine.

The coil is on the flywheel side and is first served by the incoming air.

These things to not happen by accident the engineers at Onan knew how to build an engine.

insull.png

coil.jpg

Edited by SimpleOrange

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deebig

"Turning the fuel cutoff off stabilized everything.  When I got the covers off I noticed fuel in the carb intake area."

That is the clue no one has commented on. Fix that issue first by replacing needle and seat.....could also have dirt trapped in fuel line between pump and carburetor interfering with needle seat. I have had that same problem before. 

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BLT

Intermittent exhaust smoke and loss of power would make believe a problem with crankcase ventilation system mainly the reed valve.

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maxwood

Hello, I was looking in my Predator owners manual , and they have a section on troubleshooting.

  including low oil shutdown ,and valve adjustment, & dirty air filter , these may not be your problem but  may be worth consideration

 

Thanks Ken in Mi 

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Angry Bear
On 8/11/2018 at 6:20 AM, deebig said:

"Turning the fuel cutoff off stabilized everything.  When I got the covers off I noticed fuel in the carb intake area."

That is the clue no one has commented on. Fix that issue first by replacing needle and seat.....could also have dirt trapped in fuel line between pump and carburetor interfering with needle seat. I have had that same problem before. 

I agree with this. I think something is holding the needle open. Or possibly a hole in the float, and it's filling with fuel. I've seen that before. But I definitely think it's carburetor related... excessive fuel. 

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SimpleOrange
On 11/08/2018 at 6:20 AM, deebig said:

"Turning the fuel cutoff off stabilized everything.  When I got the covers off I noticed fuel in the carb intake area."

That is the clue no one has commented on. Fix that issue first by replacing needle and seat.....could also have dirt trapped in fuel line between pump and carburetor interfering with needle seat. I have had that same problem before. 

Problem is with the carburettor, improper float adjustment, bad needle valve. The intermittent exhaust smoke is caused by wash down. on the cylinder wall with excessive raw fuel.

What fuel pressure is the Predator supposed to have, perhaps in excess.

Just a wild guess.

Edited by SimpleOrange

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tweinke

I agree with the carb issue thoughts posted by others.  Black exhaust would be too much fuel, the carb is pretty simple to work on and I would pull it and have a look in the float bowel. As I mentioned in a previous post there are also two jets under the screw with the big washer on the top. Clean out the bowel and blow out everything and I bet it will run good again. 

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rich_kildow

I forgot to come back to this and address the fix.  

On 8/11/2018 at 6:20 AM, deebig said:

"Turning the fuel cutoff off stabilized everything.  When I got the covers off I noticed fuel in the carb intake area."

That is the clue no one has commented on. Fix that issue first by replacing needle and seat.....could also have dirt trapped in fuel line between pump and carburetor interfering with needle seat. I have had that same problem before. 

deebig nailed it.  I think it was pulling a touch to much fuel and then getting rich as it pulled it in.  I pulled the carb, cleaned it up and put it back in.  Ran it hard on a few hot days catching up on mowing and no issues since.  Good suggestions all around and I'm glad to know about the potential issues with it.  

Thus far, I'm very happy with this motor.  This will be it's 4th winter and a carb cleaning is really the only issue I've had with it.  I know it's no Kohler or Briggs, but it's been a great motor thus far and at the time, throwing a more expensive motor in wasn't in the cards. 

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Gerg

I installed a predator engine in my 7117 10 months ago and had the same problem as you. As it turned out I overfilled the crankcase with oil, it was only slightly over the full mark. it smoked bad and also ran bad. By lowering the level to slightly below the full mark smoking problem solved. My engine runs lean, causing it to run rough and bog a little so I have been running with choke pulled out to first notch. I'm pretty sure it needs larger jets, I used it all year mowing the yard and never had a lack of power, probably will continue running it like this until I find some jets. 

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Pauly

I apologize for resurrecting this thread. I had the same problem as the OP, with the same solution. I want to add some additional info. 

If your pump is flooding your engine to the point it won't run, the gas will end up in the crankcase, adding to the oil level. I surmise that if your oil level is too high, it's probably because of  this excess fuel issue. I'd recommend an oil change if you have this carb issue and too much oil. You can smell the oil, to be sure. It smells like fresh gas.

I think the main issue with mixture from the factory is the idle mixture. There are caps on top of the carb that you can pop off to reveal the idle mixture screws. Adjust like any other carb.

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DuckMotorGuy
On 11/28/2018 at 10:20 PM, Gerg said:

I installed a predator engine in my 7117 10 months ago and had the same problem as you. As it turned out I overfilled the crankcase with oil, it was only slightly over the full mark. it smoked bad and also ran bad. By lowering the level to slightly below the full mark smoking problem solved. My engine runs lean, causing it to run rough and bog a little so I have been running with choke pulled out to first notch. I'm pretty sure it needs larger jets, I used it all year mowing the yard and never had a lack of power, probably will continue running it like this until I find some jets. 

I have been running my Predator 670 for about 4 years as a longtail mudmotor on my duck boat. Just pulled it out after 4 months to get cleaned and prepped for the fall season. Turned the key and it started right up like a brand new motor and it was running great on the trailer. I only have about 35 hours on it and decided to give it an oil change even though the oil looked pretty clear on the dip stick. I used Amsoil synthetic small engine oil now that it is sufficiently broken in. Just like Gerg said, I over-filled the oil to just over the full mark. After the oil change it started right up and ran fine for several starts over several hours as I was charging the battery and setting up the rest of the boat just to make sure it would start reliably after the 4 months if rest. Getting back to Gergs post, after a flawless 15 minute morning run in the water and a 6 hour rest during the hunt, it would not start. It would pop over with a couple of good ignition power strokes then die. Tried choking it full (usually starts right up at 1/2 to 3/4 choke), and nothing. Then full throttle with WOT to clear it out and start over with not so much as a pop. Any continuous cranking produced nothing. after waiting a few minutes then hitting the starter,  it would again pop over with a couple of good ignition power strokes then die, seeming like it was under primed/underchoked. I went back and forth with this trying to sort out if it was flooded or just too lean.. Eventually I pulled the plugs and they looked wet so I dried them off the best I could with a rag. Now, after reading this post,  I suppose they looked kind of oily wet, and I remember on the couple of times when it came close to getting going (more than two pops) that there was alot of black smoke even though I wasn't choking it at the time. This went on until the battery was depleted while my son dragged the boat back through the marsh to the dock. Once I got home with the battery charged up, same thing, a couple of pops and die. I pulled the plugs and blast cleaned them and put them back in. Started up and was able to get it to run in mid RPMs for 20 to 30 seconds and then die. Got out some starting fluid  becaused when it died it just seemed like it was out of fuel even though the bowl was full as evidenced by the feel of the my boat tank primer bulb and full coming out the bowl overflow tube. To my surprise, the starting fluid and no effect at all. As a last ditch effort I checked the fuel pump (and this is a trick to remember) by disconnecting the pump output tube from the bowl inlet and resting over the carburetor air intake and cranking the engine with the plugs out until fuel flowed out of the pump into carburetor. Ok, pumps ok i thought. After putting the hose back on and plug back in and giving it one more try, it started right up and ran fine up to the governer limit (without load). Tried starting it periodically over the next few days and all seems ok. So once again back to Gergs post, and overfilled oil, this is what I am thinking now. As a mud motor the engine gets tilted 20 - 30 degrees from level during normal operation (like mowing a sloping grade). On the trailer it was running level. I postulate excessive oil made it into the combustion chamber and coated chamber surfaces and the plugs. As it set during the hunt, the oil further migrated to the plug electrodes that eventually cooled and fouled the plugs to the point where on the first compression stroke, it would spark and fire when the compression is lower than what it is when the engine rpm increases while it is running. I think once the motor started spinning faster, the increased compression was enough to extinguish the spark due to the oil fouling and the engine would die. Now the last ditch fuel pump trick pumped enough fuel straight through the carburetor and out the open plug holes to wash the excess oil away from the combustion chamber surfaces to prevent continued fouling of the plugs on each start.   Thank you Gerg for your post about not overfilling the oil, I will be keeping mine somewhere between 1/4 and 3/4 going forward. Moral of the story; bring spare plugs, don't overfill the oil, and feed you son's so they grow up big and strong. Sorry for the long post; hope it helps someone.

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