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Discussion Starter · #1 ·
For the past couple of weeks my 314 K321AQS (rebuilt 5 years back) has started to get very sluggish under load (mower deck / PTO on), but this happens only after 30 -60 seconds of turning on the PTO when engine is warm.

With PTO off, all is fine. Engine revs up, with no sluggishness, no strange sounds. Sounds great!

With PTO on after 5 mins of mowing, starts to get sluggish. When moving forwards and mowing, ground speed and engine speed both start slowing / bogging down. Also, here a metallic tapping sound, frequency is maybe 2 per second.

After turning off and on, all is fine again, then after about 30 to 60 seconds does the same.

Looked at the spark plug. Fouled black. Too rich, so (gapped) and replaced plug, adjusted main carb screw clockwise. It is warmer, so thought maybe that would do it.

That didn't do it.

PTO was replaced a year back. Bearings are fine in mule drive and deck, belt is tensioned right.

Coil is 9 months old, and I placed off the engine block to stop it shaking to death. I don't think that's it. Points are same age and timing done then.

Things I am wondering:
  • bad connection to coil
  • bad condenser? I have a Kirk transdenser. About 2 years old.
  • bad timing, perhaps I should check that.
  • valves knocking on the head? Yikes. It sounds like that maybe, but
  • transmission going?
  • governor gear exploded or damaged?

What makes this strange is it only happens under load.

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Discussion Starter · #2 ·
OK, I solved one problem - the engine is no longer stalling when under load.

  • Cleaned out carb. There was some gelling on the input side
  • Pulled off head, VERY dirty in there. Cleaned that out as best I could, reinstalled and added new gasket
  • Replaced air filter
  • Drained gas (it was from early winter, with some seafoam. I guess it was going bad) and filled with fresh.
(that took me all day)
  • Started up. Still had some issues with it stalling out under load.
  • Checked the mule drive - Was really tight. I guess I overtightened, so loosened that up a bunch.
  • Then restarted, and then didn't stall under load.

However, I still have some strange tapping noise. I noticed it when I had the head pulled off. I can't figure out what it is. Occasionally I hear it when the engine is running under load, but it isn't present all the time. It doesn't seem to present itself when the engine is off, but i was hearing a slight tapping sound when the head was off. I will keep running it this week to see if I can figure out when I hear it.

Video attached of the noise when the head was pulled.. I can't figure out what it is but seems to be coming from the block area. 馃槵 - listen around 1 min mark where it is most noticeable. Perhaps the connector at bottom of rod is working its way loose??? That can be only thing I can think of - the governor seems to be functioning, and there's no balance gears.

Unfortunately on this 314 I can't just pull the pan off to take a look as there's a steel part in the way. The whole engine has to come out. That's a week of work just to take a look.
 

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Discussion Starter · #4 ·
Still battling this.

Starts hard. Adjusted the carb and made it better, but still takes a few turns to get it turning over

After warming up, and from cold, I hear no tapping from the engine. When I hit the PTO, all is fine and it doesn't bog down.

After mowing, I notice that when I go uphill, the engine starts to bog, then I start hearing tapping /knocking noises. Before that when on level ground, no tapping.

When I turn off PTO, and engine is unloaded, no tapping.

I purchased a scope to inspect the engine without pulling the block out.

Could it be transmission?



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I can't think of anything in the hydro that would make a tapping sound. The first things that come to my mind are wrist pin, piston slap, or rod knock. If wrist pin or piston slap, it'll probably get worse over time (years), but if rod knock, may break rod the next time you start.... or 100 starts from now!

It's a little work, but if it is the engine, you'll need to pull engine & inspect. Drive tractor until it starts to "tap", then park where you're gonna work on it and remove fender pan and drive shaft. If "tapping" is still there. definitely and engine problem. If "tapping" goes away could be (??) hydro problem.

Sorry Rob, all I've got! Bob
 

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Sounds like predetonating under load. Can be caused by buildup of carbon in cylinder head and valve area. Head removal is about the only way to inspect and clean. If bad enough, valve removal may be necessary. Be sure to lap head to insure flatness. Good time to set valve clearance as well. New head gasket too.
 

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Discussion Starter · #7 ·
Sounds like predetonating under load. Can be caused by buildup of carbon in cylinder head and valve area. Head removal is about the only way to inspect and clean. If bad enough, valve removal may be necessary. Be sure to lap head to insure flatness. Good time to set valve clearance as well. New head gasket too.
Ok, well seems to be a good theory. I pulled the head off at weekend and saw it was pretty built up with carbon.

I cleaned up by using a plastic razor blade as best I could and a plastic brush on my reel. I couldn't remove everything, but got worst off around the valves, on top of piston and on back of head. Still, not down to the metal but I wasn't sure how to do that without resorting to an abrasive material that would damage the metal. I used carb cleaner and soaked for a few mins, then tried to scrape. I just removed the high spots, didn't get down to bare metal.

Some questions:

1) if predetonation, what is the cause behind the cause? For example, if carbon builds up, is that just due to bad gas, bad timing? Put another way, if I fix the carbon, what else do I fix to ensure I don't get that problem in another week?

Poor valve gap?
Poor timing / need to reset points?
Bad gas?

My coil is just 6 months old, so can't be that. And I change plug every 6 months.

2) since I pulled head at weekend, I replaced the head gasket. If I pull to clean again, should I always go with new gasket?

3) any recommended way to make the combustion chamber super clean? Abrasives on a drill with some kind of compound, or acetone?

Thanks, seems like a good theory



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I have read that you can reuse a metal head gasket if you give it a coat of aluminum paint. I must admit, I haven't tried it.

The last head that I cleaned up I blasted with walnut shell media. Got it pretty clean. Diesel and a brass wire brush (carefully)
 

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Invest about $20 in a can of Seafoam and some Marvel Mystery Oil, mix together and soak as best you can to loosen/soften up the carbon...then go at it again, plus the brass brush. If it doesn鈥檛 suit you鈥檝e got some fuel/engine additive for your later use.
Always heard that carbon is due to working the engine below optimum temp & rpm. Post back with updates.
 

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Rob, I don't know anything about the operation of the transdenser, so if instructions with it say something different than what I suggest, follow the instructions.
Your description does sound like pre-ignition or detonation. I will suggest checking the point gap and set to 0.020" unless the above mentioned instructions say different. The points gap, as you probably already know, controls the ignition timing with the stock components.
As far as reusing the slightly used head gasket, you can probably get away with it, 50/50. Ultimately, once the real problem is solved, I would get a new gasket, make sure the head is lapped flat within 0.002", torqued to specs, and retorqued after a couple heat/cool cycles.
Good luck with it. Hope you find the problem soon.

tommyhawk
 

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After seeing your pictures, the predetonation from the carbon buildup is my best guess of problem. You will not hurt the block or valves with a steel wire brush. It can scratch piston and head though. It appears motor is probably using some oil at the amount I see in photos. Could be coming from worn valve guides, piston rings, or a scratch in the bore caused by a broken ring or scarred piston. Removing valves is probably the only way to completely rid ports and valves of the carbon. I used my cabinet blaster to remove carbon from the head. Once it鈥檚 good and clean, use a 220-400 grit of wet sandpaper and wd40 or equivalent to sand head on a piece of polished granite or table saw top to insure it鈥檚 truly flat. Be sure to properly set valves and points and hopefully this all will help problem.
 

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Discussion Starter · #12 ·
OK thanks all for the comments! I will have another read through in the morning.

Up through the winter (doing some heavy duty snow throwing) and early spring it was doing fine with oil consumption - hardly any used. Then suddenly in the last few weeks it has been acting like this. I guess as the weather warmed up and I started doing some mowing.

1. Yes it does look like oil is getting up from somewhere. Is that possible from the input port or just the cylinder? I will check for cracks in the block. (OMG I am having flashbacks to when my original block cracked).
2 I will pull the head again and try the cleanup with the above recommendations. I have seen on good old youtube that ATF and acetone mixed, and then scrubbed works well?
3 I will check the timing with the transdenser, will re-read the instructions. I think I was lazy last time I did the points late last summer and set with 0.020", not following the instructions.
4 I will order yet another head gasket, some new plugs. I will use this one that's been on for a few days to see if I fix the problem, then stick new one in.
5 Should I bother with the valve gap also? I did that last 4 years back. Does that tend to alter over time? I ask mostly because I stuck my breather gasket to the block with some black silicone to stop oil leaking out. I will have to buy a new gasket because that isn't going to come off intact!

Reminding myself of other things I have done - back in Jan my threaded spark plug insert came out with my plug. I reached for my tool kit and inserted a new one that was just a fraction too long for the plug. It doesn't stick out past the head surface underside. I wonder if that was a cause of poor detonation. I have bought some newer inserts since that are the right length, but can't get the existing insert out, so I have some head scratching to do there.
 

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Discussion Starter · #13 ·
Cleaned the carbon off the head and around valve area.

Pulled out the valves. Caked with carbon, but seats are very clean. I will polish the valves up, taking care to not hit the seats.

Question:
The valve seats were last done in 2016 when I rebuilt by a machinist. Is it recommended to lap the valves again while I have this out? The seats on the block and the valves look very clean.

I will set the valve gap when I'm done.



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Discussion Starter · #14 ·
Ok so after a bunch of work it is back running and running well with zero sluggishness, and no tapping!

Work done:
  • cleaned piston head of all carbon build up.
  • bought a refurbished cylinder head and new head gasket
  • removed and cleaned up the valves in my drill press
  • lapped the valves in the block, taking care to ensure no paste got into the block. Gave it a good clean out after with some q tips in the valve ports.
  • set the valve gap
  • changed out the connector from the points to the transdenser. The old one was fraying and I do wonder whether that was a culprit here as it was coming on too often
  • reset the timing, setting the gap to 0.024 after figuring out that was the right setting to get the transdenser to kick on and create the spark just as the flywheel hit S mark. Took a lot of playing around, but I got there.
  • reinstalled head with brand new bolts and washers
  • drained oil. inspected the block on the inside using a device I found on eBay (depstech) that allows a small probe with two cameras and two LED bulbs to see into the block via the oil drain port. Everything looked like it did when I installed it all and rod was firmly connected.
  • replaced oil
  • installed engine shroud

Fired it up and at first it ran rough as it wasn't getting enough gas. Fixed with some carb adjustment. Now runs perfectly... for now!


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That is impressive! So how, or maybe why, does a soda blast work? I use glass beads in my bead blaster, buy them from auto parts rebuild shop.
 

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So how, or maybe why, does a soda blast work?
Not sure. I'm just cheap and didn't want to invest in something I rarely use. There are tons of articles and youtube videos.
Just search for "DIY soda blaster"
The part I like about it is that it doesn't damage surfaces.
 

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I did a little research on it, the big box stores sell a 'crystalized baking soda' for soda blasting. There's also the option of crushed walnut shells. I once working for a company that made DC motors, these were painted different colors for different customers. If the paint shop screwed up the paint was removed using a plastic media blaster, the media felt soft as you handled it but it removed the paint quite nicely.
 
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