[jack_n]

My 320 (FD590) has developed an odd quirk over the last couple of weeks. It spits the left bank spark plug out after a few hours of running. Todays' blow out was the worst. It sounded like a small explosion, so I'm thinking it must have come out on the power stroke. The outside thread in the head got damaged this time so I can't get the plug back in. I'd like to use a tap and some grease in an attempt to clean up the threads, but I don't know what size the threads are. Can somebody help me out?

Also, anybody got an idea why the plug won't stay in, and what can I do to keep it in? Don't really want to replace the head.

I haven't been to the forum in a while. What happened to all the posts?

 

[Davet]

Hi Jack, I've only had a spark plug fly out once in my life, and that was on a motorcycle because I had not tightened it tight enough. They're not suppose to be super tight (aluminum head), but certainly more than hand tight. If you're unsure and own a torque wrench, the actual torque value is in the manual.

Of course, if it has a habit of popping out, the outer threads can get blown out like you experienced. It could also be that a previous owner had stripped the threads by over tightening, or cross threaded.

I see there is a healthy FD590 parts market on e-bay, and while I haven't been following FD590 like I do for my current tractors, perhaps this may be somewhat relevant. I've picked up used heads on e-bay (for FD620) for as low as $35. While used of course, they looked to be a fine replacement for a used engine.

good luck,
Dave

 

[jack_n]

Yea, I gave some thought to replacing the heads. I thought I'd get a used set off of a 20hp version because the porting is supposed to be slightly better. The only problem is that then you have to get the 20hp version of the manifold and carb to take advantage of the heads. Too spendy.

I decided to go the Timesert route. Really spendy kit, but at least it'll save me the hassle of tearing 1/2 the engine down, and I'll have better than original threads when I get done. I'm going to do both heads so I won't have to worry about this happening again. Apparently the aluminum is getting weak after 18 years of service.

By the way, if anybody out there needs to know the thread size for their tractor, it's an M14 x 1.25.

 

[canpatm]

I let me Dad borrow my 216 to mow his grass while I was on vacation, came back to a noisy tractor in Reverse, 3rd and 4th. He said it just started making the noise.
At first I thought it was the idler pulley bolt bouncing off the frame on the drive belt near the transmission, so I replaced both those belts and adjusted the pulley so it doesn't rub. Still making the noise.
Now I wonder if he forced it into gear while going into Reverse? I warned him to gently push it in while the gears slowed to a stop.
Could this be a chipped tooth? But why is it okay while in 2nd?

 

[KB]

it sound like it could be a chipped tooth.

as far as why some gears and not others, it has to do with each gear inside the tranny may or may not be used in a given shifter gear, many of the gears and shafts are used in more then one shifter position.

if you get the peerless service manual, it shows the path the power takes in each shifter gear, and you might be able to determine what one is bad without opening it up.

there are many reasons for one to fail, and not all of them require current abuse to cause failure. there could have been lingering cracks in a gear for decades, and it finally let go

My dad borrowed my 112 for his last time, decades ago. first time I got it back the deck was bent in on the front, the second time the frame horn was busted off, now if he wants a tractor, it needs to be scheduled when I can run it

 

[canpatm]

I'll have a look at the manual and see if I can figure something out. How's longs a tranny job like this take, replacing gears and such? A weekend job hopefully.
It sure would be nice to have a newer zero turn to cut the grass with and take my time to restore this one. Maybe one day...

Good idea, I think I'll cut his grass next time for him when I have time. He won't even let me run his backhoe when I need it. I have to wait for him to schedule me in.

 

[Grant Baker]

A tranny job can be done in a day,if you have all the parts. If you want to take the time to blast and paint the cases and stuff,then it will take a week.Plus,you'll have to find out what gears went sour and order them from JD parts