Keeps Blowing Spark Plugs Out

Cub 800 · #1 07-24-2014, 11:22 AM

I think it might be Pissed at me.

So I've had this tractor a couple years without any major problems, But about a month or so ago it blew out the spark plug. it seems someone had already put a timesert in it. I put some green locktite on it and screwed it back in and it held. But cause I knew it was going bad I bought another head off fleabay.

new head looked good, so I beadblasted it and sanded it flat, then ran a plug cleanup tap in, every thing felt good.

Next time it blew the plug I decided to change out the head......
put the new (used) one on and after screwing the plug in I remembered I did not check the plug gap. unscrewed the plug and the second time I put it in the threads just came right out!!

So I took that head back off and took it to a guy to have a timesert put in it.
( the old head had the threads gone and it was already big from having a timesert put in it)

Put it back together and I'm Golden.

Ran it two or three times, I only need it to cut the rough side yard and an area behind the house that doesn't have to be too purty. So today I get it out and go to start it and THE PLUG BLOWS OUT AGAIN!!

WTF?? .....takes the timesert with it!!

So I have the old head I can have tig welded up and redrilled then machine the plug surface flat, OR bite the bullet and try to find a NEW head, in spite of the cost I am leaning this way.

Now this is no high-compression pulling motor is just an old 8-hp k-181

This all started after I moved the tractor out of the garage because I needed the space to rebuild a Porsche motor I am restoring. so the tractor was moved into my motorcycle trailer as a temporary home... better than leaving it outside.

First the coil went, then it blew the mower drive belt, now this...

I think its PISSED at me.

jimbob200521 · #2 07-24-2014, 11:40 AM

That'll teach you to give the Cub space in the garage to some other motor, I'd be pissed, too!

I'm wondering if something was done wrong when the "timeserts" were put in your heads. I've done several heads with a heliocoil kit myself and have never had one blow out. I'd recommend trying that, and make sure when you put the insert in, use the red locktite, I think that's the color. The stuff that is meant for permanent applications. Good luck!

rwairforce · #3 07-24-2014, 11:55 AM

Good story..
Obviously the good ole American Cub doesn't like that German engine you put in it's place. Good luck. I've never had such head problems on anything I've owned. Maybe try a different plug manufacture?? If you've been using Champion, try Autolite. I have no idea but maybe the base of the plugs are made of different material. Again, this is a off the top of my head suggestion.

cubs-n-bxrs · #4 07-24-2014, 12:11 PM

I myself would not go the route of using a helicoil on a spark plug. I have seen to many of them get pulled out with the plug. Reason being the sealing ring on the bottom of spark plug when tightened down will catch the edge of helicoil and back it out with the plug. I would use a threaded spark plug insert with red loctite and for safety measures prick punch the bottom of the insert and head. Just my

J-Mech · #5 07-24-2014, 12:28 PM

Quote:

Originally Posted by cubs-n-bxrs

I myself would not go the route of using a helicoil on a spark plug. I have seen to many of them get pulled out with the plug. Reason being the sealing ring on the bottom of spark plug when tightened down will catch the edge of helicoil and back it out with the plug. I would use a threaded spark plug insert with red loctite and for safety measures prick punch the bottom of the insert and head. Just my

Agreed!

Napa sells them.

Cub 800 · #6 07-24-2014, 01:52 PM

Quote:

Originally Posted by cubs-n-bxrs

I myself would not go the route of using a helicoil on a spark plug. I have seen to many of them get pulled out with the plug. Reason being the sealing ring on the bottom of spark plug when tightened down will catch the edge of helicoil and back it out with the plug. I would use a threaded spark plug insert with red loctite and for safety measures prick punch the bottom of the insert and head. Just my

I didn't use the helicoil insert I used one of these,

http://www.timesert.com/

its a full steel insert. should have worked just fine....

I think the Cub just wants some Love in the way of new parts...

I found a NEW head I'll be putting on when it gets here, maybe that will satisfy her for a while..

J-Mech · #7 07-24-2014, 02:09 PM

Your using the correct spark plug aren't you?

Cub 800 · #8 07-24-2014, 03:36 PM

Quote:

Originally Posted by J-Mech

Your using the correct spark plug aren't you?

Well the book calls for a Champion J8 which is NLA... I am using an Autolite 295. that is listed as one of the correct replacements.

So Yes, I am using the correct spark plug.

J-Mech · #9 07-24-2014, 03:46 PM

Put anti-seize on it when you install it in the new head. And make sure you don't over-tighten it.

Jeff in Pa · #10 07-24-2014, 08:36 PM

Quote:

Originally Posted by cubs-n-bxrs

I myself would not go the route of using a helicoil on a spark plug. I have seen to many of them get pulled out with the plug. Reason being the sealing ring on the bottom of spark plug when tightened down will catch the edge of helicoil and back it out with the plug. I would use a threaded spark plug insert with red loctite and for safety measures prick punch the bottom of the insert and head. Just my

The correct type of heli coil would be a locking heli coil. ( to over simplify, they are designed with a flat spot on the outside to lock the heli coil in place.)

That said, I would use a Time Sert type repair myself.

Cub800, are you using a torque wrench to tighten the spark plug?