2 Broken spark plug anodes?

I went out this morning and within ten minutes my 260 started running bad. I pulled spark plugs and I had two NGK BPZ8HS 10 plugs and it appears that the anodes broke off in the same place on both plugs. Just destroyed two pistons. This is 2 260s in two years! Any ideas? it does not look like detonation as the piston tops are still a bit wet and no damage on the tops of the piston. You can just see where the anodes beat the pistons up. They broke off about half way in the middle of the anode.

Carter Powell

What is broken, the white porcelain insulator or the metal ground strap or both ?

look at the other pistons , where the ground strap would hit if the plug was too long, are there any marks on the other pistons?

I'm thinkin maybe some excessive cut heads ??

Or the length of the plugs, are those the right length plugs ??



Attachment 543043
I found a NGK BPZ8HS-10 extended tip, and a NGK BPZ8HS-10 commercial just to show the different reaches I believe you have the right plug which would suggest look for other issues.

Gonna Have to do your homework on this one! Good Luck! It's been to long for me, my memory is now shorter than my - - - - er!

The plugs are the correct length as I ran them in this motor last summer for about an hour. Just the ground straps were broken on two plugs. One of the ground straps flew out the exhaust port and did not hurt anything the other ground strap just tore the hell out of number five... There are no marks on any of the pistons. They all look good except for number five. I need to find a good engine builder to send this powerhead off to to see what can be done with it. I am just getting too old to build these things anymore.

There are a LOT of counterfeit NGK spark plugs sold in the US: https://www.webbikeworld.com/riders-...k-spark-plugs/

I would make an effort to verify that you have real NGK's before changing anything on the motor; even some big name chain stores got burned buying shipping containers full of fake NGK plugs.

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Originally Posted by Carter Powell

The plugs are the correct length as I ran them in this motor last summer for about an hour. Just the ground straps were broken on two plugs. One of the ground straps flew out the exhaust port and did not hurt anything the other ground strap just tore the hell out of number five... There are no marks on any of the pistons. They all look good except for number five. I need to find a good engine builder to send this powerhead off to to see what can be done with it. I am just getting too old to build these things anymore.

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They are probably made in you know where now, I quit doing this **** for customers 25 or more years ago, because of quality of parts, Now I can't buy parts and you can't hire anyone that has the talent anymore. Still some good ole boys on this site, And I do understand the getting too old part. ;)

Interesting note from NGK...

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Note also that if the spark plug is insufficiently tightened when fitted (i.e., the torque was less than the standard tightening torque), the plug may loosen. If it does loosen, it will be subject to abnormal vibration and this can cause the ground electrode to break off.

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why not just the clearance and stop guessing?

I am not very familiar with a 260 but I assume it is very similar to a standard 2.5. Flat top pistons and domed heads. A spark plug would have to be about 5/8" longer than standard to hit the piston. Spark plugs come nowhere close to the pistons in a 2.5

Attachment 543046Attachment 543047

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Originally Posted by Carter Powell

The plugs are the correct length as I ran them in this motor last summer for about an hour. Just the ground straps were broken on two plugs. One of the ground straps flew out the exhaust port and did not hurt anything the other ground strap just tore the hell out of number five... There are no marks on any of the pistons. They all look good except for number five. I need to find a good engine builder to send this powerhead off to to see what can be done with it. I am just getting too old to build these things anymore.

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Chris Carson will fix you up for a great price. I just shipped my FF block to him. He is putting an oversize sleeve in for slightly more than I can just buy the sleeve for. The FF block weighs 42lbs. 48lbs. packed. It cost me around $70 to ship the block from NY to FL. 305 852 2725

top pinned pistons? I'd look at that for sure! you'd think a lot more carnage for loose pin!