Honda BF50 Stripped Spark Plug

ATPNW · Posted: Tue Apr 26, 2022 1:53 pm Post subject: Honda BF50 Stripped Spark Plug

Well it looks like whoever changed or checked my spark plugs last jammed one back in and stripped the threads. This is the first time since I've owned the boat I've had to check them. Has anyone attempted to fix this before? I see there are a few tools I might be able to use such as a helicoil or re-thread kits. From some videos I've watched it looks moderately easy. Any advice you can shed or direction if this is more of a professional shop job?

srbaum · Posted: Tue Apr 26, 2022 2:05 pm Post subject:

ATPNW,
Using a helicoil, or like product is relatively easy. I have repaired spark plug threads in many outboards, with very good results. My toolbox has about a dozen sizes, both metric and standard.
Now, the key to success is to follow the instructions to the letter and most importantly, all metal filings MUST be removed and not left in the cylinder. Removal of the filings it tricky, as they are aluminum and a magnetic tool will not remove them. I have had a few jobs, that I had to remove the cylinder head, to ensure that the filings did not remain behind...

ATPNW · Posted: Tue Apr 26, 2022 6:15 pm Post subject:

Thanks for confirming my thoughts that its relatively easy, ill be sure to watch out for those shavings/burrs. Any suggestions on a kit? I see helicoil and time sert (time sert claims to hold up better). My plugs are NGK DR7EA, threads are 12mm and reach is 19mm/.75inch.

T.R. Bauer · Posted: Tue Apr 26, 2022 11:24 pm Post subject:

I suspect it will be fine for a very long time after you repair the threads.

Knipet · Posted: Tue Apr 26, 2022 11:39 pm Post subject:

ATPNW · Posted: Wed Apr 27, 2022 11:56 am Post subject:

Safetythird · Posted: Wed Apr 27, 2022 3:48 pm Post subject:

ATPNW · Posted: Mon May 02, 2022 8:24 pm Post subject:

Well unfortunately the time-sert went in a little misaligned. The sert doesnt sit completely flush on the head by what looks like a thread or two. This causes the spark plug to be positioned off just enough that i cant get a thin wall 18mm socket over it. Contemplating my options here:

1.Remove time sert, and try to thread a new one in. This option seems low risk and also low reward. If my thread was off by one at the initial screwin, it would have given me troubles early on in the setting of the sert i would think.

2.Remove time sert. Take the step bit and try and tap new threads. My concern here is the step bit is the same diameter as the hole now and im only off by a little, so my margin of error is small.

3.Take it to a shop and see if they have any ideas how to fix it. Although my guess is that would entail a new head and a long wait.

srbaum · Posted: Mon May 02, 2022 10:12 pm Post subject:

A misaligned insert, will require a new head.

T.R. Bauer · Posted: Tue May 03, 2022 9:25 am Post subject:

This doesn't sound good. Dang! I hope you don't have to get a new head.

ATPNW · Posted: Tue May 03, 2022 11:20 am Post subject:

All may not be lost after all. I removed the little rubber boot inside the thin wall spark plug socket and was able to get a firm grip on the hex (I know this has risks). I can’t be certain but I didn’t hear/feel the porcelain touch the socket. Either way I plan to reinsert the boot once the plug frees up to be safe. Will hopefully fire her up later this afternoon when the time is more appropriate and then call it good.

thataway · Posted: Tue May 03, 2022 1:29 pm Post subject:

With the misaligned insert, will the spark plug seat properly?

ATPNW · Posted: Tue May 03, 2022 1:43 pm Post subject:

T.R. Bauer · Posted: Tue May 03, 2022 10:51 pm Post subject:

I suspect it's done and sounds like it worked out.

ATPNW · Posted: Tue May 03, 2022 10:55 pm Post subject:

Yep all seems to be well after firing it up and running it for a bit. Thanks all for the help and suggestions!