stripped plug...possible fix

A friend has a 81 KZ750 and it has a stripped spark plug hole. He was thinking of using a heli-coil or timesert to fix it...

BUT..what if you just drilled the hole out to the next bigger size plug hole? Example: 14mm to 18mm.

Then you'd have no worry about threads coming loose or having to 'glue' in an insert.

Seems much simpler....what do you think?

Bob

Yah, you could do that I suppose.

If the head is still on the bike though, you're going to need to figure out how to get all of the metal shavings out of the cylinder afterwards.

Plus, you're going to need to find a spark plug in that new diameter with the same reach and heat range as the old plug.

Installing a timesert or helicoil would take a lot of the stress and work out of it IMHO.

Post edited by: steell, at: 2006/10/02 19:55

Well, in this world of high performance cars and bikes, finding a suitable plug should be a piece of cake.

You're only dealing with 8:5 to 1 compression and regular pump gas. Any plug will light that!!!

Bob

is there room to go that much bigger? should you worry about getting into the valve seats?

The coil kit is cheap and works. My rule is to never remove more metal than necessary. Also you're gonna have a hard time making a nice hole for the 18mm plug with the head installed. Use a collar on your drill bit! Use one size under drill and then finish with the drill for the kit. Also, fill the cylinder with grease with it about halfway up on the compression stroke before you start making chips. This way you'll get all the chips out.

-Duck

I agree Duck, min meat removed is the best way with the head on. With the heli coil you may not have to drill, just tap vary carefully with loads of grease on it to trap the shavings then clean and go again.

if its a slightly cross thread thread, then a clean up with the original tap could do it. Same thing, use the grease

heli coils don'd need glue, they just screw into the special tapped thread and are way stonger then the original
cheers

use the insert it is the best fix.
I dont think you would be able to get the right reach/heat range plug in a larger size ie: 18mm.

Duck wrote:

Also, fill the cylinder with grease with it about halfway up on the compression stroke before you start making chips. This way you'll get all the chips out.
-Duck

How do you get all the grease out?

OKC_Kent wrote:

Duck wrote:

Also, fill the cylinder with grease with it about halfway up on the compression stroke before you start making chips. This way you'll get all the chips out.
-Duck

How do you get all the grease out?

Same way you got it in:-)
Turn slowly to TDC and the grease will come out the plug hole
along with the chips. Now if you decided to use your leftover
1950's wheel bearing grease, it might be kind of tough to get
out but some modern light weight "general porpoise" grease will
work just fine.

Duck wrote:

OKC_Kent wrote:

Duck wrote:

Also, fill the cylinder with grease with it about halfway up on the compression stroke before you start making chips. This way you'll get all the chips out.
-Duck

How do you get all the grease out?

Same way you got it in:-)
Turn slowly to TDC and the grease will come out the plug hole
along with the chips. Now if you decided to use your leftover
1950's wheel bearing grease, it might be kind of tough to get
out but some modern light weight "general porpoise" grease will
work just fine.

Mmm, but not the last few tablespoons that fill up in the squish area. I can see all the chips coming out tho.

Go with the heli-coil. It will work just fine. Load the tap with lots of grease, clean and re-grease often as your cutting the new threads and there is no need to remove the head. I done my head about 8 years ago and have never have a problem since.

tw

OKC_Kent wrote:

Duck wrote:

OKC_Kent wrote:

Duck wrote:

Also, fill the cylinder with grease with it about halfway up on the compression stroke before you start making chips. This way you'll get all the chips out.
-Duck

How do you get all the grease out?

Same way you got it in:-)
Turn slowly to TDC and the grease will come out the plug hole
along with the chips. Now if you decided to use your leftover
1950's wheel bearing grease, it might be kind of tough to get
out but some modern light weight "general porpoise" grease will
work just fine.

Mmm, but not the last few tablespoons that fill up in the squish area. I can see all the chips coming out tho.

I just rinse with a little kerosene or MMO and turn her over a few more times.
I suspect it's overkill. I can't see Aluminum chips doing much damage anyway.