Spark plug stripped threads in alloy cylinder head

[RichardS]

Single cylinder 420cc Honda clone

Ah ..... I can now understand why the problem arose in the first place.

Richard

 

[skyflyer]

Ah ..... I can now understand why the problem arose in the first place.

Richard

To be fair Richard I’ve had dozens of cheap engines on chainsaws, strimmers, lawnmowers etc. Never had this problem Even the “famous name” ones are probably just badged and from the same factory in China
This one is Hyundai. No idea if they manufacture them themselves or sub contract but it looks just like a Honda
I had the plug out once before without problem but this time it was on a day when it was tipping down and I was cold and wet. It then went in my coat pocket whilst I worked on the machine (changing blades) Possibly I was less diligent than I could have been ensuring the threads were clean when it went back in?
But I think it’s a bit unfair to blame the manufacturer! Hence my reluctance regarding warranty claim!

 

[vyv_cox]

Unfortunately threadlock is destroyed by heat and will not lock an insert in place. Some mechanical method is needed, as I said in my earlier post.

 

[skyflyer]

Unfortunately threadlock is destroyed by heat and will not lock an insert in place. Some mechanical method is needed, as I said in my earlier post.

Yes but you didn’t say how
Ironic how stuff seized when want it to loosen and comes loose when you want it to stay put!

 

[Tamar]

£35? What kind of engine are we talking about?

Richard

I think I would have bought a new head and be done with it.

 

[RichardS]

I think I would have bought a new head and be done with it.

At that price it's something of a no-brainer, even for a bodge-merchant like me.

However, I'm surprised that it's that price as it's a Hyundai rather than a cheap no-name Chinese as I suspected. Hyundai are generally a reasonable quality brand.

Richard

 

[DownWest]

At that price it's something of a no-brainer, even for a bodge-merchant like me.

However, I'm surprised that it's that price as it's a Hyundai rather than a cheap no-name Chinese as I suspected. Hyundai are generally a reasonable quality brand.

Richard

I have a B&Q supplied Hyundai strimmer, actually very good. But I have seen exactly the same with two other names on them.

 

[Paulg25]

Even the more expensive brands like Stihl are now made in China.

 

[skyflyer]

I think I would have bought a new head and be done with it.

Financially yes. Time wise no. I need this beast working today. Hyundai have confirmed price at £26 plus vat so new head will be longer term solution yes

 

[Beneteau381]

Not strictly boaty, but easily could be and I value the advice of other forumites.
I started to remove the spark plug from a (4 stroke) engine today and initially all was normal. Then it started to bind. I couldnt really work out what was happening as it couldnt be a crossed thread (having gone in by hand easily a few weeks ago). I tried to screw it back in and then out again but nothing helped. Eventually I could see no option but to use more force.
So out it came - the last three threads of the plug (i.e. the part deepest into the cylinder) are clogged with alloy - so badly that I cannot clean it out of the threads.
The equivalent part of the cylinder head threads are stripped. i.e the three or four threads nearest the top of the hole.
Thread spalling seems to be the issue and I know this has long been an issue for sailors with stainless screws in aluminium and alloy boat parts.
Anyway, we are where we are - when i repair it I will use some form of anti seize compound. I will make a reapir with a helicoil type kit, reaming out the hole, cutting a new thread and putting in an insert.
My question is this. Having researched the use of these thread inserts some people say dont worry about the small alloy chips going into the cylinder as they will be blown out or melt as soon as the engine is started. I'm not entirely convinced.
I will try to stop as much swarf as I can by greasing the tapping tool but some is bound to get in.
I dont think blowing out the cylinder with air is any guarantee either.
The 'perfect' answer is to take off the head, but its a brand new engine just a month old, so I am reluctant to do that with all the dismantling that will be required.
Has anyone done this sort of job before, and if so how did you deal with the swarf issue?
Thanks

In the olden days, Triumph main dealer plenty of grease on the tap to collect the swarf was all that we did!