What are these plugs telling me?… and other questions!

[Oddjob]

Maybe number 3 wasn't fully wound in?

[Craizeehair]

Maybe number 3 wasn't fully wound in?

I’m sure it was, they all needed loosening to get them out, when I put the new ones in the original socket just wouldn’t get anywhere the spark plug, it was just too thick / wide to go into the cavity. Really strange, I even got a friend to check as I thought I was being really dumb?

In all honesty, I freaked out a bit and thought I must have done some damage somehow when removing it but the old Honda socket worked perfectly, I just don’t understand how I managed to use it to take it out?

I managed to get the phone and take a picture as I was convinced I’d done something wrong and buggered it!

[Craizeehair]

Double post

[McCabe-Thiele (Ted)]

I am paranoid about crossing a thread on alloy cylinder heads so to start them off I try to fit them in a few turns by hand.

When access is more difficult like on bikes I have a short bit of rubber tubing that fits easily on the plug insulation.
I am then able to dangle the plug into position and rotate the plug with the rubber tubing sounds a lot of fiddling but it works easily.
I then nip it up the last few threads with my plug spanner proper.

PS: Could it be that the new plugs have a slightly different height section to the previous ones so that the hex head is slightly raised from the boss even though the steel section is overall the same height?

[Trigger]

On a Cb750 it is very easy to cross thread the plus on number 2&3. I away have an old straight plug cap, pop the new plug in it and turn it in a couple of threads with the cap on before using a socket to tighten up 

[Pauarc]

Great tip with the old plug cap👏👍

[Spitfire]

Everytime I change the plugs on mine I am extra carefully of the two inner plugs, I tend to use the Ted method with some rubber tubing but an old straight plug cap sounds really good as well. Sods law also says that it will be one of those that soots up, though Denso plugs solved that one for me ages ago thanks to Hondaman over on the US site.

Cheers

Dennis

[Trigger]

Anything is better than dropping the plug in and putting a socket on  I had to make up some tooling years ago to tap number 2&3, as it was always the engine out to do a thread repair .

[Skoti]

Maybe number 3 wasn't fully wound in?

I’m sure it was, they all needed loosening to get them out, when I put the new ones in the original socket just wouldn’t get anywhere the spark plug, it was just too thick / wide to go into the cavity. Really strange, I even got a friend to check as I thought I was being really dumb?

In all honesty, I freaked out a bit and thought I must have done some damage somehow when removing it but the old Honda socket worked perfectly, I just don’t understand how I managed to use it to take it out?

I managed to get the phone and take a picture as I was convinced I’d done something wrong and buggered it!

Aye,

same here, I can take the all plugs out with a 3/8" drive plug socket, but need to use the Honda tool kit plug socket to put cylinder 2 and 3 plugs back in.
I've got a bit of 10mm hex bar attached loosely to the top of the Honda socket so I can use a 10mm spanner to nip the plugs up.

I also use the rubber pipe trick Ted mentions, I believe it's called a "plug runner" in the trade.

[Oddjob]

Pity the picture didn't show both plugs out as Number 3 looks to be a little worse for wear on the seat. If both were the same it would mean they were machined like that but if the other is pristine then maybe it wasn't tight and that corrosion is the result.

[McCabe-Thiele (Ted)]

IIRC most old workshop manuals advise to fit new washer if you remove a spark plug to ensure good seating & avoid overtightening when re-fitting.

Can't say I have ever seen replacement plug washers for sale - then again I have not really looked.

[Athame57]

I had a problem like this a couple of years ago, a thread problem in the spark plug hole. I took it to a mechanic early on and I really expected to be told that the engine would have to come out, but he said we can sometimes get away with it and he managed to repair it in situ with a quick tap. I now approach plug changes gingerly but no more trouble so far. But it begs the question when the engine finally comes out for rebuilding is it a good idea to get inserts put in if it can provide a more secure thread? This was common practice with CB250RS owners in the London dispatch industry, the bolts retaining the rocker box sunk straight into ally and stripped threads there were one of this bikes curses, I went pre-emptive on couple of my four RS250s. 

[Matt_Harrington]

Not to digress too much, what material is ideal for an insert if repairing a plug thread - also the type i.e. Helicoil or Timesert etc

[Oddjob]

Timesert are stronger.

[Matt_Harrington]

Thanks Ken. Brass, stainless or steel? ( a purely academic question....)