555 stripped thread.

[spudulike]

On 06/07/2023 at 16:11, openspaceman said:

Yes it does depend on how badly it has stripped.

 

If you can still wind a plug loosely in then it's a cinch to use the stepped tap tool, not familiar with 555 but done a few Stihl and Huskies and a car or two.

 

 If the hole is badly misshapen and you need to drill and then tap conventionally you need a steady hand.

 

It is possible to do it with the cylinder in situ if you bring the piston up past the top of the exhaust port and fill the cylinder with grease.

 

The helicoil has to be exactly the length of the thread or a fraction less as it must not extend into the cylinder or have any thread left out above.

 

When done you break off the driving tang and then expel the grease, tang and swarf.

This every day of the week. I stick to Volkel taps and use the tapered type as in the pic if the receiving thread is still marginally there.

Make sure it goes in dead square and DO NOT buy a cheap kit off Amazon or eBay.....the cheap taps are exactly that, cheap and will destroy your cylinder.

[openspaceman]

7 hours ago, Aled Hughes said:

I take it the heli is left hand thread to insert so as not to push it in further when inserting spark plug? Suppose loctite on the heli wouldn't be a bad idea?

They are a spring made with steel of a diamond cross section. In their at rest state they are a larger diameter than the hole that has been tapped to take them, if you have the correct insertion tool it fits through the helicoil and engages with a tang of the spring that has been formed across the diameter of the thread nearest the piston.

 

 

 

In the picture the tang which you drive it by is at the top, this end goes in the hole first.As you rotate this the normal way to screw it into the hole the torque  winds the spring and shrinks its diameter. Once the helicoil is level with the bottom of the thread you snap the tang off (there is a preformed notch in it to facilitate this). At this stage there must be no part of the helicoil proud of the flange the spark plug seals on. This is why you have been told to check the length.

 

Once the tang has broken off the spring is expanded against the thread and will bind on the thread to resist removal.

 

The helicoil must not have any part of it poking out of either end of the thread as snagging a loose end will pull the helicoil out like a loose wire.

[Aled Hughes]

9 minutes ago, openspaceman said:

They are a spring made with steel of a diamond cross section. In their at rest state they are a larger diameter than the hole that has been tapped to take them, if you have the correct insertion tool it fits through the helicoil and engages with a tang of the spring that has been formed across the diameter of the thread nearest the piston.

 

 

 

In the picture the tang which you drive it by is at the top, this end goes in the hole first.As you rotate this the normal way to screw it into the hole the torque  winds the spring and shrinks its diameter. Once the helicoil is level with the bottom of the thread you snap the tang off (there is a preformed notch in it to facilitate this). At this stage there must be no part of the helicoil proud of the flange the spark plug seals on. This is why you have been told to check the length.

 

Once the tang has broken off the spring is expanded against the thread and will bind on the thread to resist removal.

 

The helicoil must not have any part of it poking out of either end of the thread as snagging a loose end will pull the helicoil out like a loose wire.

Thank you so much for the very detailed explanation, that has given me a clearer picture of what's ahead of me.

[Aled Hughes]

4 hours ago, Dan Maynard said:

Go down to stores and get some left hand thread spark plugs, young lad.....

I'll get a bubble for a spirit level at the same time shall i?

[Stubby]

7 hours ago, Aled Hughes said:

I'll get a bubble for a spirit level at the same time shall i?

A long weight and a box of 2BA holes whilst you are there . Oh and some sky hooks please .

Edited July 8, 2023 by Stubby

[Dan Maynard]

2 hours ago, Stubby said:

A long weight and a box of 2BA holes whilst you are there . Oh and some sky hooks please .

That's it, and a box of sparks to help it start once you've got it all back together.

[Aled Hughes]

Helicoiling parts arrived from Germany, tapped, helicoiled, rebuilt snd now a running saw. Very happy chap thanks to the members input.

[adw]

Well done sir, the 10mm spark plug helicoil is not easy to get fitted correctly.

[Aled Hughes]

49 minutes ago, adw said:

Well done sir, the 10mm spark plug helicoil is not easy to get fitted correctly.

As i said to spud, 1st attempt went haywire as it skipped threads due to too much pressure but second attempt with no pressure went in a treat. 

[spudulike]

Glad it went well and everyone's experience helped.