MS880 spark plug

[Forest2Furniture]

Whilst milling some oak yesterday my 880 blew the spark plug out, anyone got an idea what may have caused this to happen.

 

Looks like it's stripped the first row of threads in the block as well.

[spudulike]

Whilst milling some oak yesterday my 880 blew the spark plug out, anyone got an idea what may have caused this to happen.

 

Looks like it's stripped the first row of threads in the block as well.

 

Probably someone not tightening the thing up enough. It will have come undone, high temp exhaust will have blown past the last few threads hardening them and then...BANG, the compression blew the plug out when it was only held in by the last few threads.

 

Someone may have cross threaded it at some stage weakening the thread.

 

It is best to get someone who knows what they are up to, to ream out the hole, retap it and fit either an insert or Helicoil.

 

Personally I favour the insert as they are damn hard and can be bonded in so will be stronger than the original but some rate a stainless helicoil.

 

If you haven't done this before, don't be tempted by some of the shyte kits on ebay - they are shocking and you may end up scrapping the cylinder.

 

Vcoil do some of the better kits on the market!

 

A fair bit on doing one here - http://arbtalk.co.uk/forum/1061520-post6107.html

[Al Cormack]

Time sert is another spark plug thread repair. I've used them on my Triumph Stag.

[spudulike]

Time sert is another spark plug thread repair. I've used them on my Triumph Stag.

 

Yes, another good quality option. I have found the aluminium inserts fail when hot so use Sealey copper coated stainless ones and these screw in damn tight and will never come out.

 

I have also used helicoils in the smaller M12 plug holes and used the Vcoil tapered tap which worked well.

 

Just avoid these £8 ones with a cheap reamer/tap. All you will do with these is destroy a very expensive cylinder by opening up the hole and leaving a very poorly formed thread......been there:001_rolleyes:

[Forest2Furniture]

Thanks guys, that all sounds better then replacing the pot & piston.

So, if I get it stripped down is there anyone on here who would do it or point me in the right direction of which kit and where to get it from.

[spudulike]

Thanks guys, that all sounds better then replacing the pot & piston.

So, if I get it stripped down is there anyone on here who would do it or point me in the right direction of which kit and where to get it from.

 

PM me if you need it done, if it is stripped down, it won't be that much.

[peatff]

Try a plug tap first and see if the thread is still good enough to hold the plug, worth a try for £8.

[spudulike]

Try a plug tap first and see if the thread is still good enough to hold the plug, worth a try for £8.

 

Trouble is the reach of the plug isn't much - around 9mm so if any of the thread is damaged, there isn't much left to hold it - done a few of these now.

 

If you have a plug chaser tap then try it but don't get too close to the plug when you start it up:blushing:

[peatff]

Yes there's not much metal to go at in the head, it's worked for me a couple of times when they have been crossed on starting but a proper strip could have taken too much out.

[Brushcutter]

My 660 does this same thing. Spits the spark plug out milling or long cuts. Plug is always tight and its done it from new.