660 spark plug threads

[SiW]

Have managed to destroy the threads ind the cylinder on my 660. Is it a case of replacing cylinder or can I replace threads somehow? Cheers for any help

[Haironyourchest]

There's a product called Helicoil which repairs stripped threads, its an insert, you have to drill out the damage threads, re-thread and then insert the Helicoil. Supposedly works well

[SiW]

There's a product called Helicoil which repairs stripped threads, its an insert, you have to drill out the damage threads, re-thread and then insert the Helicoil. Supposedly works well

 

I've helicoiled stuff before but not a spark plug, as can imagine it has to be quite exact

[harrythecat178]

Best idea, take saw to a motor bike repair centre, they all seem to do helicoils

[spudulike]

It can be repaired using helicoils or an insert. The helicoil or insert has to go in dead square otherwise the plug won't seal correctly.

[Gary Prentice]

I've done a couple successfully, but the drilling and tapping has to be spot on.

[GardenKit]

I have used Helicoil spark plug repairs many time successfully. You actually don't need to drill and tap for Helicoil, as the kits contain a 'double tap'. The lower end is a std 14mm plug thread which follows the old thread and guides in the larger tap size to take the helicoil.

 

But I have also had an epic fail, when the original thread was so badly damaged that the 'double tap' did not guide itself in straight. In fact it did the opposite and guided nicely to an angle, and once started on the wrong track it was impossible to correct.

 

This one required drilling and tapping for an oversize steel insert.

 

See post 8136 on the 'whats on my bench' thread

 

http://arbtalk.co.uk/forum/chainsaws/33857-whats-your-bench-today-814.html

Edited August 8, 2016 by GardenKit

[Richard Thompson]

I've only done up to an m8 thread size in steel alu and mag-alloy all have worked and as far as I know all are still running/operational.

For a spark plug I'd go to a repair shop as stated above, due to the reason gardenkit said about a misaligned thread.

I have cross threaded a Briggs cylinder head and that was bad enough when refitting a spark plug

[Little Al]

There's a product called Helicoil which repairs stripped threads, its an insert, you have to drill out the damage threads, re-thread and then insert the Helicoil. Supposedly works well

 

It would be preferable to use a "Timesert" or one of the other (Solid ) inserts as the helicoils are similar to a tightly wound spring, whereas the others are a solid unit with a flange to enable a tightly seated insert with no chance of winding in or out on removing the plug after insertion