Spark plug cross threaded

[Greg65]

Very frustrating as I have just got the bike to MOT status, however had a starting problem so have taken the plugs out. Now I was aware that No. 4 was tricky to replace as the initial damage had been done by a previous owner. Now I can't get the plug back in and more than a half to one turn, so it looks like I've lost the original thread. Are there any suggestions or is it going to be a head off and an insert fix. Suggestions from the wise please.

Thanks
Greg

[haynes66]

head off, i'm afraid. any swarf could end up inside and cause more damage. better safe than sorry.

[Saisei]

I have known folk to successfully repair tthreads with the head on. Make sure the piston is at TDC on the compression  stroke. Fill the void with carb cleaner before  chasing the thread with one of these. Finally blow out the fluid and any swarf with compressed air, repeat  the cleaning process as many times as necessary.
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[Greg65]

Thanks for the replays so far. Just spent a frustrating 30 mins trying to find the original thread start by turning the spark plug backwards and noting the drop and then carefully exploring each "lead". All to no avail. I think the thread chaser may be a lost cause but will give it a go as it may avoid a lot of work, however I think an insert may be the solution. Any recommended suppliers?

Greg

[mike the bike]

Try this;
Take the head off and wind a plug in from the wrong side.  It may realign the threads to allow a plug to go in normally.

[Bryanj]

I have many times helicoiled in situ, there is a small risk but nothing serious.

Fill the supplied drill flutes with greas and drill very slowly

Fill the tap flutes with grease and tap slowly removing frequently and cleaning re-greasing

sray carb cleaner or WD in the hole and start the engine ewithout that plug in so all the sh!t gets blown out

Fit insert and plug

Done loads and only had 1 where a small bit of alloy swarf got stuck to a valve seat--no damage and OK had to take head off but that was the alternative anyway

[Greg65]

Thanks for the encouragement. Job takes me abroad for a few days so will try and order a kit ready for a spot of engineering next weekend.

Cheers
Greg

[Greg65]

Hi, just a follow up. Finally got some time in the shed after deciding on a back tap which I got from "motorcycle products". Not a high quality too but a£30 I thought it was worth a go. I successfully managed to back tap and clear the threads. Hopefully it will last or it will be re thread time. The only complaint I had about  the tool was that the tap did not reduce in diameter sufficiently to insert without scraping the threads when inserted. This was a function of design and a comment was forwarded to the supplier.

Thanks for all the advice,

Greg

[Saisei]

Just watched a Youtube video on the Backtap tool. What a great idea. One question. Who are "Motocycle Products?"

[royhall]

M&P. Cheers Roy

Sent from my GT-I9305 using Tapatalk

[Spitfire]

Just watched the video, what a great idea, one for the memory bank.

Cheers

Dennis

[Greg65]

From these guys

http://www.motorcycleproducts.co.uk

It's great to be able to offer something back to you all.

The feed back I gave to them was that it needs something elastic to pull the tap diameter in whilst inserting. I tried an O ring I had but it was to big though it might have interfered.

Cheers,
Greg