GPZ 750 A2 (84) REPAIR SPARK PLUG THREAD

Hi, unfortunatly i have managed to cross thread an already poor spark plug thread . I have bought a reverse thread chasing tool to repair the offending thread on cylinder 3, but it will not go past the bottom of the thread as it appears there is a washer or something blocking its way. Will i have to remove the head to sort the thread, and if so can i reuse the gasket , as can't afford one at the moment.


Cheers

Benn

BENN5150 wrote: Hi, unfortunatly i have managed to cross thread an already poor spark plug thread . I have bought a reverse thread chasing tool to repair the offending thread on cylinder 3, but it will not go past the bottom of the thread as it appears there is a washer or something blocking its way. Will i have to remove the head to sort the thread, and if so can i reuse the gasket , as can't afford one at the moment.


Cheers

Benn

Hello,Benn, and WELCOME to KZr!

If using the correct size reverse tap, it starts the re-threading process at the bottom of the spark plug hole where the threads are hopefully still good.

The piston should be at the bottom of its stroke so the tool won't hit the top of the piston when the tool is inserted far enough into the spark plug hole to begin the re-threading.

Good Fortune!

Thanks for the reply . Yeah thats what I thought was possible. I shined a torch down the hole to see what was blocking the way for the tap, and it apears there is a piece of the head that protrudes over the bottom edge of the thread. Looks like a washer or something, silver in colour? will try and get a picture when the rain and wind stops.

Cheers

Benn

Sounds like a open valve so be real carefull.. If you pull the head plan on replacing all gaskets involved. Only copper head gaskets can be reused with proper cleaning and prep . IMO

yep, that would be a valve which you hopefully havent bent as that would be MUCH more expensive to repair than a head gasket.

any swarf or bits falling into the cylinder might score it, so before skimping on a head gasket, ask yourself if you have deep enough pockets to cover an even worse fate because you did.

Personally, would remove the head to do such work cleanly

If the gasket is not stuck heavily to the head, you might be able to reuse it, but if the head has not been off lately, it will most likely be heavily stuck.

now for some slashing...

I still work on a budget myself (just not as tight) and am not old enough to forget the days i was a poor student working on the sidewalk, been there, done that. And yet, on some things, cutting corners is wrong, might end up costing more.

opening the net or a book and reading about how an engine works so you know that that silver washer is an important part called a valve, is the least you can do (and free) if you have to ride a cheap old bike.

last, would help your cause if you introduced yourself nicely to the crowd and not just drop your question in here. just my 0.02$

TG

You can do this with the head on. When you get the piston and valves positioned out of the way. Pack your tap solid with grease do a few turns than remove it, clean it off, repack with grease and continue again. repeat until you have it rethreaded. All the filings should stick to the grease. I have been successful before using this method.

Got the thread sorted now. The reverse thread tool worked a treat