Sad day when the bike you picked up has stripped sparkplug holes(91 zephyr750)

14 x 1.25 is the insert EXTERNAL thread.
12 x 1.25 is the insert INTERNAL thread. 
The insert screws into the head and the plug screws into the insert. 

You will need to bore with a 12,8mm drill bit  before tapping with M14 x 1,25    Are you sure the tread pitch outside the M14 tap is 1,25mm ?
if the tap is M14 x 1,5 you will need to bore with 12,5mm drill first

So instead of a cheap rideable bike, you ended up with what could be considered an over priced project bike.  Assess what you have to start with, and if you decide to pursue it maybe it will turn into an interesting journey and education, doesn't have to be a full restoration, but possibly a decent rider.  Or you can sell some of the parts to recover some of the price.

Rolf1976_KZ900 wrote:

You will need to bore with a 12,8mm drill bit  before tapping with M14 x 1,25    Are you sure the tread pitch outside the M14 tap is 1,25mm ?
if the tap is M14 x 1,5 you will need to bore with 12,5mm drill first


Thats what the kit says. The seller also said that the tap only needs the threads to be aligned and do not have to drill out the holes.

 

sf4t7 wrote:

So instead of a cheap rideable bike, you ended up with what could be considered an over priced project bike.  Assess what you have to start with, and if you decide to pursue it maybe it will turn into an interesting journey and education, doesn't have to be a full restoration, but possibly a decent rider.  Or you can sell some of the parts to recover some of the price.

I bought it because I thought it could be a project that i could ride around while fixing it up... i dont want to do a resoration to make it look original. I was going to possibly make a cafe racer out of it, but we will see. Might just make it into some crazy looking rat bike since it already looks like it was headed that direction. Figured I can find a whatever style universal 5 gallon aftermarket gas tank, if I can find one that's long enough one of those hump style cafe racer seats with no cushioning and mounting kit. Throw some 1/4"-1/2" thick neoprene foam rubber (like the padding on a stand up jetski) as seat padding, and maybe a few other aesthetics such as handle bar grips, levers, pegs, etc. But nothing to crazy. I'd like to either rattle can it with paint, or plastidip, but possibly  paint it with rhino line. I don't know yet. Might just keep it how it looks, get it running properly, then just do regular maintenance and ride it till the engine dies. I've seen a couple engines that look to be in good shape with low miles for about $1k-$1.4k so I guess what I do with it will depend on what happens over time. 
 

I dont think you can just tap with the M14 with no drilling.You can try ,but there is a risk of cracking the thin area between the hole and valveseats.
I once forced a tap in a oil pan on a car and the result was it made a crack
The tap itself can also snap off.I would have drilled first and then used the tap with grease on it to catch most of the metal.Tap slowly just half turn in then back out one turn.It is not easy to drill straight so take your time.Good Luck

Robby2894 wrote:

Rolf1976_KZ900 wrote:

You will need to bore with a 12,8mm drill bit  before tapping with M14 x 1,25    Are you sure the tread pitch outside the M14 tap is 1,25mm ?
if the tap is M14 x 1,5 you will need to bore with 12,5mm drill first


Thats what the kit says. The seller also said that the tap only needs the threads to be aligned and do not have to drill out the holes.


 

Attachment not found

THIS IS HOW I GOT IN TROUBLE WITH A CHEAP TOOL WITH NO LEAD TAP. DON'T BUY IT OR YOU'LL BE SORRY
 

Robby,
Sounds like you're taking the right approach.  You don't have to spend a sh_t load of money, and you'll have something fun to ride.  My 2cents, you should be able to find another motor for less than 1K if you're patient, but I would look deeper into your motor to determine condition, maybe you can swap in a used head and some used parts to replace the trashed engine parts and keep with the low buck idea.
 

If you already have a 1/2" drill bit, that should do. 1/2" = 12.7mm.

Huge vac-u-lock dildo?

I would not buy any motorcycle repairing tools from there.

TexasKZ wrote:

Huge vac-u-lock dildo?


 

I was wondering when someone was going to comment about that, perhaps that's a previous search he did......

Moose1800 wrote:

TexasKZ wrote:

Huge vac-u-lock dildo?



 

I was wondering when someone was going to comment about that, perhaps that's a previous search he did......