1976 Z900 A4 Plug Thread

[Sparky63]

Hi Guys

I have a damaged spark plug thread on my Z900 A4, I wanted to run a tap through it and clean it up and wondered if anyone knew the thread size for the z900 A4?

Thanks

[Sparky63]

OK looks like M14 1.25

[warren3200gt]

This is what you want. Cleans the shit out as you unscrew it. [qu

Screenshot_20241120_161145_Samsung Internet.jpg (68.08 KiB) Viewed 2314 times

[Sparky63]

Thanks Warren, was about to buy one then realised that there was a helicoil in the plug hole that had partially removed itself as the plug was unscrewed.

[warren3200gt]

Get rid of the helicoil and put a time sert in. Do it properly, do it once.

[Hard Road]

Yep time sert is the way to go.

[Sparky63]

Thanks for your help and advice.

[sprint]

I thought with timeserts that you have to counterbore the top surface so that the lip is below the head surface face or you will be tightening up the spark plug against the lip which can result in you unscrewing it? Unless you are planning to remove the head to fit the timesert?

[Hard Road]

I thought with timeserts that you have to counterbore the top surface so that the lip is below the head surface face or you will be tightening up the spark plug against the lip which can result in you unscrewing it? Unless you are planning to remove the head to fit the timesert?

I thought the head was already off but yeah their is a recess at the top, and it flares out at the bottom to hold it in place.

[zed1015]

I thought with timeserts that you have to counterbore the top surface so that the lip is below the head surface face or you will be tightening up the spark plug against the lip which can result in you unscrewing it? Unless you are planning to remove the head to fit the timesert?

Timeserts can be fitted with the head in situ and the counterbore is cut with the tap in place as its shank acts as the counterbore cutters guide and prevents further swarf entering the cylinder.
Also additionally to the flaring / locking action of the insertion tool on the bottom threads it is also recommended that high strength thread lock such as Loctite 6020 be used on the inserts outer threads and is included in many of Wurths timesert kits.

[Hard Road]

I thought with timeserts that you have to counterbore the top surface so that the lip is below the head surface face or you will be tightening up the spark plug against the lip which can result in you unscrewing it? Unless you are planning to remove the head to fit the timesert?

Timeserts can be fitted with the head in situ and the counterbore is cut with the tap in place as its shank acts as the counterbore cutters guide and prevents further swarf entering the cylinder.
Also additionally to the flaring / locking action of the insertion tool on the bottom threads it is also recommended that high strength thread lock such as Loctite 6020 be used on the inserts outer threads and is included in many of Wurths timesert kits.

yeah ive done quite a few in the past, but never liked doing a head in situ just can't handle the thought of any bit of swarf that gets past by accident.

[warren3200gt]

Only problem is with doing in place on this occasion though guys is that the op says it's got a helicoil in it at the mo so the thread dia/pitch In the head is to the OD of the helicoil not 14 x 1.25 any longer.
It might prove a little trickier and would be easier with the head off.

[zed1015]

Only problem is with doing in place on this occasion though guys is that the op says it's got a helicoil in it at the mo so the thread dia/pitch In the head is to the OD of the helicoil not 14 x 1.25 any longer.
It might prove a little trickier and would be easier with the head off.

The thread of a helicoil is the same pitch of a Timesert so if the threads cut for a helicoil are damaged the timesert tap just needs running through to clean it up and you are good to go for fitting a Timesert .

[warren3200gt]

But the guide for the time sert cutter which is 14 x 1.25 would flop about in the OD thread for the helicoil wouldn't it?

[Hard Road]

But the guide for the time sert cutter which is 14 x 1.25 would flop about in the OD thread for the helicoil wouldn't it?

ive replaced failed helicoils with timeserts no problem, with a bit of Loctite and the bottom threads that spread out they should be fine.