Spark plug thread repair

[Mx5190]

So a friend gave me a lifan 125 for free he said it wouldn't shift and spark hole is stripped so I got it to shift again but when I tried to start it the plug shot out like a rocket I had retapped it but no luck

My question is what the best way to fix this I cant find sav a thread in the right size only 14 even online

[PlanetMinis.com]

[stunt-ur]

just replace the head.

[silvjorr]

You can drill the hole bigger and then thread it and put a copper bushing in it where You screw the spark plug. Hope You understand what i mean.

[halohaulic]

You can drill the hole bigger and then thread it and put a copper bushing in it where You screw the spark plug. Hope You understand what i mean.

Thats called a helicoil.

[Brodie]

Helicoils have an end on them which would block the spark plug anode from going in. What Silvjorr means is a copper tube with thread on the inside and out. That way you can thread the spark plug in and then with the copper tube around it thread it into the rethreaded head. As copper heats up quicker and expands more than steel it will create a seal to hold the pressure.

[Mx5190]

Great thanks for the help That's why I didn't use helicoil but I like the copper bushing Idea I'll try it out thanks

[Markopolo400]

Take the head off the engine and fix it with a helicoil or Timesert.

[silvjorr]

Helicoils have an end on them which would block the spark plug anode from going in. What Silvjorr means is a copper tube with thread on the inside and out. That way you can thread the spark plug in and then with the copper tube around it thread it into the rethreaded head. As copper heats up quicker and expands more than steel it will create a seal to hold the pressure.

Thanks! Thats excactly what i wanted to say, but my English is not so great that i can allways express myself correctly

[Charper732]

Its called a timesert and its not copper, its steel. its a Bushing that is installed to the hole once you drill it out to the correct size. Timsert bushing come in quite a few different lengths so make sure you measure the correct length you need because they cannot be cut down to size. That is hands down the best solution to your problem. A timesert kit will cost you ~$80 depending on who you get it from. Once you install a timesert you will never have an issue with those threads again.

Helicoils have an end on them which would block the spark plug anode from going in. What Silvjorr means is a copper tube with thread on the inside and out. That way you can thread the spark plug in and then with the copper tube around it thread it into the rethreaded head. As copper heats up quicker and expands more than steel it will create a seal to hold the pressure.

[Branyers]

^ Agree. Prefer timeserts over helicoils, although there is much debate over which is more reliable. The timesert kits certainly seem to be higher quality but you'll pay $30-$40 more for it.

[JanssonK]

Helicoils have an end on them which would block the spark plug anode from going in. What Silvjorr means is a copper tube with thread on the inside and out. That way you can thread the spark plug in and then with the copper tube around it thread it into the rethreaded head. As copper heats up quicker and expands more than steel it will create a seal to hold the pressure.

When you got the heliicoil in the head you knock the "stop" off. Its only used to screw the helicoil in.,

[ndubstuntz420]

if you have no interest in keep that head for a long time slap some jb weld on the plug and screw her in lol( seen it done to fix a chinese head with same problem kept the plug in it for a year and just replaced the motor after the bottom end grenaded lol)

[dirtbkr188]

If the standard plug thread size is 10 x 1.0 (CR7HSA), drill it out and retap to a 12 x 1.0 (D8HA).

[ayeyo]

If the standard plug thread size is 10 x 1.0 (CR7HSA), drill it out and retap to a 12 x 1.0 (D8HA).

This will defenitly work?

[taz69]

Yea I have used helicoils in all my heads and just knock the end off for the plug to thread in. I helicoil them from the start. Nothing like beeing at the track or the night before you go change a plug and strip the head.. Got them in my +R head and my V2 head.

[dirtbkr188]

This will defenitly work?

Yes, the D8HA (or DR8HS) both have the same 1/2" reach as the CR7HSA, they both are 12mm threads

[LongMooie]

i would retap as dirtbkr188 says cos i wouldnt be spending the kind of money for the helicoil or timesert on a chinese pos