Loud pop/crack/bang from lifan 125

[Rizzo97]

I did it, but. It felt like it had no compression like there was no spark plug :/ I tightened it up more and now the tip of the spark plug is broken and inside the helicoil that's in the head going to pull head off and drill oils helicoil out and do it again :/ I think I didn't tapp/ put the heicoil in deep enough.. Why not? Because it's 1.5?

 

[Rizzo97]

Took the head off, exhaust valve is stuck open? And helicoil was sticking way out hittin the piston/ springing it backwards, think I will cut one of these helicoils shorter and try again.. But idk whats up with tis valve :/

 

[my67xr]

that would be why you didn't have compression then
sound's like you have bent the valve ?

 

[Rizzo97]

Dosnt look bent.. Just looks jammed up. Would it be visibly bent ? Or just slightly off causing it to jam or somthing?

 

[my67xr]

dunno,
like i've said before, this thread would be so much easier with pics ...

 

[zwebx]

Heads off?
Then look on the valve covers to see if the exhaust rocker is loose..
if it is then yes you have a bent valve. Could have got hung up on the helicoil.. need to see pics.

How you tell you have a bent valve... one it will not close (unless being held up by the cam) Two it will leak and three pull it out of the head and rotate it you will most likley see if its bent.
Correct method involves a v block and a dial indicator.. i doubt you have any of them around..

 

[Rizzo97]

Cheers, yea it is, after reading that I know it's bent :/ and nah I don't lol

 

[Rizzo97]

I just got the bent one out using a c clamp and 17mm socket, and the one i want to replace it with as well. Cut one of the helicoils to the right length and spark plug is in just need to put the non bent valve back In, can I just put it straight in ? Is there somthing crucial I am missing? I plan on putting it in basic,y same way I got it out, but tipping it up so the little half Clips fall back in place then releasing it?

 

[my67xr]

you can just put a rag under the head to fill the combustion chamber, then put a socket 10mm or bigger over the collets and tap on it with a hammer.
they just fall out then.

to reassemble it, use a pair of pointy nosed pliers or even a screwdriver.
slip them inside the head and lever down onto the retainer to compress the springs
then slip the collets in, lift the pliers and then you're done

 

[Rizzo97]

Nice can I use a intake valve off a 125 lifan head for the exhaust one as well? So they are the same ?

 

[my67xr]

the inlets are bigger than the exhaust valves.
some have a different size stem too, just compare them before you go trying to swap them

 

[Rizzo97]

I have a good exhuast one, just wondering if I could use a inlet one because it is bigger, just thought it would makeit go better

 

[Rizzo97]

Like is it possible or will it not work because of somthing

 

[my67xr]

the inlet won't fit in the exhaust seat in the head, they are roughly 4 mm bigger on a 125

 

[zwebx]

Like is it possible or will it not work because of somthing

It is possible, but requires a larger valve seat.. and then you may aswell install a larger intake valve while the machinist has it.
Simple terms nope.. not worth it.

I always found a sparkplug socket with a rag over the top of the valve spring retainer with the collets in (ensuring the rag is doubled over and over the head) And a solid tap with a heavy hammer does the trick for me... to get the valve collets installed. Ensure the valve is supported and dont drive the tip of the valve or you will bend it.
It takes a couple of trial and errors to do it but no biggy.. some can do it with grease on the valve to keep the collets from falling off.. My method works the best for me..

 

[Rizzo97]

Couldi do the rag thing but press it instead of using a hammer? C clamps a bit sort so a sp socket won't work, I've been using smaller ones t get them out.

 

[Rizzo97]

Dose the rag let them go up a little then they lockin ? But without making them fall out

 

[Rizzo97]

All done just need one gasket to fini**** all off and start it up, anything I could use to make one that is good enough for the engine head? It's the rectangular like one right at the front where the four nuts are between valve covers, could I use black silicone? Or carnbourd? Off a Cearal box? Or Willie be too hot for it

 

[my67xr]

the cereal box cardboard gasket will work for a while

 

[Rizzo97]

I used the. Back of a phonebook, yea just wana start it up and se how it gose with the other valve and helicoil Iv noticed the cam chain gose really slack 360 from TDC ? Is that normal and can't tighten it if it isn't?