small rupture in head

[arnaud]

Today i took of the cylinder head because the inlet valve is leaky; the engine misses power and when you press the kickstart lever against compression, the pressure deminishes slowly while a low hissing sound escapes from the air filter housing.
Overall not a major malfunction and at most 2 hours work, but i see also this head(it is the second) has a small rupture between the hole of the injector and a valve seat.
I did never tighten the injector nozzle with much force, but had to retighten it a few times (despite proper use of loctite) because it had no compression any more. many times afer more then a week not running(after work abroad or so)
Oh yes, it is a 418cc chinese diesel engine, 66000km. (so after all, money well spend!)
I'm not sure what to do.. replace it again?
i will make use of my jawa motorcycle this coming period, while contemplating the options..

[andrewaust]

With that many K's I'd seriously think about replacing it. But only my view.

The price of parts to fix and probably rebuild it would cost more then replacing it, at 66K parts are going to be worn and if not needing replacing, soon will be.

A

[arnaud]

I'm not sure bout the injector but otherwise i think it is fine, i took it apart during a long slippery winter when about ran 44.000km's and replaced big end shells and piston rings, the latter was not nessecary, but the engine was apart anyway.
the internals were very good, no sign of wear in the cylinder.

[nanno]

Hi Arnaud,

I would replace the head and then see how long this will work out.

[arnaud]

Hi nanbo, this is already the second head with rupture...

[andrewaust]

Hi nanbo, this is already the second head with rupture...

Arnaud, you cannot have it both ways, either you replace the engine and hope it goes fine without cracking the head, which seems uncommon besides your case !! But I could be wrong. Or you just go out and purchase a new head "maybe complete with valves and injector etc" and run your old bottom end.

Mate I just don't know what or how to advise you what to do ?????? It seems you have got a heap of K's from that engine so why not retire it for parts and purchase a new engine with warranty, even if you go down to the 406cc engine which seems to have a good rating, not that it seems much is wrong with the 418cc engine, I think someone somewhere said about a crank failure, but that might be on another type of engine, been to long ago.

My reply might seem a little harsh, but it's a posted thread that tends to leave people scratching their heads wondering what you are wanting to do.


A

[alexanderfoti]

Agreed with Andrew.

66k on a petrol small capacity bike engine is high! Especially a clone, I would defo retire that, maybe make the piston into a trophy

[arnaud]

@ andrew, is 20K per head so much?
rupturing cylinder heads is a strange and uncommon problem.
the whole engine is well-maintained and capable of another 60 k's, but the head..only 1 part of the bike...

[andrewaust]

@ andrew, is 20K per head so much?
No but aren't you asking if you should buy a head or complete engine, I've given you my oppinion!

rupturing cylinder heads is a strange and uncommon problem.
Yes I have not heard of it and don't have a clue why your having that problem

the whole engine is well-maintained and capable of another 60 k's, but the head..only 1 part of the bike...
Go with your gut feeling, put another head on it then!

[arnaud]

Hi andrew, indeed i thik i will put another head on it again, ride it and in the meanwhile look for other options..