DJ2.1 Rebuild

[Stesaw]

Running lean perhaps? that's just my guess

[maxstu]

Dunno?

Im am running on E10 with timing set at 5 degrees. Perhaps l should revert back to 'full power' mode?

Matching cylinder head.

[Smiffo]

Is that blemish, or pitting on the piston going to be an issue, Stuart?

What 'damage' constitutes too much damage and thus replacement parts being needed?

[maxstu]

Is that blemish, or pitting on the piston going to be an issue, Stuart?

What 'damage' constitutes too much damage and thus replacement parts being needed?

To my poor old eyes l would call it pitting. Or erosion. Not sure, Steve. Waiting for one of the big boys to comment.

[Smiffo]

I feel your pain mate.

This is my 'concern' ( for lack of a better word. )
I could dismantle an engine, and rebuild it given the time, and instructions to follow with some complimentary guidance, but what I know I would struggle with is what to 'look out for' when checking components.

i.e. I remove something. I know I need to check it, but not exactly what I am checking for. I suspect it is something that comes with experience, but you have to do it to get experience 

Sometimes it is what you don't know that you don't know that trips you up in life. Others, as with this, it would be what I know I don't know that gets me.

Hopefully AJ can spread some wisdom for you.

[maxstu]

A few years' back this forum had three or four competent contributors replying and guiding novice engine rebuilders. Itchyfeet, mm289 (?) or Silverbullet for instance.

Now it seems it's on AJ's broad and knowledgeable shoulders to take time to advise us numpty engine rebuilders.

Shame really. I know Itchy is still here now and then. And three years ago he would be giving full support to anyone giving it a go.

Times are a changing.

[Smiffo]

Yes, it must be a thankless task though, so understandable.
After all, how much time does one commit to helping, only for the original poster to go quiet and you never see the end?

Once you are through this build, you are going to be the go-to man!! 

[maxstu]

Ha! Most kind of you.
Any mechanical advice l give will come with a 5 page disclaimer and backed up by my lawyer.
l trained as chef when l left school and have had multiple jobs since retiring (read redundant). Most l care to forget about.

[maxstu]

A few years' back this forum had three or four competent contributors replying and guiding novice engine rebuilders. Itchyfeet, mm289 (?) or Silverbullet for instance.

Now it seems it's on AJ's broad and knowledgeable shoulders to take time to advise us numpty engine rebuilders.

Shame really. I know Itchy is still here now and then. And three years ago he would be giving full support to anyone giving it a go.

Times are a changing.

And, of course Stesaw....

[tobydog]

Piston no 4 not looking too healthy. What has caused this pitting on the crown and side wall? If piston is put back in sleeve the damage sits between 5 and 7 on a clock face. No damage in sleeve though.




Regards
Stuart

Head seal gone on that cylinder? If it were timing/mixture related then other pistons would be affected?

Mind you I don't know much about waterleakers
 

[maxstu]

Piston no 4 not looking too healthy. What has caused this pitting on the crown and side wall? If piston is put back in sleeve the damage sits between 5 and 7 on a clock face. No damage in sleeve though.




Regards
Stuart

Head seal gone on that cylinder? If it were timing/mixture related then other pistons would be affected?

Mind you I don't know much about waterleakers
 

A valid observation. No compression/fire ring failure, though. Unless previous to my ownership.

The engine has had a rebuild at some point. One piston is not a Mahle. Will take a reccy at the other three.

[Smiffo]

Is that damage enough to warrant replacing the piston, Toby?

Assuming the cause is found and mitigated, is the piston a bin job?

[ajsimmo]

It's very common to see that kind of pitting on the piston top, particularly on DJs. It could be poor fuel atomisation from a dodgy injector causing washing or hotspots. Or an air leak on that one cylinder causing localised lean burn?
Obviously replacement is the best option, but then you'll need a matched set (and they're a tad pricey). I'd say the piston is ok to reuse as long as the sides are undamaged, and there's no distortion, impact damage, cracks etc. I'd probably clean it up with a bit of wet n dry just to make it a bit prettier, but it should be serviceable.

Sent from my moto g(30) using Tapatalk

[Smiffo]

It's very common to see that kind of pitting on the piston top, particularly on DJs. It could be poor fuel atomisation from a dodgy injector causing washing or hotspots. Or an air leak on that one cylinder causing localised lean burn?
Obviously replacement is the best option, but then you'll need a matched set (and they're a tad pricey). I'd say the piston is ok to reuse as long as the sides are undamaged, and there's no distortion, impact damage, cracks etc. I'd probably clean it up with a bit of wet n dry just to make it a bit prettier, but it should be serviceable.

Sent from my moto g(30) using Tapatalk

[tobydog]

Side view?

If it looks ok then polish/clean the top to prevent hot spots?