What a mess!

[neb]

I have been having problems with my DT65 it's been running on 1 cylinder I think. No power on turns or reverse.

I found a crack in the fuel filter that was the cause of it not running recently. Then after replacing this I have lost power.

I have run these tests:

It sparks on all 3 plugs (strong)

If I take the plug off the lowest cylinder when running it stalls.

When I take the plug from either middle or top cylinders it makes no difference to the sound.

I have took the head cover off to see if the gasket had blown, it hasn't.

Anyone got any ideas, the top cylinder cover pot has really bad marks (pitting) on it as you can see in the pics its also dry. Middle pot oily, bottom pot very oily.

What a mess! the head cover looks knackered to me as the pits are HUGE as you can see.

[Nos4r2]

Sorry to be the bearer of bad tidings but you've blown your rings. You're going to need a rebore.
The damage (particularly that shape of pitting) is what happens when they come up into the combustion chamber in pieces, get squashed then go out of the exhaust

[codprawn]

There is a cheap way to try to cure the pitting if you are just going to scrap the engine - metal filled epoxy. You can make your own using 24hr araldite and metal poweder of whatever type the metal is made of. Last resort though.....

Looking at the photos again though some of the gouges are at the edges so you wouldn't have much chance there - works best on a flat surface not too close to an edge!!!

[Nos4r2]

Hold that thought-I may well be wrong.

Turn the engine over and look for damage/scuffing/scoring on the bore. It may be that someone has reused the head after the rings were replaced. There's usually lumps of ring stuck in pits like that.

If you can't see anything then put it back together and do a compression test.

<edit> I enlarged the pic btw -I think I can see bore damage on the lower end of the closeup photo of the pistons so don't be too hopeful. It looks like you may have a blown crank seal too-it's not usual to have one piston cleaner than the rest unless it's letting air or water in on that pot and running too hot.

[Jono]

Originally Posted by codprawn

There is a cheap way to try to cure the pitting if you are just going to scrap the engine - metal filled epoxy. You can make your own using 24hr araldite and metal poweder of whatever type the metal is made of. Last resort though.....

Looking at the photos again though some of the gouges are at the edges so you wouldn't have much chance there - works best on a flat surface not too close to an edge!!!

Araldite in the squish band?

[jwalker]

Originally Posted by codprawn

There is a cheap way to try to cure the pitting ...

Cod, tell us why you would want to do that.

[neb]

Originally Posted by Nos4r2

Hold that thought-I may well be wrong.

Turn the engine over and look for damage/scuffing/scoring on the bore. It may be that someone has reused the head after the rings were replaced. There's usually lumps of ring stuck in pits like that.

I agree as the piston top has no real pitting to match and the shapes are like broken fragments of ring.

Originally Posted by Nos4r2

I enlarged the pic btw -I think I can see bore damage on the lower end of the closeup photo of the pistons so don't be too hopeful. It looks like you may have a blown crank seal too-it's not usual to have one piston cleaner than the rest unless it's letting air or water in on that pot and running too hot.

I can't see any bore damage, there is a little scoring but nothing obvious. It might be oil from my fingers you can see?

Thanks so much for your comments.

[Nos4r2]

Stick it back together and do a compression test if the bores don't look too bad. All cylinders should be within 10% max.

[Limey Linda]

Originally Posted by jwalker

Cod, tell us why you would want to do that.

So you can flog it to some poor un-expecting sheep I guess.

[ian parkes]

Chances are NOS4 has it right with the piston ring broken , but just check the plug from that cylinder , did the electrode break off and cause that damage , would also explain the running on one cyl.

The top of the piston looks ok and rings usually damage that aswell as the bore .

Forget the araldite business the head will run ok as it is .