44 replies to this topic

[MiniLuke]

what would cause that?

My lack of skill......

what did you do wrong?

Not honed the cylinders very well at all.

Had far too rich needles in carbs for running in phase, which apparently washes the bores preventing bedding in.

You live and learn...

[ACDodd]

Don't forget to measure up before you do anything. If the bores have been washed (which I suspect) they may have worn too big and you may need a rebore and new pistons to fix.

AC

[oltonlad]

Don't forget to measure up before you do anything. If the bores have been washed (which I suspect) they may have worn too big and you may need a rebore and new pistons to fix.

AC

or just get another block at STD bore as your D topped cooper pistons are not cheap and it would be a shame to ditch them. (theres a set on ebay at the moment with 3 hours to go and they are at £161 at the moment!!)

[MiniLuke]

http://www.ebay.co.u...3c#ht_915wt_922

Can you get rings for these tho???

[oltonlad]

http://www.ebay.co.u...3c#ht_915wt_922

Can you get rings for these tho???

i should imagine so............people aren't going to bid that sort of money for pistons that you cant get rings for....(unless they are stupid)............

[MiniLuke]

They are only that much because they're +10.

I can't believe for one minute that the bores have worn too much in such a little amount of time!

We'll see tho.

[mini-luke]

They are only that much because they're +10.

I can't believe for one minute that the bores have worn too much in such a little amount of time!

We'll see tho.

If they're worn enough to remove most of the cross hatching, there must be a fair amount of material missing.

[MiniLuke]

They are only that much because they're +10.

I can't believe for one minute that the bores have worn too much in such a little amount of time!

We'll see tho.

If they're worn enough to remove most of the cross hatching, there must be a fair amount of material missing.

True true

[MiniLuke]

i took the engine block off the box when i took my old engine out, mainly because i couldn't get hold of the engine lift when i needed to take the engine out, it took about 40 minutes to split the block from the box and lift the engine out on my own.

Right, reporting back.

It does not take 40 minutes and is a very bad idea to do this..........

It's not possible to remove the gearbox housing past the crank doing this and is a right PITA. wish I'd gone and got the lift back now, my back hurts a lot now.... And for anyone else thinking of trying this remember to remove the dipstick and associated tube before lifting the block away.

[MiniLuke]

Been playing with the dismantled engine and found that the rings seem odd in the pistons.

The top ring has a step in it, pointing downwards, and it seemed very loose in the groove. On measuring the ring to groove gap it measures 0.070". Now, I have some new pistons of the same type the same measurement is 0.015". Question is then, how important is the ring to groove gap? Could this let oil past being too loose? Should the top ring be stepped?

[MiniLuke]

Update.

All back together and running very well. No smoke yet, although not revved very high yet.

The problem seems to have been using worn out old pistons with Huge ring to groove clearances and a set of rings bought cheap off eBay. The new rings from minispares seem far better.

[The_Doc]

Update.

All back together and running very well. No smoke yet, although not revved very high yet.

The problem seems to have been using worn out old pistons with Huge ring to groove clearances and a set of rings bought cheap off eBay. The new rings from minispares seem far better.

Did you do anything more to the bores to fix it or just replaced the rings? Any updates after more running?

[Spider]

 

Update.

All back together and running very well. No smoke yet, although not revved very high yet.

The problem seems to have been using worn out old pistons with Huge ring to groove clearances and a set of rings bought cheap off eBay. The new rings from minispares seem far better.

Did you do anything more to the bores to fix it or just replaced the rings? Any updates after more running?

 

 

That was 13 years ago !!

Probably on to another engine since then !!

[The_Doc]

Still want to know the answer!

[stuart bowes]

Op was last active Jul 08 2024 @ 10:51 pm, good luck with it but they might not reply

 

if you send a PM does that send them an email notification

Edited by stuart bowes, 22 May 2025 - 11:19 AM.