8 replies to this topic

[minimaker]

i have just taken the head off my 1275 A+ engine, i have noticed that one of the pistons has a "ding" on it, i need to find out whether my rings need doing or can i get away with just doing the head. i cant see any marks on the bore.

anyone in the area is more than welcome to have a look or help!!!

please help me

or if anyone has a cheap spare engine that they know is in good working order please let me know

[Cooperman]

If it's not smoking and the bore is not scored down from where the 'ding' is, then bring the piston to TDC, gently clean up the top with a light, small file and some emory cloth, wash out the filings and re-fit the head. That'll cost a lot less than a new engine which you probably don't need.

[minimaker]

the engine was smoking but not a hell of alot, i was going to re-do all of the valve seals anyway. is there any other ways i can check if the rings are gone?

[wile e coyote]

A rudimentary check is to take piston halfway down its bore then put 20mil of engine oil in , and do the same at the same time to the corresponding piston - bioth will leak down, bar the oil caught in the dish - but the question is how fast - if roughly the same then in all probabilty you'll be ok with following cooperman's guidance - if not then it's likely theres further nasties hidden out of sight that'll require a strip down to assess. Another equally easy check is to bring piston to the top of it's bore and run a thin feeler guage around it as if there is damage the top ring will be affected.

From the pic thought for a mo that the piston crown had a crack - 99% sure its just optical illusion & carbon deposit (blasted tiny screen!)

Good luck with it! - hopefully it's nothing to worry too much about

[minimaker]

haha that is just carbon. . you had me panicing then! will try the feeler gauge thing now. have already done the 20ml of oil with 2 and 3, they seem to be the same speed.

[minimaker]

feeler gauge results - - - - - - - everything feels ok!

if a ring was gone would i definitely be able to feel it on the top ring?

also how often do piston rings crack? i have been told not very often

[Sprocket]

I recon that engine has overheated causing the top of the piston to expand and foul on the bore. As this part of the bore is un lubricated and hot, the extra heat from friction melts the piston in that area leaving metal on the bore. The rings scrape it off and can cause them to sieze. Loss of power and burning oil would be symptoms of that sort of failure

[Nightrain]

That piston will always suffer from a hot spot now, which will only get worse and end up costing you a lot more money if left in.

[minimaker]

best to change it while its apart then, any other things i should definitely change while its all apart?