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Old 23 February 2006, 17:23   #1
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pistons and rings

bet im realy pi*sing everyone of about this engine by now
right if i needed a new piston could i just change 1 or do i have to change all 4
if pistons were ok and i needed rings could i just change the one or should i change all of them(ALL PISTON RINGS I MEAN)
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Old 23 February 2006, 17:29   #2
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Quote:
Originally Posted by bigmike35
bet im realy pi*sing everyone of about this engine by now
Not at all!
Quote:
right if i needed a new piston could i just change 1 or do i have to change all 4
If it runs OK with no horrible noises, and no excessive smoke, you shouldn't need a new piston. Replacing one piston is OK in most engines though. Strip the engine, clean the parts and then decide.
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if pistons were ok and i needed rings could i just change the one or should i change all of them(ALL PISTON RINGS I MEAN)
Find out if they are sold as a set first! Personally, I would change them all whilst you've got your engine in bits.
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Old 23 February 2006, 17:30   #3
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If your changing a standard size piston with another standard size piston, you only need to replace that one not all the rest. Since your going in there you should replace all piston rings. You should also rehone all the bores if everythings within tolerance of a standard bore.
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Old 24 February 2006, 13:42   #4
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You might as well change all the rings if you can-just be careful not to run at full revs for a few hours use after-it'll need a running in period.
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Old 24 February 2006, 17:07   #5
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It is quite in order to change just one piston if this is necessary. It's even in order to rebore one cylinder and change just that piston. However, you should definately weigh the new piston to ensure it matches the weight of the original 3. Whether you change all the rings should depend on the amount of wear you find. If you choose to change the whole ring set, you should hone the bores to give a surface which the new rings can bed into. Ideally, this should be a crosshatch pattern. The problem with this is the loss of metal by honing and the subsequent loss of more metal during bedding in combined with the original wear. I've done this many times and almost always a bit of piston slap can be heard afterwards. I've also changed rings and deliberately not honed the bores and there has not been a problem.

Given that your compressions are correct for the three cylinders, if it were me, I would need to find undue wear to convince me to replace the rings and hone the bores.

There is much more advice about how to go about the job but that can be left until you've made the decision to go ahead.
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