Thank you all for the great support and good advise.
Great input, Tony.
I had the advantage of following Monte, as always he was right on the money.
I have finally gotten around to taking off the piston. The gudgeon pin came out without me heating the wrist. A few gentle knocks with the back of a screw driver and it came out.
That is actually a little cause for concern, the pin should be a very light interference fit in the piston and require a little heating to get it to move, still if you had to tap it that probably just about qualifies.... However, if there are pronounced "gold" lines either side of the center of the wrist pin run your finger gently over the "lines" if you can feel a ridge you are going to be buying some parts and time in a machine shop.
If there are no "lines' and no ridge, put the pin into the small end of the rod and try to "rock" it, any significant movement and you will need to have things measured up to determine if a refurbishment is needed.
If no significant movement, no problem. On the outside chance that you have the equipment - measure the little end and pin to check that they are within wear limits.
1. Thanks for bringing to my attention the weight range. How do I know what I need? I weigh it or are the markings on the inside of the piston by any chance the weight specification?
I may have been talking through my hat, I've reviewed my manual and i think i should have said SIZE range, pistons and barrels come in "A, B, & C" sizes - the pistons should be the same and they should match the barrels in an ideal world. In the real world you select fit, and that does include making sure that the pistons weight the same - a simple beam balance and a bastard cut file are all you need. Reading my manual I see that they say that wrist pin circlips MAY have a round side and a flat side. FWIIW I have never seen any that were not round on both sides.
2. Do I need to change the piston rings or can I reuse them?
If they are undamaged and the end gaps are Ok in the bores you are going to use them in, then yes. BUT rings are cheap, I would buy new ones and also new wrist pin circlips. Remember that if you have Nikasil bores then there is only one set of rings you can fit, but if you have iron bores you can buy R75 2nd oversize rings and then select fit the rings by installing them in the bore and then measure the end gap, use a fine flat file to adjust. For some reason R75 rings can be as little as 1/2 the price of R65 rings which is odd as they have the same basic dimensions.
3. Do I need to change the gudgeon pin?
I would hope not, because if the pin is worn, fair chance the little end will be too, which will mean to need to buy new little end bushes and take them and the new wrist pins to a good machine shop and have them install the new bushes and then ream them to fit the pins. As you will be removing the rods to do this, think about new big end bearings and the fact that you will also be buying 4 new big end bolts. I have done this job myself, but I have tools that are not usually found in most home workshops, I had to use an adjustable reamer which meant about 10 ream/measure/ream cycles, with luck a machine shop will have the correct sized reamer and will do it in one pass.
4. Is there any way to tell from these photos if the cylinder absolutely needs to be changed along with the piston?
I wasn't planning on buying a new cylinder, simply change out the piston with a low-milage 2nd hand one. Economy as well as durability is key to my repairs. I see different recommendations on whether to change cylinder whenever you change piston.
I can see a nasty vertical line in the cylinder which means that to a purist that bore is toast. However, if you want to roll the dice (and be aware that is what you are doing) you could use it and see how much oil it burns, if not offensively high you may choose to live with it. I'd like to see better photos of the bore before you decide one way or the other.
Best regards,
And the very best to you also, you have a job of work in front of you
