So i guess mine is an IU3 with a connecting rod 533?
Again a bit caution is recommended the casings can in worst case be replaced
the 533 No on the Con rod I would regard as a fact if the bike ran with that
To much work to fake that.
And I know that not even in the same year model ( I Have had 2 the same )
the same pistons are used from Factory
The radial play is matched pistons to cylinder if I recall right in three classes
Pistons has a marking on top ( Crown ) and cylinder at bottom
So at the factory at manufacturing the right pistons were matched with the right Cylinders
getting the right radial play.( We are talking quality aspirations here ) ( Might not be a big scandal if the same bore size but might as well mention it if a perfect job is what one wants )
New that is --- the pistons can wear out and the cylinder can have the factory markings left but be bored 4 times
If you put your stock nominal worn pistons in a 4 over cylinder you don't have a smile on your face upon first start
Or perhaps worse a oversize piston in a brand new cylinder .. first size or so .Some combinations is of course not possible to build and you notice it
There can happen all sorts of things
The 447 and 553 pistons also are different so doing a Rebuild in this region needs some thinking
One needs to measure ore go after the pistons markings and ring markings
One can push in the pistons known stamping s and right rings measure the gap with a feeler gauge
Above is maybe wrong to some extent .. but as a start for read up on complexity.
Replacing cylinder --- perhaps the rest is OK no need to worry about Conrods .???
New cylinder and perhaps new rings can be one way forward.
Depending on problem with cylinder.
If it is stock factory setup on your bike standard size there can be problems finding parts Piston and Cylinder.
Especially if you are looking for the exact right one of the three classes from factory.
Not done it myself but read about it that the shop gets the pistons and the cylinder and the play one wants
And bore to the right spec. Rather expensive where I live.
Yeaah you get it if you have 2 d oversize 533 in your bike fine pistons you want to use
If you then buy an 4 th oversize Cylinder ( With factory size stamping left gets fooled by that ) on e -bay cant use it cant do it smaller
$ 100 down the drain.
I took my cylinder to a shop and got it measured approved and honed It was a bit worn but got OK ..It is to much job not to do it reasonably well
once in there in my opinion