Need help with pistons

[burtshaver2021]

I really want to get them bored but it’s a little on the expensive side.
I know it’s not a good option but should I get the same exact size pistons and replace them or a different size?

I understand the expensive part, been there a few times. Best to take your time and do it right, that’s not just a cliche. You can take your cylinders to a machine shop and have them do some measurements as I’m assuming you don’t have a dial bore gauge and a caliper? In your manual, you will find the tolerances for out of round cylinders. If they are within spec you can have them honed to de glaze them and instal the standard size pistons without having them bored but if they are not you really are wasting your money by installing the standard pistons without boring. You will literally spend the money in new pistons, rings, caged needle bearings and gaskets and be back in the same position your in right now except your wallet will be about 400.00 lighter.

 

[burtshaver2021]

And spider is right, you should take the cylinders in to the shop before purchasing any pistons period. They will tell you if you can go standard, or if you need .25mm or .50 oversized pistons. And don’t forget you need to figure out why you lost the compression in 1 cylinder more than the other or it will only happen again. Don’t want to overwhelm you but it s a good idea to do a leak down test on the engine crankcase and rotary valve cavity.

 

[Poormanracing]

Have a couple questions why are you doing a top end?how is the crankshaft?how is the counterbalance shaft how long has it been sitting?is it stock and never been apart?is it a SBT shortblock that was installed at some point

 

[DI_Hoss]

The 82.5 will work, it’s the second size over, but you will have to have the guillotines on the rave valves trimmed back With these. Buy your pistons first and then take the pistons to your machine shop before they bore out the cylinders. I seen 1st over (.25mm) pistons for sale at Partzilla.

I will be having my DI 951 cylinders bored 1.00 mm over this winter, caught your comment about shaving the guillotines; I understand the how, so to speak, but who? Me with a die grinder, or the shop when they bore the cylinders? Thanks in advance!

 

[burtshaver2021]

I will be having my DI 951 cylinders bored 1.00 mm over this winter, caught your comment about shaving the guillotines; I understand the how, so to speak, but who? Me with a die grinder, or the shop when they bore the cylinders? Thanks in advance!

I’ve seen some videos of it being done with sandpaper wrapped around the piston, no first hand experience myself though. I would think the shop should be able to as well

 

[burtshaver2021]

I will be having my DI 951 cylinders bored 1.00 mm over this winter, caught your comment about shaving the guillotines; I understand the how, so to speak, but who? Me with a die grinder, or the shop when they bore the cylinders? Thanks in advance!

Here’s the video I was referring to,

 

[DI_Hoss]

Here’s the video I was referring to,

...scary...

And after my first read, I expected something much more high-tech. I know where I can get a piston or two

Thanks @burtshaver2021 !

 

[burtshaver2021]

...scary...

And after my first read, I expected something much more high-tech. I know where I can get a piston or two

Thanks @burtshaver2021 !

You could use your old pistons