Cp Pistons .please Advice On Myproblem Guys.

[rockabilly]

hi guys, just fitted some 86.5mm cp pistons to my rb26 rods.

two things really. firstly the pins fitted in the pistons with no heat, just pressed in. snug and tight. i needed to slightly reem the little end with 1200 wet & dry first because the pin was not rotating in the little end just the pistons. does this seem right.

secondly the oil scraper ring when fitted to the piston without the top and bottom rings that go either side of it seems to long. i.e. it meets end-end before it touches the piston all the way round. hence when i gapped the rings the top and second compression were fine and the top and bottom oil rings were fine in the bore, but when you assemble the three components of the oil scraper it will not go in the bore. i have e,mailed cp with part number on the 3 packets as they come in pairs, it just seem odd they are wrong. the best way i can describe it is when you fit the two oil scraper rings in the bore the end gap is .50mm, then fit them to the scraper and the end gap becomes 1.00mm?. any cp men out there. peter (pnblight) maybe. thanks guys.bernie/uk

[wrxhoon]

Put the rings in bore and measure the gap while in the bore, if they are within spec then put them in the pistons and use a ring compressor to install the piston in the bore . The ring gap will not change whe you put them in the piston groove .

Stock pistons you have to heat to install the pin but most aftermarket pins you dont. As lond as you have some clearance ( very little)on the little end it should be ok.

[rockabilly]

thanks for replying. i have already gapped them. the top ring and second ring are fine. when you assemble the three oils scraper rings they are too big for the bore without piston?. the two rings that fit either side of the brass scraper gap up fine in the bore but when they are located on the brass scraper the end gap increases because of the lip that is built into the inside edge of the brass scraper, this in turn pushes the top/bottom scraper rings outwards causing them to be to big for the bore..

i put the three oil scraper rings on the pistons and tried a ring compressor and it wont tighten them down into the piston. they will not compact enough. yet the kit came with the pistons and the top/second rings when fitted to the piston are great no probs?. i am baffled. shaun

Put the rings in bore and measure the gap while in the bore, if they are within spec then put them in the pistons and use a ring compressor to install the piston in the bore . The ring gap will not change whe you put them in the piston groove .

Stock pistons you have to heat to install the pin but most aftermarket pins you dont. As lond as you have some clearance ( very little)on the little end it should be ok.