951 new piston wall clearance. .12mm, or tighter??

[68ragtop]

Just need some clarification on running oem pistons in the 951DI

I am going to the one & only oem oversize of .25mm So, I was thinking the finished bore would be 88.25mm
The spec in the manual shows a clearance of .12mm & the pistons have 88.13 stamped on them. So this seems
to fall right in line.

However, I noticed on the piston boxes they say 88.16mm. What the dealeo here? did some machines run a tighter fit at .09mm? In the manual, it shows .09mm for the carved 951's. Im Having the cylinders bored today, was planning on having them opened up to 88.25mm, now I am second guessing myself.....

If I had to guess, I am thinking the early DI's maybe used the same clearance as the carbed, & later years opened up a bit.

Any thoughts?

 

[racerxxx]

I checked the manual too and it is .12mm wall to piston clearance so that should be correct. From my past dealings with boring cylinders this is why machinists ALWAYS should have the pistons in front of them before boring any cylinder. THEY should mic the pistons and then bore and hone to finish at the .12mm clearance. So, IF your pistons actually measured the "stamped" size on top, he should bore with those sizes + .12mm, not what's printed on the box. I would assume they run the DI's a tad looser for the extra heat, too tight and she might squeaky, squeaky.

 

[68ragtop]

I checked the manual too and it is .12mm wall to piston clearance so that should be correct. From my past dealings with boring cylinders this is why machinists ALWAYS should have the pistons in front of them before boring any cylinder. THEY should mic the pistons and then bore and hone to finish at the .12mm clearance. So, IF your pistons actually measured the "stamped" size on top, he should bore with those sizes + .12mm, not what's printed on the box. I would assume they run the DI's a tad looser for the extra heat, too tight and she might squeaky, squeaky.

Lol, you mean squeaky, scratchy? haha! I am good friends with my machinist & he's been doing it a long time & won't make a new hole without the slugs for that exact reason. What threw me on this is, I have the new oem pistons for the 2002LE engine, & the box says 88.16mm & the correct part number. but the pistons say 88.13mm I mic'd them & they are indeed 88.13mm

Once again, I am looking too deep into things , but I hate making expensive mistakes.....

 

[Dr Honda]

The cyl's are undersized, so they can be bored to finish size.

DO NOT attempt to do that with a ball hone. You MUST use a machinist's hone. (you only need to take out 0.001")

 

[68ragtop]

The cyl's are undersized, so they can be bored to finish size.

DO NOT attempt to do that with a ball hone. You MUST use a machinist's hone. (you only need to take out 0.001")

I bring all this type of stuff in. The equipment the machinists have is so crazy accurate, not too mention a perfect crosshatch. I am guessing these are normally finished off at 30 degrees?

BTW, what about the air pump? can that cylinder be cleaned up with a hone, or replace it? Already have a new piston & rings, but didn't order a cylinder yet.