After some more measurements, I'm thinking this piston and cylinder might be .5 mm oversized. I was thinking my calipers might be off (I leave my good micrometers and such are at work), but all the measurements are correct for .5 mm oversize. Also, if I had rings for a .5 mm oversize piston, the ring gap would be correct...and the oil rings...they fall right through the bore.

I didn't think the piston could be oversize since it wasn't marked as oversize. Does honda not mark them? I just have the N7 and IN markings on this one.

Thanks, Phillip

 

Piston will be marked as oversize.

 

Okay...just checked again. Cylinder measures slightly over 3.366" Piston measures about 3.364" Stock cylinder size should be about 3.3467". That difference should be equal to .5 mm oversize, correct?

...but I haven't ever seen a oversize piston that wasn't marked though.

This is just strange.

Thanks,
Phillip

 

Okay...just checked again. Cylinder measures slightly over 3.366" Piston measures about 3.364" Stock cylinder size should be about 3.3467". That difference should be equal to .5 mm oversize, correct?

...but I haven't ever seen a oversize piston that wasn't marked though.

This is just strange.

Thanks,
Phillip

sounds like the PO put over size rings on a stock bore ?. I know for a fact, any over size piston will be clearly marked on the top of the piston, such as 0.25, 0.50, 0.75 . if there is no markings on the piston..other than what you first posted ?..then that piston is a stock piston, and they stuck over size rings on it, that's all I can think of what you got. Honda will stamp a over size piston with the numbers on them, so does all after market pistons.

 

I am about to leave for work. Will be taking the P & C with me to measure them properly.
Thanks,
Phillip

 

Well, it's official...I have an unmarked .5mm oversize piston.
I checked with my calipers, then with a micrometer at work, then checked both for accuracy using gauge blocks. They're accurate, and my piston is definitely oversize.

At least we now know that they exist.


Thanks,
Phillip

 

from what you said , if it were mine I'd mail it off and have it bored , new piston , rings and gaskets , every thing you need to do the job , they charge me right at $200 with shipping included , you do have to pay to mail it to them about $15 -----sounds like you have a mess , like it was worn and then honed , when you mic it you need to do it on the top , middle and bottom of the bore , the bottom will egg shape

 

As best I can guess, this thing, as clean as it is, must have been swamped at some point. Rings were probably toasted, so in comes a .5 mm overbore....meanwhile, the ext valve got bent in the process and cracked the valve guide. When the overbore didn't stop it from smoking, the owner decided to let it go. Fast forward to the guy I bought it from...they thought it needed rings, threw in a new set, but got standard rather than .5 mm over. I buy this thing, find the bent ext valve, and the wrong rings on the piston. The bore is clean as a whistle and straight as an arrow. Piston looks like it has 5 hrs on it.

Hoping the new rings will get me where I need to be. :/

Thanks,
Phillip

 

There a ton of hours on the machine?

An entire 152 hrs.



Phillip

 

Good news...
I just got my .5mm oversize rings in. Ring end gaps are perfect for my .5mm oversized bore (and unmarked oversize piston). Going to put everything back together this evening.

-Phillip

 

good deal , you'll be breakin' it in tomorrow evening , ahhhh ! , don't forget to take it easy , what's your plan for breakin' it in ------------------- you mentioned hours , working with heavy equipment I learned to not take anything for granted , not being lead to believe anything based on hours , have found that a machine with 150 hours can be more funk'ed up than one with 1,500 hours

 

Well, I guess I plan to warm it up, ride the poo out if it for a couple hours at varied RPMs, change the oil and filter, then off to normalcy. Just seating the rings...everything else in the engine is worn in.

Yea, I got a great deal on a 1995 John Deere...1500hrs, and paid about $12,000 less than any other one with those hours, but the loader looks like it has 12,000 hrs and it won't stay in 3rd gear. Runs like a top though. The rest can be repaired. I don't mind doing a little work to save some money on a big purchase. That way, I know everything is right when I get done.

 

Got everything put back together yesterday morning (including a clutch rebuild). It started instantly, purred right along, and rides like brand new!
-Phillip

 

Got everything put back together yesterday morning (including a clutch rebuild). It started instantly, purred right along, and rides like brand new!
-Phillip

good deal . glad you got it going !. you sound a lot like me bro, you buy stuff that looks rough ?..but with alittle TLC , it will shine like new when your done.