Author Topic: Pilot pistons  (Read 2215 times)

Weed

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Pilot pistons
« on: July 25, 2006, 08:07:09 PM »
Picks of the almost seized pilot piston....

Moskito

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Pilot pistons
« Reply #1 on: July 26, 2006, 06:42:09 AM »
You can see how worn out the piston is by the brown coloration on the top part of the piston.  It's known as blow by.  The rings are getting tired, the bore's getting big and the combustion process was beginning to work past the rings.

Looks like you caught it all at the right time!

Now that you have it apart, send the jug to Bore Tech and have Bill Carbide process the bore....  Well worth the extra time/effort and the few bucks it will cost.

Is the jug stock or has it been ported?
Moskito - Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming \'WOW-What a Ride!\'

Weed

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« Reply #2 on: July 26, 2006, 09:09:31 AM »
Well while I posted this I was chatting with Nuke Em and forgot to include a narrative.

I bought the pilot back in Feb. from a guy in Michigan that needed some fast cash.....It is a 1990 and I picked this one up at a pretty decent price.

He claimed it was a 500 and it was restored. (Apparently his definition of restore is equivalent to my definition of rattle can makeover)

Anyway I drug it home, the following weekend the queen and I went for a short ride.  I rode this thing for 20 minutes and knew it was not a 500...  It was real snappy and had plenty of get up (it would keep up with the 350) but I knew it just wasn't right.  So I told the better half not to ride it until I checked it out.........It has been sitting since and I am glad I made that decision.

I finally found some time and pulled the jug.  My assumption was correct.....It is NOT a 500 and it DOES have a problem.....

The guy told me it was a new top end.......And believe it or not it does.... The rings look new......they have no running wear..........once removing the carbon the piston looks new too.  The cylinder bore is excellent with slight scuffs from the four corners.  Still has the fresh hone marks......

I would say it has maybe 3 hours on it.

The Piston is a Weisco and I will either see how it cleans up or buy another.  

The top ring was stuck so that was the reason for the carbon on the piston skirt.

This week end I will dig out my spec book and rehone and check clearances. I have new rings so I will make the judgment call when I see what I got..........

I don't know who put this engine together but I have a feeling it was done by a guy that doesn't use oil to assemble or crams the piston in the bore without properly suppressing the rings.

nuke em

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« Reply #3 on: July 26, 2006, 02:54:47 PM »
I am very curious what they bored it to over the piston size. Wiesco says .003 but I never have been able to make that work very long, at least in a 350. I always go .005, but thats just me and I am a little wierd. LOL

Weed

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« Reply #4 on: July 26, 2006, 07:31:21 PM »
It looks to be around .004  

it cleaned up nice I havent decided to reuse..........we'll see

The piston is a 81mm  I think I am going to put this jug on the 89 and make it the hotrod motor.

The 89 has the original bore and honda piston......it will go on the 90

I am eventually going to restore the 90 to original condition with all the hondaline accessories

nuke em

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« Reply #5 on: July 26, 2006, 10:31:13 PM »
Never used the .004, guess I will stick to the .005.

Better start saving now for new parts,.... :lol:  or rob some Kansas banks LOL.

PilotHawK

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« Reply #6 on: July 27, 2006, 07:45:35 AM »
Clean up the piston with some 400 grit or finer w/d sand paper and install new rings. This time when you "wear it in", warm it up to normal operating temp, let it cool, retorque everything to spec. Warm it up again, then flog it!

Weed

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« Reply #7 on: July 27, 2006, 07:59:21 AM »
I did the exact same thing to clean it up turned out pretty good...

I thought about experimenting with this piston and bead blast the skirt......call me crazy but I think that the textured surface will act like small cups holding oil..........creating a better barrier of wear protection...

We used to do this to Diesel cast pistons with great success.......but they were cast not forged.

nuke em

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« Reply #8 on: July 27, 2006, 10:00:35 AM »
Very interesting idea. I think tiny divvets should work, and maybe better than Wiesco horizontal grooves. We'll see I guess. I would write down/log compression measurments after every tank to see how she is holding up. Just a suggestion.

odypilots

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« Reply #9 on: July 27, 2006, 11:19:13 AM »
A mechanic I respect has used a small drill bit to create shallow dimples on the piston to help retain oil.
The usual 'my two cents' disclaimer applies. :)