Verify Oil Pump Flow - Top End Noise

I took the valves out, no contact with the piston. The clean spot on the intake valve must have been from me wiping clean the combustion chamber.

Here are some photos of the cam and head.

OLD CT said:

View attachment 65595 Made in Japan valves are black...If you blow up a picture of the intake valve you can see where it is ''just barely touching'' the piston ''just enough to make the sound'' but not bend it as witnessed by the ''shiny white'' section. 12 o' clock in the pic.

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Dead-on...and eagle-eyed. You'd make one helluva microbiologist, or counterfeit plate engraver.

Jmunk, it doesn't really matter if the valves were gray-silver as-received. The fact that there's an isolated, sharp-edged, gray-silver spot means metal-to-metal contact. We suspect unwanted piston contact. At the very least, I consider this (contact + noise) the proverbial "smoking gun".

I would definitely check the valve & stem for any trace of deformation, as well as the valve guide. IMHO, there's a high probability that you did get away with this. Valve guides don't bend, they break when pushed too far...this couldn't have even come close to doing that. A bent valve stem will create a friction (stress) riser; I doubt you ran the engine long enough, but that's not the same as a guarantee. I suspect that, at worst, you might need a new valve.

Tripod said:

And for the one piece oil ring, Racerx refers to that as "lawnmower tech".

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There's a very basic reason for this. I've seen one-piece, cast iron, oil rings used on 1920s-era small engines such as Briggs & Straton, Cushman and others. It persisted well into the 1990s, at least, with small engines that are most commonly associated with lawnmowers. But, the 3-piece oil ring has superseded it with just about everything else. Every Honda engine I've seen torn down has had the 3-piece oil ring since the 1990s.

The downside of the one-piece oil control ring is that as it wears, the contact faces grow wider and lose their effectiveness. They also tend to wear quite rapidly. The 3-piece design uses a more harder, but more flexible, alloy and, since the two rings themselves are much thinner than their equivalents of the one-piece ring, they last far longer, with far less friction. The contact surface also remains the same width, regardless of wear...thus oil control remains until the bore/rings become scored or extremely worn. The 3-piece oil ring assembly is also way easier to install without damage, no tools required.

Jmunk said:

I took the valves out, no contact with the piston. The clean spot on the intake valve must have been from me wiping clean the combustion chamber.

Here are some photos of the cam and head.

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Looks more scored than I'd expect...but...most of that could be nothing more than digital camera artifacts. The tiniest lines can appear huge in photos, depending upon the lighting and the digital processors between the object being photographed and the viewers' eyes.
Two things I think you should check: valve straightness and the contact band of the valve face & seat. Roll the valve across a flat surface, first with the head not contacting, then with the head making contact. A small sheet of glass is quite effective. Look closely for any trace of wobble. Lastly, there's "the brakleen test"...install the valve, spray brakleen into the port then look for wet spot(s) inside the combustion chamber. If it stays completely dry, the valve is sealing well.

I think jmunk got very lucky and I am almost certain that the intake is ok to use and not bent. The ever so slightest contact occurred.

Thanks everyone for the help.

I think I’m going to order one of these pistons since it’s a “ART” brand along with a set of rings with the 3 piece oil ring setup. I’ll closely examine the valves and test the seal as RacerX stated.

https://www.ebay.com/itm/NOS-ART-St...268563?hash=item1c797c3953:g:kY8AAOSw-0xYa-1A

I will be sure to put the ART piston into the cylinder before fitting rings to make sure its good to go.

Looking at ring sets, I’ll try to find some NPR brand but if not maybe I’ll try these:

https://www.ebay.com/itm/Piston-Rin...l:CT70&hash=item2cde4196e5:g:MXAAAOSwIGxb2OMq

OLD CT said:

I think jmunk got very lucky and I am almost certain that the intake is ok to use and not bent. The ever so slightest contact occurred.

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X2

Jmunk said:

Thanks everyone for the help.

I think I’m going to order one of these pistons since it’s a “ART” brand along with a set of rings with the 3 piece oil ring setup. I’ll closely examine the valves and test the seal as RacerX stated.

https://www.ebay.com/itm/NOS-ART-St...268563?hash=item1c797c3953:g:kY8AAOSw-0xYa-1A

I will be sure to put the ART piston into the cylinder before fitting rings to make sure its good to go.

Looking at ring sets, I’ll try to find some NPR brand but if not maybe I’ll try these:

https://www.ebay.com/itm/Piston-Ring-Set-Standard-Bore-Domed-Piston-Honda-ATC-C-CL-CT-SL-XL70/192707401445?fits=Model:CT70&hash=item2cde4196e5:g:MXAAAOSwIGxb2OMq

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ART is/was the OEM of Honda pistons from that era.

That said, if the `doc supplied you with an incorrect piston, I fully expect that they'll make good on it...in which case, the smallest number of bucks will escape your piggybank if you order the ring set from dratv and have it shipped with the replacement piston. Or, did I miss something earlier in this thread?

I would show the doc the evidence, wait for a response for a replacement, and pick up a set of his aftermarket rocker sets. The pads are worn enough, the tell tale ''wear line'' across em. I would replace them. The head looks great otherwise.

I sent the vendor a email, I have bought several orders and never an issue. At this point, I’d rather not go aftermarket again on the piston. I do understand he’s a vendor and not a manufacturer, I have nothing but good things to say for him. I’m sure he will make everything good.

I will look at his aftermarket rocker arms.

Looks to be about 1mm taller. Plus the dome angles are bigger than on an oem piston.

Can the five piece ring set still be used? Can the newer oem five piece ring set for a long rod be used?

Tripod said:

Looks to be about 1mm taller. Plus the dome angles are bigger than on an oem piston.

Can the five piece ring set still be used? Can the newer oem five piece ring set for a long rod be used?

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To get a true height measurement I think you need to measure from the wrist pin up since that’s the locating point. I measured mine and had a hard time with my dial calipers getting an accurate measurement. When I put it on the rod as mock up and slid the cylinder on with the base gasket I saw the real difference.

I wouldn't put new rings on. Test it in the bore @TDC ring less. Looks like another dud.

OLD CT said:

I wouldn't put new rings on. Test it in the bore @TDC ring less. Looks like another dud.

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Ive got a nos 2nd over piston coming. What im referring to for the rings is will i need to source another set or can the ones that came with the dud piston be used.

I think they should work, Check the ring lands when the new piston arrives.

My apologies if anyone thinks im hijacking the thread. Hopefully the following info can help jmunk as well as giving some info based on known parts.

I am currently in the process of rebuilding my HK0 motor. I have the same brand of piston, only difference is its for a second overbore. The other dimensions should still be valid though.

Heres some photos of my setup.

Original 4spd crank. Original barrel bored out second over. Vesrah base gasket. Vesrah head gasket.

I put the piston in with no rings on for these pictures. Cylinder barrel was not bolted down yet. The engine is standing straight up on a stand.

A few pics show the piston at tdc with no head gasket. A few pics of piston at tdc with a head gasket...

Tripod - Looks like yours also sticks up, maybe not as much but still more then it should. I believe the rings from that piston will fit the NOS one you have coming as I was able stick them into the ring land
grooves on the OE piston. I’m glad you possibly saved your self some time and effort catching it now.

I’m glad someone was able to benefit from my situation.

Does this wear on the wrist pin look normal? I was curious if this was normal or if it was an indication of something.

All I can see on my screen are two dark lines. Those are 100% normal...the only exposed areas of the wrist pin. The rest is either covered by the piston or the rod.

I should have clarified, the two bronze colored rings were what I questioned. I wasn’t sure what they were from.

You misunderstood my previous post. I was referring to those rings...they're a result of normal crankcase gasses, resulting from blowby.

Just run your finger over it to see if its smooth and, if there's any pitting, scratches, or warpage, its gone.