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Discussion Starter · #1 ·
IN putting it back together again noticed this today. These valves where bought new less than a year ago. Less than 2000 miles on them.

Is this a valve defect or is it possible that my timing is off somehow? Never seen this before! Valves bought off flea bay. probably my problem right there.
 

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Discussion Starter · #2 ·
This is the set. A lot of them on ebay. My brother the real mechanic lol says they were probably made with metal of the wrong tensile strength. It's only the intake valves with this problem. exhaust is fine. Luckily I have a fresh head with a fresh valve job with the original OEM honda valves on the shelf ready to go.

HONDA CB350 CL350 CB360 CL360 INTAKE EXHAUST VALVE SET - SET OF 4 VAVLES | eBay
 

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Is it all or just one?
How do you drive it?
Valve clearance too loose?
What work was done with the head, springs and camshaft details?
 

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Probably made in China (or India), not up to the task. Better to use genuine Honda parts, even used ones.
 

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Discussion Starter · #5 ·
It is only on the intake valves. All 4 valve clearances were set correctly. The head was bead blasted, redecked, new valve guides, new valves, valve job, new seals. Basically a total rework. Done by a very experienced machine shop in Raleigh that has never steered me wrong in 20+ years. I'm with you Mike, pretty sure it was cheap chinese crap and the metal formulation was not right. The intakes probably dimpled because they are softer than the formulation used for exhaust. I am sticking with only honda parts after this. Although I have done that for almost every single thing else at great expense. (CMSNL loves me BTW. They probably have a pool in my honor lol)
 

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I just wanted to update this thread with some info. I messaged the seller about this. I have an interest as I have 350s and may someday need replacement valves. The seller says these are sourced from japan, and they have sold a large number and haven't had any complaints about this.

From the corespondence, I took the seller to be professional and serious, and may consider a purchase from them, should my excessive parts stash ever run dry.

Just curious, the shop you had your work done at, a car or bike shop?
 

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Discussion Starter · #7 ·
That's interesting. I also messaged the seller repeatedly. He has yet to answer me at all. I was going to either try to get replacements or get a refund. I told him he should definitely get the metallurgy of these valves checked.

The machine shop work was done at a large machine shop that handles bikes and cars, new and vintage, and racing stuff. they have been around almost 40 years. they are very competent. I also had the head looked at by a local motorcycle dealer shop that does machine work and they came to the same conclusion as everybody else. The metal was too soft. Possibly a bad batch?

I still have the head and will take photos tonight. There were no interference problems with the pistons. Pistons were brand new NOS ART pistons. Crowns were clean on disassembly no scoring or valve imprints. Mechanically there is just no other way this could possibly happen except the metal was too soft.

Since the guy actually replied to you maybe tell him to check his ebay messages and get back to me? Right now I'm out the money I paid for the valves, the valve job, and all my time having to tear down a freshly rebuilt motor again. So hundreds. Would be nice if he would at least reply instead of ignoring me. While he may be professional and courteous pre sales, he's a trail of crickets chirping after the sale.
 

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You can kiss those valve guides goodbye when you remove those valves..........if they're badly mushroomed, I might heat the head up and let the guides drop out with the valves still in them - instead of trying to beat the hell out of the valve through the guide.
Or maybe you could grind the tip off first - that might be risky too, any sort of irregularity will screw up the guides.
 

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If the tips were ground for clearance of height that may be the issue. Like the valve faces the tips are hardened and grinding may have gone thru that.
 

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Discussion Starter · #10 ·
No grinding on the tips was done. My plan was to take a dremel and grind the ends back to smaller than the original stem diameter after taking off the springs and keepers. Then hit edges with sandpaper progressing as follows 150 240 400 800 1200 2000. (Its what I have). Hit it with a micrometer around the end to make sure I got all the overhang. I may be able to get them out. Brand new bronze guides. sigh. Will only buy genuine honda from now on.
 

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If you replace the Valve you should replace the guides as well.

They are meant to be Reamed to the exact size of the Valve Stems.

It's unlikely the new Valves will have identical size stems.

The Service Process and Clearance spec for the stems is:
Right - CLICK and Open in NEW TAB to view larger.

ValveGuides001.jpg
 

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Valve guides are fairly cheap, as these things go.
As mentioned, they are NOT the correct size "out of the box" - they have to be reamed to size.
Any competent machine shop can do it.
If you happen to have a precision 7mm reamer, you can do it yourself - the guides are fairly easy to remove.
 

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Discussion Starter · #14 ·
I had actually pondered investing in the reamers and valve seat cutting faces. then I saw how much a valve grinder costs and was like ummm nope! Just takem to the machine shop again!
 

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That's interesting. I also messaged the seller repeatedly. He has yet to answer me at all. I was going to either try to get replacements or get a refund. I told him he should definitely get the metallurgy of these valves checked.

The machine shop work was done at a large machine shop that handles bikes and cars, new and vintage, and racing stuff. they have been around almost 40 years. they are very competent. I also had the head looked at by a local motorcycle dealer shop that does machine work and they came to the same conclusion as everybody else. The metal was too soft. Possibly a bad batch?

I still have the head and will take photos tonight. There were no interference problems with the pistons. Pistons were brand new NOS ART pistons. Crowns were clean on disassembly no scoring or valve imprints. Mechanically there is just no other way this could possibly happen except the metal was too soft.

Since the guy actually replied to you maybe tell him to check his ebay messages and get back to me? Right now I'm out the money I paid for the valves, the valve job, and all my time having to tear down a freshly rebuilt motor again. So hundreds. Would be nice if he would at least reply instead of ignoring me. While he may be professional and courteous pre sales, he's a trail of crickets chirping after the sale.
Open a case with him on ebay, he'll have to respond or ebay will contact him. At least you could get a dialogue going. Although I think something else other than the valves is at fault here. Valve to guide clearance maybe? Tight valves would take a beating, what do the tappet adjuster tips look like? At least they didn't get to the point of dropping.
 

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Discussion Starter · #16 ·
Ebay won't let me open a case. Its been a year since I bought them new. I was pretty meticulous about keeping the valve cleareances set becasue I was just breaking in a new rebuild. So I was checking valve cleareances and timing often.

Pretty sure it was a metalurgy issue. Tappet adjusters look fine. In fact I put them back on the bike.
 

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Original Honda Parts are always a safe bet. But if you want to consider aftermarket then I've heard that the valves from Schuman Motorworks are of really good quality. He also makes different sizes. Some people are worried by NOS Honda Valves because they are welded and can break at the weld. Not sure if this is really realistic or not
 

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Discussion Starter · #18 ·
well I got em out without a single scratch to the guides. Lots of dremel tool and 5 progressive grits of sand paper to 2000 grit on the ends after grinding off the mushrooms. The next question is a I have a set of used honda brand valves. Can I just take those to the amchine shop and get them ground and drop them into this head I already had the seats ground? OR do I need to have the seats ground again?
 

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Valves cannot be ground, replacement only. The seat area is a thin hard face, @.002" thick. With new valves you can do a very light lap and see where the seat is on the valve, should be in the middle or slightly towards the outer edge.
 

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Discussion Starter · #20 ·
UPDATE I managed to get in touch with the folks who sold them to me finally. Must have been some type of mixup at ebay or something. They seem very nice and where eager to help me figure out what went wrong. They say they deal with a lot of folks who really punish these things racing them and have no problems. We discussed the work I had done and it would seem I did everything right. We came up with no good explanation as to why this happened so it could just be a fluke? They are sending me a fresh set and I'm going to give this a go again. I'm going to take the whole head back to the machine shop and have them do the work again. I'm also going to go get some NOS honda tappet adjustment screws and replace those as a precaution.

So long distance rider, I'm a bit confused. So do you not grind the angle son the new valves? Do they come pre ground that way? There seems ot be a lot of debate as to what the "right way" to do a valve job is. I was doing some research myself to try to get a better understanding of this topic so I can make sure my machine shop is doing things the right way. I found this... Which made interesting reading. Kind of where I'm at is this machine shop work and parts are expensive and I;d like to just get this thing fixed and done once. lol Valve Jobs Done Right
 
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