Valve/guide seizure

Sergio

Sergio

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Jan 17, 2020
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Another chapter to share with this nightmare restoration project:
Few weeks ago (Sept 10th) I finalised my Norton restoration project. Last saturday my bike was still in the break-in period, a bit more than 300 miles done. Suddendly, a ringing sound came from my engine and my so happy ride finished on a towing.

The engine head showed a time side stuck inlet valve, a dent on the piston crown and a hit with the exhaust valve. A deeper inspection showed a premature wear on the drive side inlet valve, precursor of possible future seizing. KW guides and valves we involved. The machine shop (specialied and tooled for engine rebuild) affirmation is that they respected the KW .0008''-.0012 intake guide clearance and .0012''-.0015 exhaust clearance. Of couse I don't have the tools to test their testimony. But they suggested that new valves should be ordered and more clearance should be done for the guide sizing.

My question to you gentlemen who have KW guides and valves installed on your bike: What clearances do you use on a RH10/ 850 head?

Thank you all.
 
I use the workshop guidance of 0.008" exhaust and 0.006" inlet.
Never heard that KW has anything that supersedes those figures. Bike has done over 6k miles since head work. All good.

Have you got an extra zero in your post:
"they respected the KW .0008''-.0012 intake guide clearance and .0012''-.0015 exhaust clearance"
As that would be 8-12 TEN Thousandths, not the required 8 thousandths.
 
Last edited:
Also, you state you had no way to confirm clearance? So you did not check/adjust clearance following head re-torque after initial running?
 
Oh, looks like you stated Guide clearance, I assumed rocker to valve tip clearance. Sorry about that. So we're wondering how much the shop reamed the guides. Can't answer what mine had.
 
jseng1 said:
.0015" on the intake and .002" on the exhaust and you have no problems. I've tried them tighter and had them seize.
Click to expand...
This

Also not sure what guide material was used, KW sells different types. If C630 they need special equipment to size correctly
 
Are the Kibblewhite guides aluminium/bronze type?
From the recommended clearances it sounds like they are.

Glen
 
Tornado said:
I use the workshop guidance of 0.008" exhaust and 0.006" inlet.
Never heard that KW has anything that supersedes those figures. Bike has done over 6k miles since head work. All good.

Have you got an extra zero in your post:
"they respected the KW .0008''-.0012 intake guide clearance and .0012''-.0015 exhaust clearance"
As that would be 8-12 TEN Thousandths, not the required 8 thousandths.
Click to expand...
You mis understand. He is referring to the clearance between the valve stem and the valve guide inside diameter, not the valve lash clearance.
 
worntorn said:
Are the Kibblewhite guides aluminium/bronze type?
From the recommended clearances it sounds like they are.

Glen
Click to expand...

They are C630 bronze. KPM also makes guides in cast iron, but not for Nortons.

+1 on what jseng1 said. .0015" intakes and .002" exhausts. Usual spec for Norton race engines with bronze guides and hard chromed valve stems back in the '70s was .0010" - .0015" for intakes and .0015" - .0020" for exhausts. Like Jim, I prefer the upper end of that range.

Ken
 
worntorn said:
Are the Kibblewhite guides aluminium/bronze type?
From the recommended clearances it sounds like they are.

Glen
Click to expand...
yes it is C630 , but cannot tell you if it is the same as AMPCO45, try to find but they are propietary names , and no excat answer , but you must use the proper tool , it took me a day to ream them !
 
lcrken said:
They are C630 bronze. KPM also makes guides in cast iron, but not for Nortons.

+1 on what jseng1 said. .0015" intakes and .002" exhausts. Usual spec for Norton race engines with bronze guides and hard chromed valve stems back in the '70s was .0010" - .0015" for intakes and .0015" - .0020" for exhausts. Like Jim, I prefer the upper end of that range.

Ken
Click to expand...
Ken , you are and will be allways faster than me , on track or in the shed :D
 
Sergio said:
Another chapter to share with this nightmare restoration project:
Few weeks ago (Sept 10th) I finalised my Norton restoration project. Last saturday my bike was still in the break-in period, a bit more than 300 miles done. Suddendly, a ringing sound came from my engine and my so happy ride finished on a towing.

The engine head showed a time side stuck inlet valve, a dent on the piston crown and a hit with the exhaust valve. A deeper inspection showed a premature wear on the drive side inlet valve, precursor of possible future seizing. KW guides and valves we involved. The machine shop (specialied and tooled for engine rebuild) affirmation is that they respected the KW .0008''-.0012 intake guide clearance and .0012''-.0015 exhaust clearance. Of couse I don't have the tools to test their testimony. But they suggested that new valves should be ordered and more clearance should be done for the guide sizing.

My question to you gentlemen who have KW guides and valves installed on your bike: What clearances do you use on a RH10/ 850 head?

Thank you all.
Click to expand...
Read it wrong twice then re-read. You're talking about the valve stem to guide clearance. I can see how that could cause a stuck valve and even an exhaust valve hit. Can't see how that can cause a piston hit. Did either of the valves bend?
 
marshg246 said:
Read it wrong twice then re-read. You're talking about the valve stem to guide clearance. I can see how that could cause a stuck valve and even an exhaust valve hit. Can't see how that can cause a piston hit. Did either of the valves bend?
Click to expand...
If the intake valve got tangled on the exhaust valve, it could delay it's closing long enough for the piston to arrive and hit it.
 
lcrken said:
They are C630 bronze. KPM also makes guides in cast iron, but not for Nortons.

+1 on what jseng1 said. .0015" intakes and .002" exhausts. Usual spec for Norton race engines with bronze guides and hard chromed valve stems back in the '70s was .0010" - .0015" for intakes and .0015" - .0020" for exhausts. Like Jim, I prefer the upper end of that range.

Ken
Click to expand...
I had one tighten up on a new motor. Bike started missing. No damage fortunately. I wasn't racing. It was just new and with little clearance. Had to tear off the head and go through it again. Never again.
 
Hopefully they checked the clearances after the guide was installed as the bronze guides tend to squeeze a bit on installation.
 
Educate me. Is this C630 bronze alloy so hard that reamers won't work? Back in the day, I did all the head work in our shop and I used hand reamers on both cast iron guides and phosphor bronze (I think that what I remember they were made of). The boss did the race engines and had cautioned me about tight guides. This was and is not as desirable as tightness in particularly body parts elsewhere. I never had a comeback for a seizure or excessive oil consumption.

However, on my pickup engine I had a head specialist do the head with hard seats, phosphor bronze guides, stainless valves and Perfect Circle seals. I trusted his work and just put the head on the engine and went on down the road. A few weeks later I did have an exhaust valve seizure after 100 miles on the freeway. It released by itself after a few minutes of cool down. I subsequently richened the main jets (adjustable) an eighth of a turn and advanced the spark a couple of degrees. Forty thousand miles later I had that head off and checked a couple of exhaust guides at random. No stem wear and no guide wear according to my bore gauge. They make a nice pop sound when you pull them out with your thumb over the end of the guide. This was just as I would have expected had I newly set up a Norton head in the past.
 
Thomasa said:
Educate me. Is this C630 bronze alloy so hard that reamers won't work? Back in the day, I did all the head work in our shop and I used hand reamers on both cast iron guides and phosphor bronze (I think that what I remember they were made of). The boss did the race engines and had cautioned me about tight guides. This was and is not as desirable as tightness in particularly body parts elsewhere. I never had a comeback for a seizure or excessive oil consumption.

However, on my pickup engine I had a head specialist do the head with hard seats, phosphor bronze guides, stainless valves and Perfect Circle seals. I trusted his work and just put the head on the engine and went on down the road. A few weeks later I did have an exhaust valve seizure after 100 miles on the freeway. It released by itself after a few minutes of cool down. I subsequently richened the main jets (adjustable) an eighth of a turn and advanced the spark a couple of degrees. Forty thousand miles later I had that head off and checked a couple of exhaust guides at random. No stem wear and no guide wear according to my bore gauge. They make a nice pop sound when you pull them out with your thumb over the end of the guide. This was just as I would have expected had I newly set up a Norton head in the past.
Click to expand...
Hi thomasa , I was doing the same with the old reamers in the 80s an 90s and know what you mean , hard to ream and I just moved on when K-liners were coming , with carbide ball sizing , not sure if most know but as with piston sizing etc when guides are reamed to the standard size say 5/16 or .3125" the valve has the manufacturers desired clearance it would be up the machinist with experience to sort it out and as mentioned. .0015 Intake and .002 exhaust or a tad more was general , another thing to note some engines have specific seals for the exhaust valve , like honda engines have a small step at the top of the seal to hold a little oil ..
 
With the SEALS , the Full Surface / BORE of the guide , and the Valve Stem , its obligatory to oil / lube , for assembly .

If its gone together DRY - it could stay that way . A lotta dudes'd throw a cup or half a cup ( not a plastic one ) of OIL
over the valve gear - for Start Up , on a Overhauled Engine - And blow the smoke . Tight Clearances & its mandatory .
 
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