Valve guides.

Rohan · Jul 27, 2015

comnoz said:
Why is it that every Norton cylinder head I see with over 10,000 miles on the iron guides and OEM valves have very worn guides? - Not to say they wouldn't run that way for a lot longer if you don't mind the noise or performance loss. Jim

So how is that that all these big mileage engines, apparently untouched, can still have their original guides. ?

Maybe some of the guides weren't so chilled ??!!

I must have a look at my spare 850 head, it has about 10,000 miles on it.
I seem to recall the guides still looked like new, but maybe I didn't measure them.
Might examine my dommie head collection too.

How do you measure worn guides - ovality, or flaring ?
Or just clearance.

comnoz · Jul 27, 2015

Rohan said:
comnoz said:

Why is it that every Norton cylinder head I see with over 10,000 miles on the iron guides and OEM valves have very worn guides? - Not to say they wouldn't run that way for a lot longer if you don't mind the noise or performance loss. Jim

Click to expand...

So how is that that all these big mileage engines, apparently untouched, can still have their original guides. ?

Maybe some of the guides weren't so chilled ??!!

I must have a look at my spare 850 head, it has about 10,000 miles on it.
I seem to recall the guides still looked like new, but maybe I didn't measure them.
Might examine my dommie head collection too.

How do you measure worn guides - ovality, or flaring ?
Or just clearance.

All three, I use an electronic probe.

Or you can get an idea by moving the valve just off it's seat and wiggling it. If the valve head moves more than about 1/2 mm I would call it beyond specs. Of course I have seen them come to my shop with 3 mm wiggle and still running. The bad part when they get worn that much is they wear the seats off center. Jim

Rohan · Jul 27, 2015

So what does that make the clearance spec for a Commando valve/guide ?

Bronze guides can be fitted tighter than iron guides, right ? (as long as the bronze gets lubed).

comnoz · Jul 27, 2015

Rohan said:
So what does that make the clearance spec for a Commando valve/guide ?

Bronze guides can be fitted tighter than iron guides, right ? (as long as the bronze gets lubed).

With bronze I fit them as tight as .001 intake and .0015 exhaust. With iron you generally want at least .0025.

.005 clearance is shot - About .015 is about the worst I have seen still running.

Except for a single cylinder job I did a while back that was more like .080. The exhaust that was coming up around the guide overheated the spring to the point it collapsed. Jim

worntorn · Jul 27, 2015

This is the stuff that the UK suppliers such as Molanr Manx and others are using now. The valve guides in my project bike are also made of Colsibro. Valves are Tuftrided stainless. Supposedly a good combination.

Is Colsibro similar to Ampco45?

http://www.columbiametals.com/products/ ... mark-alloy

comnoz · Jul 27, 2015

[video]https://youtu.be/dKlpL1-p92M[/video]

comnoz · Jul 27, 2015

worntorn said:
This is the stuff that the UK suppliers such as Molanr Manx and others are using now. The valve guides in my project bike are also made of Colsibro. Valves are Tuftrided stainless. Supposedly a good combination.

Is Colsibro similar to Ampco45?

http://www.columbiametals.com/products/ ... mark-alloy

Colisbro is silicone bronze.
Ampco 45 is aluminum bronze and is tougher to machine but I can't say much about the durability as a valve guide as I haven't used it.

The tuftrided stainless valve is similar to the Nitroneg stainless that KPM uses. Jim

CanukNortonNut · Jul 27, 2015

Jim,
What would be the Mileage expectancy using Kibblewhite black diamonds and their valve guides over the stock iron guide/valves. Just curious.
Cheers
Thomas
CNN

comnoz · Jul 27, 2015

CanukNortonNut said:
Jim,
What would be the Mileage expectancy using Kibblewhite black diamonds and their valve guides over the stock iron guide/valves. Just curious.
Cheers
Thomas
CNN

I can only give you my experience.
At around 30,000 miles on my bike with KPM guides and Black Diamond valves the guide clearance was about .003 -.0035.
The longest I have run them was around 50,000 and both the valves and guides were pretty well shot. [but not as bad as the video above]

I generally check the guides and touch up the seats every 10 to 15 thousand miles. When I used iron guides they needed replaced at that mileage also -to keep things fresh. Jim

jug · Jul 28, 2015

Sorry guys, I meant Bronze not Brass.

JUG

Mr.Sparks · Jul 31, 2015

comnoz said:
Rohan said:

All the reports of Commandos with untouched motors with big mileages under their belt are with cast iron guides.

??

Click to expand...

There is no question. All untouched motors with high mileage have cast iron guides....

That was pretty good, you crack me up Jim.

Rohan · Jul 31, 2015

The problem here is that there are at least half a dozen Commandos we could name that have 100,000 + (or thereabouts) miles on their original motors.
How can that be, if the iron guides are 'worn out at 10,000 miles ??

Either the owners are telling porkies, or not all iron guides are created equal. (???).
Or or or, Smiths might have some explaining to do....

comnoz · Jul 31, 2015

Rohan said:
The problem here is that there are at least half a dozen Commandos we could name that have 100,000 + (or thereabouts) miles on their original motors.
How can that be, if the iron guides are 'worn out at 10,000 miles ??

Either the owners are telling porkies, or not all iron guides are created equal. (???).
Or or or, Smiths might have some explaining to do....

I would not say that a stock motor could not run 100,000 miles. I have not seen it personally.

I would say that if a stock motor had that kind of miles on it it would be a long ways past it's prime.
What about the plain piston rings. They are only really good for 30,000 miles with no "accidents". Not to say they couldn't "run" for more.

I would call a fresh set of rings and a valve job just normal maintenance -just like installing new spark plugs when they are due.

jug · Jul 31, 2015

Got a quote to replace the guides and seats, $Aus1500 :shock: . This cant be right.
If its going to cost me that to keep this 40+ year old head, I will go with a new unit from Ken at Fullauto.
Jug

comnoz · Jul 31, 2015

jug said:
Got a quote to replace the guides and seats, $Aus1500 :shock: . This cant be right.
If its going to cost me that to keep this 40+ year old head, I will go with a new unit from Ken at Fullauto.
Jug

Guides and seats. That price wouldn't surprise me.

Seats don't usually need replaced -unless someone has been at them with an automotive grinder. Maybe 5 out of a hundred of the heads I do need seats. A lot can be done with a proper set of cutters. Jim

Rohan · Jul 31, 2015

comnoz said:
I would not say that a stock motor could not run 100,000 miles. I have not seen it personally.
I would say that if a stock motor had that kind of miles on it it would be a long ways past it's prime.
What about the plain piston rings. They are only really good for 30,000 miles with no "accidents". Not to say they couldn't "run" for more.
I would call a fresh set of rings and a valve job just normal maintenance -just like installing new spark plugs when they are due.

The late Gerry Bristow RIP, of the old NOC-L chat group had a bought-from-new Mk3 that he and his wife had travelled all over Europe on in their retirement, and had 85,000 miles up last I heard, nothing other than routine maintenance. He claimed, and he did his own.
He was an oil exec with Duckhams from way back, and had always run it on the newest latest and greatest oils,
and had switched to Mobil F1 as soon as it became available too.

I was surprised, a project 850 I had needed a rebore with quite worn jugs with the speedo showing 12,000 miles.
No telling what it had been subjected to, or if the speedo was original.
The valve guides and valves did seem in very good shape I'd comment however.
No telling if they were original either of course, but the motor didn't show any signs of being touched.

highest-mileage-non-rebuilt-commando-t20851.html

Hobot · Jul 31, 2015

those that crave essentially daily Commando holidays should buy a spare head to switch out while the other is in slow fine grind restoration and home art till its turn again.

kerinorton · Jul 31, 2015

4.2 l Jag engines would never do more than 60,000 miles without rings and exhaust valves [ valve stem wear ]. And probably wouldn't do much more than that before cracking heads as well. But you know what the original Jag owners were like. Drive it till its stuffed and couldn't care less, until it came time to pay the bil,l then the shit would hit the fan..

Dereck

kerinorton · Jul 31, 2015

4.2 l Jag engines would never do more than 60,000 miles without rings and exhaust valves [ valve stem wear ]. And probably wouldn't do much more than that before cracking heads as well. But you know what the original Jag owners were like. Drive it till its stuffed and couldn't care less, until it came time to pay the bil,l then the shit would hit the fan..

Dereck

Rohan · Jul 31, 2015

hobot said:
those that crave essentially daily Commando holidays should buy a spare head to switch out while the other is in slow fine grind restoration and home art till its turn again.

I thought thats why we all have a spare bike.
Or 6...

Valve guides.

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