Machining out Valve Guides

Shelby-Right · May 29, 2023

When I did my apprenticeship, we were shown to put a wisker of copper coat in guide bore , none fell out .

elefantrider · May 30, 2023

I know one builder who uses Hylomar Advanced. And Comnoz in his video said he uses a Teflon-based product.

Stephen Hill · May 30, 2023

it seems like using some kind of lubricant is a good idea if you are trying to reduce galling in the aluminum guide bores when installing the guides.

I was surprised how much force was needed, even after the guides were placed in the freezer, and the head was heated to 400 degrees. I thought they were going to drop in place with little to no force. Wasn't the case at all.

dobba99 · May 30, 2023

Stephen Hill said:
it seems like using some kind of lubricant is a good idea if you are trying to reduce galling in the aluminum guide bores when installing the guides.

I was surprised how much force was needed, even after the guides were placed in the freezer, and the head was heated to 400 degrees. I thought they were going to drop in place with little to no force. Wasn't the case at all.

What did the interference fit measure up to? and what did you use to measure the bore and guide?

Shelby-Right · May 30, 2023

Also we always used to press them in with a type of old hand press type thing it had a large old rack and pinion , if you hammer them in they can sort of crumble a bit at the top edge where the valve comes out , and if they have a step or circlip groove the top half can fall off , mainly with cast iron guides .

Stephen Hill · May 30, 2023

Not knowing what I needed, I purchased standard guides and .002 over.
When I got the old guides out, they measured .002 over.
Because the bores looked great, and the old guides were a very secure install, I just used the new .002 overs.
Probably the interfernce fit on the first .002s was excessive. But you can't go back.

baz · May 30, 2023

Stephen Hill said:
Not knowing what I needed, I purchased standard guides and .002 over.
When I got the old guides out, they measured .002 over.
Because the bores looked great, and the old guides were a very secure install, I just used the new .002 overs.
Probably the interfernce fit on the first .002s was excessive. But you can't go back.

Always measure new valve guide diameter
I once fitted some that turned out to be tapered
They were wider at the bottom than the top
They appeared to go in tight but smoked excessively
I took the guides back to the shop and they let me go through a whole box of guides until I found a set of 4 that were perfectly parallel, checked with my micrometer

dobba99 · May 30, 2023

baz said:
Always measure new valve guide diameter
I once fitted some that turned out to be tapered
They were wider at the bottom than the top
They appeared to go in tight but smoked excessively
I took the guides back to the shop and they let me go through a whole box of guides until I found a set of 4 that were perfectly parallel, checked with my micrometer

Talking to Steve Maney a few years ago about valve guides. He said that he ended up making his own as the ones available at the time weren't consistent in dimensions and not concentric with the guides bore.

baz · May 30, 2023

dobba99 said:
Talking to Steve Maney a few years ago about valve guides. He said that he ended up making his own as the ones available at the time weren't consistent in dimensions and not concentric with the guides bore.

Concurs with the problem I had
The guides were in and tight at the bottom only
The bike was smoking like a pig
As soon as I changed to perfectly parallel the smoke stopped

Stephen Hill · May 30, 2023

I did the measure the guides and they were to spec. Kibblewhites. I didn't meaure the bore because of how the old ones came out and what it looked like (perfect).

I wonder if when shops find a loose standard guide if they ream the bore before going up .002 in size.
Not a lot of material to play with. I am guessing they dope the guide and reach for the big hammer.

acadian · May 31, 2023

The bores must be reamed to parallel and concentric to the seat, any competent shop should do this

kommando · May 31, 2023

Stephen Hill said:
I wonder if when shops find a loose standard guide if they ream the bore before going up .002 in size.
Not a lot of material to play with. I am guessing they dope the guide and reach for the big hammer.

Walk away if you know of a shop that does that, more likely the DPO diy approach would be this and not a shop.

Stephen Hill · Jun 1, 2023

I take the point that the bore should be reamed before going up in guide size.

My point was that if the guide was loose and you need to go up in size, you aren't going up in increments of .002. I doubt there is enough spare material to deal with setup error and machine a correct oversize .002 bore.
Or maybe I just don't have the right skills or machinery.

Shelby-Right · Jun 2, 2023

Stephen Hill said:
I did the measure the guides and they were to spec. Kibblewhites. I didn't meaure the bore because of how the old ones came out and what it looked like (perfect).

I wonder if when shops find a loose standard guide if they ream the bore before going up .002 in size.
Not a lot of material to play with. I am guessing they dope the guide and reach for the big hammer.

Don't forget , even an oversize valve guide can be put on a mandrel and machined to the required size for correct interference , you'd be better off if the slightly loose guide bore being + .001 (theoretical) than ream it out bore , and just machine guide to suit, unless guide bore is really galled up .

ashman · Jun 2, 2023

What's wrong with using the proper guide removing tool to remove the guides and to install the new guides, freeze the new guides heat up the head before removing the old guides and when they ready to put the new ones in heat up the head and pull the new guide out of the freezer worked great when I replaced mine 30+ years ago, they went in easy and once cooled down were nice and tight, seems a lot of work machining them out.
Just my opinion, I done this with a few Norton heads in the past 40+ years and I have only had the removal/install tool for about 12 years now.

Ashley

Larry S · Jun 2, 2023

ashman said:
What's wrong with using the proper guide removing tool to remove the guides and to install the new guides, freeze the new guides heat up the head before removing the old guides and when they ready to put the new ones in heat up the head and pull the new guide out of the freezer worked great when I replaced mine 30+ years ago, they went in easy and once cooled down were nice and tight, seems a lot of work machining them out.
Just my opinion, I done this with a few Norton heads in the past 40+ years and I have only had the removal/install tool for about 12 years now.

Ashley

I did the same thing on the head I’m riding with now. The only thing I didn’t do was to ream the guides after install. Took it to a local machine shop and they reamed to fit my valves. 30.00 was all it cost. I’ve ran probably 2k mi. so far and all is good.

kommando · Jun 3, 2023

Nothing wrong with using the proper tool but preparation is vital or any spec of dirt/carbon is going to be dragged through the guide bore and create a small oil groove. Boring out the guide so it thin enough to collapse is safer.

Stephen Hill · Jun 3, 2023

Not to mention that Ashley has owned his stuff so long that he knows all the history.
The rest of us are working on bikes there were put together by unknown and often dubious characters. So we need to proceed like a bomb squad dismanting an improvised explosive device.

ashman · Jun 3, 2023

Stephen Hill said:
Not to mention that Ashley has owned his stuff so long that he knows all the history.
The rest of us are working on bikes there were put together by unknown and often dubious characters. So we need to proceed like a bomb squad dismanting an improvised explosive device.

Mind you I have done a few rebuilds on mate's Nortons and have come across a lot of butchery jobs done by ex owners and what better way to get to know your own bike by doing as much work as you can and fixing the butchery that has been done to doing it right, when I brought my Norton new at 17 years old I didn't have a clue at all in working on my bike and when I did the conversion to the Featherbed frame in the early 80s was the first bike I ever built and that was long before the internet, yes there are things that you can't do but doing most of the work yourself is a great way to learn and know your own bike, also helps if something does go wrong while out and about and only 3 times my Norton didn't make it home (one blown EI 100 miles from home, one broken chain from doing a burn out in my younger days, and about 10 years ago a rear chain throwing it joining link) not bad for 47 years ownership.
But its so rewarding doing the things yourself and if you do run into problems think about it first but there is always some on hand to help with forums like this great place.

Ashley

Machining out Valve Guides

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