Valve Guides

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May 12, 2005
Hi Guys
1970 commando.

I occasionally have oil blowing out the exhaust port past the clamp, the plugs are also a bit oily, this points to rings or guides, the rings are easy to check and replace, but is there anyway of checking the guides to see if they are worn. or do you just replace them.

Also do need any special tools to the guides in and out, or can you just use basic equipment eg a big hammer.

All you need is a big hammer, a proper drift and - the most important part - heat. I don't know the temperature off the top of my head, but I'll look it up when I get home and revert accordingly.

Heat head up in oven to 150 - 170 degrees centigrade, allow at least half hour for whole head to heat up

same heat to fit new guides, proper tool can be bought for £15 - 20

oversise guikes can be bought if holes are worn, but these should be reamed parallel as they will wear oval

valve seats will probably need to be recut as well as lapping in to get proper seating

hope that lot doesnt frighten you off, its not too hard really!!!!
Valve to valve guide

Hi Ron,
Valve to valve guide clearence can be checked a couple different ways. Using a micrometer measure the diameter of the valve stem in three or four spots to check for wear. then you insert a ball gauge into the guide, set it, withdraw and measure it with the mic, compare your readings to those from the valve stem. As a rule 0.002inch is about as much clearence as one would want to see.
A second way is to position a dial indicator against the edge of a partially open valvehead. push the valve back and forth and watch the dial, once again 0.002inch is about maximum that you would want to see.
However, if you are going to go through the trouble of pulling the head and if there's any question the guides and valves are relatively cheap. If you've got the head off might as well make sure everything is correct.

justa thought,
You also could have oil passing between the guide and the head, something else to check for.

I have not installed guides by the head heating process since my machinest turned me on to the liners. He installs bronz or steel liners in my old guides.Works great and have not had a single problem. Used them on Commandos, Tridents, BSAs and Guzzis. Caution must find someone who is skilled at installing them!!!!!
Do yourself a big favour and take the head to a shop that does this work. If you have to ask how to do this job then it is definately not for you. As far as hammers go. They might be the tool of choice on a Texas oil rig but not on a Norton head.
Like Geo46er said while you've got the head off might as well do the guides and valves. All of the parts are relatively inexpensive and readily available. Getting a machinist to do the job is another good point, mine charged $80 to R&R the guides and I consider that money well spent. BTW even if the guides aren't worn you may want to replace the cast iron ones with the Ampco or Colisbro bronze ones for better heat transfer.

Boy howdy there Ron!

You forgot to say BIG Texas hammer.

Actually, hammering out valve guides with a proper drift and with the head at optimum temperature (200C but no hotter) is a viable and appropriate procedure. In fact, a hammer can also be used to install the new valve guides, again with a proper drift and with the head thoroughly heated to 200C.

I quote the Norton Villiers Commando Workshop M...rdner; it’s just that easy. Jason [url]

Do you mean iron guides? I dropped an Ampco45 Kibblewhite guide on my shop floor (gotta stop fondling and drooling over new parts) and it cracked like glass.

Seems like a hydraulic press might be more suitable for brittle bronze alloy guides.

Just curious,
After making a mess of a guide with the famous drift and BIG Texas style hammer, I built a puller from sockets, a rounded off nut washers and a threaded rod and pulled mine out....used same puller to insert new ones. Everyone is right about a HOT head though....if it's too cool and the guides are not frozen in a baggie in the freezer....forget it. Seats had to be re-cut too.

Inserts for the guides sounds it might be a winner. Give us more information!!!!

Point doesn't sound like the original problem from ron53 has much to do with guides...if the guides were that bad...there'd be a cloud behind the bike....sounds like a blown head gasket or his valve cover is leaking and running down around the pipe. If a guide is so bad...wouldn't, due to the pressure, the oil/pressure, be blown into the upper part of the head, rather than getting sucked towards the exhaust? Intakes will suck oil...but exhaust shouldn't....

PS The source of an oil leak can be hard to find....oil everywhere...but from which gasket? trace an oil leak to it's source....clean the it for a few miles...spray the suspected area with spray foot powder from the bathroom and the oil and it's route will appear as a dark can trace it to the source then. Clean oil is rather hard to see...the spray helps make it visible...wash off the motor and then repair the gasket. Smile

I’ve used the Texas hammer on cast iron as well as bronze guides. The bronze guides should not be brittle; I’m very surprised that yours broke; there's something fishy about that.

The problem with a hydraulic press is alignment. It’s too difficult to get the ram, valve guide and support base all directly in line. If not perfectly aligned, side loading and scuffing will occur, which will damage the cylinder head.

You have to work fast as the head is cooling and contracting rapidly. There’s no setup time with a Texas hammer and a few quick, precise blows will drift those guides right out before you mama can say homemade ice cream.
Before you whack away at the guides, make sure to glass bead the part of the guides that extend into the ports to remove the fused debris on the end of the guide. If you whack it out with that stuff on the end, you will remove a lot of the alloy in the head and need bigger guides.
When reinstalling, freeze the guide and heat the head to boiling water temp (approx.) I also freeze the drift and tap them in reasonably briskly. The tapping allows the guide to self align, which might not happen if pressed.
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