Wee warning

[DrFarkoff]

If you have purchased "Standard" valve guides from Motorworks recently please check them for clearance on the valve shaft before you fit them

I have just sorted a set out for going back as they weren't made right unfortunately I had the heads these new ones pressed in Before I found out the problem and I'm not prepared to feck about trying to sort it in case they are also out of true!

So hopefully if anybody has bought some you'll catch it on at a stage before I did!

One of the lads went down and checked the batch and said about 50% weren't right and they had a set going out first class tomorrow as I'd missed the post today

 

[Sylvester]

Bollox, do you have any further info on valve guide batch? I fitted mine last year. Clearance on the valve seemed ok and the head held white spirit overnight after the valves were lapped in. I'm about to ride back to UK next week for a 7 day tour and this was not something I want to think about!!!!

 

[DrFarkoff]

I think this is just a recent thing

Believe me you would know if there was a problem

You can only insert the standard valve a cm or so before they get tight REAL tight and I was going down the track of reaming etc but fear that Since the machining is obviously off there is maybe misalignment off the perpendicular to the seat thereby meaning seat recutting etc and I'm not prepared to waste any more time than necessary now

 

[(RIP) Arkwright]

The valve guides should always be reamed after fitting as they often shrink when fitted. The machining should be straight whatever, it's just the tolerance of the hole!

 

[Sylvester]

It was major service time this week end. All oils and filters plus tappets. Overhauled the heads about 2k ago and they seem to be bedding in well. Its nice to not see all the oil burn stains on the top of the heads after changing the valves and guides. Gear box still makes a noise like a helicopter until you pull the clutch in. My old R80 made the same noise and was on 150k last I heard. I'm looking to get an exchange box in the near future with the longer 5th gear.

 

[cookie]

Valve guides should always be reamed to size and seats cut if new guides fitted.
It's standard practice.

 

[John Roberts]

Valve guides should always be reamed to size and seats cut if new guides fitted.
It's standard practice.

That's what I thought too. However, I called MotorWorks yesterday and Darren said that he had replaced his guides three times on his Airhead which had done 170,000 miles (IIRC) and all he did was to lap the valves in. He pointed out that it was the wear in the guides that allowed the valve to strike one side of the seat at the instant of closing that produced a bending /tipping of the valve head that did the damage and ultimately broke the head off the valve.

So, what should it be? Ream and seat cutting, or just lapping?

 

[(RIP) Arkwright]

That's what I thought too. However, I called MotorWorks yesterday and Darren said that he had replaced his guides three times on his Airhead which had done 170,000 miles (IIRC) and all he did was to lap the valves in. He pointed out that it was the wear in the guides that allowed the valve to strike one side of the seat at the instant of closing that produced a bending /tipping of the valve head that did the damage and ultimately broke the head off the valve.

So, what should it be? Ream and seat cutting, or just lapping?

I think the answer John is all three! (DAMHIK)

 

[DrFarkoff]

I order standard guides and standard valves, I (now) test fit the valve for clearance

I then heat the bayjaysus outta the head okay Gas mark 8 for Arf an Hour and the guides come out with very little pressure

The new guides are in the freezer (with their depth rings fitted) I drop them in and only a light pressure with a small hammer and drift is required to set them to depth (and decent flexible welding gloves)

I then try the valve and if the clearance is neat but not tight and the valves glide in and out i.e. as it should be! I lap the valves in!

I've done quite a few standard engines this way and have had good results this is the first one that has given me this much grief

If the head compresses the guide (during fitting or after cooling) then you will find the valve fit to be too tight and it won;t "Glide" thru the guide so then you will need to ream or clear it

At the end of the day it's a 50 plus year engine design when tolerances was tolerances not X microns required

.

 

[(RIP) pastyman]

This is why I like the K-line system. Leave the old guide in, drilled and phoshor bronze liner inserted, reamed by blowing a suitable ball through it. lazer cut seat and hey presto, no lapping, perfect fit and tolerences. Mind you I am lucky, contact/friend does it here cheaply and quickly.