Cylinder head rebuild UK

I've had ongoing issues with a valve seal coming off on the RH inlet side of the head.

I just replaced it again (4th time) and it looks like it has slipped off again within a few miles.

I'm thinking of removing the head & getting a complete head overhaul done. I might get the Cosworth seals for the guides.

Can anybody recommend somebody in the UK, I've dealt with Les in Norvil but only for parts. I've also dealt with SRM in Wales but they tend to specialise in BSA's.

I think Comnoz is at the top of my list, anybody of similar caliber in the UK?


Thanks

Kevin

I just did my own guides with the tools purchased from RGM. It was a pretty simple exercise. I also ordered a Neway valve seat cutter off of ebay. All in with tools and parts I am cheaper than having somone do it for me. And I am setup fot the next time. Mikesxs.com also sells an affordable valve seat cutter set. Just an option for you.

It's easy to do yourself but otherwise Mick Hemmings or RGM as they are honest..

bwolfie said:

I just did my own guides with the tools purchased from RGM. It was a pretty simple exercise. I also ordered a Neway valve seat cutter off of ebay. All in with tools and parts I am cheaper than having somone do it for me. And I am setup fot the next time. Mikesxs.com also sells an affordable valve seat cutter set. Just an option for you.

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Hmmmm an excuse to buy more tools :mrgreen:

I'll look into this option, thanks for the suggestion.


Kevin

FastFred said:

It's easy to do yourself but otherwise Mick Hemmings or RGM as they are honest..

Click to expand...

Thanks for the suggestions.


Kevin

FastFred said:

It's easy to do yourself but otherwise Mick Hemmings or RGM as they are honest..

Click to expand...

+1
SRM are also well qualified; I guess it's a case of who can offer the best turnaround.

With a small investment in tooling (less than the labour cost, I would think) and access to an oven it's a straightforward enough job, and opens up a whole new world from basic spanner-twirling.

Hi Lads,

Has anybody any pics of standard guides for a 75 850 MK3?

I'm trying to figure out if my inlet guides have the grove for the seal and it would help if I had a picture so I know what I'm looking for! I'm trying to do this with the head still on the bike so it's tight in there!


Kevin

Machine the guide and fit ford cosworth, they have steel bands,and dont come off.

john robert bould said:

Machine the guide and fit ford cosworth, they have steel bands,and dont come off.

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This is on the list of 'things to do'

For the moment I'm just trying to figure out why the std seals keep popping off. The last one I put on 2 days ago and it lasted about 2 miles!

If the guides I have don't have the grove for the seal it might explain why they keep coming off? Hence the request for pictures.

I'm going to run the bike today on the bench with the inlet valve cover off to see how much oil is accumulating in the rocker chamber. I know the drain hole is not great at removing oil and if its even slightly obstructed oil will accumulate in the rocker chamber.

I've also checked the rocker spindle & it has the hole pointing to the back, away from the rocker/engine.

I've been avoiding removing the head so I can still use the bike, if I decide to remove the head I'll get it overhauled or maybe try it myself but I'm still deciding on this one!

Kevin

Do you have a part number and supplier for those Cosworth inlet guide seals?

Thanks

Anybody have any experience of these guys for general head work?

www.blrengineering.co.uk

I have one that needs work, but needs dissasembly and vapour blasting to assess the potential, so since its within a hour of my home I was going to take it to them at least for the cleaning.....and suggestions...

SteveA said:

Do you have a part number and supplier for those Cosworth inlet guide seals?

Thanks

Click to expand...

+1 :mrgreen:

SteveA said:

Anybody have any experience of these guys for general head work?

http://www.blrengineering.co.uk

I have one that needs work, but needs dissasembly and vapour blasting to assess the potential, so since its within a hour of my home I was going to take it to them at least for the cleaning.....and suggestions...

Click to expand...

I have these on my list, a forum member mentioned them, I sent an email with a list of specific Norton question I'm awaiting their reply.

From the VERY little I understand, general cylinder head work can be done by any cylinder head shop but motorbike heads, in particular, Norton cylinder heads need an experienced Norton hand to fettle correctly.

Again from the VERY little I know I'm sure I can 'bash' out guides & pop in new ones BUT I'm aware of many subtleties in doing this job which I know I don't have the experience to understand let alone practically apply.

OK, I started the bike and had it running on the bench for 5 mins. For the first 2-3 mins no smoke, then small puffs of smoke when revving the bike 1K to 2K.

I had the petrol tank loose & whipped it off when I stopped & had a good look in the rocker chamber and there was only a few mm of oil in the bottom, not overfilling! I'm sure if I went for a spin revving up to 3-5K there would be more oil but the test was to see if the oil drain hole was allowing oil to pool in the rocker chamber & I don't think that is the case.

I'm using Ludwig's method again to remove the spring & I'll have a really good look for a grove in the guide.

One thing of note, the original seal I removed had a spring on the rubber part which is around the valve stem. I'm sure the other side is the same & there is no problem from this side . . . . . yet

My little brain tells me this spring would grip the stem & there would be more of a chance of the seal popping off but another part of my little brain says there must be some reason/logic for having such a spring, anybody want to help my little brain!!

Kevin

Kevin - if the seal keeps coming off the top of the guide it may be that a previous owner has made up a non-standard guide, possibly one with an oversize OD because the standard guide was loose in the head and maybe did not machine a grove for the seal to locate.

If you decide to farm it out to Mick Hemmings, then your worries should be over, and it is simply the amount of money you will shell out for the job.

It is something that you can do yourself, admittedly a bit nerve-racking the first time you do it but if you take your time, not too difficult. You mention bashing out the guides. You would use a mandrel which is a two diameter shaft, one of which is the same OD as the valve stem but with a larger diameter that goes against the tip of the guide and tap it with a hammer. It should come out without difficulty once heated to 200-250 deg C in an oven. You will know if a guide is loose in the head because there will be little or no resistance. If that is the case, then you will need to measure the hole in the cyl head and get an oversize guide to match. Not sure if same are supplied off the shelf, but a guide is simple for an engineering firm to make.

You would not bash the guides into the head. Norton supplied a tool to draw the guides into the head, which is the right way to do it. I duplicated this tool, and the guides went in without difficulty - but - the seats will always need to be re-cut afterwards. There are several competent engineering shops in Dublin that I employ to cut or grind seats. My experience was that the guides did not need reaming after fitting and that was with the RGM cyl head overhaul kit. Again, those shops will ream or hone the ID of the guide to a good fit if necessary.

PM me if you decide to do the job yourself. You can borrow the guide insertion tool and I can give you the contacts for the engineering shops.

Dave

click said:

One thing of note, the original seal I removed had a spring on the rubber part which is around the valve stem.

My little brain tells me this spring would grip the stem & there would be more of a chance of the seal popping off but another part of my little brain says there must be some reason/logic for having such a spring, anybody want to help my little brain!!

Click to expand...

The modern replacement seals do not appear to have the garter spring. I queried this with Phil Bargh of L P Williams some time ago, after noticing a set of Trident valve seals I ordered from him didn't have the springs. He said they were the same seal as the Commando and, quoting from his e-mail: "...are correct without the spring."

Hi Dave,

It's difficult to see the guide with the head still on but I think I can feel a grove at the base of the guide with a fine screwdriver.

The seal I took out was completely split down the side, this is either from me incorrectly fitting or faulty seals (this is the 2nd one to do this)

I really appreciate the offer of the valve insertion tool. I used the word 'bash' in a lighthearted way berating my lack of skill, I'm aware of the finesse and technique involved in replacing valve guides, I'm just unsure if I have the ability to do this type of job to a high standard. If I decide to do the work myself I'll give you a buzz and get the details of the contacts you have.

I've replaced the seal again and will bolt everything back together later today & test tomorrow but I'm not holding my breath :roll:

More Anon

Kevin

L.A.B. said:

click said:

One thing of note, the original seal I removed had a spring on the rubber part which is around the valve stem.

My little brain tells me this spring would grip the stem & there would be more of a chance of the seal popping off but another part of my little brain says there must be some reason/logic for having such a spring, anybody want to help my little brain!!

Click to expand...

The modern replacement seals do not appear to have the garter spring. I queried this with Phil Bargh of L P Williams some time ago, after noticing a set of Trident valve seals I ordered from him didn't have the springs. He said they were the same seal as the Commando and, quoting from his e-mail: "...are correct without the spring."

Click to expand...

Hi L.A.B.,

Thanks for the info. All I'm doing at the moment is pushing the seal onto the top of the guide, this is a bit tricky as it's very tight for space. Once it's on I run my finger as best I can around the seal to see if its damaged/split. It's nearly impossible to see if the base of the seal has engaged with the slot. I tend to just work the base of the seal with my finger to ensure it's engaged.

When compressing the springs with the Ludwig tool I'm aware the spring can be slightly off center (due to my poor tool making ability!) My theory is that the smaller middle spring could contact the seal & cause damage? Not sure just a theory.

As I said above I've replaced the seal yet again, fingers crossed this one works!!

Kevin

Here is a pic of my guides i just replaced

dougmatson said:

Here is a pic of my guides i just replaced

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That's fantastic, thanks a bunch.

My inlets look the same as yours. So to summerise:

1. I have standard guides with the grove

2. I'm fitting new std seals from RGM

3. My seals keep splitting or just popping off

Possible problems:

1. Installation error. I might not be seating the seal properly and/or the inner spring might be catching the seal and causing damage (not sure if the spring thing is even possible?)

2. The guide is worn allowing the valve to 'wobble' and dislodging the seal. (I don't think this is the problem based on my vast experience of assessing worn Commando guides :roll: )

3. A lad on this forum had an issue with the valve stem having some text stamped on it causing it to snag the seal, I don't see/feel anything on the stem

4. My RH inlet exhaust is possessed by a leprechauns who keep pulling the seal off :roll:

I'm leaning towards 1 above. I just can't figure out what I'm missing in terms of technique? You pop the seal on, ensure its sitting OK and put everything back together. As I said the only other thing I can think of is the inner spring catching the seal.

I've installed a new seal & put the springs back on. I might just strip it again & have a look, if the seal is split then its my technique!