inlet valve seals

[DAVE BRADY]

Good afternoon,

As it is miserable outside I thought I would ask a question.
Does anyone fit the inlet valve seals on their late A65?  Mine have gone a bit hard and started to split so before getting new ones I thought that I would canvass opinion.

Dave.

[Allan G]

What do you need the opinion on Dave? I assume you mean where to get them from as regards a quality item?

I've only ever had valve stem seals on my 400/4. I have found however that with the A65 it's often the valves which are poor quality and wear quickly. That said I use where possible the plasma hardened GE valves as sold by SRM (I'll be using the black diamond valves in my A50 when I do it) using the GE valves I haven't yet had issues with valve guides leaking oil. I have also used K-liners in some heads which have been very successful.

Sorry it's not the answer which you hoped for, but has been my observation.

[DAVE BRADY]

Hi Allan,

On one of my A65s I have oil seals on the inlet valves.  The guides are designed for the seals to fit and I assumed that some of the later A65s had them fitted as standard but having looked into this a bit more this afternoon I suspect that it is a non-standard modification although SRM and Steadfast Motorcycles list them.

I suppose my question now is if anyone has such seals on their inlet valves and if they are actually worth fitting.

Dave.

[Allan G]

I've only seen SRM sell the guides machined to take seals. In 71 they changed from iron guides to bronze. The iron guides seem to last longer. Mark at PES makes calisbro guides for the unit singles - he might make some for the twins too. These are supposed to be very good.

The SRM valves are slightly larger on the OD than the originals, I've found a lot of pattern ones are narrower. Thus I often ream the guides out with an expandable reamer until the valve spins and drops nicely without any perceptible wobble.

So I don't think their use is particularly required. I know your bikes have covered many thousands of miles, so it's quite possible that you will have seen issues on yours before I will on mine.

Ps. Change of subject, but the 823 OIF thunderbolt is running really well and pulls like a train! It's a bit rich so I need to address that but apart from drinking fuel, it doesn't seem to bother it any.

[DAVE BRADY]

Hi Allan,

I noticed that pulling the trailer increased fuel consumption on my 750.  Oil consumption increased as well.  I suppose with the engine working that bit harder it is understandable but I also noticed that my air filter needs replacing.  As I have a Mikuni fitted I have to use a 3/4" pancake filter and it does not last as long as the standard ones before needing a clean and then replacement.  I also suspect that I am running the bike a bit on the rich side but before changing anything I will do a fuel check with a new filter fitted.
I think that the guides supplied by SRM are Calisbro.

Dave.

[EDDIE SIMPSON]

i think oil seals on valve guides are worth fitting if the engine burns a lot of oil like tridents do. but the bsa twins dont seem to suffer as much at the speeds i travel at anyway.

[DAVE BRADY]

Hi,

There are no seals on the exhaust but I also reckon the exhaust guides are a bit worn so new valves may be needed as well.

Dave.

[DAVE BRADY]

Hi,

I checked the wear as best I can and reckon there is about 5 thou side to side movement with the valve in the open position.
It looks like I will have get a 'K' liners fitted and probably new valves.
I had look on youtube and the process of fitting them looks quite straight forward but great care is needed so I thought, buy a kit and do it myself, but as it does involve some special tool a price tag of over £1000 makes it prohibitive.
So now I need a reliable engineer to do the work for me.

Dave.

[Allan G]

If done badly k-liners can fail and drop out and cause some damage. Lockside engineering in Castleford did mine after recommendation from Tim B' after they did his rocket3 and as you know that has done many miles.

[DAVE BRADY]

Hi,

It seems a bit odd replying to my own posts but here we go.

Reading a bit about 'K' liners and valve guide material there seems to be debate about colisbro vs silicon brass especially for road use.
Colisbro being able to have tighter tolerances especially with SS valves thus reducing oil consumption but not lasting as long as silicon brass.
I suppose another question is what are the 'K' liners made from?  Longer lasting than colisbro but maybe not as good as silicon brass?

Dave.

[EDDIE SIMPSON]

hi dave,
k liners sound very exotic but i dont think you can beat a set of iron guides and new valves for diy maintenance and economy.
personally i believe a multigrade oil will burn oil no matter what as its a thin oil with additives i am led to believe.
dont srm recommend straight oils now?

[DAVE BRADY]

Hi Eddie,

The 'K' liners have been around for quite a while and widely used in all kinds of engines from tractors and HGVs to tuned sports engines.  I think the main advantage of using them is that as the existing valve guide, that is concentric with the valve seat, is not disturbed and the liner is therefore concentric with the valve seat.  This means that minimal work is needed on the valve seat to get a good seal with the valve and so they last longer.
I think that another advantage of the liner could be that it is relatively cheap to have replaced and unless the valves need replacing they can probably be used for a prolonged period. 
As regards oil, SRM do seem to specify a straight grade oil for engines they have worked on and even for end feed conversions.
They sell a 20/50 oil and in the list of bikes are A10 and A65 which are also in the list for the mono grade oils, so a bit confusing.

Dave.

[Allan G]

without turning this into an oil thread.

All oils will have a certain amount of evaporational loss, "modern oils" so synthetic oils for example will generally and in theory have a lower % evaporational loss than a typical mineral oil.

for your reading pleasure:  https://www.astm.org/d5800-21.html

putting it simply - As oil is heated you get oil vapour, this will travel (usually out of the breather), if its passage remains of a certain temperature or above then it remains as vapour, but like steam, when it meets a cold front it turns back into vapour. We have all witnessed oil dripping from our engine breather at the end of the cam. If you find the tech sheet of your favourite oil you may find the % volatility of the oil (this is the expected loss as a percentage for the amount of oil you have put in the bike) this is under perfect conditions so.... note also that oil will degrade quicker with effect of blowby gasses from poor ring seating, an air cooled engine will run hotter than a water cooled engine an-on an-on. Either way your engine is going to deteriorate what ever oil your using much quicker than your car, or modern bike will do... A good sign of its deterioration is its colour, soon as it starts turning you want to look at changing it.

and yes Eddie is spot on, a 20w-50 is a 20w oil with viscosity modifiers to simulate a 50w oil when at a running temperature (for a car its about 90 degrees c, so higher for our bikes). The aim being as Ian C listed on another post is that the viscosity over the whole working temperature range remains at a near constant. Any monograde oil will reduce in viscosity as it gets warmer. So a sae40 will be much thicker at startup, it will be harder to pump and not flow as well to the big ends etc when cold when compared to a 20w-50, but when at working temperature the sae 40 will have a lower viscosity than the 20w-50.....

The only difference being that over time, the (PVL) permanant viscosity loss of a multigrade oil will be much higher than that of a monograde oil due to the sheer stresses as it passes past the journals. But now i digress.

Either way I would still change any mineral based oil at regular intervals and use colour and smell as a rough indicator.

[Mike Farmer]

 

Really only peripheral to this discussion. I was told many moons ago, that when reassembling heads, put a slight film of sealant around the valve guide under the lower washer. This will stop any seepage taking place at the valve guide/head casting joint. I've used it but of course its impossible to quantify its real use value. My thoughts are that I have nothing to lose by doing so.

As for valve guide liners of any type. To me that is preferable because it should retain the original spec more easily and it cannot place any stress on the " valve guide/head casting interface". It is usually cheaper and quicker. BUT use great discretion with open valves. In fact I know of a couple of engineers who will not fit them unless you sign a disclaimer and at least one who will simply not fit them to open valve engines.

As for the issue under discussion: no real idea and I've used or not used according to Head Type instructions.

These are simply my observations/thoughts and honestly not possible to prove either way

Mike

[DAVE BRADY]

Hi,

I went to the Cylinder Head Shop in the end.  A bit more local to me but almost on the edge of the world in North Somercotes almost on the Lincs. coast.
He has been around for a long time (although in different locations) and offers gas flowing as well Colsibro guides, Nucleus valves and 'K' liner fitting etc. He also had the inlet valve seals.
Now I just need some new springs and away we go.

Dave.