Big Inlet and Exhaust Valves (+1mm)

[sanddune51]

After a long an fruitless search for bigger valves for my TRX project I'm on the brink of commissioning a set of +1mm Inlet and Exhaust valves. I'm happy to go ahead and commission one set for myself but if I make it 10 sets the cost comes down to under £200 sterling including VAT@20% (If you're outside the UK,Value Added Tax is a 20% puchase tax that goes to the government) per set of 10 valves.This is roughly two thirds of the cost of new standard valves from Yamaha.

If there are another 9 enthusiasts that are interested,the prospect big valve Trx's and Tdm's terrorising the countryside becomes an affordable proposition.

I have selected +1mm as good compromise between cost,performance gains and reliability (which I'm not prepared to sacrifice). Any bigger increase in size would (I believe) encroach into the hoop stress and subsequent reliability of the valve seat inserts and would require the fitment of larger diameter seat inserts(prohibitively expensive).Plus 1mm will give worthwhile improvements to:

larger valve area (7.9% inlet and 7.1% exh)
larger throat area (7.6% inlet and 7.2% exh)

After porting my spare head to accept these valves,it's also apparent that the port short side radius can be improved with a much more progressive radius which will improve flow at low lift.Also the throat blend into the bowl can be greatly improved when using bigger valves. Further, a better valve diameter to port diameter ratio is established when larger valves are fitted.
These potential improvements would be worthwhile on any 850,but an engine that already benefits from big bore pistons/raised compression/ FCR's/alternative cams and or freer flowing can and headers is just crying out for bigger valves. As you'll have gathered, I can't wait to get them made and fitted to my Trx.

The company I will be using is long established,is British,and is an approved supplier to Cosworth. The valve material is Austenitic and is classified under En 10090 as 1.4882. If you happen to a metallurgist you'll be pleased to know the composition is X53CrMnNbN21-9.

I will let the Tdm forum know as well in case anyone there is interested in a set. If we surpass 20 sets the price will drop by another 10%.(economies of scale and all that stuff )

Let me know if you're interested,but do appreciate I'm not a business man, nor am I looking to get rich quick by undertaking this. I will have have to front up with just shy of £2000 if I commission 10 sets to be manufactured. Nearer the time of order I will regretably have to ask for a modest down payment of say £25 per set. I hope everyone who wants a set will consider that fair.

Well that's about it I guess. Let me know if you want a set.

If you'd like to "talk" to me, pm me and I'll phone you or give you my landline number.


Mark

[Mincehead]

Mark, is this the company I already know about?

[sanddune51]

Mince,

Good to hear from you. Funny how our overiding love of our bikes is able to distract us from our troubles and lift our spirits when they are low.

Yes, after a lot of research I think the supplier is the best in the country and supplies many manufacturers.You already have prior experience of their products,so your endorsement would be welcome.

Just think how a set of these will look and perform when they are eased into your head casting
Seriously though they are top quality precision manufactured one piece Austenitic stainless steel forgings and they work out much more cost effective than std Yamaha valves.

Could we be up to 3 sets already? I hope so
If I ordered tomorrow the lead time on their manufacture would take us to mid January 2013.

Forgot to mention that shipping Down Under or anywhere else (including Edinburgh ) is not a problem and won't be ruinously expensive.

Mark

[Mincehead]

Hahahaha, yes Mark the love of all things bikes does tend to `overwrite` a lot of other things that life brings when you really don`t need it!
So, as you say I`m already familier with the company and products, was it the one I had put you onto some time back perchance?
I`m not sure if you know but I have a brand new head, still in it`s original box and packaging that I am planning on having `worked` by my pal and engine tuner, so YES some bigger valves will fill out the necessary holes nicely.
Let me know an `up front` cost that`ll help support your outlay in this Mark, I`m not a rich man but can always find money for bike projects.

Geoff.

[sanddune51]

Hi Geoff,

I certainly did know about your new "bare" head. I remember you mentioning it some time ago.
Reckon it it'll be about ripe for for some decent valves by now

Anyway have pm'd you.


Mark.

[bubbaad]

How much power do you expect to gain by doing this and how much should I expect to pay to have them fitted ??? How will it affect power delivery ??? I'm running FCR41's and a large bore exhaust system. Cheers.

[Mincehead]

You could `expect` another 10 bhp plus if you had the head worked to suit them, more torque and better midrange too as long as the porting wasn`t too extreme.

[Mincehead]

C`mon folks, roll up, roll up, this is an absolute BARGAIN, price those `stock` Yamaha valves and you`ll see it`s a no brainer!

[SDN]

Who would you go to for porting and valve seat cutting? - I am assuming that you can just cut bigger valve seats for the new valves?

What sort of money for a decent porting job? Also would it be worth a head skim? I have a spare cylinder head sitting in my garage - ho hum

[Killerwhale]

Who would you go to for porting and valve seat cutting? - I am assuming that you can just cut bigger valve seats for the new valves?

What sort of money for a decent porting job? Also would it be worth a head skim? I have a spare cylinder head sitting in my garage - ho hum

I´m just now checkin with my tuner....he done it all...will report a yay or nay!

[Kenny]

I will take a set please.

[Mincehead]

Well done lads, Mark has taken it upon himself to sort all this out we should all be supportive of him and his venture into organising this as he`s done all the hard work.
I`ll take some credit for finding the company initionally through an engine builder friend but Mark`s the star here.

[Mincehead]

Who would you go to for porting and valve seat cutting? - I am assuming that you can just cut bigger valve seats for the new valves?

What sort of money for a decent porting job? Also would it be worth a head skim? I have a spare cylinder head sitting in my garage - ho hum

Yes the seats require recutting, the porting can follow any individual tuners idea if you like but I`m certain Mark has already got profiles in mind.
Head skim? Yes of course if you`re using stock Yamaha pistons.

[sanddune51]

Who would you go to for porting and valve seat cutting? - I am assuming that you can just cut bigger valve seats for the new valves?

What sort of money for a decent porting job? Also would it be worth a head skim? I have a spare cylinder head sitting in my garage - ho hum

Any decent engine shop will be able to cut the seats and machine the throats. I did my own throats, taking my time, they came out perfectly.

I ordered some 5.5mm Silver Steel via the internet. I then calculated the throat diameters that I required;
86.5% of inlet valve dia. = 27mm x 0.865 =23.35mm
85.5% of exhaust valve dia = 29mm x 0.855 =24.79mm

Using a lathe,I machined up a steel plug to throat diameter (less 0.1mm) to act as a "Go Guage". I driilled it whilst in the lathe and reamed the hole 5.5mm for my Silver steel "dummy" valve stem.I also machined a shallow taper approx.3mm by 5 degrees.
The silver steel was fitted and loctited. A few minutes later I was able to polish the silver steel down to stem size with fine emery.
I now had perfectly concentric taper plug guage to insert into the throat. Obviously I made one of each size for inlet and exhaust.
I opened the throats carefully with a Dremmel working in a rotary motion.When I felt I was very close to size I used coarse valve lapping paste to run the plug through the valve seat by hand until the parallel portion entered. Once I had made the plugs, it really was a very simple (although slow) job to end up with 10 valve seat inside diameters matched to my as yet unseen new valves.
I finally blended the throats to the valve "pocket" or "bowl" using my Dremmel and an old Black and Decker drill.

The valve seats are "stellite" or something very similar which old valve seat cutters just skid off. I will entrust the valve seats to a local motor engineers and then hand blend the 30degree cut into something approaching a radius into the bowl.

Head skimming is very worthwhile to raise the compression. The concensus here seems to be that 0.5mm is very safe. I will do the measurements and calculations and see if I can't up mine a little more.

Sorry there are no photos,but I'm bloody useless with computers, and haven't mastered the knack of posting photos here.

If anybody interested in the bigger valves wants to see photos,I will happily email them. That is something I have mastered.

Hope that helps a little

Mark.

[Mincehead]

Nice one Mark, great description of work done so far.