Changes through the years?

[dfh]

This valve `stretch` has been discussed many times over on this forum and I can assure you that vlaves DO NOT start out stretching as such.

They do... I have direct experience of this, I have the old inlet valves as a keepsake & I did a direct comparison between my new valves & the old. My stem seals stopped sealing from a combination of hardening up from age and the stems "waisting".

They in fact pocket themselves into the seats first thereby giving the same issues with lack of clearance and then accelerated burning of valve head seating face and valve seat surfaces.

This was not the case with my head, my valve seats were in surprisingly good condition & the wear on the seating surface of the valves was not enough to account for the fact that the inlets were a long way from establishing correct clearance with the thinnest shim available from Yamaha. I do agree that wear on the seating surface of the valve was a factor in the terminal wear my inlet valves suffered but it was not enough in its self. Weather it was solely stem stretch, valve seating surface wear or a combination of both the key point is that it was inlet valve wear, not valve seat recession that caused my problem. Replacing the valves with the later versions has solved my problem.

Can you turn up those valve part numbers, I can have a word with a Yamaha storeman I know very well to check out the authenticity of the need for part number changes in relation to the `toffey valve` claims?
Remember many manufacturers modify numbers as the range increases and some parts overlap models or are generic.

I can try, or maybe a PM to HansJ may be in order. One bit of interesting info that tends to refute the above point is that only the inlet valve numbers changed, not the exhausts.

Cheers DFH

[dfh]

Did early TDM`s suffer from the valve clearances closing up too A?

My understanding is that the TRX was fitted with an inlet cam that had the same lift as the TDM but with more aggressive ramps with stronger valve springs to suit. This was enough to cause the difficulties mentioned above in 95-96 TRX's but not 96 TDMs. The coincidence that TRX owners may well be a bit more aggressive in riding technique....

[Mincehead]

Have you mic`ed up those old and worn valves, would you be up to posting images of them with their current, worn dimensions quoted?
Valves of course are manufactured and engineered to thermally grow when the motor is running. That`s why there are clearances between buckets / followers and valve stems to start with, but the consensus of opinion is that stretch is a misused term and that they are in reality compromised by taking a thermal set / distortion more than they actually stretched beyond tolerances.
Surprisingly many of the new breed of short stroke four valve and relatively high revving dirt bike singles utilise titanium valves. I`ve not heard too much good spoken of them in that use either, they seem to distort much more easily than stainless valves, in fact a great many dirt bike owners replace them with stainless valves and never suffer from the same problem after.
I`ll give you an example of why I do not believe that valves stretch excessively, and that is if you`ve ever watched destructive testing of metals on hydraulic strain guage equipment you`ll see that ANY hardened steel or complex alloy, albeit very hard, is inherantly brittle and if you pull it beyond it`s tolerance it breaks / shears.
I`ve never heard of any member here loosing a valve head in their TRX, plenty of valves hitting pistons due to cam chain and / or tensioner failures though.
Another thing to consider when talking of valve distortion is that it CAN be accelerated by the fact that a valve and it`s assembled train of components actually spins a little each and every time it`s pushed open by the cam lobe. This is because of the fact that a lobe is slightly off centre to the bucket, and it has to be because if it was dead centre it would bind and something in the valve train would soon break.
So, we have valves that YES, do indeed `grow` as a new engine is first run but they settle to a tolerable limit in overall length. They don`t however settle in the way that distortion might affect them and as soon as the seating is compromised those combustion gasses play on their stems at a point where they are often undercut in diameter to improve gas flow. They then distort more and CAN after time, stretch at that waisted point too.
Of course usually all this that we are discussing affects the exhaust valves far more than the inlets simply because of the combustion cycle and the region where most heat is produced.
I`ve good friends who are seriously into their drag bikes, they run turbo`s, nitrous, methanol etc and they do indeed see valve stretch but it`s simply not seen in your everyday road prepared engine, the conditions to make it happen rarely exist unless fuelling is way out and very weak.
When my friends drag bikes close their valve clearances they don`t even bother with adjustment they replace them because the next stage in their behaviour will be to break!

[Rural Rat]

Surprisingly many of the new breed of short stroke four valve and relatively high revving dirt bike singles utilise titanium valves. I`ve not heard too much good spoken of them in that use either, they seem to distort much more easily than stainless valves, in fact a great many dirt bike owners replace them with stainless valves and never suffer from the same problem after.

Aint that the truth. I race dirtbikes too. I have seen a few riders driven out of the sport due to the cost of maintaining these small 4 strokes. Especially the early red ones

2 strokes only for me. I am an old bloke from the old school.

Sorry a bit off topic

[Mincehead]

Off topic? Don`t worry about that too much I`m the worlds worst for off topic posts!
In fact there`s another one right there.

[dfh]

Have you mic`ed up those old and worn valves, would you be up to posting images of them with their current, worn dimensions quoted?

Well you will have to cut me some slack here Mince 'cos I did the top end overhaul @ around 80,000 on the clock & it now has 123,000 on the clock. I do not have my measurement notes to hand & the new valves have spent 43,000 fitted in the bike.
Firstly I would like to point out that in my TRX's first 80,000 I had to re-shim the clearances four times, for an average of 20,000 between needing shims.In the subsequent 43,000 I have not needed to re-shim although I should open her up again soon & check. Same head, same exhaust valves, new 97-on inlets. FYI in this country the TRX was marketed initially as a direct Ducati 900ss competitor as there were 12month waiting lists for the 900ss & the 600 supersport market was minuscule at the time. One of the initial marketing ploys for the TRX was heavy promotion of a 42,000km inspection interval for the TRX unlike the onerous intervals for Ducati 2 valve donks. I believe this pitch at the time is the reason Yamaha Oz do not list the part number change but supply the new valves as a matter of course as to clearly indicate such a running change would be to throw their arms up & say whoops, with all the liability issues to follow. Me? I don't give a rats dingle, all engines need maintenance, such is life. Although my Suzuki GS500 commuter & ex track bike has only needed on shim in 100,000km
Secondly like your good self I find this stuff fascinating, so I did pull out the micrometer and compare the old & new. I did find measurable "waisting" of the original inlets. The cause is open to discussion, my conclusion is the stems elongated. As a professional photographer there is no way to accurately photograph the old & new valves to any technically valid standard, especially compressed enough for transmission on the inter-nerd. However as a photographer I have a supply of optical flats, pieces of glass produced accurately enough not to cause optical distortion when put in front of a lens. I did use these flats to compare the length of the old & new valves & yes there was a difference, measured by feeler gauge. Now this measured difference is between the bottom of the valve & the top of the stem so it is not influenced by valve face wear. I cannot remember the figure as the period between replacing the valves and now is measured in years so it needs an act of trust on your part if you accept my testimony or not.

Valves of course are manufactured and engineered to thermally grow when the motor is running. That`s why there are clearances between buckets / followers and valve stems to start with

The mechanical necessity for setting cold clearances to allow for differential thermal expansion rates in use is well known, and I familiar with the concept.

the consensus of opinion is that stretch is a misused term and that they are in reality compromised by taking a thermal set / distortion more than they actually stretched beyond tolerances.

The facts in my case are simple. I was on a week away with some mates. I live in a big country so this involved close to 6000km in 8 days. Towards the end of the trip the TRX became hard to start first thing in the morning, but started fine during the day. Suspecting the battery I replaced it. No change. Tested charging output, all was good. On the final day with 1500km to travel the bike was difficult to start hot. Bike ran well at speed but idled poorly. Once at home the bike would not start at all. So I opened it up. Most of the inlets had zero clearance. Checked compression. Not good. Did leak down tests. Still not good. Valves held off seats when cold but thermal expansion allowed sufficient compression when hot. Checked charts and Yamaha did not make shims thin enough to get within range. Once the new valves were fitted to the same head it could be shimmed with shims slap bang in the middle of the available range of shims. The head was fine, the valves had stretched beyond tolerances. Actually taking on board your good point in the previous post the combination of valve stem stretch and valve face wear resulted in valves worn beyond tolerances. "Consensus of opinion" matters little without references, I had the hard parts in my hands.

I`ll give you an example of why I do not believe that valves stretch excessively, and that is if you`ve ever watched destructive testing of metals on hydraulic strain guage equipment you`ll see that ANY hardened steel or complex alloy, albeit very hard, is inherantly brittle and if you pull it beyond it`s tolerance it breaks / shears.

There is a world of difference between single event distruction testing and the cumulative effects of multiple events well below peak tolerance.

I`ve never heard of any member here loosing a valve head in their TRX, plenty of valves hitting pistons due to cam chain and / or tensioner failures though.

I agree, but a red herring.

Another thing to consider when talking of valve distortion is that it CAN be accelerated by the fact that a valve and it`s assembled train of components actually spins a little each and every time it`s pushed open by the cam lobe. This is because of the fact that a lobe is slightly off centre to the bucket, and it has to be because if it was dead centre it would bind and something in the valve train would soon break.

Well across that fact, but this does bring us to one of the more interesting flaws of Yamaha 5 valve heads. Unlike 4 valve heads in which the inlet valves are parallel to each other the centre stem is not parallel to the two outer stems and the inlet cam "straddles" the difference between the two angles. I suspect the reputation for all Yamaha 5 valve engines be them singles, twins or IL4's to burn oil is caused by unusual side loadings on the valve stems giving the stem seals merry hell.

So, we have valves that YES, do indeed `grow` as a new engine is first run but they settle to a tolerable limit in overall length. They don`t however settle in the way that distortion might affect them and as soon as the seating is compromised those combustion gasses play on their stems at a point where they are often undercut in diameter to improve gas flow. They then distort more and CAN after time, stretch at that waisted point too.
Of course usually all this that we are discussing affects the exhaust valves far more than the inlets simply because of the combustion cycle and the region where most heat is produced.

Bingo, the fact that we are discussing INLET valves, that I needed to replace ALL my inlets but still use ALL my original exhaust valves, that there are new part numbers for the 97 on inlets but the exhaust valves have not changed points to a underspecification of the 95-96 inlet valves, however slight, that was rectified as a running change in production. That was the OP's question, changes through the years. I have direct experience of a running change and piped up with what I know. Thats all.

DFH

[Mincehead]

Ok, good reply.
But, we NEED some proof of these inlet valve part number changes so we can hang Yamaha out to dry on this and satisfy some of our hardened attitudes (mine actually ) as to whether valve`s were indeed stretching once and for all!
The Genesis theory was as much a bike `gadget` statement as it was about efficiencies, Quan-time has proved that on his homebrewed flow bench, search Quan`s threads, all very interesting reading.
Yamaha have dropped five valve heads in their motorcycles but were still sticking to their use in jet ski engines which are pretty powerful and efficient it must be said.
The New XTZ1200:

http://0.tqn.com/d/motorcycles/1/0/O/-/ ... inside.jpg

A four valver.
Actually I`ve just looked at the 2012 jet ski range and these too are now four valve heads, click on the brochure download:

http://www.yamaha-motor.eu/uk/products/ ... utput.aspx

[dfh]

Ok, good reply.
But, we NEED some proof of these inlet valve part number changes so we can hang Yamaha out to dry on this and satisfy some of our hardened attitudes (mine actually ) as to whether valve`s were indeed stretching once and for all!

HansJ was of invaluable help at the time I was doing my top end overhaul. Not only could he quote the part numbers but he knew which were the old & which were the new. It seems Yamaha Sweden were much more transparent than Yamaha Oz or UK. Is HansJ still active?

The Genesis theory was as much a bike `gadget` statement as it was about efficiencies, Quan-time has proved that on his homebrewed flow bench, search Quan`s threads, all very interesting reading.

I live in the same city as Quan & have found his work fascinating, but getting him out on a ride has been an insurmountable difficulty If Quan found that the 5 valve head was an efficiency liability rather than an advantage then I am not surprised. My work puts me in the world of advertising where a USP (unique selling point) is king.

[dandywarhol]

I'm enjoying this thread and noting some educated responses. Not sure about the 5 valve heads all with oil burning issues - the Tdm900 with ceramic bores and much tighter piston/cylinder clearances simply don't use oil anywhere as much as the 850 engines.

I believe the oil burning issue to also be caused by first owners being too gentle with running in the engine - and probably more oil burning with the TDM as a result, although I don't doubt your experiences with hardened valve stem seals. I would expect most stem seals to show signs of being brittle at 80,000 km though.

[Rural Rat]

Image0662.jpg

This is the bike this thread relates too. I have owned this one for 6 years now. Had 10000kms on it when I bought it. Just over 85000km now. Cosmetically it is near excellent and of course it looks a lot better without the luggage . I have just had it in the workshop for an engine assessment. My mechanic informed me it is still mighty fine so cam chain, valve clearances and a good tune were all that was done. All coolant hoses were also replaced. Next step is the rear disc/pad replacement. Then all the consumables, chain/sprockets front brake pads and wheel bearings. Final step will be a full suspension overhaul. Trying to use OEM stuff as much as possible. I do still have the original pipes to go with it.

Not sure what it is with these machines. This is my second one. I had one of the first black ones in Adelaide in 1996 and in a moment of stupidity I sold it with about 60000kms on it. My other big roadbike is an '09 Triumph Speed Triple, more power, far better brakes and suspension BUT the TRiXie gives me more satisfaction to ride. As I try to explain to my riding mates I consider I pilot the Triumph but I ride my TRiXie.

[Mincehead]

It`s the way a TRX allows all kinds of riding styles some real `leeway`, you can make silly mistakes, push them too hard, run out of brakes, flip them over really quickly, change your line mid corner, and where another bike would become very unsettled and give you a sphincter twitching episode the TRX takes it in it`s stride, forgives you and clatters on regardless.
Then, when you really get to know her well and find her erogenous zones, you get the ride of your life!
I`ll NEVER sell mine but then I do fall madly in love with any motorcyle I own in general.