Inlet valve seat damage
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Inlet valve seat damage
Thought it best to start this as a new thread even though it started elsewhere.
Microscope pics below of middle inlet valve from Sandune51's motor before rebuild.
Question was why do inlet valve clearances sometimes close up? Is it due to plastic deformation of the seat?
Lots of damage on seat area, nothing on the top collet end and a close up of the transition from the valve end and the stem. Not sure how these are made but I thought the stem was a different material grade to the business end?
Microscope pics below of middle inlet valve from Sandune51's motor before rebuild.
Question was why do inlet valve clearances sometimes close up? Is it due to plastic deformation of the seat?
Lots of damage on seat area, nothing on the top collet end and a close up of the transition from the valve end and the stem. Not sure how these are made but I thought the stem was a different material grade to the business end?
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Re: Inlet valve seat damage
Superb photos Phil , thanks for posting them.
What a clever piece of kit that camera must be.
I hope this puts to bed the myth once and for all that Trx and Tdm 850 inlet valves stretch.
The photos show really clearly that the valve seat area has become concave seating deeper into the head and slowly reducing valve clearances. I assume this was a material issue that was long ago rectified with the introduction of a revised valve part number suffix.
Mark.
What a clever piece of kit that camera must be.
I hope this puts to bed the myth once and for all that Trx and Tdm 850 inlet valves stretch.
The photos show really clearly that the valve seat area has become concave seating deeper into the head and slowly reducing valve clearances. I assume this was a material issue that was long ago rectified with the introduction of a revised valve part number suffix.
Mark.
- Rod.s
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Re: Inlet valve seat damage
Fantastic photo's
It's great to see this kind of detail. really does tell a story
It's great to see this kind of detail. really does tell a story
If it's not made in China, it's a fake!
- dandywarhol
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Re: Inlet valve seat damage
Thanks for sharing. That means my head is salvageable - just need to fit new valves, although I have a complete late TDM head to fit. Still not got any concrete proof that the TREX and TDM cams are different
Valves are normally 2 piece with the head "spun" onto the stem by friction welding
Valves are normally 2 piece with the head "spun" onto the stem by friction welding
1996 TRX 850, blue, Ohlins 46HRCLS, Race Tech Gold Valves, 0.90 springs, Venom pipes, R6 brakes............
1974 Yamaha RD250A, Candy Blue
1998 Yamaha SZR660, blue of course
1967 Yamaha TD1C 250, Blue and white
1974 Yamaha RD250A, Candy Blue
1998 Yamaha SZR660, blue of course
1967 Yamaha TD1C 250, Blue and white
- Con Rod
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Re: Inlet valve seat damage
this is very useful info, my 1996 valves clearances have closed up on the last 2 checks so new valves will be on the cards
Paul
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Re: Inlet valve seat damage
Will get some more images today of inlet valve seats from my spare head to see how they compare with Sandune51's.
Hope they are not shot because I was going to use the (already ported) head this winter.
Hope they are not shot because I was going to use the (already ported) head this winter.
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Re: Inlet valve seat damage
Don't worry the seats in the head are intensely hard, but have a lot of metal.
I've never seen an (cyl head) inlet seat that I would consider to be less than 90+% perfect. Exhaust seats have a tougher time but fare hardly any worse.
Mark.
I've never seen an (cyl head) inlet seat that I would consider to be less than 90+% perfect. Exhaust seats have a tougher time but fare hardly any worse.
Mark.
Last edited by sanddune51 on Sun Sep 15, 2013 3:52 pm, edited 1 time in total.
- Snod Blatter
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Re: Inlet valve seat damage
Well this is just brilliant
Awaiting pics of the seats in the head, hopefully they aren't affected by this and a straight swap of valves is all that's necessary..
Awaiting pics of the seats in the head, hopefully they aren't affected by this and a straight swap of valves is all that's necessary..
'95 4NX with K&N filter, Motad Venom cans, YSS PD valves, Ohlins fork springs, 530 C+S, Green CDI, 11/16 radial master cylinder, +30mm jack up dog bones. Enjoyable money pit.
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Re: Inlet valve seat damage
Just did mine and the valves were the same. Seats were fine though, so good news, you just need to swap out the valvesSnod Blatter wrote:Well this is just brilliant
Awaiting pics of the seats in the head, hopefully they aren't affected by this and a straight swap of valves is all that's necessary..
This is one of the new inlet valves for comparison
Paul
- Snod Blatter
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Re: Inlet valve seat damage
What mileage/kilometrage was that, Mr Rod? And what prompted you to do the work? Do the clearances start to close up more frequently?
'95 4NX with K&N filter, Motad Venom cans, YSS PD valves, Ohlins fork springs, 530 C+S, Green CDI, 11/16 radial master cylinder, +30mm jack up dog bones. Enjoyable money pit.
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Re: Inlet valve seat damage
I don't know for sure what the mileage is but best estimate is about 80,000miles.Snod Blatter wrote:What mileage/kilometrage was that, Mr Rod? And what prompted you to do the work? Do the clearances start to close up more frequently?
Yes valve clearances closed up on the inlets over 3 separate adjustments. I was using a 1.50mm shim on that and I believe the original shim would have been about 1.82mm.
I was also using oil, which also prompted the work
Paul
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Re: Inlet valve seat damage
my personal view is that it's valve head deformation. fortunately you are going to do something about it before it trashes the head.
Wonder if Yamaha did a recall for shit valves?
Wonder if Yamaha did a recall for shit valves?
- Con Rod
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Re: Inlet valve seat damage
They changed the part number on post 96 models. Didnt do a recallRich wrote:my personal view is that it's valve head deformation. fortunately you are going to do something about it before it trashes the head.
Wonder if Yamaha did a recall for shit valves?
It is indeed the valves that are the problem, no damage to the cylinder head at all. In fact, and this is bizarre, the shims required for the valve clearances when i put it back together were the 1.82 and 1.86mm shims that were in the bike from factory. Pretty impressive manufacturing tolerances from Yamaha
Paul
- dandywarhol
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Re: Inlet valve seat damage
Just to be pedantic, it's the valve face that is damaged/pocketed - the valve seat is in the head.
4 of my inlets had minus zero clearance at a genuine 9500 miles
4 of my inlets had minus zero clearance at a genuine 9500 miles
1996 TRX 850, blue, Ohlins 46HRCLS, Race Tech Gold Valves, 0.90 springs, Venom pipes, R6 brakes............
1974 Yamaha RD250A, Candy Blue
1998 Yamaha SZR660, blue of course
1967 Yamaha TD1C 250, Blue and white
1974 Yamaha RD250A, Candy Blue
1998 Yamaha SZR660, blue of course
1967 Yamaha TD1C 250, Blue and white