US Sourced TDM 850 Valves and Camchain in TRX Head??

[MotoBloke]

G'day,
I just read this whole thread. I'm actually a 1998 TDM850 owner and have been reading and contributing to the sister site Carpe TDM (the Yam TDM forum) for over three years.
I always understood that the TRX motor differs from the Mk 2 TDM 850 only in actual cam timing (cam lobe shape, so the cams are different), carb specs and engine electronics. The Mk 1 engine is the '3VD' that so many parts of other later models carry over from. Also, the TRX has different crankshaft timing compared to the 3VD series or Mk1 TDM. It went from the first TDMs (and XTZ) 270 degree crank to the 360 degree crank - adopted by the Mk2 TDMs as well - producing that V-twin fruitiness to compete, it is often suggested, with the Ducati V-twin sound.
Do you think the Yamaha check digits in their part numbers are just to reassure the dealer of the number of revisions corresponds with the number of models the bike has evolved through?

[rob dog]

Yep, those check digits 00,01,02 etc are the revision numbers. You will see in most parts catalogs an 02 revision number for the intake valves as the 00's and 01's were soft as shit and stretch quickly (found that out when the bike wouldn't start one cold morning).

Exchange rate is still good so ends up being about half price for us here in OZ

[fung]

I I R C
MK1 was 360 crank.
MK2 was 270.
TRX is 270 as is the TDM900.
cheers
fung

[Mincehead]

G'day,
I just read this whole thread. I'm actually a 1998 TDM850 owner and have been reading and contributing to the sister site Carpe TDM (the Yam TDM forum) for over three years.
I always understood that the TRX motor differs from the Mk 2 TDM 850 only in actual cam timing (cam lobe shape, so the cams are different), carb specs and engine electronics. The Mk 1 engine is the '3VD' that so many parts of other later models carry over from. Also, the TRX has different crankshaft timing compared to the 3VD series or Mk1 TDM. It went from the first TDMs (and XTZ) 270 degree crank to the 360 degree crank - adopted by the Mk2 TDMs as well - producing that V-twin fruitiness to compete, it is often suggested, with the Ducati V-twin sound.
Do you think the Yamaha check digits in their part numbers are just to reassure the dealer of the number of revisions corresponds with the number of models the bike has evolved through?

As fung has pointed out it`s the other way around, the Mk1 TDM`s had a 360 degree crank (both pistons rise and fall together but only one fires), the later Mk2 onwards to the latest 900 and even the XTZ1200 all share a 270 degree crank along with the TRX.
The Mk1 TDM`s had a very punchy bottom end power delivery because of the 360 degree crank.
As far as I`m aware the valves for ALL the 850`s irrespective of crank / firing configuration are the same. As for the valve `stretching` issue there`s plenty of technical discussion here on the forum regarding that too, the term used being somewhat anbiguous in all honesty, folk actually imagine valves elongating along the stem without any other effects happening beforehand and this is not the case.
Anyway I digress, ALWAYS check with Yamaha for the latest part number revisions, then go buy spares much cheaper elsewhere.

[dandywarhol]

I think motobloke got his arse and elbow mixed up and meant the 360 was the mk1 and XTZ750 setup. As everybody agrees, the later TDM, TRX and XTZ12 are all 270 (crossplane ) cranks and cams

Does anybody actually have the valve timing differences between the TDM and TRX - I always thought the cams were the same.

[Mincehead]

Some great reading here, Ron Valentine `through` Dave Nourish was doing 90 / 270 degree / cross plane, whatever you want to call it long before Yamaha:

http://www.dotheton.com/forum/index.php?topic=26347.0

A comparison animation for those who struggle with the information in the above link:

http://www.dinamoto.it/dinamoto/8_on-li ... /twin.html

[dandywarhol]

I'd forgotten about Nourish's motors - I very nearly bought one tocontest the British Twin Cylinder sidecar racing in 1980, having campaigned a Rickman Triumph engine with an 8 valve head the previous year. I went down to the Nourish factory to see their engineering shops - the only part which they didn't make in house were the Triumph cam followers - Triumph could make them cheaper!

In the end I got hold of a Kawasaki 984cc drag engined outfit which was ok for a 1/4 mile blast than allowed to cool down - but didn't like circuit work - this little blow up caused the late Jim Silvers some grief as he was launched through the air sideways on my oil slick at EF in 1980................... Sorry - lets get back on track.........................850 valves.......

[Mincehead]

Was Kenny Andrews about on that day A? I know, I know, still off topic.

[dandywarhol]

Yep, he was Scottish Champ that year.

[Mincehead]

I`ll ask him for an `on the day report`.

[dandywarhol]

We'll continue this by PM - get this thread back on track.

Can anyone confirm the valve timing for the TRX - I've got the official Yamaha TDM 850 figures figures................

IO - 29
IC - 59
EO - 59
EC - 29

For anyone interested, the 900 timing is 30, 50, 50, 30 which means although the comp. ratio is 0.1 lower on the 900, the inlet valve closes earlier so actual compression starts earlier.