Yamaha TRX850 Enthusiasts Forum

Tealman wrote: Who's Pieter - is there a company name to make him easier to find?

Yes: http://www.hps-motoren.nl/

I've seen from an old thread that forum member sanddune51 was selling oversized valves so I've PM'd him to see whether he has any left.

I don’t think Mark (Sanddune51) has anything left. But I always assumed that Pieter (HPS) got the valves from Mark (Sanddune51). But then again, assumption is the mother of all....

I've no doubt that I'll be changing the head and valves at some point but, for the time being, inlet cam journals have been cleaned up. The cams have been fitted and the chain went on and lined up perfectly with the various reference points. Noted that the exhaust cam is 'off valve' when in the correct position, whereas the inlet is 'on valve' so took a little effort to line up. 5 of the inlet valves have been re-shimmed on the basis that the valve gaps were at zero, whereas there may have been positive pressure on the buckets. Tomorrow I'll re-fit the cam chain tensioner, rotate the motor a few times and check the clearances. I may get lucky and find that all are correct, but I'd be happy with clearances I can at least measure, even though the cam will need to come out again.

Have checked the gaps and, as suspected, further adjustment is needed. I've got my eye on a 'good' 1991 TDM 850 head - did that also suffer from 'soft' valves?

The valves were revised in 1997, I wouldn't use anything earlier than that. If you find yourself looking at a '97 head and wondering if it's okay or not it is usually quite clear when the valves have "sunk" into the seat, you can barely see where the valve ends and the seat begins. The later good heads all have much more prominent valves.

You never hear much about the Mk1, I dunno if perhaps they were okay because the cams were milder?

Any good? I've asked for clear pictures of the cam journals.

https://www.ebay.co.uk/itm/Yamaha-TDM-8 ... 1438.l2649

Same issues with the valves on the 750,850 up till 97

From recollection I paid about AU$25 for each of the inlet valves, granted there are 6 of them but not prohibitively expensive

Finally managed to get out for a short spin today on a very naked looking TRX - happy to report that it's running well and seems a little more punchy than it was prior to valve adjustment. Plan is to put some miles on it now and then take another look at the journals/gaps in the autumn. I am on the lookout for another 'good' head so if anyone has one they're looking to sell please let me know.