Yamaha TRX850 Enthusiasts Forum

I should really have undertaken this job before I started to modify my head.

I think the photos will be useful to anyone fitting the +1mm bigger valves and or gasflowing their head. It should give a lot of reassurance to those people concerned about the lack of material around the valve seats.

The head is a bog standard Trx/Tdm 850 head. I acquired it (cheaply) after every single valve had been bent. I had to punch out every valve with a big hammer. One valve was so bent,it even dragged out it's valve guide complete with circlip!

Both sectioning cuts were made as close as I could reasonably get them,through the centreline of the port right down through the middle of the valve guide.

I was very impressed by the quality of the casting. Both the finish,and especially the control over the positioning of the port with regard to the water jacket and oil gallery.

Inlet Port: The smallest wall thickness is 3.8mm,19mm upstream of the valve guide in the port roof adjacent to the water jacket. The port floor adjacent to the water jacket is 4.55mm thick.

Exhaust Port: The port wall is consistent between 4.55mm and 4.9mm thick.

Number 2 cylinder, right hand side inlet port


and the other half of the same port.


Again number 2 cylinder, this time the right hand side exhaust port


and the other half of the same port,also showing the previously sectioned inlet port



Mark.

That is great stuff!

Thanks Mark

Having seen this head when we met up at Tagg racing I was going to ask you for pics ready for my own head work later this year.

Valve seats are pretty substantial on Japanese heads. Yonks ago a mates Kawasaki Z1 motor dropped a valve seat while still running when we were down at the Bol 'D'Or in S of France. A local machine shop made a seat from scratch and knurled the outside edge to help it fit in the head better as the head was slightly damaged with the seat rattling about - great job and got us home, including a few hard revving laps of Paul Ricard circuit. That was 30 years ago but they only charged £20 for the job.

Wow how good is that.. Reminds me of the 4 Autopsy programs on TV where they dissect real human bodies to teach you on the workings of the human body.

dandywarhol wrote:Valve seats are pretty substantial on Japanese heads. Yonks ago a mates Kawasaki Z1 motor dropped a valve seat while still running when we were down at the Bol 'D'Or in S of France. A local machine shop made a seat from scratch and knurled the outside edge to help it fit in the head better as the head was slightly damaged with the seat rattling about - great job and got us home, including a few hard revving laps of Paul Ricard circuit. That was 30 years ago but they only charged £20 for the job.

20 quid!!! A damn fair price considering the work that was involved.

T'was a bargain Mince. We pulled the head off in a mountain village square in south France and took it down to Toulon on the back of my CX500, came back next day with the job done. Got a head gasket at a local Kawa agent and slapped it together again. The motor was squeezed into a Harris chassis so it was a bit fiddly in the street. The owner of the restaurant/B&B we were staying at wouldn't let us use his garage for shade but loaned us his socket set. To compensate for Jean Pierre's lack of garage use my mate shagged his delightful daughter in the old man's room while he was serving the rest of us in the restaurant It was all go at the Bol in '82..........................

When I say £20 - it was £20 plus a case of beers cos we thought it was too cheap

PS - sorry to get off track sanddune

Cheeky use of the daughter but hey these things happen.

Mincehead wrote:Cheeky use of the daughter but hey these things happen.

All legal and above board................. (apart from daddy not knowing)

Great shots. Any problems with copying these photo's to give to head porter?

Don`t see that there is, they`re posted here for forum members interest and use.

any pics of the daughters ports?

Stankflapper wrote:any pics of the daughters ports?

+1

Mincehead wrote:Don`t see that there is, they`re posted here for forum members interest and use.

Thanks Mince, I sectioned the head for the sake of my own curiosity and knowledge advancement.
I took the photos to post up here and on the Carpe Tdm forum to help others understand the ports and wall thickness if they were considering reworking their own cylinder head.
No one need ask permission to reproduce my photos,they are in the public domain.Feel free to use them.
John,Brian and Phil,thanks for asking anyway . I hope the shots I took help a little with your upcoming head work.

Mark.

Sanddune, would you fill the potential eddy point just before the inlet valve guide?