Yamaha TRX850 Enthusiasts Forum

I decided to the the valve clearance on my new (to me) TRX.

When I pulled the inlet cam to swap out shims, I noticed the journal on #1 pot has some scoring on it. From what I've read in here it's a relatively common problem, so a bit of wet'n'dry to smooth it out and all good.

Or so i thought.

Putting the inlet cam back in, it freezes solid as soon as I put any tension on the cam caps - even finger tight the cam won't spin.

I've torqued up the cam cap on the timing gear end and the cam spins (stiffly, but it spins).

Loosen that one off, and torque up the cap on #1 pot and she freezes solid.

Is it possible I've bent the camshaft somehow???

Dodgy way but has worked in the past...Put a little wet n dry on a broom handle and tighten down the cam cap then rotate the broom handle for an even scrub.
Doubt very much you've bent the camshaft ( is your name Cameron??) unless your playing cricket with it, and why the sandpaper...

Roger that, thanks, will get cracking with the wet 'n' dry

Hate to ask the bleedin' obvious, but you sure you got the right caps back in the right places? I assume they're line bored in place?

I had the same, check here:
http://www.trx850.com/phpBB_forum/viewt ... 45#p101647

I'll try to fix the pictures.
Edit: done.

Yup - same here too. I didn't think of the broom handle method - I just used a steel rule as a scraper [1], using the adjacent seat as a guide to keep things nice and straight and parallel.

Was very careful torquing down the cap bolts. I can't remember the figure now, but it's surprisingly low. I think what had happened previously is that one of the owners didn't have the figures to hand, and just tightened it down 'til it felt about right.

Really should pull the cam cover off again, to check the head bolts and cam cap bolts. It's been a couple of thousand Ks since the rebuild.

[1] Yes yes, I know - I can hear you all cringing from here.

10Nm.
But it's more important to feel if the cam moves freely after tightening all bolts.

Good approach, but I want to avoid pulling the head.

So far I've concentrated on the caps, as I figure they're probably more likely to be distorted than the head.

That, and they're easier to work on

Maybe I should hit the journals a bit more too.

Oil starvation is the issue on start up and probably more prevalent if the bike has been sitting for some time. You need to do both, the head and the cap to keep some kind of symmetry. Whip the head off do it on a bench , and 2 choices with the head gasket.
Replace with a new one or clean up the old head gasket, spray it with a sealant and re use. Technically there is no reason why you can't reuse a MLS gasket.
Another lad local here even went to the extreme of separating the 3 sheet MLS headgasket and removed the thicker inner spacer. Cleaned and coated 1 of the thin 0.2mm outer sheets and Vroom... Upped his compression in the process. 4 yrs later it's still running to this day.

Make sure you have the cam in the correct position, with the least pressure on the valves, it will make all the difference.
Checkout the Haynes manual available on the forum.

Well, I did the sandpaper thing and reassembled it.

The inlet cam is still stiffer than I'd like, but I didnt want to go too far with the dodgy repair,

The bike starts OK, I might just let it idle for 15-20 mins and see if it siezes.

My example also came from a running bike. Surprisingly, I had to do a lot of sanding so everything moved smoothly.
At the start the cam wouldn't even turn without the caps on it!
I didn't like the sanding at all, but realised the cams just have to move smoothly, so I kept going.

Before you go and do this, bolt the head to the cylinder and cases then check for true, on some engines the head can warp slightly due to overheating (in a past life/ownership) this will cause the cam issue, once the head has been released from the cylinders it will spring slightly. So torque the head down (with gasket) then fit the cams etc and check...

Well I want to avoid pulling the head for now, coz if i do then i may as well do the rings, and the cam chain, etc etc etc,

I guess I could pick up a second hand head and keep in on hand in case the current one turns to custard.



However, I have a new problem,

This stupid coolant pipe that comes out of the head into the thermostat housing - it keeps leaking.

I've cleaned up the mating surface, i've replaced the o-ring, hell I've even put in TWO fkn o-rings, but still it leaks.


Is there a trick with this?


Edit - THREE o-rings seems to have sorted it out. WTF?

I do have a spare cylinder head going - for a small consideration if you're interested