Yamaha TRX850 Enthusiasts Forum

Well, i dont know how, but dang, i demolished the bike pretty badly, both exaust valves were snapped, and one of them welded onto the head. *Jake pats him self on the back "Good work JAKE"*. Anyway, Someone has to rebuild the head now, anyone got any good sites or tips on doing this, and what needs to be done, or do i consult the haynes manual ?

Cheers

I guess your valve timing was off, or your cam chain jumped. Possibly your inlet cam siezed.

Have you checked the timing gear on the crank? Do that before you go any further.

As long as the head isn't bent you can replace the valves easily enough, but it's possible there is damage to the crank which will be less fixable.

Eeeh - what a mess

Haynes manual or download the manual from this site is a good starting point

Just re-cut the valve seats... you'll be fine, you'll be fine ...

Yikes

What a bummer. Hope you didn't do any damage to yourself when this happened. Good luck with your investigations. Hope it's fixable!

Yeah its a bummer, i think the head is ok, What happend is i started the bike, ran for about 30 seconds, and as i was putting my riding gear on it just died. and thats it, no noise nothing, so im hoping its all ok, i was gonna ask, is it easier for me to give the head to someone to just do it for me, or do it my self ? its a bit of a project bike, so id like to do it myself.

diy - only way to go.

sounds like lack of lubrication or overtightened cam caps to me. check that crank!

You have more fun triple checking everything yourself, Oh and then you check it again. But the feeling of pride when you fire it up is great, And you know you've saved a heap of cash compared to letting some 16 year old grease monkey do it, probably enough for those FCR's.

Dave E

Bad luck mate. I'd offer to help if you lived in the UK....

Thanx for the offer of help honkdawillydahonk, and yes i think i will do it my self, some of the guys that do these jobs do it very poorly, so ill give it a go, what kind of tools would i need ? and i think ill change all the valves and springs yay or ney ?

1: strip the head right back.
2: get it refaced (its probably warped due to the force of the piston / valves)
3: get ALL your valve guides redone (buy new ones, press em in)
4: buy new valves (get a full set, no harm done)
5: get your valve seats redone by a pro. He can possibly redo all the valves and springs, but will obviously cost a fair bit.

I live in adelaide, so i cant really help either. I have no problem helping if i can. I have a valve spring compressor and a little magnetic stick i can send to you, and you can send back if you want to do it yourself.

I can machine the head for you and also press in the new valve guides. You can supply or i can buy them and give you a receipt.

I can do the valve seats, but i can say they are best done on the appropriate machine. I can still do them if its only a simple replace job, but if they need machining, i wont do it, as i dont have a multi angle seat cutter. But replacing is fine.

Im only offering to assist you, not do the whole thing.

As previously said, you would be wise to change your cam chain and inspect your drive gear on the crank. It could be damaged. If its fine (take a pic and show us) then id say just get a new chain and go from there.

Hope this helps and i can be of some service.

Has anyone noticed the difference inside the headers?

yer, but please note thats a by product of an engine going pop.

You have a fair bit of black on the other cylinder, fair bit of built up ceramic (most ppl call it carbon or something similar) on the valves.

Good time for a clean up then.

Nice job!

Haven't seen something like that since my 1953 Morris Minor popped the crown off a piston..... (won't go into it here..)

As well as what's been advised, check the bore for any scoring. The R/H bore looks OK in the photo's but the one with the damage is close to top stroke - be interesting to see what lurks beneath....

sherlock wrote:Has anyone noticed the difference inside the headers?

Do you mean that the pistons are called "4NX" and some valves "3LD" and other valves have nothing on them?