Top End Work

[cobbadiggabuddyblooo]

TRUE..I'll wear that one on the chin... should be more specific... if they checked the valve clearence or have found which cylinder is giving the problem...But just going with the information supplied... Obviously if you know which valve, which cylinder is playing up, switching the coils will eliminate this as it will still occur on the same side.
An additive in the fuel will decarbon the top end
Eliminate these two and find out from them if they checked the valve clearence or know which cylinder/valve is the problem on idle.

[foo]

So,
1) put in an additive like this one:
http://www.supercheapauto.com.au/online ... escription

2) swap coils to eliminate them as being the problem

3) do a compression test - I should have a gauge floating around in the garage somewhere..

If none of this works, pull the heads off and check valve clearances and have a look?
It's not the plugs coz the dyno guys replaced them to check.

Thanks for the help guys!!

[phuk72]

1) put in an additive like this one:
http://www.supercheapauto.com.au/online ... escription

I don't have any experience of these additives and am not convinced that they would remove a significant build up?

2) swap coils to eliminate them as being the problem

yep

3) do a compression test - I should have a gauge floating around in the garage somewhere

yep

If none of this works, pull the heads off and check valve clearances and have a look?

You're good at this game

[cobbadiggabuddyblooo]

First try your comp test to give you a reference point
Give the additive a go,with some it works to get a little down the air intake.. go for a good run to clean it out
if you know which cylinder is missfiring to start thats a bonus as it's easy to eliminate your coils when they are reversed
Still no improvement ,take off the cam cover and check clearence.. if you find all are within tollerence, try the search engine here to see what others have come across before you tear it down too far...
What about when you have the choke on or partly on, does this make any difference???
See if you can isolate the problem to before fuel gets to the cylinders of either air leaks or vaccum lines or carby problem.

[cobbadiggabuddyblooo]

here's a link to somewhere to give you a idea on prices... not just 50 pounds ... plus gaskets
it all starts to add up and then convert to Aust dollars at 65c to the pound.
Rough estimate 120pound for gaskets and seals
50 for a timing chain
25 for an inlet valve (exhaust are twice the price)
50 as stated but couldn't see them for rings

$400 plus postage then a little engineering costs, to give you a starting point on a price

http://www.kedo.com/?f_support=www.xt6.nl

[alextrx850]

Have YOU had any TOP-END-WORK....cobba ?

[cobbadiggabuddyblooo]

i got pills that deal with that

[foo]

timing chain??

[bagmaker]

I would be budgeting on a grand foo.
do it yourself, Empowering!

[cobbadiggabuddyblooo]

like I said just a reality check.. how many K's do you have up on the motor??? if your getting up over 70,000 while apart you may as well replace it if your goin to the trouble of doing all this work and rebuilding the top end. This is the reality to it... you can have a pig and spend 50 pounds and throw a set of rings in it and spend the same amount of money on all those gaskets or have something that you know should be good for atleast another 100,000k's plus..
It may be ok for some who have a complete workshop in there back yard but for some they don't have the option and you just don't throw a new set of rings in on the old bore. Why not while at it skim the head to make sure you have a good flat surface to work with, it's worth that extra couple of dollars if your going to go down this route.
I'm sure if you posted you rebuilt and you found a problem here ,you would have every man and his dog jumping ... so it's dammmed if you do,dammed if you don't or just take a chance and have a 50 pound pig....with new rings ...
So can you see where I'm coming from, I'm only making you aware of your options..
Do it all for that little more and you have peace of mind and you have that devil you know and know well ... if carbies are fine and bikeshop hopefully dealt with that, you will have a good motor.
The bikeshop would hit you big bucks as the parts prices here are a lot cheaper than from your retail m/cycle shop. Allow yourself a few hundred up your sleeve just incase for incidentals so if you want to do it yourself and have the tools and space and time go for it...
Post some pics and let us know how your going

[cobbadiggabuddyblooo]

http://www.oemmotorparts.com/oem5.asp?M=Yamaha&T=TRX 850&Y=1997&L=YA-TRX-850&O=CYLINDER HEAD&F=YA-TRX-850_aa&L2=YA-TRX-850_aa
here's a link that will give you a comparision on the OEM yamaha prices and these are in pounds also but you will notice a 25% difference alone in the head gasket so it pays to shop around and provide your own parts

[fung]

for my TDM900, i bought an OEM yamaha camchain, OEM yamaha tensioner and OEM yamaha gasket for $120 US from cyclepartswarehouse.com recently.
part number for the camchain is 94591-40138-00 for a 138 link chain.
the chain was $28.45 US.
same chain for TRX/TDM850 i think, but i haven't crosschecked the numbers yet.
cheers
fung

[cobbadiggabuddyblooo]

someone else went down this path getting all the parts for a tdm 850 to do a top end rebuild of late also from the states. What was the postage Fung... was that on top of the price also

[fung]

all inclusive.
surprisingly good mr yamaha makes many bikes with the same bits .
the tensioner is FJ12
just crossreference the part numbers and try to source photos to compare.
many part numbers carry hints to their character. for example that camchain is 138 link and tells us in its number 94591-40138-00, the two zeroes on the end denote first/original fitment and 10 means first supercede, 20 means second supercede etc.
a wonder, this world wide web thing is eh
cheerss
fung

[cal]

Hi Foo, before this goes much further, a quick question? do you have the space and most of the tools needed to do this job?
I havnt had my engine in bits (yet) but Im sure there are some on here who could inform you of the sort of tools you will need, when you start to factor in the cost of buying a load of tools it might put a different sway on the descition.

If you do have the tools and space then im sure the folks on here would help every step of the way if you feel a bit stuck, the folks on here probably know all that there is to know about the trx

You might even be able to get a fellow trxer to lend a hand, there are a few of you around melbourne arnt there.