Yamaha TRX850 Enthusiasts Forum

Hi guys, right at the wrong time, the bike has developed a problem, right as its for sale.

Today i took it for its mot which all went well after a bit of head bearing adjustment and an advisory on the 'zorsts but on the way back i noticed oil on the left hand cases. i traced the oil up and found its coming from what seems to be the left hand side carb from an overflow tube (the tube that mounts at a right angle to the carb near the diaphragm on the outside).

After deciding the bike was okay like this (and it was possibly down to being slightly overfilled with oil) i rode home - but as the bike began to get nice and hot the bike also began to start bogging down at low revs and feeling quite lumpy throughout the rev range up to about 5k revs where it was still apparant but less so.

I have recently had the carbs out and played with the mixture screws because my fueling was appaling and it seems i have resolved that to some degree at 2.5 turns out (as standard) but im wondering if:

a) its burning oil (but theres no smoke)
b) its overfueling

Furthermore, my fuel tap on the tank leaks when the bike is in any position, could it be that i need a repair kit and this could be part of my problem?

I appreciate any help guys as the bikes for sale and otherwise its perfect now, its such a shame!

Thom

I reckon what you are seeing is oil mist residue from the airbox, you overfilled the motor with oil you say? The cam cover breather goes into the airfilter box to reburn any residues.
There is an oil drain on the left of the stock airbox, I reckon that`s where your oil leak is starting out from.
But..................
The rough running?
Typical emulsion tube and needle wear symptoms.

hi mate, thanks for the info, the oil deffo appears to be coming from the carb tube as its wet inside where as the airbox is dry.

and the needles in the carbs have no wear (to the eye), these are the emulsion tubes, yes?

The tubes wear oval at the worst symptoms! There were some pics on the site somewhere of a badly worn tube.

Dave E

ah cheers mate, ive got two sets of carbs so ill strip both tomorrow and rebuild to one good set, both sets had pros/cons but hopefully i can form one goodun - i'll also take a bit of oil outta the bike just to ensure thats eliminated.

cheers

Thom

I'd keep it if I were you, you will only be disappointed with the next bike unless your going to take it on track, and even then.......................!

Dave E

im doubting my decision to sell it now to be honest, but its going to take a lot of money for me to be perfectly happy with it... its my dream bike, but its not a dream to ride for me!

So alter everything then! I have rear sets, which are comfortable, but I have my bars at the top of the forks due to a back problem. Seats are recovered as well! You can tailor it to your needs!

Dave E

i think FCR's would do a world of good but unfortunately im a student with little cash!

Depends what you want it to do? Yes they add horsepower, but so do aftermarket cans! and in the real world, the standard carbs are fine, by the sounds of it you need the riding experience first before you start on the standing quarter times. Bring it along to the Waterman1 lol.

Dave E

The emulsion tubes were infact worn, slightly oval.

Ive replaced with a very good condition set from a set of carbs i had lying around and the bike seems to be well now, although i havent been able to ride it yet due to weather!

Hi Thom, Just reading through the thread, You mentioned that the fuel tap leaked, and also there was a bit too much oil in the engine and the bike was running rough

You changed the carbs over and now seems ok, and you might have overfilled it a bit

The fuel tap problem might be somthing to do with overfill of oil, petrol leakdown into crankcase.
I think the diaphrams in a part of the carbs have to be away for this to happen, but could explain the "rough running, overfill of oil, dodgy fuel tap"

Tbh I have not stripped out the carbs ever on my bike but from reading the threads all of your symptoms seem to be connected by this diaphram fault.

Might be worth having a check on the oil levels and giving it a sniff, the oil level would go up slowly when the bike is left standing due to the petrol leaking int the crankcase, as I understand it, if this problem is there.

It shouldn't be that hard to check for all this.....much easier than trying to sell a bike with a f**ked enginge for good money!!!

There are prev threads on this problem which will explain more.

If the fuel pump diaphragm is split / holed, leaking fuel enters via the vacuum hose on the left inlet stub, directly into the inlet tract.
Of course in a motor with some wear this WILL seep past the valve and seat interface down into the bore, contaminating the engine oil.
When you first start up that `washed` bore could grab up too!

Im pleased to announce that my problems seem to have gone away, and there is certainly no contamination of my oil - i did drain a wee bit of oil from the engine after running to check but all seems very well there. now i just need a proper test ride!

Okay the test ride went brilliantly today and the bike is running absolutly perfectly however ive discovered a problem which has re-reared its head.

When i bought the bike it was leaking fuel from its float bowls even through the screw and thread were clean and tight, i couldnt understand how this was even possible but it did and it still does - through both carbs.

Could it be my float level is too high and so is overflowing through the brass pipe in the float bowl (the pipe which is permanently fixed to the inside of the float bowl?

The bike appears to only do it when on the sidestand, and doesnt do it when running as far as i can tell - but i may be wrong.

And for anyone concerned im a dodgy bike seller - the bike is due to be removed from sale because having been testing the bike i cant sell it with problems and im concerned it wouldnt be 100% in time for a sale.

I'm buying a fuel tap repair kit because obviously the tap is leaking fuel all the time (not much but a bit and enough) but i think i may also need to reset the float height. Why are TRX's such a ahndful? ive never had a project so complex!