Yamaha TRX850 Enthusiasts Forum

My TRX has been a fairly consistent 1l/1,000 m oil drinker since running in. I'm getting the distinct impression that this has dramatically increased in the last 500 miles (it's now at 23,500). As in at least doubled. There is _no_ smoke warm or cold, and there is no leakage with the engine off - i.e. no puddles or drips. So clearly it's burning it. No change in engine behaviour or reduction in performance. It sounds a bit tappety warm or cold, but then it's been that way since about 15,000 miles and it's had its scheduled valve clearance checks. Stock aside from K&N, Micron cans and a DJ kit (using the DJ recommended settings).

Just wondered if any of the cleverer forum members could make any suggestions as to likely areas to investigate? I will probably be paying someone to fix the problem, as I need the job done quickly (commuter bike) and properly, but would like to be able to point them in the right direction, and not give them an excuse to do more than is necessary.

As there are no clouds of smoke, no obvious oil contamination and no 'orrible noises, is this most likely to be just one or more of the rings finally giving up and allowing more and more oil into the combustion chamber to be burned?

Also, if it will end up needing (at least) the head taking off, any suggestions on things to fix or upgrade while it's apart? I think I recall that a mild performance cam is pretty much pointless without porting, polishing and a lot of airflow work on the intake and exhaust side of things. Similarly, I guess the old 29cc overbore is only worth it if the liner's shot (someone will now point out that the TRX mill is linerless, no doubt) or you're doing a shedload of other work?

Thanks in advance...

I can add one thing...
I found a place wich sells Q8 SBK fully synth oil from barrels....cheap so i changed from Silkolene Comp4 and now it gulps kinda twice as much.
So it´s really down to oil choice as well!


...but new rings and a hone would probably do a lot!!

It could be many things but if you are losing 2 litres per 1000 miles I would guess at you needing new piston rings as a minimum - and probably a hone of the bore

If it does need over boring, you don't necessarily have to go hi comp aftermarket pistons - Yamaha sell oversize pistons.

and don't forget to do the valve stem seals while its in bits ,,,this is what i will be doing at the end of the season,,

steve speed wrote:and don't forget to do the valve stem seals while its in bits ,,,this is what i will be doing at the end of the season,,

Indeed - I would guess it is losing oil through either or both past the rings and/or valve seals

phuk72 wrote:

steve speed wrote:and don't forget to do the valve stem seals while its in bits ,,,this is what i will be doing at the end of the season,,

Indeed - I would guess it is losing oil through either or both past the rings and/or valve seals

Thanks guys. I should have thought of the valve seats as well.

If the rings are re-done, does that automatically mean the bore has to be re-honed/re-coated to get them the rings to seat properly? I guess the answer is probably yes. Not sure whether I shouldn't just big-bore it if that needs doing anyway, but if the small ends are OK, I'd prefer not to have the extra cost of replacing the pistons. Are Yamaha oversize pistons actually any cheaper than the higher-comp (presumably) JE 878 kit items? Or is it just a question of how much grief you want to give the rest of the engine?

I don't think it's an oil issue - unfortunately! The bike's had various synthetic and semi-synth oils in it over the years with no change in behaviour. It's been topped up most recently with rock oil semi-synthetic 10w/40, which is hardly an exotic lightweight blend, and I think the last oil change was Castrol 4T semi-synthetic, also not unusual stuff.

So if it is ring wear, is it OK to just keep topping it up regularly until I can get the work done, or could they disintegrate totally and the whole thing go pop? Sorry if that's a dumb question...not experienced with this _particular_ sort of problem.

How do you all get an acurate level reading? A few times now I have got consistent low readings, so i've topped it up a bit, gone for a ride somewhere and the oil that apparently wasn't there has returned and I end up draining the same amount of oil I put in out again. wtf.

I'm fast approaching 2k miles (3200km) since Martin rebuilt it and it doesn't seem to have lost any at all.

gregs656 wrote:How do you all get an acurate level reading? A few times now I have got consistent low readings, so i've topped it up a bit, gone for a ride somewhere and the oil that apparently wasn't there has returned and I end up draining the same amount of oil I put in out again. wtf.

I'm fast approaching 2k miles (3200km) since Martin rebuilt it and it doesn't seem to have lost any at all.

I´ll do a run for at least 15 min, then when i stopped i wait exactly the time it takes to open garage door and get the helmet off....put it down and back to the bike then read it.
That way i know i check it the same way all the time...

gregs656 wrote:How do you all get an acurate level reading? A few times now I have got consistent low readings, so i've topped it up a bit, gone for a ride somewhere and the oil that apparently wasn't there has returned and I end up draining the same amount of oil I put in out again. wtf.

I'm fast approaching 2k miles (3200km) since Martin rebuilt it and it doesn't seem to have lost any at all.

Have to say, I have the same problem sometimes. Unfortunately in my case the difference in oil level is such that mine definitely is turning into a diesel.

well for sure when mines cold the oil is about half way in the window, but as soon as it get warm it goes to to full mark ,, as above mine also does not smoke or leak but it still uses 1lt per 1000 miles , so i will be honing the bores, new rings and fitting new stem seals ,, that's the best i can do , if it still uses oil after that well so be it,,, and to answer the above if you are going to fit new rings you should really hone the bore ,,and depending who you listen to it should be done in two steps , first step 180 grit for about 1 min ,,then 280 until you get a nice cross hatch ,,what lube to use when you are doing it varies with who you speak to,, some say wd40 others say thin engine oil ,, i will use wd40 with a bit more oil

idl1975 wrote: Thanks guys. I should have thought of the valve seats as well.

that's seals, not seats.

youngy wrote:

idl1975 wrote: Thanks guys. I should have thought of the valve seats as well.

that's seals, not seats.

Ah, ok!

idl1975 wrote:My TRX has been a fairly consistent 1l/1,000 m oil drinker since running in. I'm getting the distinct impression that this has dramatically increased in the last 500 miles (it's now at 23,500). As in at least doubled.

Thanks in advance...

What year model TRX? .. 1996/97 models like mine would streach inlet valves. This results in the valve stem seals not sealing properly increasing oil consumption dramatically and the valves taking up clearances to the point that it is impossible to set clearances correctly. Is it hard to start when stone cold? If so then the valves are being held off their seats. The cure is fitting later model inlet valves (1998 on). If you dont catch the problem it is possible to burn the valves, but the head does not have problems with valve seat recession. When I did mine @ about 84,000km it got all the inlet valves replaced, new stem seals on all valves, seats recut. As the head was off I fitted new piston rings but both the pistons and the bores were like new. Now it runs like a steam train and oil use is negliable.

DFH