Replacing piston and / or rings

[robi_kihm@yebo.co.za]

Hi guys , need some advice please.

Have a TRX 850 with approx 45,000 kms on the clock - going very well
but using a bit of oil. If I had to strip the motor , and land up honing
the barrels and putting on new rings , or possibly going oversize one piston size , would I have
to consider doing crank bearings and big ends as well ?
, or if I feel they are in good condition just do
piston and / or rings and valve stem seals.

Let me know your thoughts guys ?

Regards

Robi

[Smithers]

If it where my machine I wouldn't even contemplate doing any engine work unless the oil consumption was getting inconvenient Nearly all TRX,s use oil, it's normal. Might even be an occasional Yamaha thing, with some of their models. These engines have a good lifespan and at the mileage your machine has, wear would be measurable but well within tolerances, as my engine was at 43000km when I stripped it to check a previous gearbox repair, carried out due to a broken chain. My engine had close to nil wear and the timing chain was slightly stretched, which I replaced, but it could have done twice the mileage easily. It now uses less oil than it did before and I never replaced the rings or valve stem seals, just lightly scuffed up the bores with #240 wet&dry. The issue with these engines is that owners forget to keep an eye on the oil level and this is the major contributor to engine damage, and if you search through the archives, you will see that it's one of the big-ends that fails first through lack of oil. That pretty well puts the engine beyond retrieving immediately.... I wouldn't know what to recommend as the normal oil consumption but it will have been mentioned many times previously, on this site. Hope this helps, just hate to see you open up a perfectly good motor for nothing.....Cheers

[SDN]

My oil consumption is ridiculous, it does not smoke, performance is good, so I just keep sticking oil in it, I use Halfords own brand semi synthetic - which has the benefit of being cheap.

[phuk72]

Yamaha regard 1 litre per 1000 miles of oil usage as 'normal' so I really wouldn't worry

[robi_kihm@yebo.co.za]

Guys , thank you for the input , so i will leave well enough alone .........

[cobbadiggabuddyblooo]

Just don't waste your money on expensive oil

[alextrx850]

If people are having oil reduction problems...could that be they are using cheap oil ...glazeing the rings and or vaporising in the motor..?
Just a thought, as ive mostly run the quality oil and no oil useage..?
Confusing to say the least.

[cobbadiggabuddyblooo]

Plenty of bikes that have had full device history from a yamaha dealer still suffer glazing , it's the way you run it in that causes it. And both your motors already had Km's on them so someone done something right before you Alex

[alextrx850]

Fair nuf

[lenny]

I think the standard carbies are part of the glazing problem. Most (all?) TRx's have spent much of their klm's running very rich due to the infamous worn emulsion tube and needle problem of the standard carbies. A sure way to glaze bores. Do Ducaties that run the same carbies also have bore glazing problems?

[Tarwetijger]

I think the standard carbies are part of the glazing problem. Most (all?) TRx's have spent much of their klm's running very rich due to the infamous worn emulsion tube and needle problem of the standard carbies. A sure way to glaze bores. Do Ducaties that run the same carbies also have bore glazing problems?

That's a very interesting statement. The YZF750R uses the exact same carbs (but only 4 of them) and is also well known of the use of oil!