A forum for owners of Yamaha TTR250 trail and enduro bikes!

burton500 · Veteran Member

loads of oil smoke

Cubber · Super Guru

It would seem that it's burning oil from somewhere, unless you filled the tank with twostroke oil/petrol mix by mistake. biggrin

The only way it can burn oil is by getting it from above or below.

CHECK:-

Valve guides
Valve seals
Piston for integrity - is it holed or split?
Piston fit in cylinder
Piston rings fit - in piston and cylinder

If all these items check out OK then you have a unique engine. confuse confuse confuse

Martyn

burton500 · Veteran Member

Cheers Martyn,

This oil smell is defo not 2 stroke oil - I never thought I'd have an RG500 and RD400 that were less troublesome than a 4 stroke single!

Piston and rings are fairly new - 74mm Wiseco, and in good nick, with good compression. Valve seals are brand new, so valve guides could be the problem.

Lee

Markvan · Guru

Pistons rings maybe in wrong order or upside down. But then again you have good compression. Maybe google if you can have good compression with 4stroke rings fitted wrong. Thats my backyard mechanic opinion. . Good luck.

burton500 · Veteran Member

Yep, rings are right way up, and in correct order. End gaps were good as well.

ttboof · Super Guru

Check your crank case vent if it's blocked the pressure may force the oil past the rings

JOHNYBOY · Super Guru

check piston ring gap in bore possible light hone bore possibly glazed de glaze & fit new rings while you have barrell off

Padowan · Senior Member

Incorrect orientation of the ring gaps? All in line for example..

burton500 · Veteran Member

Rings have correct orientation as per manual, end gaps good, rings in correct grooves and right way up. Barrels all good and deglazed, and as I said, 150 psi is pretty good.

I will check crankcase breather tonight as I have never checked that.

JOHNYBOY · Super Guru

could the smell or burning be in exhaust have you ridden the bike for a few miles to burn excess oil out of exhaust or take front pipe off have a look inside exhaust port see if it is wet

burton500 · Veteran Member

The crankcase breather is clear - however when I blow down it, the air comes out of the cam chain adjuster hole. Is that right?

TTRfan · Super Guru

Presumably you have the bolt off the end of the cam chain tensioner for that to happen? If so, that sounds OK.

If the engine isn't smoking then could you be losing oil from a leak? Park over some clean cardboard or newspaper to check.

If you can get someone to follow you then they should be able to tell you if you are burning oil. The smell is easy to identify whereas you can't always see the smoke.

Brian

burton500 · Veteran Member

Brian,

Yes, bolt was removed so that is all ok then.

As for the smoke, it is putting out more smoke than a Pink Floyd concert, but only once it is warmed up and on a ride. So ruling out breather, piston, bore and rings, it must be top end.

New valve stem seals are fitted, so maybe valves/valve guides etc.

TTRfan · Super Guru

Sorry to be the bearer of bad news but I think it unlikely that valve guides would explain your symptoms. Worn guides or valve stem oil seals usually only cause smoking on start up.

In my opinion smoking like that when the engine has warmed up indicates a problem with piston, rings or bore cry

Brian

burton500 · Veteran Member

Cheers Brian - even with 150 psi?

TTRfan · Super Guru

I understand your point and would be interested in the opinion of other owners.

I just think that the valve guides would have to be incredibly worn (very rare on TTRs) to cause significant smoking - but I am not a mechanic!

Brian

admbnm · Veteran Member

just to say i have had a xt500[field bike] that had worn valve guides,it would smoke a fair bit,but it would foul/oil the plug up fairly quickly and had to have a cleaned plug to start,is it possible that the new stem seals have failed?

TTRfan · Super Guru

The seals are very simple and I can't see how they could fail unless damaged during installation?

I install them by having the valves fully closed, fitting the new seals over the valve stem and then pushing both valve stem and seal down together until they "pop" into place.

burton500 · Veteran Member

Yep, I fitted them the same way. Not to worry, I'll strip the motor again and double check everything.

hanzo · Senior Member

Sounds from your post you are fairly competent with the spanners .Im guessing you have the rings in the correct orientation .valve stem oil seals correctly fitted .youve replaced with standard rings this points to the the sleeve being out of spec and probably best case is a rebore .I would refer to manual and carefully measure all parameters also on dismantle look for tell tale signs on face of cylinder .

burton500 · Veteran Member

Ok, quick recap. Loads of oil smoke when riding, or blipping the throttle. Valve stem seals are new and fitted correctly. New rings fitted, right way up, correct orientation, and end gaps in spec. Good compression 155 psi., and crankcase breather clear.

And here is the but.... I noticed on tickover after starting it up, the oil remained level in the sight glass. Shouldn't the oil be pumping round, and therefore not at the level it started at? The top end showed no signs of oil shortage or wear and tear. After a quick short ride, the oil must have been pumping round, as it took a few minutes to return to its level. I can check the pump, but is there an oil pick up somewhere that could be blocked?

TTRfan · Super Guru

A simple check is to remove the oil pressure check bolt just above the oil filter housing, surround it with a rag to catch oil and turn the engine over.

Oil check bolt.jpg

Within a few turns of the engine oil should be spurting out of the hole in some volume. If it isn't then there is a problem between that point and where the oil pump picks up its oil.

The oil pump picks up its oil from the sump near where I have pointed with the purple arrow in photo below.

Oil pick up.JPG

There is a diagram in the workshop manual showing how and where the oil circulated which may be helpful in understanding the plot wink

Brian

mossproof · Super Guru

RE The oil burning, are you using a new head gasket? Couldn't find this mentioned in your posts. Oil can be drawn into the cylinder from the oil galleries.
Can't help with the oil level query though. Brian's tip of checking pressure at the bleed screw, and you can also crack open the top banjo to the head if you're feeling brave(!) should give you peace of mind that the oil is circulating.
Good luck,
Simon.

saintken · Veteran Member

Maybe this is an explanation, my bikes oil level through the sight glass also stays level at tickover but drops when revved, I think this is fairly usual on a number of bikes I've owned. The oil returns to the sump by gravity which is constant so the speed at which it returns is constant. When you are running at tickover the pump takes oil from the sump at a steady rate which is matched by the oil returning therefore the oil level remains stable when viewed through the glass. When you rev the engine the oil pump turns quicker and takes oil at a greater rate (volume) than before but the oil is still returning by gravity therefore the level in the sump drops.
I think what Lee describes is normal and if you were suffering oil starvation on startup (tickover) you would quickly seee some damage to your top end.

burton500 · Veteran Member

Thanks for the pic Brian, will have a look in there. Simon, yes a new head gasket. Ken, you may be right there.

Anyway, at the end of the day this bike is 22 years old, it cost me £900, so if all else fails I'll buy a late blue model and will have plenty of spares from this one - it has a new sprag clutch, and came with an oil cooler which are worth a few bob.

Lee

burton500 · Veteran Member

Fitted new rings even though compression was good, and previous rings were fitted correctly. Now smoke free. Just been left with an irritating leak from the oil feed pipe where it fits to the top of the crankcase. New copper washers haven't fixed it, but other than that, good to go.

-- Edited by burton500 on Thursday 22nd of October 2015 04:33:08 PM

locky · Guru

Wonder what the problem was with the old rings ? Strange one but at least you sorted it.

TTRfan · Super Guru

burton500 wrote:
Just been left with an irritating leak from the oil feed pipe where it fits to the top of the crankcase. New copper washers haven't fixed it, but other than that, good to go.

Try annealing the washers.