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

Susan Parker · Member

Where's all the oil going?

JOHNYBOY · Super Guru

possible stem seals if it was piston rings you would see slight smoke have you changed the oil recently if not makes sure when you do put the specified oil not too thin like 5 w 40 put 10w 40 its mot using too much as tho its old oil too thin try it

Susan Parker · Member

Yep, I have changed oil and filter recently, and always use the recommended 10w 40 oil! As this bike has done very few miles since it's 350 conversion, I would be surprised if it was the valve stems; but always a possibility - I was hoping not to have to go groping around inside the engine!

ttr steve · Super Guru

Susan. Remove the spark plug and see what colour it is, if its really sooty its burning oil.

JOHNYBOY · Super Guru

its obvious burning oil if no leaks either stem seals or glazed bore due to being too carefull on running in procedure

Susan Parker · Member

Just got back from a 70 mile ride out - the rider behind me said he could smell the burning oil on the overrun; although, apparently not actually smoking! I have checked the compression and that was within the specified tolerances. So looking more and more likely to be the stem seals - really hope it isn't a glazed bore! I took the spark plug out about a month ago and it looked pretty good, but obviously need to check it again. Looks like I am going to be busy.............

JOHNYBOY · Super Guru

on over run is usually stem seals

Susan Parker · Member

Seems to be looking that way!

Ttboof · Senior Member

It you take the exhaust off after its been parked a while looking at the valve stems with a torch they tend to appear wet/oily . A fairly easy check . Also if the stem seals are crook after sitting for a while you may have a bit of smoke on first start up as the oil burns .

Inlet valves are a pain to check though as it involves taking the carb off

-- Edited by Ttboof on Sunday 29th of December 2024 08:42:35 PM

JOHNYBOY · Super Guru

yes i agree smoke on start up after been stood overnight stem seals cheaper fix than glazed bore

Tstrainer · Newbie

Susan , before you pull anything apart just check the crankcase breather is functioning, ie not blocked or a crimped or collapsed pipe. It would give high oil usage.
Cheers Tim

JOHNYBOY · Super Guru

where is our brian i would like to hear his thoughs about this subject

Susan Parker · Member

I have checked the crank case breather - all OK there. I have been advised to have a 'leak down test' before I jump in and start pulling the engine apart. Apparently that will help to establish which bit of the engine is causing the problem!

-- Edited by Susan Parker on Friday 3rd of January 2025 09:18:00 AM

ttr steve · Super Guru

Good to check, will you still need piston ring's?

Susan Parker · Member

I will let you know, Steve, when I have the result of the leak down test. My brother raised the point that if I have to get a re bore, presumably the new piston rings will not be standard? This is all getting rather alarming!!

JOHNYBOY · Super Guru

if its had a 350 conversion no wear to rings possible glazed bore i dont think so doing leak test would not prove stem seals only poor compression valves worn bore piston rings glazed bore would not show low compression

dlee22 · Senior Member

I had to replace the sleeve in my 350 barrel when I trashed my motor.

A small engineering firm was able to sort this out very easily and it was done within 2 hours.

It has held up for 9-10,000miles since.

I hope if just stem seals, OEM ones don't harden anywhere near as much as some aftermarket ones for the ttrs

Susan Parker · Member

So, it sounds like the leak down test would not show any more than the standard compression test that has been done, which showed that the compression was within accepted parameters. Looks like I am going to have to get in there and take a look!

mossproof · Super Guru

Johnnyboy might be right with glazed bore if the bike has not really done enough hard work in it's early life. If there is not much/any smoke, it won't be anything catastrophic I think, but it looks like a tear-down is in order.
Do the valve stem seals anyway (use genuine only).
As Dan suggests, it is fairly straightforward to replace the sleeve if necessary, and will be much cheaper because gaskets, rings and sleeve work out considerably cheaper than a first oversize piston from Wossner. (PM me if you want details)
My 350, number #1, tends to burn a bit of oil on long high speed road trips, not slow pootling round the lanes. As does my 325. I have been advised to change to Motul fully synthetic 20w50 by XT600 guru David Lambeth, which is supposed to be THE THING for big bore over-square thumpers. Lyndon Poskitt also used this until he got sponsorship from Motorex... I have just done an oil change with it, but have yet to get out for a long thrash...

Susan Parker · Member

Thanks for your reply Mossproof. As you say, it looks like I am heading for a complete tear down......I have ordered valve seals and gaskets from Steve, so as soon as they arrive I shall be set up to have a look at that end of things. As this 350 conversion was done by Brian, I am certain it will have been run in correctly! I am aware that the owner prior to me did not use the bike much during his two year ownership; so there could be some 'lack of use' damage; but for now it's 'wait and see'.

Susan Parker · Member

I have attached some pictures of the top of the piston, with 'interesting' marks, presumably made by the valves. Can anyone shed any light on how this might have occurred?

TTRfan · Super Guru

Welcome back to the forum!

The valve cutouts are cast into the new pistons so all OK!

Clean piston.jpg

Susan Parker · Member

That's very reassuring to hear, TTRfan! I was beginning to think something really catastrophic was going on.............. shows how little I know; but learning fast.

mossproof · Super Guru

On a standard piston, the valve pocket cutouts appear much deeper, but to retain a standard compression ratio with the greatly enlarged bore, some material needs removing from the piston crown. These fingernail marks are all that is left of the original profile. Compare with the picture of a standard piston from Totally TTRs:

totallyttrs.com/epages/699105d9-e4cc-4b32-b236-84e72cd67f84.sf/en_GB/

Did you take a pic of the piston before cleaning? How sooty/tarred over was it?

Susan Parker · Member

All rather unpleasant!

Susan Parker · Member

All rather unpleasant!

dlee22 · Senior Member

How does the sleeve look Susan? Are there any marks that you can feel with your nails or is it almost glazed?

Susan Parker · Member

The piston sleeve seems fine - cannot detect any scratches and it doesn't appear glazed. So, having cleaned everything up, reground the valves and adjusted the shims, I am currently in the process of putting it all back together. I have decided I enjoy taking things apart more than reassembling them; wondering if it will ever work again!

ttr steve · Super Guru

Good work so far. You will be fine 👍🙂

Susan Parker · Member

Allelujah - it runs! Now it just remains to be seen if all this has solved the problem.

ttr steve · Super Guru

Everything is crossed for you

Not sure why I did the emoji, but it looks funny !

JOHNYBOY · Super Guru

amazing job from a lady of 68 years of age

Susan Parker · Member

It remains to be seen if it is an amazing job or not............But I do appreciate all the support and good wishes from this forum. I will report on the final outcome when I've had a chance to give the patient a proper run out, after a few gentle 'running in' type rides.

AussieChookchaser · Veteran Member

That is good news, now you can enjoy getting out there on it.