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

dern · Veteran Member

Couple of questions - brakes and oil leak

TT-R250M · Super Guru

Hey Mark and welcome to the forum.

Brakes

Check adjustment at the front brake lever.

Check caliper pins and re-grease if necessary.

Oil leak

Seems you have got things covered, you may want to include the cylinder O-ring also-

Diagram of Yamaha Motorcycle Parts 1999 TTR250LC CYLINDER Diagram

I would advise to check your cam chain and guides thoroughly and replace the valve stem seals.

If you need a full repair manual PM me your email address and I'll send it through.

Jarrah

cesar · Member

hi mark.

before remove the barrel, get start the engine and look

-cylinder head cover gasket;

oil pipe bolts and washers;

-decompressor bolt and oil checking bolt.

your problem can be one of this. good luck to you

cesar

TTRfan · Super Guru

Bleeding the front brake can be quick and simple but it can also sometimes be a right royal PITA . I had one of the latter recently. I replaced a front hose and it seemed to take for ever to get the air out. Fortunately I had Mrs TTR's help on the lever and topping up whilst I did the business at the bleed nipple end. Got there in the end though biggrin

With regard to the oil leak, it isn't common for the base gasket to leak. Cesar's suggestions are good and mat save you a rebuild. The decomp plug just above the exhaust outlet is the most common culprit. There is quite a reservoir of oil behind the plug which can continue to leak out even when the engine is switched off.

However, are you saying that your engine is leaking oil from the base gasket when not running? This seems odd.

Brian

dern · Veteran Member

Thanks for all the replies.

With regards to the brakes... all the calliper pins are clean and greased and in good condition and the pistons have been cleaned up. I'll try a new hose I think and go from there. There's only so many things it can be ;)

ETA: I have put on a new brake lever and have adjusted the nut so that it just touches the plunger with the lever open. If I adjust it any more to give me more 'throw' on the plunger I get brake binding with the lever fully open. I think that this is normal, right? I'm just assuming that the hose is old and expanding unless I've failed to get the air out of the system which I think I have.

The oil leak... it's definitely coming from the base of the barrel. I've degreased the engine and can see the oil oozing out of that joint. This only happens when the engine is running though, I think the accumulation of the oil in the bash plate and on the bottom of the engine was responsible for the pool of oil on the floor. The barrel itself is completely dry and there's no leaks from the top or the decompression plug.

I'll order the gaskets and crack on.

Thanks,

Mark

-- Edited by dern on Monday 12th of May 2014 08:29:03 AM

dern · Veteran Member

TT-R250M wrote:
If you need a full repair manual PM me your email address and I'll send it through.

Thanks very much indeed, I'm PM'd you my email address.

Regards,

Mark

TTRfan · Super Guru

Hi Mark

The engine strip is quite time consuming and I tend to follow the line that, now I'm in here lets do all that's necessary to save a further strip down later on.

Once the head is off, strip out the valves and clean them up. If all looks OK then grind them in and fit new valve stem oil seals.

Check the piston and barrel for wear and, if within specification, fit new piston rings.

If the cylinder base O ring is flattened or damaged then it is worth replacing it, especially as you have an oil leak from that area.

The job I find the hardest is cleaning the old base gasket off but that's the job you have to pay most attention to.

Hopefully you have a torque wrench because, to make your efforts worthwhile, it is important to torque the head back on to the values and in the sequence specified in the workshop manual.

The parts you might need are:

Head & base gasket set
4 x valve stem oil seals
New piston ring set - if the existing piston is oversize then this will be shown on the piston crown
Cylinder base O ring

Any questions, just ask wink

Brian

dern · Veteran Member

Hi Brian,

I have all the required tools as have done this sort of thing a few times on cars and once on a fire blade that decided to go pop :)

I'll email you for a quote on the parts, thanks.

I was hoping to avoid going through the palaver of changing piston rings and measuring bores and just stick it back together as apart from the leak it's all working well. I think what I'm going to do is just do the gaskets and the valve stem seals, inspect the rest and if it needs attention take it apart this winter and do a proper job if necessary. I know this is counterintuitive but to be honest, having just got the bike, I just want to get out on it. I'll see what it looks like when I have it apart.

Hope this doesn't sound to 'bodgy' ;)

Cheers,

Mark

dern · Veteran Member

All the 'outside stuff' is off and now just to take the head and the barrel off. Not too bad at all so far :)

Quick question... the exhaust... it's supposed to be studs and not bolts, right?

Cheers.

Mark

glynn4623 · Member

yea studs on mine

dern · Veteran Member

Cheers, I'll order some from Brian to go with the rest of the stuff as soon as I get the rest of it apart and find out everything I need this time.

Note to self... buy a new bike next time ;)

Cheers,

Mark

TTRfan · Super Guru

dern wrote:
Quick question... the exhaust... it's supposed to be studs and not bolts, right?

Mark

In 99% of the TTR header pipes I have removed, the steel nuts have rusted onto the stud so the stud comes out with its nut and looks like a bolt!

Not a problem - just treat them as a bolt wink

Brian

dern · Veteran Member

Thanks Brian. One of them is a stud with the nut welded on and the other is some random screw that looks too short. I'll need a new gasket anyway as the old one is ruined and it looks like I'll need a new front brake line also so I may as well put some new studs in. I'll take the barrel off and then drop you an email for a quote for all the bits I need.

All the best,

Mark

Padowan · Senior Member

TTRfan wrote:
Hi Mark
The engine strip is quite time consuming and I tend to follow the line that, now I'm in here lets do all that's necessary to save a further strip down later on.
Once the head is off, strip out the valves and clean them up. If all looks OK then grind them in and fit new valve stem oil seals.
Check the piston and barrel for wear and, if within specification, fit new piston rings.
If the cylinder base O ring is flattened or damaged then it is worth replacing it, especially as you have an oil leak from that area.
The job I find the hardest is cleaning the old base gasket off but that's the job you have to pay most attention to.
Hopefully you have a torque wrench because, to make your efforts worthwhile, it is important to torque the head back on to the values and in the sequence specified in the workshop manual.
The parts you might need are:
Head & base gasket set
4 x valve stem oil seals
New piston ring set - if the existing piston is oversize then this will be shown on the piston crown
Cylinder base O ring
Any questions, just ask
Brian

I'm contemplating doing similar work on my engine - I've also got a small leak at the base of the barrel (so the base o-ring and gasket beed doing) and some smoke on cold startup (VSO's I expect).

So while I'm in there I'd like to check the bore - how do I tell if it's "in tolerance" or not and needs a rebore or not or whether I can get away with just new rings?

As I've not done it before, for grinding in valves, how long is that likely to take (I don't have a fancy oscillator like you Brian!) and I assume that I'll need new shims as the clearances are likely to change a touch?

I'm off to Spain with the bike in July for the Vince so I don't want to embark on work that I can't comfortably complete in the time, so would prefer to do the minimum necessary (to be honest none of it ie absolutely essential, but I'd like the bike in tip top condition), but at the same time if I remove the barrel to replace the gasket and then decide to rebore at a later date, I'll need to replace that gasket again I assume?!