mains bearing o rings

[dinogt]

I speak about a T 500 but I think the others T and GT have the same problem

On the bottom crankcase there are smalls hollows in front of the (bearing) o rings.
Each hollow is different from one crankcase to another.
When we close both crankcases (bottom & top) the o ring must go a little in the hollow to do sealing.
Some crankcase have hollow too big and o ring can't do his job.
O ring suzuki 500T origine (09280-76001) are 68 x 2.5 mm (for a 80mm external bearing)...but it seems that they are less than 2.5mm and 2stroke oil leak are possible.
So I put o ring (viton) a little bit stronger it does 67.95 x 2.62 and to put it well, it just must do a little 0.2mm deburring (just to break the corners) on both crankcases just in front of the o ring . If you don't do this small deburring the 2 crankcases hurt too much this big o ring.

[GT500Andy]

Hi Dinogt,
I know what your talking about, Had the same problem with my GT after a rebuild crank seals. leaking at the bearing o rings. see film on you tube: http://www.youtube.com/watch?v=T4zat0lbeDo" onclick="window.open(this.href);return false;
Had to strip down the engine and clean up the casings, indentations by the o rings just like your photo.
Andy

[dinogt]

Yes, the o ring notch is 3 x 1.75 mm = 5.25mm²
The origine o ring is 2.5 mm = 4.9mm²
The bigger o ring is 2.62mm less because thinner so 2.6mm = 5.3 mm
With the mathematics, the bigger is best.
I will mesurate one origine in a few days...and I think he does not do 2.5mm...but less...if someone have one new, he can give us the dimension...I think about 2.2 max....

[Phil C]

OK, thanks ,this is a great help but do I have to split my crank to fit the larger O- rings?

Also,where can I buy the larger O-rings?

Phil C

[dinogt]

For you, I think also at too much wronf round, control it.
For buying O ring VITON, take a bearing saler or me

The maths I have wright are a little wrong, so it's worst than I think, I'll explane that this night...or you are found ?

[dinogt]

yes indeed.
we MUST take crankcase and control them if they are ok one by the other.
What is " barrel mating surface " please ?

[ja-moo]

yes indeed.
we MUST take crankcase and control them if they are ok one by the other.
What is " barrel mating surface " please ?

It is the surface of the cases the cylinder bases bolt against.

[dinogt]

Thanks, it's what i was thinking but as I don't see cylinder...IDU...

[dinogt]

I come again at maths
The hollow oring is about 5mm²...aftermore measure on more bearing about 4.5 to 5mm²
The origine o ring is 68 x 2.5mm...but the bearing external is 80mm and the hollow 1.75mm so the diameter is 80-1.75-1.75 = 76.5 and not 68...there is about 12% less...idem for the 2.5mm becom 2.2mm
so the o ring 2.2mm DIAMETER is 3.8mm²
See now the stronger 2.62 -12% = 2.3mm give 4.15mm².
The difference is important between both but I wait for measure an origine o ring....
Have I bad explane ?

[rbond]

If the 'O' rings have to be changed, then the crank has to come out. Next bad news is the crank has to be separated at the center to change those two 'O' rings as you cannot stretch them over the flywheels, so it would also be best to change the center seals too while it is apart. My favorite compound is Hylomar. It has the consistency of a medium heave grease and does not harden, does fill in gaps really well, comes apart easy and cleans up easy. It is also not affected by fuel like silicone based sealers.

[dinogt]

You don't need to separated the crankshaft to change the o ring seals but only to change the normal seals.
You change o rings when you separate crankcase but if you bearing seals are olds, they have to strong lips and dammage the shaft , and you motor drink oil box...and your box eat his teeth....

[tz375]

+1 on Hylomar. I first used it when I worked for Rolls Royce in the aero engine overhaul shop in Scotland - all those decades ago. It is or was made by Marston Lubricants and was sold as SQ32M (medium). It's non-setting and is best applied with a stipple brush very lightly to both faces.

AFAIK it is available again from an on line supplier.

[rbond]

Hylomar is available from Permatex here in the states and is found in most auto parts stores. I was told the 'O' rings could not stretch enough without breaking to go over the flywheels, guess I was told wrong. That is what this board is all about.

[rbond]

Great!! I appreciate that. I have another 500 engine I will practice on, maybe this winter (such as it is here) I will rebuild it and put it in the frame.

[dinogt]

O ring suzuki 500T origine (09280-76001) are 68 x 2.5 mm (for a 80mm external bearing)...but it seems that they are less than 2.5mm and 2stroke oil leak are possible.

Yes , it is possible they are less than 2.5mm, they are 2.4mm and this difference is too much from the first origine.