yamaha labyrinth seal, for 100cc 125 cc twins

[Bluehaze]

You will never see pure aluminium in an engineered product - maybe a saucepan?
There is no lack of nay-sayers. Find a machinist with a more "can do" attitude.

[Bluehaze]

I had a response from someone with a TZ engine, with a used but pristine lab seal.
He used a telescopic gauge and micrometer and measured both the seal lands and shaft (actually a sleeve).

Seal diameter = 40.10 to 40.11mm
Sleeve diameter = 39.99mm

So clearance (half of differences in diameters) between the labyrinth seal and shaft/sleeve = 0.055mm to 0.060mm

[martin1957]

I wonder if they can be made from other things? They dont touch the crank......

What about these modern engineering plastics? Delrin?

Guess you need to consider expansion coefficients.

[robrd]

I think that I have one in one of my drawers in the workshop, Ill have a look and let you know.

[robrd]

Hi all, yes I do have one, if any one is interested I could take some photo's showing the dimensions. It came a few years ago with an RD125, 1975 I think, along with a couple of other crank parts. Being as there are no parts touching the labrynth I wouldn't have thought there is much wear if any?

[Bluehaze]

Another set of meaurements would be good, to compare with the ones we have.

Does anyone have close-up photos of a worn labyrinth seal?

[GTDWH]

Hi all, yes I do have one, if any one is interested I could take some photo's showing the dimensions. It came a few years ago with an RD125, 1975 I think, along with a couple of other crank parts. Being as there are no parts touching the labrynth I wouldn't have thought there is much wear if any?

under normal circumstances they work just fine, it's over time they wear, given how some bikes are thrashed and ridden very hard, they do wear and are needed from time to time.
I just got a rebuilt crank back, which didn't need one, so I still have 2 new labs, but have 2 more cranks to get rebuilt.
over all they have stood the test of time, in the past when I was in the trade, most were needed after an engine failure, or very high mileage.
Biggest problem now for anyone needing 1, is they are very rare and hard to find.
When you do find 1 the price tends to be very high, 1 on ebay now for around £200

[martin1957]

I would be interested to see images of a worn one as in normal use, nothing touches it except oil. Corrosion due to water could get it as well....

[robrd]

Here are the photo's with dimensions, sorry it took so long.

[Bluehaze]

Thanks for the photos.
What engine is the seal from?

When it comes to internal measurements, be aware that calipers can introduce error.
Although very thin, the jaws normally have flats (so they withstand wear in use) that give a smaller reading.
Gauges with rounded anvils are used to better measure IDs.

[robrd]

It is from an RD125, 1975 I think, I also have the filler piece as well which I have photo'd.

[GTDWH]

Here are the photo's with dimensions, sorry it took so long.

these are from 200cc labyrinth

[GTDWH]

It is from an RD125, 1975 I think, I also have the filler piece as well which I have photo'd.

It's from a 180c-200cc it's close to being the same, but the 100cc-125cc are thinner
The ID AND OD from 180-200 and the 100-125 are almost even maybe the same, depends how it's measured and by who
10 differant people could measure them and all come up with differant size all be close.

The 100-125 seal has only 3 grooves 180-200 5 grooves..

[robrd]

Thanks for that GTDWH, now I will know what they are when I sell them.

[Bluehaze]

10 differant people could measure them and all come up with differant size all be close.

You could ask a machinist with expertise and the right gear to measure for you?
While s/he's at it, ask for a quote to reproduce it?
And no, CNC is not a requirement.

When someone needs a lab seal that cannot be found (or too expensive?), having one made could be the only other option.