AIRCOOLEDRDCLUB FORUM

Tech Zone => Aircooled RD Tech Help 250cc and Above => Topic started by: tore on June 22, 2021, 02:46:16 PM

Title: 350A fork seal
Post by: tore on June 22, 2021, 02:46:16 PM
I discovered that one of the fork legs is leaking oil. It was renovated by a company for about 2 years ago. Can not see any damages on either the chrome or the seal. The seal has likely just lost its strength.
Any suggestion of good source for fork seals?
I have a pair of fork seals from simplybearings. Worth to install those?
Title: Re: 350A fork seal
Post by: 5port on June 22, 2021, 02:54:39 PM
I have always used the Gen Yamaha NOS ones with the steel backing.  Not had one leak yet and the oldest was overhauled by me nearly 30 years ago with new chrome on the legs. I have ones on original chrome legs still good as well, were just replaced with fork overhaul, they were not leaking but decided to renew seals with the legs stripped.  In fact, one leg was very slightly bent and I had it straightened.  ;)

Cheers

5port
Title: Re: 350A fork seal
Post by: tore on June 22, 2021, 03:09:20 PM
I have always used the Gen Yamaha NOS ones with the steel backing.  Not had one leak yet and the oldest was overhauled by me nearly 30 years ago with new chrome on the legs. I have ones on original chrome legs still good as well, were just replaced with fork overhaul, they were not leaking but decided to renew seals with the legs stripped.  In fact, one leg was very slightly bent and I had it straightened.  ;)

Cheers

5port
Does the yamaha genuine ones have a spring?
I can see the ones installed do not have a spring pulling the seal tight
Title: Re: 350A fork seal
Post by: tore on June 22, 2021, 03:17:00 PM
Anyone tried this?
Pricey though
https://www.ebay.com/itm/Leak-Proof-Seals-5207-Pro-Moly-Fork-Seal-34X46X10-5-/192680405952 (https://www.ebay.com/itm/Leak-Proof-Seals-5207-Pro-Moly-Fork-Seal-34X46X10-5-/192680405952)
Title: Re: 350A fork seal
Post by: 5port on June 22, 2021, 07:27:51 PM
I have always used the Gen Yamaha NOS ones with the steel backing.  Not had one leak yet and the oldest was overhauled by me nearly 30 years ago with new chrome on the legs. I have ones on original chrome legs still good as well, were just replaced with fork overhaul, they were not leaking but decided to renew seals with the legs stripped.  In fact, one leg was very slightly bent and I had it straightened.  ;)

Cheers

5port
Does the yamaha genuine ones have a spring?
I can see the ones installed do not have a spring pulling the seal tight

I think they do have support springs.  ;)

5port
Title: Re: 350A fork seal
Post by: tore on June 22, 2021, 08:15:15 PM
I just found out the reason for the leak. Rust! There is a pocket where water is collected at the seal. The seal has steel casing and therefore rusted. Are there any remedy for this?
Title: Re: 350A fork seal
Post by: Barnett on June 22, 2021, 10:21:30 PM
Simply bearings and bearing king do a good range of seals but check as most are for rotating shafts not axial. Exposed steel  banded ones are a pain, they rust but helps if you grease of course. Yes they should have garter springs.
Title: Re: 350A fork seal
Post by: tore on June 23, 2021, 12:17:32 PM
Simply bearings and bearing king do a good range of seals but check as most are for rotating shafts not axial. Exposed steel  banded ones are a pain, they rust but helps if you grease of course. Yes they should have garter springs.
The simply bearings seal does have steel band as well as garter spring. If I understood 5port correctly, this is same setup as the original Yahama seals.
It is maybe a good idea to install and fill the space above the seal with some rust inhibitor.