[tr6rvrider]

Quick question
Iv got a 72 tr6rv with a leaky intake push rod tube. I see that the part numbers for the upper and lower O ring seal's are different. I have some on hand but I'm not sure how to tell them apart. Both look to be the same diameter and thickness. Maybe I have a bunch of one and none of the other. Can someone give me a bit of help

Thanks Mark S

 

[BMF]

Just get proper viton ones and use them on both sides. Triumph tried to save 5c using cheaper less heat resistant ones at the bottom (often red). You can buy them cheaply from oring suppliers by dash number. Hermits website has a list of orings and their dash numbers.

 

[StuartMac]

Hi Mark,

part numbers for the upper and lower O ring seal's are different
Both look to be the same diameter and thickness

not sure how to tell them apart.

E11283 (71-1283 in '73-on format) at the top is usually black and made of Viton.

E7310 (70-7310 in '73-on format) at the bottom is usually red and made of Buna-N.

If a Buna-N O-ring is fitted at the top of a PRT, it fails fairly quickly as Buna-N cannot stand the heat in the cylinder head, particularly the exhaust PRT betwen the exhaust valves.

As @BMF Brett posted, easier is just to use O-rings you know are Viton both top and bottom of PRT.

Hth.

Regards,

 

[tr6rvrider]

Thanks for the info.
Turns out that there were Viton orings in top and bottom. The top intake p.r.t. oring was pinched some how when it was put together last. Luckily I still had four new viton (black) orings in my parts box. Should be back together tomorrow .

 

[TR7RVMan]

Hi tr6rvrider, Depending on supplier the viton can come in various colors. Raber's sold brown ones. I've seen green also.
In general viton is made in many different colors. I've worked with viton seals for years at work as manufacture introduced viton seals. I can say I cannot feel or see a difference in viton to the other common oring rubbers. The silicon based rubbers are generally softer to the touch. So be careful to keep known viton seals separated & marked as needed with string tag or the like. Viton lasts many times longer than normal seals.

When in comes to viton we are at the mercy of our parts vender & their supplier. So we must think about how trustworthy our vendor is. Most Triumph vendors have ebay presence. Do your home work on eBay sellers to be sure. If a trusted seller doesn't specifically state it's viton, don't buy it without verifying from seller it's viton.

What to have a leaky motor, by a generic gasket kit such as Emgo. Flip a coin as to how long it will stay leak free....

Viton is a costly material that is worth every penny. I piece meal my gasket kit getting what I perceive is the highest quality gaskets & seals from various sellers. I hate leaks & am very picky about my seals & gaskets.

You're probably already together, but the head can have sharp/rough edges & surface where PRT goes. This can scratch, cut, catch oring & twist, distort it. It's good practice to smooth lead in of bore & the sides of bore to give oring best chance of sealing. Same with OD of tappet block where PRT passes over.
Don

 

[upstateTrophy]

TR7RV,

Following up on your post, are there any more modern materials, e.g. silicon, polyurethane, etc. that are even more durable, softer and better suited than Viton? It would seem with today's materials, something superior would have evolved compared to Viton of 50 years ago. Or is Viton still the best available material for these O rings?

 

[StuartMac]

Hi,

are there any more modern materials, e.g. silicon, polyurethane, etc. that are even more durable, softer and better suited than Viton?

"Viton" isn't a single material but a family of materials. The "Viton" Triumph used 50-odd years wasn't a spectacular improvement over the original Buna-N at the top of particularly the exhaust PRT, it just lasted a bit longer.

I suspect the "Viton" '69-on twin owners use now is probably not the same "Viton" Triumph used 50-odd years ago; however, we need someone with access to an O-ring maker's scientists and enough interest to ask the questions.

Regards,

 

[newsh]

FKM (Viton) Wiki page here.
There’s actually a note in “applications” on their use on Corvair pushrod tubes.

https://en.wikipedia.org/wiki/FKM

 

[TR7RVMan]

Hi Upstate, Viton is the material if choice for most engine orings.
The PRT & rocker shaft brown Viton from Rabers did not not leak for several years if installed thoughtfully. Rabers shut down.

I started getting viton PRT orings from Bonneville shop. They are black & have same good durability.

Rocker shaft rings Bonneville shop did specifically state viton. But Steadfast Cycles states viton, so I get them from there.
Other shops offer similar. Tax is 9% from California sellers for me. Out of state zero tax. Do the math, I’m cheap, but I’ll pay for quality.

Still no oring is forgiving of poor finish on the head bore or tappet block. Micro scratches on the rubber may not leak in 1 year but it will not last the expected 6+ years.

Crank seal matters. Genuine Pioneer Weston is my seal of choice. It lasts a long time on cam seal seal too. I use only PW on both.

John injured his foot. Just yesterday we rode & I started his bike for him. He has oil gauge. Was 48f. Cold start showed 90# on gauge 2500 rpm. 20-50 oil. This is normal & expected cold. Never a worry about PW seal inverting cold.

Back to oring material Porsche back in later 70s & early 80s experimented with silicone PRT seals as the original black rubber leaked soon. Was actually worse! Finally got viton, problems solved. Mercedes did same on Transmission electrical plug in 90s. Original rubber leaked. Silicone was disaster. Viton was cure. No leaks on mine for 12 years. Still dry so far, but I sold car last week. So I can’t track longer.
Don