Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Drive side rocker spindles leaks

Don't ask me. Even with the tool I end up smearing some black silicone around the ends of the shafts to get them to quit leaking.

Sure you aren't using tar? I haven't found a silicone that works. I think my last resort will be weld.

Sometimes the holes become enlarged and oval, nothing helps then except a proper repair or a new rocker box.
No way you can weld to seal, forget that. Unless you mean weld it up and bore it out, which I have a hunch you don't.

SR

Hi Splash, I’ve seen Suzuki bond silicone hold for 2 years now. The type of silicone really matters.
Cleaning really matters. Oil will seep under silicone on oxidized aluminum. Clean until bright.
The little metal discs is a good cosmetic cover. But don’t squish silicon too thin.
Don

Many (most?) silicones have acetic acid with will eat aluminum.

The factory drawing has a very shallow chamfer on the leading edge of the rocker box. In real life very few rocker boxes have the chamfer. The sharp, square acts like a knife to shear the o ring.

I use a machinst's knife made from a three sided file to put a chamfer the box before I offer the shaft and new o ring. If ANY bit of the o ring gets sheared as I am offereing the shaft I remove the shaft and fit another o ring until there is no part of the o ring sheared as the shaft is offered. I also use a small screw driver on the o ring just as it enters the chamfer. I tuck it in a little repeating until I get the O ring in place and is not damage by being cut by the sharp edge.

P-80 rubber lube also works the treat with this job.
Machinsts scraper made from 3 corner file. If you are going to modify your 3 corner file make sure the grinder tool rest is right up to the face of the grinding wheel. If the tool rest is awaqy from the edge of the face of the grinding wheel there is a chance the file will catch the file and suck you fingers into the spinning wheel. It hurts!

https://www.zoro.com/general-tools-...TQJd4kY_oYaAju6EALw_wcB&gclsrc=aw.ds

One of those hand held de-burring tools works for putting a slight chamfer on the hole
but it does mean you have to take the shaft right out whereas you can just tap the
shaft through a little to replace the oring and gloop it up with silicon.

Can't remember if its for the twin or triple...haven't had to replace those O rings for ages.......but a .50 cal brass cartridge cut down and only using the neck and some taper is a good home made compression tool.

Thats what I've always used. But I [like others here have said] have chamfered my rocker boxes.

The redneck engineering is working the best so far. I cut a sliver of a Pepsi can, uh huh, with a small amount of copper silicone I was only able to jam it in the voided top half of the spindle/rocker box as the bottom half is very tight (too tight for the with of a pepsi can). 30 miles on it so far. It's not leak proof but it has slowed down drastically like 90%. This is a temporary fix and no silicone shows.

I didn't cut or shave anything down.

The problem is that the o-rings supplied for both the B and C range rocker shafts are oversized for the application. They have too much volume to fit into the rocker shaft groove. The rubber can be deformed, but if its volume exceeds the available space it can not be compressed to fit. It squeezes out when trying to get it in and the result is the the well known sliver of material cut off.

I faced and dealt with this problem on my '72 Daytona. A phenomenal amount of force trying to get the rocker shaft in and then finding the well known sliver of rubber, with the shaft then not sealing.

I went back to basics and measured the volume of the groove in the shaft and the using the standard design guidelines from the o-ring manufacturers, found an o-ring that was the closest match. There is quite a lot of calculation to be done, working out the volume of each size of o-ring, until an optimum match is found.

The Design Targets for an o-ring are: 75% gland (groove) fill, 25% compression and 1-5% stretch of the o-ring in the groove.

Its quite a long process to find a suitable o-ring size, but once done, o-rings can be sourced from o-ring suppliers, the only down side is that you may need to buy a lifetime supply to meet their minimum quantities. On the plus side, they are not expensive.

For the C-range, I found that the best available rocker shaft o-ring was a 12mm x 1.2mm Viton. I had to buy 26 of them, but when I fitted them, with P80, I could push the rocker shaft into the rocker box with my THUMB! They have been in there for 15000 miles, without the slightest trace of any leak.

The B range rocker shaft are bigger in diameter, so would need a different o-ring to be calculated.

Incidentally, I've gone on and done the same exercise for two other difficult o-ring applications on the bike, the gear lever shaft and the fork dust cover o-rings. The process has been success for these as well.

Here are how I did my calcuilations:



Terry

Polymax do have an amazing range of O rings, I just wish I could remember the spec I bought for B range (which also work)!

Perhaps somebody would like to measure the groove dimensions and shaft diameter of a 650 rocker shaft and then the size can be specified by the same process.

Hi, On my '73 The OD of the end cap is .626". The root diameter of groove is .553-.555". The groove is .057-.060" wide.

The viton rings Steadfast Cycles sells does not fill the groove. There is room for the oring to flatten into groove with no problems. Again, you must not have too much grease or oil on ring or in groove. This includes rubber lubes such as P80. Liquids do not compress so it will not allow ring to flatten.

I had no problems at all installing these o-rings in 2 motors. My friends didn't either.

There is earlier oring that is slightly fatter. Problem is, you don't know which you get until it arrives. Somehow some sellers seem to think it doesn't matter. You can lay straight edge over outside of ring in groove & see if when compressing ring you have clearance or not.

On a side note I bought the stainless steel cap set. They had similar groove size, but OD was slightly smaller. I felt on my bike they were a tad loose in rocker box so I just reused the slightly discolored original caps. My originals fit snuggly in bores. I'd say very light press fit. Warming boxes to just hot enough to where I could still handle them allowed the cap of shaft to slide into box bore without a struggle.

Don

"The OD of the end cap is .626". The root diameter of groove is .553-.555". The groove is .057-.060" wide".

Hi Don, When I have some time, as a fun exercise, I'll crunch the numbers you have provided and see what size o-ring will work. Incidentally, are the T120/TR6 rocker shaft caps the same diameter as the T140 ones?

Terry

The T140 and all B range from the year dot had the same cap dimensions, but up to and including 1953, there was no O ring.

I have always had trouble keeping the spindles on my Trident from leaking. At this point they are basically covered with silver silicone (and they till weep!). Are the Trident spindles the same size as the T140?

Ed from NJ

I've crunched the numbers and here you can see which o-rings are best matched to the B range rocker shafts. It is best to use Viton ones. It cames as a surprise to see how thin the o-rings are compared to what is usually supplied by many dealers.



Terry

Thanks for your calculations and the very detailed table. Just to get it clear in my mathematically challenged brain, is the conclusion that the ideal (or near as dammit ideal) T140 rockershaft O rings are 13mm ID with a cross section of 1.2mm? And Viton as the material?

26 of them. That should be about right for enough practice before I finally get two to go in without shearing.

LMAO...DavidP

Beginning to think I should have been a rocket scientist or brain surgeon........I've done the rocker O rings a few times and every time it's been successful and years of trouble free service. So tbh, I don't get or fully understand the troubles people have.

One thing I always do is use a small smear of black silastic as well as a new O ring. This helps with the seal PLUS makes the O ring and housing slippery so that everything gets pulled in without a struggle. Just wipe away any excess once seated. And I only smear the O ring and back from there, don't want any getting into the rocker box area.

I also assume that everyone uses a spacer and nut on the other end to draw the spindle in - nobody is [tapping it into place?

One other trick is to mark the end of the spindle with a texta so that you can see that the spindle hasn't rotated at all. And as soon as it tries to you stop trying to draw it in any further, it should be home/seated by that time.

Hi Tigernuts,

Yes, the optimum o-ring size for the T140 is 13mm ID and 1.2mm cross section in viton. Polymax here in the UK have them and the good news is that their minimum quantity for that o-ring is only 9 items.

Hi trident150v, Finding the correct o-ring size is hardly rocket science . If you have the correct o-ring, the job is easy. All you need to do is stay as close as possible to the three ideal design guidelines the o-ring manufacturers provide: 75% gland fill, 25% o-ring compression and 1-5% stretch.

The problem is that many dealers have no idea what they are selling, ignore customer feedback and will supply the wrong sizes year after year. Problems fitting rocker shaft o-rings have been talked about for decades. Get suitable sized o-rings and the shaft slides in with no difficulty. When I did this on my Daytona, I was able to push the rocker shaft in using only THUMB Pressure! It seemed too easy, but 15000 miles later, there is not event a hint of a leak.

There are also other areas where people have difficulty with o-rings on these bikes: the gear change shaft and the fork dust seal holders. Using the same process, I have had success there too. What has surprised me, is that when carrying out the calculations, the o-rings always seem to turn out noticeably thinner tan what we being supplied with from many of the usual sources.

Thanks all for a great discussion. My T150 rocker boxes are off at present. I'll check dimensions on the O rings which came with the gasket set.
I do have a triangular scraper, I'll chamfer the leading edge if needed.

" My T150 rocker boxes are off at present. I'll check dimensions on the O rings which came with the gasket set."

Hi DavidP, If you have the rocker shafts out at the moment, it would be great if you could measure the cap diameter, the groove width and the root diameter (bottom diameter of the groove) if possible. Thanks.

Terry

Thanks, I'm too lazy (or perhaps inept) to find that sort of information myself, and I need to up my game...

SR

What I have in my stock (from Polymax) are 12 x1.2 marked up for 500's and 12 x 1.4 for 650's. Haven't run the calculator past the 1.4's, but I do know that they are much thinner than what is normally supplied, easy to assemble and don't leak. That said, better to go with Shippy's recommendation!