I have asked this question to a few people and every one tells me the spring goes to the inside, even though the triumph manuals says the opposite. All I know is there must be alot of bikes built by shops running around with that seal in backwards, with no problems. I would like to know the reason it should go in with the spring to the outside? Is there more negative pressure than positive?
Very interesting. The two engines I have recently torn down both had the seal spring inside the crankcase. As 303Brit said there must lots of incorrect installations about. I had thought that was spring inside was correct based on the two teardowns. When the engine I am working on goes back together it will be spring outside.
If you examine the seal and the seal surface on the sprocket it should be clear to you which way the seal is installed.
The back edge of the seal surface on the sprocket is chamfered to aid sprocket installation into the seal. When the seal is installed with the spring facing the crankshaft, the seal edge sits way down on the chamfer and not the ground seal surface. Some sprockets have a larger chamfer than others. This dramatically reduces the effectiveness of the seal. In some case it is almost the same as using no seal at all.
While all this is meaningless if you use the same oil in the primary as the engine. With the popularity of using automatic transmission fluid in the primary there is some concern. I don't think you want the automatic transmission oil mixing with the engine oil.
Joined: Sep 2010 Posts: 85Torch
BritBike Forum member
BritBike Forum member
Joined: Sep 2010
the same type spring seals are used in master cylinders, if you install that seal backwards you won't get any hydraulic pressure. since the engine develops pressure in the crankcase and the primary case does not. then it would make sense the crankcase seal is there to keep the engines pressurized oil laden air out of the primary cover. So in my mind, the seal spring goes to the sprocket side. Plus, like Mr. Healy says it makes the sprocket real easy to install and the seal lip runs on the smooth part if the sprocket.
Last edited by Torch; 09/15/113:49 pm.
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Does anyone happen to know if the seal used on the bonneville and daytona are the same ? I have the engine breathing into the primary case but want to revert to the original set up to fit a dry running belt drive kit and i have a seal from a bonneville.
Didn't Triumph use a different sprocket for the later bikes that breathe through the primary? (i.e. one without the chamfered edge)
I think this would necessitate using the chamfered sprocket to achieve a dry primary with the seal on the later bikes, yes? (along with the obvious chaincase-drain-to-the-sump and breather hose modifications)
Not that bon has that particular set-up, just curious is all...
'77 T140J "Vintage Bike". What's in your garage?
"The paying customer is always right."
Fitting round pegs into square holes since 1961...
I use modern engine oil as i cannot get monograde easily and when i can it is very expensive, i run a full flow oil filter so its not a problem apart from the anti-friction additives in the multi-grade causing slip and of course if i fit a belt drive i also eliminate another potential oil leak.
In theory, due to the timed breather, the crankcase runs in a vacuum state. This being the case, the seal would only be effective with spring side out, as the vacuum would pull the seal lip tighter to the sprocket. If it were spring side in, then the vacuum would lift the seal lip off the sprocket and allow air into the case.
The early pre-units didn't have a seal at all. These weren't a problem and I've even seen them with open primary and still not any issue.
Theories are wonderful things.... but it's what works that counts!
I find it difficult to answer ihines question without knowing what year triumph he is talking about. Does he even need a seal? Is it an oil sharing motor or not? I've found lots of drive side crank seals in oil sharing machines that were in both directions.
73 Triumph T140 Main Ride 70 Bonnie 67 BSA West Coast Hornet
I find it difficult to answer ihines question without knowing what year triumph he is talking about.
Fair enough but it should be simple to figure out:
If it is a 1963-1969, that breathes through the end of the camshaft, it uses a seal and the spring faces the sprocket.
If it is a 1970 or later, that breathes through the primary (no matter what the 1970 parts book says), it does not use a seal.
While you may have found seals in non-seal cases, or seals with the spring facing inward, it is not how it was designed to work. It was not how they were installed by the factory.
Is there any harm in installing a seal backwards in a 1963 to 1969? Other than cases where one chooses to use automatic transmission fluid in the primary, probably not.
May I quote the Overhaul manual written by Tom Gunn and used exclusively in the Triumph "Tri-Cor" Dealer Service School:
"o) Install the primary crankshaft oil seal open side (wire ring side) facing out toward the primary. (note: authors underline) DO NOT drive the seal all the way in - it must not seat against the drive side bearing and cause a drag on the crankshaft."
Is there any harm in installing a seal in a 1970 or later, that breathes through the primary, Yes! Basically the engine will not breath and the crankcase pressure will rise. This increases the chances of oil leaks and premature gasket failure.
Seeing as my clutch plates with the inserts are now contaminated with the anti-friction additives contained in modern oils , what is the best substance to decontaminate them ? Acetone ? Petrol ? Parts washer fluid ?
The spring definitely faces out on a 64. When you fit an oil seal the spring goes on the side where there is something you want to hold back. I am certainly glad that the spring faces the primary on mine because of the amount of crud that collects in there!
In the timing cover the two seals face in different directions. One is stopping oil getting into the points compartment and the other is making sure the oil goes only into the crank end. If you put the latter the wrong way round some of the oil could bleed out into the timing chest losing crank pressure.
Read all the above superficially but can confirm that timed breather engines should have the seal lip facing outboard to isolate primary oil [ATF ?] from being drawn into the crankcase past the DS main bearing during upward stroke of pistons.
When I first bought my bike I noted approx 70cc of primary oil "gone missing" over 100 miles and engine oil tank level increased.
The '69 has an oil tank filler cap dipstick which helps immesurably [LOL] in gaguing such things.
A mystery is why the factory left it until late in dry frame production to fit the dipstick ?