I have in the main a couple of annoying oil leaks on my 1956 Dominator 99 which in particular I seek advice. ( do have others too of course ).
a) Although the oil level in the oil tank is a tad below it's full mark , after a good run oil is leaking from the oil filler cap despite a decent cork gasket. I assume that oil is jetting out of the return pipe and overwhelming the cap gasket. I do not know as to whether I have a standard oil pump or an upgraded one. During a good run the oil weeps back onto the exhaust silencer and towards the rear tyre. There is a vent pipe from the top rear of the tank but surprisingly very little oil comes out of it which I assume it should rather than the oil cap.
b) Again after a run there is oil on the head and barrel fins. I have nipped up the head nuts but it has made no difference. I understand that oil can migrate up the studs and if so do I need to act promptly. What is the recommended torque in lbs ft for the cylinder head ?
Head torque on an early motor is 15 lb / ft on the small ones and 25 lb / ft on the big ones.
Owners of later bikes (eg Commando) will tell you it's 25 and 35. Do not go to these figures.....
The centre rear nut is very difficult to get a spanner on, especially if the carb is in place. A long reduced-hex nut is a good plan, you can get a ring spanner on it. I got one made for me, I wish some parts maker would do them for sale.
To have oil leaking from the top end and your oil tank filler cap, you have crank case pressurisation problems. That suggests excessive piston blow-by.
Could be a blowby issue,but first check the tank breather pipe is clear. Its also possible that someone has arranged the engine breather to go to the tank?,if so the std tank breather may not cope. Its only designed to clear the bubbles from the oil return. My 99 leaks a small amount from the head barrel area ,has done so for years ,comes and goes. A little goes a long way, stops rust!.
Does the oil tank cap have a breather hole? Mine does, but it ought not to!
Thanks for the response to my query. I have routed the engine breather pipe and the oil tank breather pipe into a catch tank which is mounted behind the gearbox. I will check that the oil tank breather is clear.
The oil tank cap does not have a breather hole in it.
One of the weaknesses of the Later Dominator twist oil tank caps is the very action that is supposed to help them seal. Basically the cause is wear and tear due to years of hard twisting abuse.
There are two things that happen when the caps are over-tightened........which most of us tend to do when in a hurry. Firstly as the cap reaches its stopping point during the clockwise turning, the two metal tangs inside the cap actually pull up on the sides of the tank spout. Over time this causes these two areas to bulge upwards and eventually the cap gasket ends up sitting on two bumps rather than a full flat metal ring. You can test to see if this has happened by rubbing a little oil over the spout lip and then laying a small sheet of glass on the spout. If you do not see a full circle through the glass then some distortion of the lip has occurred.......time for some panel beating!!!
The second problem that sometimes causes drips of oil in this area happens just inside the spout where the metal has been folded over to join the spout to the main body of the tank. If this joint is no longer perfect then hot oil vapour will be pushed through the smallest of gaps and appear on the outside of the tank under the cap. Giving the appearance of a leaking cap.......which probably isn't. I cured this problem on my bike by thoroughly cleaning the tank, then warming it to around 100*C in the oven before spreading a layer of Araldite on the inside of the spout. The heat of the warmed tank plus a hot air gun helped to make the Araldite go thin enough to spread over the metal joins and seal any gaps in the metal folds.
Thanks for your thoughts on the oil tank cap leaks Philip. Will have another look at mine when I return home.
Interested in how the catch tank works out George. Can you let us know? Re- ringed my 650, but still getting blow by / mayonnaise on filler cap. Catch tank may be the answer.
I will endeavour to attach a couple of photos later today Chas.
Thanks George, much appreciated. Suspect that there will be a few more interested folks.
Not a good idea to have acids and water mixing with engine oil.
The catch tank is made from aluminium rectangular box section and is mounted behind the laydown gearbox and is easily removed if required. There is also an oil drain at the bottom rear just about visible in the photo.
The copper pipe has a short flexible tube between the crankcase output and the copper pipe to ensure that the copper pipe does not over work harden and crack due to normal bike vibrations. It is just visible lower left in the photo.
The aluminium plate which is fitted under the carburettor and over the engine plates is not fitted in the photo.
hello all now catch tank are suppose then breath out via a pipe fitted to the rear chain-guard with the 650s vent out of throff tower in to a pipe via a T pipe fitting with oil breath from engine then to chain guard , fitting so the oil lubricates the rear chain , well that how mine works yours anna j
Nice neat job George.
I have some thin wall 2x2" steel box section, which I have available to use to fabricate a tank. Not geared up for Al welding at present.
I Was thinking of making a detachable top and filling the body with steel wool to act as a baffle. Maybe I over thinking on this?
location of tank looks good. Will probably follow your lead on this.