Oil leak from primary chain

[John.Newbury]

I have recently acquired a 1956 NH and on going through the routine of a thorough service and check to get everything as it should be I topped up the primary chain oil to the level hole. Now when running the engine oil streams from the drive exit of the chain case and also runs into the enclosed drive chaincase. I had a 1957 NH many years ago and never experienced this amount of loss. I have had the clutch and primary assembly apart and checked all is well and am now at a loss as to the next move other than running with a very small amount of oil. Any thoughts anyone?

[john.nash]

Both of mine do this (47 and 54 singles).
I remember reading this (from silas siliprandi on the Yahoo forum) and have adopted the "fill so that the chain just "kisses" the oil" approach.

This recurring topic always mildly puzzles me. I had some ropey old nails back in the earlies, I couldn't afford anything else. Many of them were Ariels. Putting things back together "carefully" made them less ropey -slowly. I still have Ariels. Then or now I've never had the slightest problem with a primary chaincase leak from any Ariel model once it was basically sorted. Yes, you can MAKE them leak, it's quite easy. The best and simplest way [as everybody else has already pointed out] is to put too much oil in. The level plug is for amusement only. As already said, you can make things even worse on either rigid or S/arm models by filling to the level plug with the bike on the stand. You can fill to the level plug and get it somewhat right if you believe in the impossible, have faith in the unlikely fact that oil lurks somewhere until you put the plug in and then gleefully tells you "Too Much".

Try propping the bike on the primary side footrest with the bike canted over by a small amount, three or four degrees is enough [use a standard housebrick under the footrest; Ariel special tool no. 01]. Put the oil in until you see it appear in the level plug hole. Put a tray under the case and go away, make tea, play your Jess Conrad records and be truly grateful that pop music is no longer what it once was. This method is usually OK if you want to be a traditionalist and have a strong stomach.

If in a hurry the torch and, "bottom run of the chain just touching the oil surface" is excellent [a dentist's mirror is an excellent aide if you remember not to drop it in]. Shine the torch in through the level plug hole [the best use for it] and scope the action in the mirror. I use a tin pump can to dole oil sparingly in through the inspection hatch. Much more controllable than pouring; even if it takes forever. This method soon becomes very easy and speedy. You don't need to do it that often anyway.

A slack chain will throw up more oil than you want or the system will cope with. A tight chain will do all sorts of unwelcome things, so be pedantic about checking with the chain in at least 4 different points of rotation. [Who was it who did this with the engine running?]
I've never paid anything more than ordinary care to assembling the inner chaincase/gearbox/crankcase interface by the way; just getting it all decently centred and the joint faces carefully aligned is what it seems to need.

Heavy oil won't help. I still use straight 30. Sealing the rear chain oiler off won't do anything to help; it just means that your rear chain gets dry. The metering screw and oil flow drip rate is no problem if adjusted 'by the book.' OK, OK so you DO get a bit of oil fling off the rear chain from time to time. So what are you going to do? Buy an S8? You need to get some oil out of the primary case because of the oil et.c carried into the case by the engine breather, and the chain oiler does this job to perfection, provided that you haven't got a problem with excessive engine breathing due to worn bore/s forcing too much oil out.

I wouldn't, really wouldn't, endorse using chain spray on the primary chain. A bit of oil is just what the clutch rollers and [much more importantly] the
shock absorber drive requires.

Personally I don't think it is that bad a design; mind you I speak as somebody who can compare the decent Ariel attempt with some other truly horrendous things. Yes, BSA C series I am talking about you. Silas.

[John.Newbury]

Thanks for your prompt reply John. Just can't understand why I didn't have this problem with my other NH, just lucky I guess.

[john.nash]

Mine do still leak, a bit.
Nowhere near as bad as my early enfield or my mate's matchless (which has a massive hole, where the dynamo attaches to a second chain in the primary).

As there is just enough oil in there now, then I guess I put a drop more in more often (not that often though).
As long as I get "oily finger" off the chain top run, then we're good.

[david.anderson]

The cure to chaincase oil leaks is available through the singles spares section of the club. "Special alloy rings for rivetting to chainwheel to stop oil leaks" are available and come with instructions. I have fitted them to my square 4 and my VH and I now fill the oil level to well above the level screw and I dont have oil leaks. You will have to drill 6 holes through the chainwheel. Advice not given in the instructions is that you cannot drill the chainwheel with a HSS twist drill. You will need a tungsten 1/8" drill. I used a 1/8" spade type tungsten drill that was meant for drilling glass. Run the drill at a slow speed in a post drill with plenty of cutting oil. Dont try it with a hand held drill. The finished result will be no oil is kicked out through the gearbox or clutch side holes.