Author Topic: Plunger A7 Primary Chaincase  (Read 1406 times)

Offline starfield

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Plunger A7 Primary Chaincase
« on: 15.04. 2011 21:04 »
 I have never needed to add any engine oil to my A7 tank and I am sure that the level is now higher than when I first got the bike. The only place which loses oil is the primary chaincase. Never leaks when the bike is at rest (even when the case has just been topped up) but virtually all of it will disappear during the course of a days riding. There are some oil drips underneath when parked during a run but not I fancy enough to explain the rate of loss. The rear tyre is also pretty clean so I don't think its coming out from behind the clutch.

I have heard of engine oil leaking into the primary drive on a bike but can  it go the other way and is there a cure?

regards

Peter thinking he is going crazy

Offline beezalex

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Re: Plunger A7 Primary Chaincase
« Reply #1 on: 15.04. 2011 22:56 »
Unless it's been modified, or the primary is grossly overfilled there should be no way for primary fluid to get into the engine.  Typically engine oil only get into the primary if there's been a lot of wetsumping and the level in the engine is up to the DS main bearing.  I can't imagine anyway for the Primary oil level to get that high.
Alex

Too many BSA's


Online RichardL

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Re: Plunger A7 Primary Chaincase
« Reply #2 on: 16.04. 2011 00:16 »
Peter,

I'm going to risk an explanation,  others will surely follow shortly,  agreeing or pointing out my many personal flaws.  I looked back at your posts and see the bike was acquired last mid November.  Then,  you did quite bit of work on it,  now,  finally,  riding it somewhat regularly.  I am guessing that there was significant oil in the sump,  the P. O.  then topped-up for the sale and now,  with you riding regularly,  it isn't building up a lot in the sump and,  yes,  the tank has more in it than when you acquired it.  At the chaincase,  my guess is that you are indeed losing it from behind the clutch or other leak and that it is just not tracking back to the tire.  I suggest taping paper towels (or other, see below)  against all possible leak paths and going for a ride.  Then inspect the towels to see where the leak is.  The fact is,  I've done tbis using feminine napkins and was able to find my timing-side leak right away.

Richard L.

P. S.  If this post is to live,  please don't bother with humor regarding my choice of leak detection material.



 
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Offline starfield

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Re: Plunger A7 Primary Chaincase
« Reply #3 on: 19.04. 2011 08:31 »
Thanks for the suggestions. I did not really think there was any way oil could be transferring from primary chaincase to engine but I did want to check. I did  drain the sump to check the magnetic plug (its one of the later posh alloy housings) before using the bike regularly so I don't think wet sumping is the whole explanation.

Anyway I will resume more scientific investigations into both areas and report back if I find the answer. Never thought of putting a nappy on the bike before but it is a good idea in this instance.

Peter


Offline beezalex

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Re: Plunger A7 Primary Chaincase
« Reply #4 on: 19.04. 2011 23:25 »

P. S.  If this post is to live,  please don't bother with humor regarding my choice of leak detection material.

I'm not sayin' nothin! *grins*
Alex

Too many BSA's


Offline starfield

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Re: Plunger A7 Primary Chaincase
« Reply #5 on: 23.05. 2011 22:30 »
Apologies for resurrecting this post.  More research under controlled conditions seems to confirm that the engine oil level is actually rising roughly in proportion to the amount that is disappearing from the primary chain case. Started with a complete oil drain and replenish including the sump. Let everything settle down overnight, then ran the engine until the return oil started spitting rather than a steady stream and noted the oil level on the dipstick I have fitted to the tank cap.

Topped up the chaincase and did a run of circa 100 miles - result, little oil in the chaincase and a rise of about 1/2" in the oil tank level. Topped up the chaincase again and did another 150 mile run last Sunday and the level has gone up another 3/8".  Its not a temperature thing as I do all the measuring when the oil is cold and its not a result of wet sumping as the engine is run for a few minutes each time to the point where its pumping air and oil. I know the increase is not huge but across the area of the tank its pretty close to the 4-5fl oz of oil I am losing from the chaincase. I have not been able to detect any external oil leaks from the chaincase. There is a small but steady leak from the engine at the rear crankcase joint, not enough to unduly worry about but which should cause the tank level to drop a little but its obviously well under the amount it's actually 'making'. I know its impossible but it is happening. However, for the moment that is not my major concern.

After a run there is still a small amount of oil in the chaincase, enough to wet the bottom run of the clutch chainwheel. As far as I can tell it stabilises at that level but I will do some more testing to prove the point. The oil level in the chaincase is set by one of the chaincase screws. The previous owner tells me that he read somewhere that it was recommended to reduce the level in the primary chain case to the next lower screw. That is pretty much where my level now is. Does anyone have any knowledge of such a recommendation and is the lower level adequate to lubricate and cool the chain? I have kept an eye on tension and it has not changed at all over circa 600 miles of the above treatment.

This is one really weird motorcyle what with making oil and self discharging ammeters (see other post). But it now goes well and is a pleasure to ride so I don't want to risk damaging it.

regards

Peter


Offline Andrew

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Re: Plunger A7 Primary Chaincase
« Reply #6 on: 25.05. 2011 07:54 »
i can't remember the correct armount of oil in chain case, but it is not a lot just below clutch sounds right, looking at my plunger and running a level from the drain level srew its only about 1 inch of oil over about 6inchs i guess  around 150cc or less
Andy

Offline shabashow

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Re: Plunger A7 Primary Chaincase
« Reply #7 on: 28.05. 2011 17:24 »
According to BAcon's book, the47 to 51 plunger should take 284cc, 52-53 90cc and 54-57 115cc. Swingers can take 225cc.

90cc is fine for me, as the chain just dips into the oil. Usuall I end up with more oil in the chaincase, as there will be leakage from the crank case, which will be under higher pressure. I can't see how it can go the other way. Even if the primary case was filled to the top, and the crank case was under negative pressure, the level couldn't drop below the bottom of the crank case.

You've got a real brain teaser there;-)

Offline Andrew

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Re: Plunger A7 Primary Chaincase
« Reply #8 on: 31.05. 2011 16:37 »
Apologies for resurrecting this post, just a thought 'petrol'
Andy

Offline starfield

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Re: Plunger A7 Primary Chaincase
« Reply #9 on: 01.06. 2011 16:42 »
Confused by the reference to Petrol?

The info about capacities for the various years was interesting. I have been putting in near 1/2 pint to my chain case as that's what my manual states so perhaps mine is for the earlier model. Whereas it seems 90cc would be enough for the 52 engine. Decided to get scientific today and measure what was left as I reckon its close on 90cc. However, failed to find a drain plug, unless you are supposed to fully unscrew the adjuster. I removed the lowest fixing screw  but no oil cam out (and yes there is some in there, enough to wet the bottom of the clutch chain wheel). This bike continues to confound me.

Peter