Author Topic: rocker box breather  (Read 3176 times)

Offline bonny

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rocker box breather
« on: 27.06. 2010 18:17 »
is it a good idea to fit a rocker box breather ? i was thinking of one in the form of an inch or two of aluminium tube welded to one of the rocker box caps with a length of plastic or rubber hose attached and vented into the oil tank or somewhere.   

Online chaterlea25

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Re: rocker box breather
« Reply #1 on: 27.06. 2010 18:37 »
Hi Bonny,
In my opinion no extra breathers are required, properly setup the standard one is fine!

Search the forum and you will see many posts on the topic or any other questions you may have
Theres a mine of information / opinions and experience already written on the vagaries and fobies of these bikes

HTH
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline bonny

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Re: rocker box breather
« Reply #2 on: 27.06. 2010 19:27 »
i did a search for breathers and came up with nowt, its just that i heard the a10/a7 engine leaked oil at the head/rockerbox face and thought a breather might help.

Online bsa-bill

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Re: rocker box breather
« Reply #3 on: 27.06. 2010 21:34 »
I'm with John on this one bonny, don't think there is a need to relieve pressure up there it should get away all by itself, others will disagree of course.
I've never had a problem with oil leaks from the rocker box, but up till today I never used an alloy head which I believe are more prone to leaks, my mate has one on his A7 SS but admits to being his own fault ( tried filing to cure a very small weep, ended up with quite a good leak).
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline A10Boy

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Re: rocker box breather
« Reply #4 on: 27.06. 2010 21:42 »
If your engine is blowing oil bad enough to need a breather, there's something seriously wrong. Correct that and it should stop leaking.
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Online chaterlea25

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Re: rocker box breather
« Reply #5 on: 27.06. 2010 22:24 »
Hi Bonny,
Again my opinion,
the leaks from the head /rockerbox joint stem from the head steady being attached to the top of the rockerbox,
everything nice and solid!!!! the weakest link is the gasketjoint!!
imagine the torque forces around the crank centre trying to twist the engine around the crank!!!!!

I made a new head steady which has a compressed rubber bush between the rocker box brackets
the metal outer of this has 2 legs welded on which bolt to the frame in the normal fashion
Well over 10k miles later, no leaks *smile* *smile* *smile*
HTH
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline bonny

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Re: rocker box breather
« Reply #6 on: 27.06. 2010 23:57 »
you've gotta post a picture of that chaterlea  *smile*

Online muskrat

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Re: rocker box breather
« Reply #7 on: 28.06. 2010 08:50 »
Sounds like a good idea John and has merit. The rocker box on my '51 never leaks, it has the head steady from the head to the front down tubes. The cafe on the other hand has an over the top, super heavy duty stay and jack bolt to the top frame tube. I can't get a seal for luv nor money, and it has a Bunn breather so there is no crank case pressure at all, ever.
 And on that note, I swear by the Bunn breather. As discussed in another topic the timed breather is only working a small portion of the time and there is a lot of the time a pressure or vacuum is working against the piston. Less pressure = less leaks & more revs, less vacuum = moooore revs. *eek* LOL
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline alanp

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Re: rocker box breather
« Reply #8 on: 28.06. 2010 10:58 »
Rocker box joint leaks....mine did it even though it has a breather. I stripped the rocker box off twice to fix it but eventually I fixed it. I think it sensed me getting increasingly furious at having to get those push rods seated properly without messing up the gasket goo with the push rod aligning tool. Seriously though, mine was leaking on the inner edges so I tightened the centre bolts down first in case I was somehow causing it to bow up in the centre. It could have just been luck though!
I'd love to see photos of John's head steady mod. I wonder if that would also reduce vibration transmitted into the frame? I might try it without the head steady fixed to the frame one day (so as not to disturb the rocker box joint!). Anyone tried this?
Alan
Member of the 'Last of the Summer Wine Club - Jennycliff'.

Offline bonny

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Re: rocker box breather
« Reply #9 on: 28.06. 2010 11:32 »
any advantage in using an ariel type rocker box ? i picked one up at a jumble for 4 quid complete apart from its caps , i know the pushrods are easier to fit with these type.

Offline BSA500

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Re: rocker box breather
« Reply #10 on: 30.06. 2010 11:51 »
I found fitting a vent to the rear rockerbox cover stopped water vapour building up and turning the oil to that creamy white gunk.
Andy

Offline Big Nick

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Re: rocker box breather
« Reply #11 on: 02.07. 2010 22:02 »
i use one on my tuned A10 but not on my plunger A10 with flat top pistons
1932 500cc rudge
1936 500cc cotton pyton
1952 M20 with B31 motor
1952 Plunger A10
1954 New Hudson Autocycle
1962 A10
1982 BMW R100

Offline JohnH

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Re: rocker box breather
« Reply #12 on: 05.07. 2010 21:05 »
Hi to all on the forum. I'm definitely a newbie here, having just obtained a 1959 Golden Flash. Whilst looking for information, I chanced on this forum and have been spending a lot of time lurking - you seem to be a very knowledgeable crowd - and I hope to be able to access all the resources here and over time, maybe add my ten penn'orth!

It's been quite some time since I had a bike that I could ride. I started on a Francis Barnett Plover when I was 15 (I'm now 65) then got a 350 Jampot AJS (16MS), followed by a BSA B31 350, then a 250 Greeves, and then a 650 Triumph Trophy. After throwing my wife-to-be into a bed of nettles when I over cooked it on a corner, my next steeds were all basket cases: BSA C15, AJS 250, Triumph Tina scooter (awful!) and more recently, a 1930 Francis Barnett twin port 200cc (that I ended up selling - still not sure why).

I got the A10 about a month ago and it's already clear that the head (cast iron) is going to have to come off - there's an oil leak that looks as though it's from the head gasket on the drive side - I suspect that a non-annealed gasket was used. The rocker box seal also seems to be leaking - so I shall be really interested to see any information that John (Chaterlea 25) is able to post on his modification to the head steady system. The engine starts and runs OK but has a rough tickover, spitting back a lot. I was hoping to leave things be for the summer - just getting it MoT'd and taxed so that I can ride it in any halfway reasonable weather we might get and then  work on it over the winter  - but it looks as if I'm going to have to get the spanners out sooner than that!

I'm really looking forward to being an active member of this forum.

John
Triumph Bonneville - long gone (sadly)
AJS 16MS - keeps coming back (thank goodness)
BSA B31 - also long gone
Greeves 250 twin (good fun)
Francis Barnett 197 (first bike)

Online muskrat

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Re: rocker box breather
« Reply #13 on: 05.07. 2010 21:53 »
G'day John,
                  Welcome to the forum. The GF will serve you well, not such a big job to lift the head. While it's off check everything else. Looks like you've had plenty of experience over the years.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7