Burman GB gearbox

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Brian.Challinor
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Burman GB gearbox

Postby Brian.Challinor » Fri Nov 23, 2012 12:54 pm

How much oil/grease approx does a GB burman gearbox hold.

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Re: Burman GB gearbox

Postby john.nash » Fri Nov 23, 2012 1:56 pm

Isn't there an oil level hole, just underneath the kick-start ?
I fill mine with a mixture of oil and grease to that ....
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Re: Burman GB gearbox

Postby Brian.Challinor » Fri Nov 23, 2012 3:37 pm

John
Penrite make a special ''semi fluid grease'' for Burman boxes, the oil/grease comes in 500ml bottles. The reason for my question is how many bottles do I buy.

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Postby nevhunter » Sat Nov 24, 2012 12:08 am

I thought the GB box used oil. There should be a quantity listed somewhere but can't you see the oil level through the filler plug orifice.
as a general rule, if you have enough oil to nearly reach the layshaft centre that would be enough.
Many gearboxes that run oil during the 50's recommended engine oils. Many of todays engine oils do not meet the earlier specs. A gearbox oil meant for a two stroke would meet the requirements.
The grease filled gearboxes are hard to determine the level. I mix enough good oil to a good grease to make it flow and fill it till I can see it churning on the BA box which has a large enough filler, to see this happening. You have to run the engine with the bike on the rearstand, and select a gear. Trouble with the BA box is there is no drain plug. Nev

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Postby brenton.roy » Sat Nov 24, 2012 2:21 am

Hi Brian, As with Nev, I don't think this is the right stuff for a GB box. The factory suggestion is "summer weight engine oil"..
To my mind, thats a bit thin - but a light gear oil?
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Postby bob cottam » Sat Nov 24, 2012 8:44 am

I would always go for oil over grease in the box-I cant see how grease, however "thin" will ever penetrate between shafts and bushes.I have two bikes with Burman boxes,a `55 AJS and my MK11 Sq.The Ajay handbook recommendation is the heavier (summer) grade of engine oil (SAE50) and I have wondered why, when my old Commando box (AMC type) was recommended to use EP80 or 90 gear oil.I have heard that EP oils have additives that attack bronze? (bushes etc) thus engine oil for the AJS but this dosen`t make sense when the commando box also has bronze bushes in it, plus earlier bearings had brass cages etc. I`ll stick with sae50 even if it means the odd drip-at least you know its lubing on its way out past the shafts!! Bob.

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Re: Burman GB gearbox

Postby david.anderson » Sat Nov 24, 2012 9:36 am

A grease oil mix or Penrite semi fluid grease will lubricate a GB box just as it did the prior BA boxes. A GB box does not have any proper oil seals so a grease mix in the box will always look cleaner externally. J B Nicholson recommends the oil grease mix for GB boxes in his book Modern Motorcycle Engineering. The grease will also be a little quieter if the box has a 3rd gear whine. My 57 VH had a grease oil mix when I first bought the bike in 1972. I went to oil but subsequently went back to grease oil mix and may have done close to 100,000 miles with grease.
Beware of any Norton Commando gearbox unless the layshaft inner ball bearing has been replaced with a roller bearing. The layshaft ball bearing cages are prone to disintegrate dropping the balls through the box. instant lock up.I recently replaced a commando layshaft bearing and it was clear that the brass cage on the ball bearing had been eaten away by the use of an early EP oil. The Brass cages in the Portugese bearings that were originally used also had a habit of coming apart prior to being eaten. As far as I know modern EP oils will not attack brass/bronze.
David

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Re: Burman GB gearbox

Postby robjameson » Sat Nov 24, 2012 10:46 am

From memory I think it only takes about a pint, so I'd buy 2 bottles just to be sure.

I use a similar product made by Morris on my vh, which seems fine so far, biggest issue seems to be keeping it inside the gearbox not on the garage floor!
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Postby Brian.Challinor » Sat Nov 24, 2012 7:44 pm

Its description on the bottle ''Penrite semi fluid grease NLGI 00 ,for Burman Motorcycle gear boxes and some veteran car transmissions''

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Postby nevhunter » Sun Nov 25, 2012 1:18 am

Thick oils and grease can impose loads on bearing cages especially at high revs. Early EP oils have SCL additives Sulphur Chlorine Lead. I believe the damage comes more at high temps and maybe the later oils don't have the same additives an 80 gear oil is only 60 SAE weight as they run a diferent scale. Thin oils are noisier and on some boxes the changes are more drastic. Snickey/ Clunky). Many early BA and CP boxes I have dismantled have very hard grease in them and the layshaft bearings are (originally) sintered metal to hold the oil better. Layshaft bearing overheating due shortage of lubricant is not uncommon in the earlier boxes. The grease can be there but does not circulate or get into the close fitting bearings, or the geaars sometimes. Grease is only oil with a "soap" like Lithium stearate to make it less runny. It's the oil that does the lubricating...Nev


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