oil

[townsends20]

Hi again
    I am still getting up to date.
             With so many oil's on the market I need to know the best to use in this bike (rgs). I am running with 10w/30 in engine, gearbox and forks at present (the primary drive is on dry belt) I have done 60 miles since a complete rebuild and it is going like a dream, the book says gtx 20w/50 for eng & gearbox / forks10w/30. I have fork damper rods and it's a bit hard. I know I need to go up a grade with engine & gearbox,  I only intend to run with this oil for the first (slow)100 or so  miles until it loosens up. So please some advice, you all have been first class.
     Many thanks.
                               Steve
 

[t20racerman]

Do you have an oil filter fitted to your return oil line? If so, use modern 20/50 multigrade - Halfords do a good one. If you don't have a filter you need a non-detergent oil so that the crank sludge trap can work effectively.

Much debate on gearbox oil type, but to be honest, ANY good oil will do. I prefer 20/50, others swear by gearoil - both work perfectly well.

[townsends20]

yes I have a oil filter on the return, I might try a light gear oil for the gearbox it is a rr 2t .box. any suggestions for the forks or is that going to be trial & error. And are we talking semi synthetic.
   Steve.   

[BSA_54A10]

After 50 years of riding just about every thing BSA ever made I can say without any fears in make absolutely no difference which oil you use.
How long it is in there is much more important than what went in in the first place.

When your bike was made, oils were nothing like they are today.
In your forks use fork oil, they are well worth the extra cost as they will add life to your seals and go a long way to kill rust from water settleing out in the bottom of you fork legs and will not form an oil/water emulsion clogging the oil holes. Add to that they are directly blendable so you can experiment to find the right grade for you.

Ditto for gearbox oils.
When BSA gave their recommendations, gearbox oils were agressive towards copper bushes.
modern gear box oils are not as most syncro cones are bronze

[chaterlea25]

Hi Steve,
Heres my 2 cents worth  
Fork oil was developed because there was a need for it!!,
I use medium (10W) and adjust the amount to suit myself, I'm using damper rods as well in the forks
Add or drain some till you are happy

I would stay away from synthethic or semi for the engine until it has several thousand miles on it
In actual fact there is no need for synthethic oils in our BSA's, These oils are developed for long service intervals in modern high performance engines
I think everyone here changes their bikes oil very frequently probably at 1000 miles or at least once a year if less milage
I run my Super Rocket on straight 40, no issues over 10 years, and its ridden fairly hard
I use gear oil in the gearbox
and 10/40 MOTORCYCLE oil in the primary DO NOT use car oil as it will lead to clutch slip
Others prefer ATF and its fine as well

HTH
John O R

[Butch (cb)]

I run with a cartridge on the return side. I'm using Silkoline Chatsworth straight 40. This has detergents and should carry any 'bits' through to the filter. I figured this would be more likely to avoid wet sumping than 20/50 and that seems to be the case. I've just gone through 1500 miles since the build and have been changing the oil at 250, 500 and 750 miles though I shall be extending that to 1000 miles once I get to round numbers. I emptied the filter this time and refitted it rather than putting a new one in. Not sure how often I want to be changing that. I've got a magnetic plug in the SRM sump plate and that showed a light covering of fine 'mud' this time around.

Swapped out the primary oil for ATF as the six spring was showing a little slip after the running in period. Clutch feels like it's still slipping a little with the ATF being as thin as warm psis I now have a leak from the primary case. Time to pull it all for adjustments and resealing I guess.

[bsa-bill]

popping my head up to be shot down here but

popular belief is that multi-grade starts of thin and get thicker, now my memory plays tricks same as anybody else's but I'm sure that someone on another list (sadly no longer with us ) who was in the oil industry stated that multi-grades started off thick (50) but did not get any thinner than the stated lower grade (20) whereas mono grade started of thick (40) and got thin as it got hotter without any limit so would go way down to water.
Now could someone with oil industry knowledge like to tell me if this is true - or not (bearing in mind (oops pun there) the speed of light has been challenged)

[alanp]

popular belief is that multi-grade starts of thin and get thicker, now my memory plays tricks same as anybody else's but I'm sure that someone on another list (sadly no longer with us ) who was in the oil industry stated that multi-grades started off thick (50) but did not get any thinner than the stated lower grade (20) whereas mono grade started of thick (40) and got thin as it got hotter without any limit so would go way down to water.
Now could someone with oil industry knowledge like to tell me if this is true - or not (bearing in mind (oops pun there) the speed of light has been challenged)

Multigrades e.g. 20W 50 oils start at the viscosity of 20W when cold (I can't recall the exact test temp so let's just say 'cold') and their viscosity decreases with temperature rise and matches the viscosity of say, 50 grade when they are both at around 100C i.e.their viscosities are much lower than they were when cold.  Hence the inclusion of the '50' in the ref. 20W 50. It doesn't get thicker, it gets less viscous with increase in temp and crosses the decreasing viscosity curve of 50 grade at around 100C.
The 50 grade will start at a thicker viscosity when cold and fall more rapidly to the viscosity of the 20W 50 at around 100C.
So 20W 50 is more 'runny' at your typical garage temp than 50 grade and definitely will sneak through the pump when parked up more readily that 50 grade and will be easier to kick over when cold. A friend of mine changed from 20W 50 on his Commando to 50 grade (he can't recall why or if he can he's too embarassed to say) and found he struggled like mad to kick it over so changed back to 20W 50.
Hope this helps  

[bsa-bill]

cheers Alan - always wondered if I understood him right