Primary case capacity in a '73 850

I know all the books call for 7oz. but I could have sworn that someone on this board made a good case for 5 oz. since there is less chance of getting oil in the clutch. Does anyone believe that 5 oz. is just not enough? I'm using F type ATF.

I use ATF, and stick with the 200ml / 7oz recommendation. I note the factory manual says don't use anymore than 7oz, so I guess thats OK. Any less may compromise chain lubrication? But here's the intersting thing. if you put 7oz in to the case, and have the bike upright, take out that little level plug and see what doesn't come out! I erred on the side of caution and topped it up to the level plug and I never had an issue with oil on the plates.

Mick

Yellow_Cad said:

I know all the books call for 7oz. but I could have sworn that someone on this board made a good case for 5 oz. since there is less chance of getting oil in the clutch. Does anyone believe that 5 oz. is just not enough? I'm using F type ATF.

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I have never had a problem with a slipping clutch running in 30W engine oil up to the fill hole. I think this about 170 cc. I am running bronze clutch plates and have always wondered what all the fuss was about regarding clutch slippage, ATF versus engine oil etc. in Commandos. Never had a problem with the clutch on my Commando. As long as the bottom of the primary chain is contacting some sort of oil you should be good to go.

Please remember when using "fluid ounces" that an Imperial fluid ounce is a slightly smaller measure than a US fliud ounce, (however, an Imperial gallon is bigger than a US gallon because there are 20 Imp.fl. oz in an Imp. pint, 8 pints = 1 gallon) so "7" Imp. fl oz = 6.7 US fl. oz. = 198.9cc/ml.

Since the only purpose is to lube the primary chain, the oil level is not terribly critical. There are arguments for using 5 oz, which just touches the lower run of the primary chain. I use ATF and fill with 200 ml with no problem or clutch slip, but I know others that use 5 oz with apparently no ill effect.

tpeever said:

Yellow_Cad said:

I know all the books call for 7oz. but I could have sworn that someone on this board made a good case for 5 oz. since there is less chance of getting oil in the clutch. Does anyone believe that 5 oz. is just not enough? I'm using F type ATF.

Click to expand...

I have never had a problem with a slipping clutch running in 30W engine oil up to the fill hole. I think this about 170 cc. I am running bronze clutch plates and have always wondered what all the fuss was about regarding clutch slippage, ATF versus engine oil etc. in Commandos. Never had a problem with the clutch on my Commando. As long as the bottom of the primary chain is contacting some sort of oil you should be good to go.

Click to expand...

I agree never had a problem with slip either, kept chain drive and used 30w for a good 15 years so I always wondered about the clutch slip prob's.

On my earlier Commando I had fiber discs. These always caused me problems with slippage until the bronze ones came out.