trans/driveshaft vibration

[cycle builder]

I own a 1981 XS1100 with 50,000kms/ 31,000 miles. It suddenly developed a vibration under exceleration in 4, 5 and 6th gear. Back off and it stops. The vibration is similar to taking off in a high gear and very low rpm on some chain driven bikes. The bike had a new tire about 1000 kms ago and it seems to be in balance spinning it in 6th on the kickstand. There are no noticeable noises that shouldnt be there either. Scared it might be a bearing or something in the driveshaft which could bring me to a sudden stop, hopefully not on a corner. Thanks Ron

[bikerphil]

Had a similar problem once. Thought it was a bad U-joint, same symptoms. It turned out to be loose 3 loose Allen bolts on the middle drive unit, behind the yoke under the rubber boot. Check your middle drive, make sure it has gear oil in it.

[cycle builder]

cycle builder

Thanks. That does make sense. When I think about it I have felt that feeling in a truck before and it was in the driveshaft steady bearing.

[tarzan]

You have 6 gears?Never seen an 11 with 6th.