Noisy, Rough Gear Box On The 2016 Bonneville T100

I would agree that the shifts are 'clunkier' and not always as positive as I would like but nothing I can't live with...definitely helps if you match revs by blipping the throttle.

 

The oil you are using is not too light, it is too thick.
The specified grade of oil is 10/40.
Are you using a car oil? They have additives which are not compatible with motorcycle wet clutches and cause slip.

 

I've agreed with the previous poster, but....
you could make a case for 20/50 in a hot environment. Personally I've always used semi synth 10/40 and had no problems, over many miles and years, in the hot parts of Europe as well as chilly old Blighty. And some high mileage bikes too. But as mentioned, bike specific matters too, don't just chuck in some WalMart crap at $2.99 a bucketful, as some of our American brethren have advocated in the past. It's not big and it's not clever

 

Yes, l noted your location and figured you had used 20/50 intentionally. My son had similar reservations driving over the Pyrenees when his car hit some pretty high oil temps. Was fine though-modern oils have a destruction point of something like 400 degrees. To clarify-l use semi synth oils. I used Castrol Power, then moved over to Silkolene/Fuchs Super. Always 10/40. Silkolene l found gave best gearshifting. No idea if these are available in US, but in your position l'd be tempted to use something of that ilk to see if it helps. Bit of an expense l know but my feeling is you'd see a benefit . Good luck

 

Yeh... Automotive oil is hard on motorcycle transmissions. I have made that mistake myself in the past. I also live in a climate like yours [Mohave Desert]. I would use a oil with a higher viscosity rating on the second number, but the first number in the rating is the low temp viscosity. I would not change that. But now I only use oil rated for motorcycle use. ...J.D.

 

It's not what's in car oil that's causing problems if the clutch doesn't slip. It's what's NOT in the oil that's the problem. Motorcycle specific oils use additives to deal with the high loads and increased sheer from the gearbox. Car oil isn't made for lubricating transmission gears and will thin out in no time.

 

My 2017 T100 is clunky too. When shifting in first from standstill or when shifting from second to third.

 

My 2022 SS is like this, as was my 2020 model, quite clunky from 2-3 but smooth and slick everywhere else. My ZZR has always given a hefty CLUNK on engaging 1st but offers slick changes up through the box and is perfect for clutchless up shifts in the top 3 gears. I've had two GSXR1100's in the past and they both had the sweetest gearbox's on any bike I've ever ridden.

 

My Bonnie gearbox is one of the best I've had, although max temperature in UK is only about 30C. Its an air/oil cooled model which is possibly the same as yours, although I don't know (water cooled came out in 2017 here).

One point on oil, I cannot see any reason not to use fully synthetic oil, readily available for motorcycles here, although I welcome any comment on this from someone more authoritative on the subject.

 

Imho, it is the design of this gearbox that makes it clunky for 2-3 shifts. Changing oil will not make any significant difference.

 

Castrol make a 20/50 semi synthetic bike oil.....I would never risk a car oil.

I to use 20/50 semi synthetic castrol motor cycle type.....my box it quieter with it.

No probs with gear changes.

How old is your bike.....any warranty left on it.

 

Might be worth checking the slow running speed has been set right too, because that can upset the neutral to first gear change if set too high.

 

Span "adjusters"

 

My 2022 Speedmaster has had no difference in the “ clunk “ with conventional oil or semi-synthetic when engaging 1’st gear at a stop, however in the upshifts, I believe that the smoothness of the upshifts are related to the rpm of the engine.