Downshift Problem

[eeorheim]

Hello all,

I am a long time reader first-time poster. I own a '93 K75S with 57,000 miles on it. Within the last week it has developed a problem down shifting from 5th to 4th and from 4th to 3rd. If I'm pulling up to a stop it will down shift very smoothly at low speed, but when I get into the twists I'll occasionally have to put more weight to the pedal than I should have to. Is this signs of a spline lube needed or something worse?

Thanks for any input,
Eric E Orheim

[soldemall]

Hello all,

Is this signs of a spline lube needed or something worse?

Thanks for any input,
Eric E Orheim

Perhaps, but try refreshing gearbox oil. Makes a big difference.

[PGlaves]

The symptoms you have described - difficult downshifting at speed - while sometimes smoothly downshifting either at speed or while decelerating - are absolutely classic symptoms that a spline lube is needed.

The clutch disk needs to slide smoothly a short distance so that when the pressure plate moves (releases) the disk also slides away from the fixed clutch ring. Otherwise, the transmission still receives torque as the disk drags on the fixed ring. In this case, downshifting is smooth only when input/output speeds are matched, as when decelerating or double clutching.

I would remove the transmission and thoroughly clean and lube the splines before the lack of lubrication, rust, dust, and other grit destroys the input shaft, clutch hub, or both

[eeorheim]

Well according to the local weather guy we should have an upcoming weekend of rain so it looks as though I've got a project to keep me busy off of the bike instead of on.

Thanks for the help,

Eric E Orheim

[wmubrown]

The symptoms you have described - difficult downshifting at speed - while sometimes smoothly downshifting either at speed or while decelerating - are absolutely classic symptoms that a spline lube is needed.

The clutch disk needs to slide smoothly a short distance so that when the pressure plate moves (releases) the disk also slides away from the fixed clutch ring. Otherwise, the transmission still receives torque as the disk drags on the fixed ring. In this case, downshifting is smooth only when input/output speeds are matched, as when decelerating or double clutching.

I would remove the transmission and thoroughly clean and lube the splines before the lack of lubrication, rust, dust, and other grit destroys the input shaft, clutch hub, or both

Wouldn't he also notice the clutch lever getting harder to pull? Or would that change so gradually to not be an indicator?

[PGlaves]

Wouldn't he also notice the clutch lever getting harder to pull? Or would that change so gradually to not be an indicator?

A dry spline doesn't really affect the clutch pull. The movable pressure plate does not contact the splines, so if they are dry it makes no difference to the pressure plate. There are a few spots to dab grease where the pressure plate contacts the spring, but even when these are dry it is hard to feel at the lever.

[roy]

Paul, how often should the clutch splines be lubed?

I lubed mine with Honda Moly 60 two years ago at 42K miles. Now at 60K miles and I have been noticing the same problem especially when the bike is cold I.e. grease is stiff.

I totally pulled the tranny and clutch disc to clean/ inspect the splines. The splines still had the machining marks on them. I am using Mobil 1 75W-90 lube that is chaged every fall before winter storage.

Any recommendations on a different lube or is every two years what is required.

Thanks

Roy

[cjack]

Paul, how often should the clutch splines be lubed?

I lubed mine with Honda Moly 60 two years ago at 42K miles. Now at 60K miles and I have been noticing the same problem especially when the bike is cold I.e. grease is stiff.

I totally pulled the tranny and clutch disc to clean/ inspect the splines. The splines still had the machining marks on them. I am using Mobil 1 75W-90 lube that is chaged every fall before winter storage.

Any recommendations on a different lube or is every two years what is required.

Thanks

Roy

Trouble is, Viki and I had two '86 K100RSes, new, and never lubed the splines. They were never disassembled for any reason. They shifted like a dream as long as we had them which was about 2005. But only about 60K miles each 'til then.
YMMV.

[PGlaves]

Paul, how often should the clutch splines be lubed?

I lubed mine with Honda Moly 60 two years ago at 42K miles. Now at 60K miles and I have been noticing the same problem especially when the bike is cold I.e. grease is stiff.

I totally pulled the tranny and clutch disc to clean/ inspect the splines. The splines still had the machining marks on them. I am using Mobil 1 75W-90 lube that is chaged every fall before winter storage.

Any recommendations on a different lube or is every two years what is required.

Thanks

Roy


Every couple of years or about every 50K miles seems to be a good practice. There is some variability from machine to machine. Some of the K75s ate splines early while other bikes didn't seem to wear them much at all. There also seems to be a broad variation in how well the splines were lubed at the factory in the first place. Also, as they wear, the rate of wear tends to increase so more frequent cleaning and lubrication is called for.

The only real way to know what you have is to clean and lube the splines once - I have done this every time we have bought a used K75 - 6 of them by now.

As for the lubricant - Honda Moly 60 is good, but it has some limitations. To define terms: by lubricant folk's standards, a moly grease contains a minimum of 3% moly and is usually in the 3% to 5% range. A moly "paste" must contain at least 50% moly. Honda Moly 60 is 60% moly in a petroleum base. Moly (molybdemum disulfide) is a ground fine powder similar in appearance (only) to graphite.

Honda Moly 60's limitations are that it dries out fairly quickly and it's anti corrosion characteristics are modest.

I have mixed Honda Moly 60 with a boat trailer wheel bearing moly grease 50-50. That gives me a lubricant about 30% moly content which is stickier and has better anti corrosion characteristics than Honda Moly 60 by itself.

You can also get powdered moly and mix it into any suitable extreme pressure grease.

For those interested you can find more about moly than you probably wanted to know by browsing the various pages and products at:

www.tsmoly.com

[lkchris]

Your BMW dealer will have something called "Microlube GL261" intended for this purpose.

Last I read, Oak likes it.

On mine in the last month--will see how it works.

[eeorheim]

Thanks again for the advice. The job went easier than I expected it to. Even the weatherman was right about the rain so I didn't even miss any ride time.

Cheers,
Eric E Orheim