Tuesday, July 07, 2009

Brigitta's stripped transmission input spline

I got Brigitta, my 1987 R80 Beemer back from Pete Homan today. Pretty fast work really, the most time was spent trying to fix the neutral sensor switch and they ended up replacing it instead.

I thought I'd show you what went wrong this past Saturday, which left Brigitta and me stranded for a short while on the side of the road.

Basically, the transmissions on these airheads use an input spline to mate with the clutch plate to engage and disengage the gears in the transmission when shifting gear. I thought you were supposed to lube them with special lubricant every 15,000 miles, no more than 18,000 miles. Well, according to Pete, one should do this service with every major service, every 10,000 miles!

I had been planning to lube the input spline when Brigitta hit 79,000 miles which I had calculated was roughly 15,000 from when I got her. I guess I should have done it sooner. Here's the result of what happens when this is neglected:

Here's the forward end of the old transmission, note the plentiful shiny metal flakes splattered about, they're the metal that was sheared/worn off of the input spline's gear teeth!

A closeup of the failed input spline, note how far down the teeth had been worn down! The correct height for the teeth is shown at the base of the input spline. Yikes!

Here's a shot of the input spline from the transmission I bought on Ebay and which now is mounted on Brigitta.

Pete Homan was able to get Brigitta back on the road in two days because I had bought previously a used 1981 airhead transmission thinking it would take the place of the one Brigitta came with when it came time to rebuild it at 100,000 miles.

Turns out, I was wrong about that too....sure the engine might go to 100,000 miles before needing an overhaul but transmission are really expected only to possibly make it to 50,000 miles! I'd been on borrowed time ever since I bought the motorcycle it seems.

I cleaned up the failed transmission this evening, I think I'll be having it rebuilt with a new input spline (rumored to cost $300), have the rest of its innards checked out and have it ready if/when the one I got from Ebay fails or needs work.

Pete wants me to change out the transmission fluid about 500 miles from now, or when Brigitta hits 76,000 miles to check out the fluid's condition. He'd noted some water had leaked into the Ebay transmission and was not 100% sure of it without cracking it open.

So, hopefully this Ebay transmission will work out well for a long time. I've got to save up the money to have the failed one rebuilt so I hope it lasts at least that long!


Jack Riepe said...

Charlie6 (Dom):

There is nothing like a little breakdown to bring one closer to mechanical reality. I have not really had a major problem with "Fire Balls," my 1995 K75. But I did manage to bust the gear indicator switch. This may not seem like a big deal, but it screws up the neutral light and makes this rig a little flakey to ride.

I had a real breakdown on my 1986 K75 "Blur Balls," when an oxygen sensor failed in the engine, causing injector problems.

I ewant to know why BMW motorcycle transmissions cost more than replacing the same unit in my GMC Suburban?

Too bad we will not run into each other in Tennessee next week. I am leaving on Sunday. I'm delighted the shop got your machine running again.

Fondest regards,
Jack "R" Toad.

irondad said...

It's good that it was you who suffered the breakdown. What I mean is that, if it were me, somehow or other it would all take about a month.

Some of these bikes are like kids, aren't they? You get them, fall in love with them, then feel obliged to throw good money after bad to keep them in circulation! :)

Charlie6 said...

Jack and Irondad

yeah, mechanical reality bites. All the stuff I carry for repairs and what ends up breaking I can't fix without new parts!

oh well, it's only money right? I could be wasting it on college tuition for the kids or some such silly nonsense instead.

Jack Riepe said...

Dear Charlie6 (Dom):

Isn't that the truth? You carry tools and spare parts figuring you've got everything covered... And Wham! It's a big ticket item where nothing is cheap!

I am carrying a spare headlanp, spare clutch cable, and a bottle of oil this weekend -- plus a plugging kit (but the tires have only 108 miles on them). That's it. Anything else will require a flatbed.

Fondest regards,
Jack "r" Toad