Transmission problem on an R90/6

[Julio A.]

Hi Guys, This isn't for an R65, but I'll ask anyway.

I have an R90/6 that as this weird problem, Then the bike is pulling hard( such as from a stop or overtaking) It pops in and out of 1st gear by itself.
I tried replicating the problem on other gears, but it seems to be isolated in 1st gear only.

Plus, it has this weird loose, bearing sound at idle when the engine is warm.

I already completely overhauled the engine so I'm pretty sure the transmission has a problem. I also saw evidences of gasket maker goop all over the mating surfaced of the transmission. I think somebody tinkered with the tranny and messed something up.

I'm down with buying a whole new unit. Problem is that I don't know where to start looking for one.

[Tony Smith]

I'm down with buying a whole new unit. Problem is that I don't know where to start looking for one.

Your fault can have  numerous causes but the three most likely are failing input shaft bearing (consistent with the noise you are hearing in neutral), failing dogs on either 1st or intermediate gear, or (long stretch) selector cam failure.


It doesn't really matter as all three require the box to be pulled apart, the only variation is which parts you get to buy. Sadly the best advice I have is find a shop with a good reputation for gearbox rebuilds and pick the best price/freight combination.

[Julio A.]

Yeah, I think it'll be the best option.

Although It's too much of a risk to buy a 2nd hand one from ebay and have it shipped for rebuild elsewhere, Does anyone know a good specialist they can recommend that sells refurbished transmissions?

[georgesgiralt]

Hello Julio,
As I do not think there is such a specialist in the Philippines, why don't you contact a very esteemed one like Tom cutter in the USA ?
I bet he can ship to Manila and you won't have to worry about the quality of the job done ....
Just my 2cents.

[Matt Chapter]

Then the bike is pulling hard( such as from a stop or overtaking) It pops in and out of 1st gear by itself.

I just had this repaired on my R65.  The local shop pulled the transmission and sent it to a specialty shop in California.  I hear there's another shop somewhere on the east coast that also has the knowledge to make the repair.  The specific fix was to machine a groove so that a bearing would not move along the shaft.

Sorry I don't have more detail.

[wilcom]

There has been much discussion on the Airhead list about the 1974 tranny and it is a "first run" problem child. I would suggest goint to Snowbums site and have a look at the issues.

http://bmwmotorcycletech.info/transmission.htm

Have some time and a cup of your favorite beverage and you will find more than you ever wanted to know about BMW transmissions. It's a tough read but bear with it, lots of great info inside snowbums site

[montmil]

East coast area would be Tom Cutter with Ted Porter on the western edge of 'Murica. There are other experts in the gearbox game such as Bud Provin in the Midwest.