Hello ! I've bought the bike new, so know her history very well .... The gearbox has been renovated in 97 by a renowned French professional. so far so good. A month ago, I broke the small spring pressing the changing arm... the gearbox was stuck in third. As I thought I am clever enough, I opened it up to change the springs. I bought a set of the 3 springs from BMW dealer and a reinforced spring for the arm from BMW Boxer Dienst Berlin. I also bought a roller bearing to replace the locking nylon ring on the gear change assembly and of course a set of gaskets. I opened up the gearbox, was totally unable to find the broken part of the spring, removed the changing gear assembly, put the new springs and the roller bearing, removed the input shaft to remove and change the input seal, then reassembled the gearbox again, calculated the needed spacers and closed the gearbox after changing the output seal and the change gear level seal. Upon the first try, I noticed something that bothers me a lot : All gears change are as smooth as they where, but the changing mechanism has a strange behavior : when I push the lever up to go in upper gears, it is fine. When I push it down, the gears shift down, but the lever does not come back up so I'm unable to get down one gear. I have to help the lever back in position in order to render the lever operative again. Sometimes, the lever behaves as it should so I'm puzzled and seeking advice and remedies... Of course, I would be pleased to hear there is a cure without disassembly.... Waiting to read from you Guys ! Thanks for your help.
You replaced 4, 7, 17 and 14. Number 7 was found broken when you opened the box. I suppose you found part of this part, the part still on the pawl, which is # 8, and the rest of the pawl spring was missing? So far do I understand what has happened so far? It is possible the broken piece of the pawl spring was thrown out with the old oil. Or I guess it is possible it is still in the box. But to replace all three springs you would have to take the shift linkage apart and it seems rather impossible that you missed it. Still you say you removed the input shaft in a way I wonder, did you leave the other two shafts in the trans? Only the input shaft was removed? So maybe the missing piece of spring was hiding in one of the other shafts and it fell into the shift linkage after you put it back together. This is rather involved, I don't think this is it. My best guess at this point is that you assembled the shift linkage wrong. One of the springs which you think you have correctly installed is in fact not right. (I'll be honest with you, I've not done many of these so some kind of an expert may have different news for you). Still, no mater what the problem I think you have to take the trans out. You can probably fix this yourself still. It's part of the learning process to make mistakes and there by learn. Didn't you ever hear, "Learning is painful."?
Hello Disston, Thanks for your help Yes you're right. The spring # 7 had one of it's arm missing. But the remaining part was still on it's place. The missing part was not in the oil. I have a filter into the funnel on my reclaiming tank and no metal has shown here. Maybe it got eaten by the gears ? There was a lot of metal on the drain magnet ? Yes the intermediate shaft and output shaft remained in the box. I was confident the bearings where good so I did not plan to change them. so no need to remove them. But to change the input shaft seal, I thought it was safest to remove the input shaft. I do not think the missing spring part is the culprit here ... I bet on my knowledge and mechanics skills ... Well, this is what I would not ear... As this bike took me too much time these last months (and too much money too ). So all I would like to know is if it's risky to use the bike like this (I bet the gearbox will not block itself out, right ) because I have used it on this last few days and it is quite fine. I'm beginning to get used to help the gear change lever up at every gear change... If yes, the box will stay like this 'till the wife calms down and I have the force to dismantle this all again... Thanks a lot for your help ! P.S. the four O-ring #9 are on the fiche, but not in my box, and there are not any groove to mount them... What's their purpose ?
The 4 O-rings are not found ever I think. This was an attempt to fix the noise the trans makes in neutral but it didn't work and so they are never there. I'm not really sure of this info but I think this is the explanation I was given a couple years ago when I insisted there were supposed to be O-rings in the box. I don't know if it is OK to use this trans as is. If it were me and I had to use it I guess I would. If you are correct that the spring was chewed up then it will be OK. But I can't say for sure that you are right. I want it to be right but I don't know. The next time you take this apart will be faster. You know the drill and you own all the tools, correct? And the next time you take it apart do a complete take down. Take all the shafts out. You do not have to replace any bearings that are still good. Make sure you check the large bearing on the front of the out put shaft. This one gives some trouble. Other than the funky down shifting everything is good? Good luck with it.
Yes, everything is good. She makes the same noise and "clunks" as before. she's just more fun to put back into neutral when you where cruising in 5 ... As per the O-rings, my dealer told me that they're available, if I needed them ... funny !
Yes, everything is good. She makes the same noise and "clunks" as before. she's just more fun to put back into neutral when you where cruising in 5 ... As per the O-rings, my dealer told me that they're available, if I needed them ... funny !
If you do need transmission parts again, ask. It is one of the things that dealers charge a lot for. Oh, I guess you are in France? Not sure what your choices are over there. But you can use generic bearings which are much cheaper than dealer bearings. Actually you guys can get better parts in general I think. On my way back to work right now. I have to change the gear oil in my bike this week.
Yes, our neighbor at work is an industry parts dealer. I can find here special greases, bearings, o-rings and quite all the seals I need. Plus the tools needed to pull bearings or make an oil pressure gauge to test the left mileage in the oil pump ... The only bearing they could not have (as far as I know) are the needle bearings into the valve rocker assembly. They are very friendly (I change them from their boring work selling the same bearing again and again.... )
The funky shifting could be the shift shaft seal. This might be a perfect example of why I don't replace those springs unless they are broke. From my experience I bet those springs were replaced during the last recent rebuild. I would guess much more than half of the broken springs I have replaced were just recently installed. I haven't rebuilt nearly as many trannys as robtg, for instance, but I have never run into any problems leaving good springs in there. I think you are better off not replacing them.
This one is also a FAG made for BMW... So you won't get it out of BMW hands... But, I've seen they're available at the BMW Classic Shop .... so it's a good news, isn't it ?
Should I replace it ? Is it too sticky ? What do you think ? Yes the three springs where replaced by the guy who did the rebuild in '97 (the bike didn't run much since) with the input shaft (splines worn to death) the thrust spring and of course all the bearings. The bike had 120 000 km then and now has around 170 000. On the invoice there is a saying about a couple of modifications on the selection system to make it more reliable. Dunno what that means... (the parts looks correct for the year and serial of the bike)....
Pull it out and see of that fixes it. It sounds like you won't even have to ride the bike to find out. If that is it, don't put in back in so deep. So it was put back together with a worn out input shaft? The only problem I can think of right now that those cams have is the gear on the one cam separating from the cam. Was that welded or brazed? I don't like the K bike rollers either. I am too use to the plastic. I have only seen a couple of them split.
He's probably talking about the shift kit. It was an upgrade that likely happened right after your bike was made. As for the sticking shifter, were any of the c-clips hard to reinstall after the springs were changed? I know there is a place in the shift mechanism where there have been two thicknesses of spring: the thicker one binds up on some bikes. I think it's #17 which wouldn't explain the problem fully, but if it were #4 it definitely would.
No, the pawl is exactly the same as the early one. As I've no selection discs to compare to, I can't tell for the discs.I wonder what the changes where ? No, no C-clips where hard to install. And everyone came back to it's original place. I've played a bit with the shifter this morning in the garage. When the lever sticks, it made a definite click when I return it in place. I can't hear any click when I up-shift one gear. But maybe I'm a bit deaf ,
What I mean is that BMW changed this design shortly after your bike was made. They are often retrofitted to older bikes. Your mechanic may have simply mentioned that there was a possible upgrade. Anyhow, they are described on my website under "Airhead Transmissions." I think you're going to be taking it apart again. Too bad it didn't show up during assembly and bench testing.
Hello ! So, I ran the bike everyday to go to work (a 10 miles job ). So when I arrive at work the tranny is a bit warmer (it's cold here...). The gears are much much better with the hot gearbox. Going down is quite perfect except sometimes from 3 to 2. I ran the bike for about 35 miles and the box does not get hot nor noisy so I think end play setting is good. I checked the oil level often, and no leak either. As i installed a reinforced German made spring on the pawl, I contacted the seller and explained my problem. He told me that this is caused by the thicker spring. The wire used has a bigger diameter than the stock part. So the two parts rub more than they should and the spring is not strong enough to get the pawl back. (this explain why it's better when the gearbox is hot, play is more important and oil not so thick so does not stick as much). He told me I can use the gearbox as it is and save the installation of a stock spring when I have to open the box again. As the garage is freezing cold and the wife complains on the long hours spent in it instead of shopping or going to places together, I'll run the bike as is and wait 'till spring or another mechanical problem to fix it proper. Thanks all of you for your help and sound advices !
Which sounds like now. It doesn't work right, simple as that. Nice that the seller told you of the problem after you found out about it already.
Hello Anton, Actually the seller told me these springs won't fit all gearboxes. He was quite sure I will have problems with them. So he gave it to me and sold me a BMW OEM one. I decided to give it a try. I was foolish enough not to thoroughly test the gearbox BEFORE putting it back on the machine. So if someone is to blame here, it's me and me alone.... Now the box has made around 200 miles and gear change is going better every day. I think the mechanism has to settle. As I have to inspect the bike after the 750 miles run in (new rings and valve touch up) I will decide what I do then... But of course your advice is very sound. I can't let the bike like this. I could be dangerous.
