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52 R25/2 kick start noise/trans issue
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52 R25/2 kick start noise/trans issue
I'm new to this forum but not new to vintage bikes. This is my first BMW and when i got it it was a non runner with no spark. I couldn't acheave a spark until i got an after market electronic ignition and now it's a runner. Starts on the first kick every time. My problem is that when it runs there is a "ratcheting" sound coming from the kick start and it goes away when i pull the clutch in but also seems that 4th gear is non existent. There are 2 screws under the carb and the one closest to the cylinder is loose and i can't seem to get it in. I'm thinking it has something to do with the problems i having. What are these screws for? It seems when u try to get the screw in it won't catch wether the motor is running or stopped no matter how i manipulate the trans/motor while turning them. In order to get the screw even part of the way in i have to turn either the drive shaft or motor and i can feel that there is something trying to line up but i'm not sure. Any advise on this will be much appreciated. Ready to ride but not quite. Looking forward to chatting with replies.
Thanks ahead.
- caker
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Re: 52 R25/2 kick start noise/trans issue
Pretty sure those two screws hold the shift fork upper ends in place (one for each of the two forks), but I'm only looking at the parts diagrams - I've never been into one of these single transmissions.
https://www.bmwbike.com/index.php?e=mhs "Online Shop", then "1-Cyl", R25/2", "Manual gearbox" and the fourth subcategory shows the shift forks at the top of the image.
You need to open the transmission and inspect, is my guess. Sorry. Maybe someone else here knows better...
-Chris
- schrader7032
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Re: 52 R25/2 kick start noise/trans issue
I've not seen any pictures of the inside of one of these transmissions, but I'm guessing these screws connect to some kind of baffle plate, maybe that helps with the oil splash or something. Might be that the screws are held in by a nut and lock washer which has loosened...maybe dropped to the bottom of the case. I suspect you're going to have to have that serviced because it could cause trouble down the road. I think it takes a bit to get the transmission apart, heating the back cover in specific spots...that seems to be the case with the later model bikes. There are specific clearances needed and shimming when putting things back together.
Or what Chris said...he types faster!! Still I think you will need to get inside as the shift forks might be the issue you're having with shifting.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
Re: 52 R25/2 kick start noise/trans issue
Good luck!
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Re: 52 R25/2 kick start noise/trans issue
- schrader7032
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Re: 52 R25/2 kick start noise/trans issue
With that out of the way as well as the battery, you should be able to easily remove the transmission. I removed the clutch pack with things still in the bike. There are three screws that hold the clutch pack together. You will need long bolts with washers and nuts on them to slowly release the tension on the clutch pack. Here's a picture of the removal of one bolt and then replacing it with a threaded bolt to continue to hold pressure. Once all three bolts are removed and replaced, then you can slowly turn the nuts back and release the pressure.
It gets a little fiddly removing the electrics at the front. You'll need the appropriate hardened "puller" bolt to push off the rotor for the generator. Doing this part is a little fuzzy, but I think if you just study things, it will become clear on what to remove.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
- jwonder
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Re: 52 R25/2 kick start noise/trans issue
I am not sure about the R 25/2, but for the two cylinder plungers you can remove the transmission quite easily. The biggest pain is removing the driveshaft from the rubber disk and you really want to do that on the motorcycle if possible. Removing the final drive with the driveshaft intact is a bit painful (I have seen it done but even with 2 people its a balancing act).
Following is how I do it for the two cylinder plungers, please let us know if it works for the R 25/2:
1) Remove the rear wheel.
2) Loosen the right plunger top and bottom bolts.
3) Loosen and slide the driveshaft bell forward. (It should be a LEFT hand thread!)
4) If you have a removable rear fender cove, remove it. (the indent in the rear fender for driveshaft clearance)
5) Once that is all done you can then rotate the final drive counter-clockwise (while looking from top-down). By doing this you are pulling the driveshaft out of the rubber drive donut. Do not let the driveshaft fall on the frame, I typically put a tie strap loosely on the driveshaft before I do this so it does not fall.
6) Remove the battery and air cleaner.
7) Disconnect the ground wire and the clutch cable ad pull the clutch cable free.
8) On the twins the center stand spring goes to the gearbox. Without the spring the stand might fold and the motorcycle fall. You can use a ratchet strap from the center stand to the engine mount to ensure it does not fold. I have a jack I made up specifically for this, but the ratchet strap works. Let me know if this is the same on the R 25/2.
9) You can then remove the gearbox. Two springs will fall down. One large one for the center stand and a smaller one for the rear brake pedal.
I typed this completely from memory so I may have forgotten something, but post here if I did and we will help ASAP.
It is actually easier than it reads.
I hope this helps!!!
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York
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Re: 52 R25/2 kick start noise/trans issue
tg
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Re: 52 R25/2 kick start noise/trans issue
1) Remove the rear wheel.
2) Loosen the top and bottom shock bolts allowing the drive shaft and rear drive to "swing" in toward the empty space where the wheel was.
3) Gently pry the rubber "puck" away from the transmission and the drive shaft will hang to the side.
4) Disconnect clutch cable and neutral light wire.
5) Take off the 4 transmission bolts and the trans pops right out....pretty gravy really.
Took me less than an hour. The problem was the nut inside was jammed and special shape had to be held on the inside to get the screw on the top of the trans started. After i got everything back together i started it up and no noise and all of the gears now. Thanks again for the advise and the photo was especially helpful.
tg
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Re: 52 R25/2 kick start noise/trans issue
I've ridden the bike and it starts and runs great but the motor is overpowering the clutch. The clutch plates were pretty heat checked and the friction disc looks ok so I started by cleaning up the plates and "scuffing" them with sandpaper and did the same with the friction disk. The clutch still slipped so I "shimmed" the springs with 1/16" washers and it was better but it still slips when you get on the throttle. Can anyone tell me the specs of the friction disc? I saw a set on Ebay but they don't look any better than the ones I have. Any ideas will be helpful.
Thanks
tg