Vintage BMW Motorcycle Owners

Hello,

I started the fork rebuild project on my 1952 R51/3 and I found some things that I think are interesting.

1) The fork tubes look like they have been undisturbed and you can see from the pictures that they have a green coating on them. Is this original from the factory? Could these have been undisturbed?

2) After much research I thought that the forks were upgraded to rubber gaiters from metal shrouds and my thought was to convert it back to metal shrouds but now I am not sure if my other information is correct. My VIN number is 529205 and the handbook has mine with shrouds but the production numbers has it with rubber gaiters. Not sure if the production numbers or the handbook number is more accurate in this case.

3) As I mentioned in a previous post I have the sidecar springs and I am planning on putting the solo springs on to make the ride better. Looking at this its possible that the motorcycle came with sidecar springs but I am not sure.

4) The left shock tube seems to have the chrome rubbed off most of the tube while the right one looks much better. How important is this and should I look at re-chroming the tubes?

5) The damper rods are the new style which was nice to see, because the motorcycle is a mid-1952 I was not sure if it was going to have the new damper rods or the old ones.

So, I am still very torn if I should put the metal shrouds back on because I only want to do it if it is original. Originality is what matters most to me and I want to keep the motorcycle as original as possible. I would love to know how people feel about the chrome on the shock tubes and anything else you may see/not see in the pictures!

All help, comments and direction is much appreciated!!!!

James

If you read my reply to your first post the answer lies within. Your 529205 is well into the rubber gaiters period. Your front fender should also be indented where the gaiters meet the fender. If you change to solo springs you'll have to get new spring mounts as the threaded portion is different. I don't see anything wrong on your tubes, just make sure they are smooth.

Yea as Brian sates the upper and lower spring mounts also have to be changed as the springs have a different diameter

https://www.bmwclassicmotorcycles.com/p ... r51-2-r68/

Tommy

1. The green paint on your upper fork tubes and pinch bolts is interesting, and hard to say why it’s there. I highly doubt wouldn’t have been on there from the factory for a civilian bike, and if these forks maybe were taken off an older war bike maybe an R66 or R71 they would have been blue gray or beige, if they would have been painted at all. I’ve never seen a green BMW military bike. When you say they appear “undisturbed” I’m not for sure what you mean...just the green pinch bolts alone show that it didn’t roll off the assembly line like that. Heck in 70 years time virtually anything could have happened to the front end of that bike. Factory replacement fork tubes, CJ750, who knows. I would guess that the tubes and pinch bolts may have come off another bike for whatever reason and they had been painted by an individual.

4. As far as the chrome, I see the spot you’re talking about with the chrome worn through...as far as having that repaired I guess it completely depends upon the trouble and expense you are willing to go through. There are places that do hard chrome on fork tubes, I’m assuming it’s not particularly cheap. New fork tubes are available as I’m sure you already know, and they’re definitely not cheap either. Since your bike appears to be a rider, and not a concours level bike, I’d be inclined to leave the tube as-is as long as it feels smooth enough operation-wise for your liking. Deal with it if and when you ever decide to restore the bike. On the other hand if you want the best chance of the forks operating as well as they possibly can, then you’re looking at new or restored tubes and new bushings.

Thanks for the replies!

Brian, I did not discount your information, I am just learning more and the Barrington book states that the "production numbers" show mine with rubber but the workshop manual says its metal shrouds. Barrington say they trust the production numbers more, which makes sense with what you're saying. It is a learning curve.

The green is not paint, it looks and feels like a lubricant or rust prevention and not a paint. You can rub it off with your fingers and its a somewhat greasy coating. I was unsure if the factory used that type of spray or coating to protect from rust.

I am relieved that no-one feels I should re-chrome the fork tubes. The motorcycle ran great, tracked straight and had no issues all the way up to 140 KPH (which is as fast as I wanted to run it), it just felt "stiff" and the sidecar springs are what I am blaming for that.

I chucked the fork tubes up on my lathe and I have less than .008" runout in the middle which is what Barrington says so I think I am fine there as well.

THANKS!!!!!!!

Would BMW be able to indicate which type of forks your bike left the factory with? An email to their archives might provide some clues.

I had the same paint on a 51/3 that was from the French police…

I wanted to give an update on the fork shrouds and what I have found.

1) I contacted the BMW Archives and they let me know that my motorcycle was born with metal shrouds, half hubs and duplex front brakes. Thanks for the suggestion Kurt!!!

2) After reading the Barrington book more at length and doing more research it was interesting to find that the Steering Stem/Fork Bottom Plate fork tube holders for the metal shrouds was 35mm and the rubber gaiter bottom plate fork tube holders was 33mm to compensate for the leather gasket. My fork tube holders on the bottom plate is 35mm which further tells me that the metal shrouds were used.

3) I did some research on the green coating and it is an anti-rust coating common in the 50's and 60's and I am going to leave it alone and let it be. I am not sure when it was sprayed on but thanks to Michael for letting me know his French Police bike also had the same coating.

Because of all this, I ordered the metal shrouds and figured I would share all the updates in order for everyone to see in case someone else has the same question!

Thanks to all!!!

James

I have a question on a spacer in my R51/3 and wanted to know if anyone can look at their R51/3 and guide me on this.

If you look at the first picture of the R51 front-end you will notice the parts being; head bearing nut (Adjustment lock nut) #3, then the top bracket #2 then the top nut #1. There is no spacer like is found in the later models shown in the R50 diagram as part #1.

My R51/3 has a spacer between the bearing nut "Adjustment lock nut" and the top plate.

My issue is that without the spacer the top nut will NOT tighten down on the top plate.

So, I either have the wrong bearing nut "Adjustment lock nut" or at some point this was added and is not on any diagram I can find.

Help is greatly appreciated! Thank you!!!

James

Yeah, I read that all wrong, 529205 is at the tail end of the metal shrouds! I had know idea BMW had that info available.
Brian