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R50 valve guides - correct ordering; needing camshaft

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kenrcruise
Posts: 86
Joined: Tue Apr 05, 2011 12:00 am

R50 valve guides - correct ordering; needing camshaft

Post by kenrcruise »

Fellow old BMW fans:

I need knowledgeable advice. My 1955 R50 is being fitted with new rotating valves and unleaded exhaust inserts. The thing I need to do is order the correct size valve guides. My machinist specifies .519 mm OD (or slightly larger) and 13.18mm, which I presume is the length (I could have my local repair shop do this but I am reluctant to order from them as the prices are excessive -- 10 years ago I paid $500 for a set of R75/6 guides!)

A number of suppliers have them. The Euro is at par with the US dollar so I am considering Meyers or Ulis. I just don't want to end up with the wrong size! I have one of the old guides to measure. By the way my R50 is # 551610, if that makes a difference.

I need a camshaft, and have a similar situation. My shop advises there are 4 different versions. How to get this right?

Regards,

Ken Cruise
Ken Cruise

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jwonder
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Re: R50 valve guides - correct ordering; needing camshaft

Post by jwonder »

Ken,

I will address the Camshaft question first. It is my OPINION (yes, take it for what its worth) that you should replace the camshaft with the same version that BMW made it with. BMW tuned the intake, carbs, compression, etc etc together and the motors run great for many thousands of miles. That is my opinion on it and if it was mine I would use the standard camshaft.

As for the guides, the person rebuilding the heads will know how they "feel" as they are extracted from the heads. A good rebuilder will know when the guides are too loose as they are extracted from the head. If your rebuilder told you to order oversize guides I would follow his recommendation.

I think your numbers are a bit backwards. The 13.18 should correspond to the outside diameter of the guide itself. Most of the guides I see are 50mm long. Check https://www.bmwclassicmotorcycles.com/p ... nder-head/ for the various sizes. If he is asking for 13.18mm you will need to go with a 13.2mm OD guide.

I would also check KibbleWhite and they have great valves and components. Find the R 60/2 page here: https://shop.kpmivalvetrain.com/c/sport ... .1125934.0. The components for the R 60/2 should the same as for your R 50 but I would measure and check. The KibbleWhite guides are ~ 47mm long.

Please also note that most exhaust guides are countersunk, you may want to get counter sunk guides of the right diameter.

I hope this helps!!!

James
James Wonder
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York

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