1989 BMW R80 build


New Member
Hello all,

Just fresh back from collecting my R80.

I'm hoping to achieve something similar to this http://www.bikebound.com/2016/04/13/bmw-r80-cafe-racer/

I will keep the thread as up to date as I can. I suppose my first question is, where is the best place to start and is there any must haves/ definate jobs to do.

Thanks in advance
Get the factory service manual first. Do all the normal service work and spend some time riding it around for a while. Fix anything that doesn't work perfectly. Everything will be far easier if you have familiarity and some expertise with your bike before you take it apart to modify it. If something does not work properly after your changes, it will be vastly easier to figure out why if it worked perfectly before hand. It is important to ride it around a while so you can become good enough at riding it to determine what you like and/or dislike about it so you can get that sorted out first. Tires and suspension make a great deal of difference so start there. Don't fool around with rim widths or diameters, or consider swapping the front suspension for something "better". Stick to tires, rear shock(s) and front suspension internals. Very few people know enough to improve on the factory chassis design, and a lot of (if not the majority of) the custom bikes you see may look cool but don't drive as well as the factory intended. If you plan to modify the engine, do that next. Be conservative. Hot rodding your engine for more power comes with a price. It takes skill, experience and time - sometimes a very great deal of each - to get most modified engines to behave as friendly as stock. The factory selects its compromises very carefully to achieve the results that sell. Just be aware that generally alterations trade one thing for another.

Once you have the mechanics of your bike sorted out, you can work on the aesthetics. Of course we all want to do that first, but it's a bad idea. Get your bike to function like you want it to first, and you will know all about the parts that are now off limits for cosmetic changes. You can try different gas tanks and seats and bars and pegs all you want and still have a good motorcycle underneath.

When you are done with all that, and you have the perfect bike, you'll find it a simple matter to take the whole thing apart and powder coat the frame, paint the tank and polish up all the shiny bits. Do things in this order, and you'll end up with an excellent vehicle than not only looks great, but works great as well. If you do the shiny bits first, you'll probably find that they are not so shiny after the whole thing has been apart a hundred times getting all the mechanical parts just right.
Thanks for the reply. I intend to keep the engine and suspension stock and just service them.

I've had a look inside the gas tank and it's thick with rust. Before I run the bike for any period of time I want to clear this. I'm not keen on going down the acid route, what are the best alternatives?
Put some fresh gas in and a hand full of nuts and bolts. Dance around shaking it repeat once or twice and see how it looks. If it doesn’t look to bad put some in line filters on and run with it. I’m a fan of filters I can see into and easily clean. BMW’s have 7mm fuel line usually cheapest on Amazon. A lot of people get 5/16 from their local auto stores and use clamps or it leaks (it’s to big). If you can’t get 7mm go down to 1/4” it’ll just be a tight fit. Better than a loose fit. These filters where like $10 and have been great.


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Also what state is the bike in? Is it a runner? Get it running well and ride it a season like said. Keeping getting on here and other forums in the meantime you’ll start to get ideas for what and where to start and gathering the things you need. Advrider.com is a great airhead source, however many grumpy old men will say mean things to you for wanting to molest an airhead. Still a great pool of knowledge on bmw’s.
I would say the tank is fairly rusty. I'm not sure if the nuts and bolts will clear it all. The bike runs and the previous owner had the carbs ultrasonically cleaned.

Has anyone used any of that Metal Rescue stuff, it looks good. Would be expensive though to fill the r80 tank with it.
I use phosphoric acid (sold as Phosphoric Prep and Etch at Home Depot or Dairyland Sterosol Milkstone Remover & Acid Rinse at Tractor Supply). Guys get good results from Evapo-rinse, too. Phosphoric acid is a mild acid commonly used for cleaning and in the production of cola like Coca-cola. I've saved some pretty destroyed tanks with it. The phosphoric acid doesn't hurt the good steel at all. Instead, it converts the rust to iron phosphate which in turn provides a protective layer to keep rust at bay. I'll take a small box of roofing nails with the acid and shake it around.
The screws/nails/bolts/etc and phosphoric acid advice are good and absolutely work. The phosphoric acid is quite benign and has no downside. You can submerge the tank in a water-baking soda solution to finish if you have neutralization concerns. Hydrochloric acid will more or less instantly completely clean the tank but is very difficult to neutralize and of course is fairly hazardous - I recommend against using it unless you know what you are doing. Or you can get it most of the way with the abrasive shake and finish with the evapo-rust which won't harm the paint. Evaporust is great for rust, but also removes cad and zinc plating so keep that in mind on other projects. The key is to get the heavy stuff off mechanically and finish with chemical. You can turn the tank and let it sit in various positions to save chemical. The filters are a good idea if you have doubts about the cleanliness of the tank. I have done some pretty rough tanks with water and gravel and a lot of shaking, Then rinsing thoroughly and then a gallon of vinegar and a lot of swishing and sitting and turning and then water rinse, then alcohol rinse and done. The alcohol mixes with water and then dries off quickly. Fill the tank immediately with gas. I almost never add filters as most often the petcock has 2 filters already, and most petcocks have a sediment bowl as well. I can't remember what the BMW petcock construction looks like though.
I think I'll use filters just in case. Does anyone know where you can obtain the phosphoric acid solutions over here in the UK? Would using Coke be sufficient?

I think I would start with the water gravel combo to get the big chunks off then go with the acid.

Once at the end of the process and you are happy with the finish, do you need to coat it in anything to prevent the rust from coming back?
A quick Google search shows you guys have a product called Rust Off, Phosphoric Acid, Rust Remover and Descaler that's sold by a place called Bonnyman's: http://www.bonnymans.co.uk/products/product.php?productID=6183 . They also sell through Amazon in the UK: https://www.amazon.co.uk/Rust-Off-Phosphoric-Remover-Descaler/dp/B00BP60ULM . I suspect there are other home improvement/hardware stores or farm supply stores there that sell it, too.
Does anyone have guidance on neutralising the tank after using the acid. I've seen baking soda and water but what type of measurements are we talking and how long to leave in the tank?

It depends on how concentrated the original acid solution was and how much of it remains in the tank. Assuming you pour it out and are only intending to neutralize what's left it will be easy. The concept is that you are not trying to exactly neutralize a specific quantity of acid, you simply want to neutralize all of it. That means you merely need to have a surplus of the neutralizing agent to that needed. Even if you use very concentrated acid, the very small volume left will be easy to overwhelm. A cup of baking soda (sodium bicarbonate/NaHCO3) in a gallon of warm water should prove to be overkill. This won't take any significant time as the materials will react pretty much immediately. Just pour it in, swish it around, and maybe turn on sides and top to make sure it gets into any joints or crevices around the filler neck or any other seams. Give it a few minutes (just to be sure and have peace of mind) and drain it out. Rinse with plain water several times and immediately throw in some gas with oil in it and swish to coat everything or fill to the brim with gas. The freshly etched steel will almost instantly surface rust. Don't worry about it, just coat it to stop the reaction with the oxygen in the air. If you are going to paint, you will want the gas out so go heavy on the oil to leave a residue after emptying.
You don't need to do anything to neutralize phosphoric acid. Just a rinse with an alcohol/water solution is fine. On tanks I don't intend to line, follow that with a rinse of 2 stroke fuel mixture, then I run it like normal. The only time you need to neutralize a phosphoric etch is on aluminum parts.
Going with metal rescue in the end. Have wet sanded the tank with gravel inside and its was a pain in the arse to get back out. These tanks are huge. Anyway will put the solution in some time this week.

On another note I'm looking for some clip ons over here in the U.K. The forks are 38.5mm but all I can find are clips ones at 38mm or 39mm. Any suggestions?
If you haven't already flatracer.com is worth a look.
Have you thought of fitting R100RS bars? Unless you're going to put on some rearsets they are low enough,
For future reference, instead of bb's or gravel or nuts and bolts for cleaning tanks, use a length of chain. Most hardware stores have many different shapes and sizes, they work great, their cheap its way easier to get back out of the tank.

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semmins said:
If you haven't already flatracer.com is worth a look.
Have you thought of fitting R100RS bars? Unless you're going to put on some rearsets they are low enough,
I have bought parts from and hae been very happy with the quality, prices and shipping time.
I'm not finding flat racers website great to use. A lot of stuff seems part of a package.

If I can only find 38mm/39mm is it best to go with 38 and file away or has anyone got any other suggestions?
My understanding is that the Tomasselli adjustable clip ons fit all the airheads. It may be that the 39mm have enough cinch to get down to a tight fit. I would call someone who sells them. Lots of vendors sell Tommaselli.
Karl1989 said:
I'm not finding flat racers website great to use. A lot of stuff seems part of a package.

If I can only find 38mm/39mm is it best to go with 38 and file away or has anyone got any other suggestions?

They have changed their website since I last visited it, it's harder to find stuff.
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