below are a few pics of,the inside of the gas tank of our bmw we just got which had been sitting for about 2.5 years.    Dave says we need to clean out the old gas( it does smell bad). What’s the best way to get the gas and inside if the tank cleaned up? Those chunks you see are rust. 
I tried using the search tool but am struggling getting results I am looking for.   Thank you

I just found a thread using the search tool, and they are recommending oxyclean.  They talk about rubber components  could be mush when sitting long.  I’m not sure how am I supposed to know what things are supposed to look like?   I’m going to start taking things out of the tank to clean it out. Maybe I’ll post pictures to see if you can tell if things need replacing .

A common method is to fill the tank with white vinegar, agitate it, let it soak for a few days, agitate it again then dump the contents. Repeat as much as necessary. Another method with apparently satisfying results is a solution of OxiClean. If you type clean fuel tank in the search box on the Forum page, several methods will surface.

Some of the tank interior might need scrubbing where it can be reached. The fuel level sender in the tank might need cleaning, too. You might as well remove the fuel pump assembly. The fuel pump is held within a rubber vibration damper that often will decompose during long periods of idleness. The damper is mounted in a plastic ring secured to a metal platform by two spring tabs on opposite sides from each other. Keep the damper if it isn't gooey and degraded. The fuel hoses and fuel filter should be replaced. Those are high-pressure submersible hoses and must be replaced by hoses of the same grade.

Sometimes volatile solvents are used for cleaning the tank. They are effective. They are also costly and should be used with caution.

Do not vacuum the fuel tank. That can cause explosion and fire.

Laitch wrote:A common method is to fill the tank with white vinegar, agitate it, let it soak for a few days, agitate it again then dump the contents. Repeat as much as necessary. Another method with apparently satisfying results is a solution of OxiClean. If you type clean fuel tank in the search box on the Forum page, several methods will surface.

Some of the tank interior might need scrubbing where it can be reached. The fuel level sender in the tank might need cleaning, too. You might as well remove the fuel pump assembly. The fuel pump is held within a rubber vibration damper that often will decompose during long periods of idleness. The damper is mounted in a plastic ring secured to a metal platform by two spring tabs on opposite sides from each other. Keep the damper if it isn't gooey and degraded. The fuel hoses and fuel filter should be replaced. Those are high-pressure submersible hoses and must be replaced by hoses of the same grade.

Sometimes volatile solvents are used for cleaning the tank. They are effective. They are also costly and should be used with caution.

Do not vacuum the fuel tank. That can cause explosion and fire.

Thank you. How do you empty the contents as you say? Do we need to take the gas tank off and how difficult is that? Or suck on end of a tube to get it out? I’d like to get the current gas that’s in there out .

I usually just siphon the old gas out.

Put on some disposable gloves before you even touch the fuel pump. That black vibration dampener goo takes a bit of scrubbing to remove from human flesh. Have a bag ready to dispose of the old fuel pump and dampener. Treat it like a toxic substance.

I haven't cleaned out a tank in a while but last one I cleaned out I used paint thinner and steel wool to scrub anything I could get to by hand. Acetone would probably work well but it's fairly nasty stuff and has vapors you probably don't want to breathe.

Here’s what the fuel pump and parts look like.   Does the damper need to be replaced? How many bolts does the pump run off of? Dave wants to test it

I meant volts not bolts.   Or by the look of all of it should we just replace it?

Kathysresto wrote:Thank you. How do you empty the contents as you say? Do we need to take the gas tank off and how difficult is that? Or suck on end of a tube to get it out? I’d like to get the current gas that’s in there out .

The damper and fuel sock at the bottom of the pump are shot. What you are experiencing is a common condition of old bikes. It's a twelve-volt pump. It might work but it also should have a cleaning soak. It can be tested for function with a 12V battery.

Removing the tank will help promote thorough cleaning. It's aluminum so won't take kindly to being dropped.

Pretend you're draining a stock pot; otherwise, a $4 syphon can be purchased from NAPA or Walmart. It consists of a squeeze bulb connected to a semi-rigid tube and a flexible tube.

First, the fuel intake and return lines are removed. They are under the forward left side of the tank. Then the water drain and vent hoses are removed. They are under the tank rear right. Hoses might not be attached to the ports—so much the better for this procedure. It's mounted at the rear on a post at each side. There should be a small, horseshoe shaped clip holding it onto each post. The clips get pulled straight off the posts. Then the tank is tipped upward and pulled and lifted rearward.

There's really no point asking if something's easy or difficult to do. Most every maintenance task on a K-bike is doable without a van-sized inventory of specialized tools. Time, incentive, determination and a couple of good manuals are what's needed. There are downloadable manuals here and at other sites.

Keyboarding skills enough to solicit help are useful. You already have those.

The pump is 12 volts as is the rest of the bike.
Parts you need are available from Euro Moto Electrics https://www.euromotoelectrics.com/ and the fuel pumps are available on eBay any of these with the Mapco a good choice


ALFA ROMEO 33 Alfetta 75 90 GTV Spider
BMW M3 E30 M5 E28 318i 320i 323i 325e 325i 520i 525e 528i 535i 633Csi 635Csi E23 733i, E23 735i
CITROEN
FIAT Argenta Brava Regata Strada Ritmo X19
JAGUAR XJ6 XJs Sovereign
LANCIA Beta Delta Gamma Prisma Trevi Y10 Turbo
LOTUS Esprit Turbo
MASERATI Bi Turbo
MERCEDES-BENZ
MG Metro Turbo Maestro Montego
MITSUBISHI Colt Turbo Lancer
OPEL Ascona Corse Kadett Manta Monza Omega Rekord Vectra
PEUGEOT 205 309GTi 405 505
RENAULT R5 Turbo R11 Turbo R18 Turbo R19 R21 Turbo R25 Turbo Espace Quadra Fuego
ROVER SD1 Vitesse 3500 Vanden Plas RANGE ROVER LAND ROVER 3.5 & 3.9 EFI
SEAT Ibiza Malaga
VOLKSWAGEN Transporter Caravelle
Mapco 22301
 
 
Fuel line is SAE30R10 8mm or 7.5mm. The 7.5mm is 13mm OD so better suited to BMW OEM clamps

Laitch wrote:

Kathysresto wrote:Thank you. How do you empty the contents as you say? Do we need to take the gas tank off and how difficult is that? Or suck on end of a tube to get it out? I’d like to get the current gas that’s in there out .

The damper and fuel sock at the bottom of the pump are shot. What you are experiencing is a common condition of old bikes. It's a twelve-volt pump. It might work but it also should have a cleaning soak. It can be tested for function with a 12V battery.

Removing the tank will help promote thorough cleaning. It's aluminum so won't take kindly to being dropped.

Pretend you're draining a stock pot; otherwise, a $4 syphon can be purchased from NAPA or Walmart. It consists of a squeeze bulb connected to a semi-rigid tube and a flexible tube.

First, the fuel intake and return lines are removed. They are under the forward left side of the tank. Then the water drain and vent hoses are removed. They are under the tank rear right. Hoses might not be attached to the ports—so much the better for this procedure. It's mounted at the rear on a post at each side. There should be a small, horseshoe shaped clip holding it onto each post. The clips get pulled straight off the posts. Then the tank is tipped upward and pulled and lifted rearward.

There's really no point asking if something's easy or difficult to do. Most every maintenance task on a K-bike is doable without a van-sized inventory of specialized tools. Time, incentive, determination and a couple of good manuals are what's needed. There are downloadable manuals here and at other sites.

Keyboarding skills enough to solicit help are useful. You already have those.

Thank you so so much!   My keyboarding skills are much better on an actual computer, but at home I use an I pad and pec.

I'd replace the external fuel lines too. If they're original the front one coming out of the tank is pretty much guaranteed to be cracked at the right angle.

In the US 5/16 (7.94mm) fuel line works fine for the external lines. Make sure it is rated for fuel injected systems.

You'll need to buy 4 ft of it since replacing all of the external lines takes just over 3ft.

Thank you all. This is very overwhelming to me seeing it is all new and confusing.   I try to tell dave what I’m reading and special considerations, and he gets mad because he knows what he’s doing but has never really worked on bikes before.  He’s worked on cars, but I don’t want anything to get screwed up or ruined.   I’m going to take a step back and regroup to figure out what to do.   I might be throwing in the towel.

Dont give up yet.  Let Dave tackle that nasty tank, it's a filthy job, and he may already have some experience and his own ideas on how to clean it up. 

With the tank off and the bike not running, it is a great time to do some disassembly and detailing of the bike.  Start at the tail cowl, cleaning, touching up the paint and making a list of missing and damaged parts.   A clean, good looking machine is always more pleasant to work on. 

From personal experience, the rear part of the frame under the tail cowl has never been cleaned and is probably in dire need of a good scrub, derusting and a bit of paint.  Might be a good project for you while he he gets the tank and fuel system addressed.

And don't forget to lube the exhaust bearings.

Oh, please, stop with the muffler bearing lube.  We'll have arguments on what lube to use for the next week.

Don't be intimidated by pulling the fuel tank.  I knew I had to remove mine when I got the bike, but kept putting it off.   Once I'd done it, it seems like I was removing it on a regular basis.  
It isn't bad, and allows easier access to a lot of things you will be working with to get it freshened up.

Be warned: When I emptied and cleaned my tank, I left it off and open for several days.  The exposure to the air caused parts of the fuel lever sensor to rust.  Next time, if i have to leave mine empty fora while, I'll either close it up orspray some rust preventative in there, and probably both.   I knew the aluminum tank would be OK, but didn't think about those pieces.

Heed the advice to replace all fuel lines.  I planned to replace every line on mine, and had them ordered, when I started mine up one day last winter.  For reasons I still don't know, I reached out and touched a line with my finger- the line that feeds the fuel injector rail.   As soon as I poked it, an unseen crack opened and shot fuel over my shoulder and out the garage door (wow).
As I said, I planned to replace all lines anyway, but that one looked best of all...but was 25 years old. 

I changed all the fuel and water lines/hoses on mine as a precaution.  Just from looking things over, I don't think there is a line anywhere that if it leaked would cause a small problem.  I read and hear the coolant lines have a long lifetime, and maybe they do, but I didn't want that concern whispering in the back of my mind as I rode.  

I don't know if anyone has mentioned it yet, but there is a molded line or tube that should be replaced also.  It's a breather tube that's sort of Z-shaped.    They are $10 here:
https://www.beemerboneyard.com/11151460480.html

To be honest, I'd just get their 12/24 month service kit.  It's under $90, and has that tube, plus the filters, O-rings, etc, you'll be changing anyway.
I'm not affiliated with them, but became pretty familiar with them last winter.  You might as well start an account.

Go up to the tabs at the top of the page, Kathy. Click on Profile, scroll down to bike*:  type in 1989 K100RS then click Save at the bottom of the page.

When finished, your bike's model and year will appear at the bottom of every post you make. That will help readers know what is being discussed without having to backtrack to find out. Parts and techniques vary sometimes by model and year.

Kathysresto wrote:. . .  he knows what he’s doing but has never really worked on bikes before.  He’s worked on cars . . .  

A K-bike engine is a fuel-injected car engine rotated sideways. The K-bike even has a driveshaft and dry clutch like many cars have. He shouldn't have a problem. The greatest problem with motorcycles is how everything is crammed together and exposed to weather and road grit. Of course, if he's ever worked on a Honda Civic engine, he knows about crowded conditions.

R
I do and did have my bike details listed in the profile but it must not have been working.  I redid it again.  Not sure if I need to be at a different member status or something?  Where can people send money to keep this site running?   All help is appreciated.  


Thank you for the encouragement and continued guidance.  The timing of this find couldn’t have been worse. We just built a huge garage and are in the middle of Getting it finished(sealing , electrical, excavating, building mezzanine,etc.).  But I think dave was feeling bad and set up a small work area for the bmw in the limited space we have at the moment.   I’m going to try to trust Dave, and also continue to tackle the  other areas that are new to me.   And decided to stop and smell the flowers on the way:) thought this looked cool just opening. Sorry for the duplicate pics. Couldn’t erase 

You're not going to be able to check the oil sight glass properly if you hang your K100 from the ceiling like that.

I think you said you were in Michigan, but it looks like your garage is in OZ.

You have been holding your phone the wrong way so the pictures come out upside down. They look OK on the phone but the top is seen as the bottom when this site gets them so it displays them as it sees the pictures attributes.

Things are wonky because it shows under my pic that I’m from WI and I’ve also listed my bike details which are not showing.  My pictures are showing correct orientation on my end so I’m not sure how I’ll know if they show correctly to the viewers?  I’m holding my phone not upside down, but have turned it to the side for a landscape pic but the majority are taken correctly.   Hmmm.... I’m sure all of this is not helping my plea for assistance. Thanks for letting me know.

Kathysresto wrote:Things are wonky because it shows under my pic that I’m from WI and I’ve also listed my bike details which are not showing.  My pictures are showing correct orientation on my end so I’m not sure how I’ll know if they show correctly to the viewers?  I’m holding my phone not upside down, but have turned it to the side for a landscape pic but the majority are taken correctly.

First off, your bike details are showing. Look under your post.

Secondly, if your phone doesn't have the ability to correctly orient photos for transfer to the Web, there are apps to help. Get that together the same way mechanical procedures are undertaken.

Kathysresto wrote:. Sorry for the duplicate pics. Couldn’t erase.

If you can post them, you can erase them. Click on them one at a time and click your delete key.

Yes, details are now showing after I made a change and still trying to sort out the picture problem.  I had already edited the multi pic post once and it wasn’t letting edit a second time.  

None of that matters because I got the tank off!   Thank you all for your help!

Finally somebody in the US knows how to orientate pictures for all the Ozinians. It gets tedious having to rotate my screen just to look at pictures from the northern hemisphere.
Regards Martin.