1971 r50/5 sat for a decade - re starting

Discussion in 'Airheads' started by madtownadv, Aug 13, 2021.

  1. madtownadv

    madtownadv Adventurer

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    Aug 13, 2021
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    My neighbors have the above bike sitting in their garage and I want to help them get it started.

    I want to drain the fuel. What is the best route?

    • remove 'plugs' at the bottom of the carb float bowls??
      • I'm worried turning bolts that haven't been turned in 50 years. Are they likely to make a good seal when I install them. Don't want to create a leak
    • remove fuel line at petcock and drain
      • won't remove old gas in the carb bowls. Also, fuel lines may be brittle
    • siphon gas out of tank
      • will leave the most old gas in the system
    • Other suggestions
    Plan on changing oil as well. Is this enough to try an start it? What else should I be concerned about?


    I originally posted in 'old is cool' and am moving to 'airheads'.

    I had received a detailed list of suggestions. I am wondering if I risk anything by only changing the gas and oil....
    #1
  2. thetubespoke

    thetubespoke Long timer

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    Why not just pop the bowls off? It's super easy to do.
    #2
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  3. jrunberg

    jrunberg Been here awhile

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    Popping off the float bowls works but I’d prefer that old gas not flow through there. Instead I’d remove the line at the petcocks. You should probably pull the tank off and make sure all the old gas is removed as well.
    #3
  4. dave0

    dave0 Been here awhile

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    Remove fuel lines from the pet cocks. Drain tank into a fuel jug.
    Remove float bowl, dump into fuel jug.

    New fuel lines wouldn't hurt. The old ones are probably brittle and likely to tear on removal.

    Might want to search around in airheads for a checklist on getting an airhead back running. Think it's a Tom Cutter list, but it was always posted by the late BigBamboo when these questions cropped up.
    #4
  5. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    Remove and clean the oil pan…
    #5
  6. WooPig

    WooPig Redundant Supporter

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    Make sure the mice haven’t filled the air filter box with gravel before cranking it.
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  7. PaulBarton

    PaulBarton Long timer Supporter

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    In terms of draining the tank, just remove the fuel line from the "T" below the petcock(s). This will allow you a little room to direct the fuel stream away from the bike. Depending on how much fuel is in the tank you could be holding the gas can a while ;-)

    Of course, with petcocks closed you could drain the carb float bowl without having any more fuel run through the carb. Lots of riders park their airhead this way.

    Then as others have suggested...drop oil pan and check air filter for varmint remnants (mufflers too).
    #7
  8. AZ Pete

    AZ Pete Been here awhile

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    parked that long, I doubt any fuel is in the carbs, if the petcocks were off. I would siphon the gas, drain the lines, inspect the inside of the tank for rust and plan from there.
    #8
  9. Mista Vern

    Mista Vern Knows All - Tells Some.

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    I am as fastidious as a racoon so I would drop the oil pan and clean out the sludge that is gonna be there. When the pan is off you'll see the oil sump hanging down so pull off its screen and clean it. It's all an easy job BUT people generally overtighten the bolts so use a torque wrench if you haven't gotten the "feel" for tightening fasteners.

    Once you have fresh oil in the engine spin it over with the plugs out and grounded to make sure oil gets circulated before you try and start it.
    #9
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  10. madtownadv

    madtownadv Adventurer

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    I just looked at the carb and see the 'clip' for the float bowl. Is it as simple as removing the clip and the bowl comes off?

    Will I need a new gasket for the bowls if I remove them??
    #10
  11. Disston

    Disston ShadeTreeExpert Supporter

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    The float bowl gaskets have dried out but if they remain on the carb body as they should they will seal again. The trick is to remove the bowl with out disturbing the gasket. Once the gasket is removed it can never be reused, it won't fit.

    I think you are going to have to have a few parts just to start a bike that's sat this long. Order new gaskets for the fuel bowls and the crush washer for the engine oil drain. Do not try to buy the large crush washer on the dipstick, it never crushes. If there's a BMW motorcycle dealer near you they should be able to supply these items. Not all dealers are Airhead friendly, these bikes are getting old, but most will have some simple basic parts.

    It would be best to clean out the tank but you can get away with merely draining all the gas that reaches the reserve setting of the petcocks. Reserve is the handle sticking up. After replacing the fuel hose and the float bowl gaskets, if needed, and the fuel is drained as much as possible thru the reserve setting, put 2 or 3 gallons of fuel in the tank. This is enough of a dilution for what remains of the old gas to not matter.

    I don't think we've told you what oil to use. At this point get Dino motor oil not synthetic. Use 10w40. Something like Valvoline Racing VR-1. Changing the oil filter is complicated for a novice so we are going to skip that because we were told the bike ran when parked.

    If you do all this at the bare minimum and have a good or new battery you should be able to start it.

    Choke on, the choke lever is on the air cleaner above the left carb, down is on. A little twist of the throttle and hit the button on the right handle bar grip. As soon as it starts put choke at half mast for 1 minute. Then turn choke off which is horizontal.

    The process of actually starting the bike when cold varies a bit bike to bike. If you aren't having any luck use more throttle, or less, use less, or more choke. Etc.

    Try to only use the starter for less than 10 to 20 sec intervals. If you have been at it more than 5 mins the starter is getting tired and you should stop and review your position.

    Let us know.
    #11
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  12. Disston

    Disston ShadeTreeExpert Supporter

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    New fuel line may be the only thing that you can not skip.

    Sometimes an old battery can be brought back with a large enough charger, 10 amps, no higher. But it is important that the batter reaches 12.5 volts to start.
    #12
  13. Plaka

    Plaka Brevis illi vita est

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    I'm always amazed with how much "advice" will be shoveled at you when they haven't bothered to read what you have written.! Then, if you've been around this forum awhile, you'll realize people have their pet...um....issues. The slugemeisters see evil sludge everywhere and the only way to deal with it is to rip the bike apart. ( you really don't want to do this). Others see everything as britting, dried out and waiting to break so make a big shopping list. it goes on and on.

    The 50/5 has slide carbs. If there is a bowl held on by a wire bail flipping the bail will drop the bowl. Good for having a look see. But if the carbs have been sitting 15 years with gas in them you will see much varnish. the carbs will be coming off for some cleaning and fresh rubber. Easy work but time needed to learn them.

    Simply take the tank off, undo the two knobs underneath the rear and lift carefully up and back. Don't loose the rubber thing at the front. Dump the gas.

    You need at least some battery to get it going. You can kick it to move the oil around but with cruddy carbs you can be kicking all day.

    The sense I get is that these people want to sell it and hope to get more if it runs. If I were you, I would charge the same rates as any shop to make that happen for them. They want to get max profit out of an old hoopty but the thing needs a fair bit of work to make it road worthy and this is easy to hide in front of the buyer if it will start and run....as many of us have found out.
    #13
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  14. Disston

    Disston ShadeTreeExpert Supporter

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    What woo pig says about mice in the air box is important. Enough garbage in there and it won't start.
    #14
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  15. dazz

    dazz 1947 Famous James.

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    I'd really like to see a picture of this beauty!
    #15
  16. dazz

    dazz 1947 Famous James.

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    tempImage8bzlAo.jpg Actually, there is no telling where a mouse might be.
    #16
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  17. dazz

    dazz 1947 Famous James.

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    This one sat for a while also. tempImage1ajW6N.jpg
    #17
  18. 100RT

    100RT Long timer

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    That bike would be a good yard ornament! Whoops I forgot that where you put it!
    Show it off!!
    #18
  19. madtownadv

    madtownadv Adventurer

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    Gas tank is full of rust - my plans to drain gas and oil and start it were a bit naive :-)

    I plan on removing the tank today. I have watched a few videos on cleaning rust from a tank. What are suggestion on this process? I've seen using vinegar and other commercial products....

    r50.jpg
    tank rust.jpg
    #19
  20. Beemerguru

    Beemerguru Beemerguru...G/S guy

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    Early Bing slide carbs like this or /2 don't have a bail or bowl. Just a couple screws to pull the top off along with the float.

    This is so funny...I gave a seminar at the MOA National on how to determine if that free or cheap beemer is really a $1-5K project before it can ride down the driveway.

    Air, Fuel, Spark

    Air
    Means no starter cover or air filter full of nuts (more than a few of these), a mouse nest ( even more), or filter collapsed from oil breather tube cracked/leaking

    Fuel

    Means no turpentine or varnish. Gas older than about 6 months (depending on state formulation) will gum things up. Also gas sitting for more than 10 years with grab moisture over time and drop to the bottom of the tank..and over time, rust out the bottom of the tank. Thin metal you can poke your finger right through. Even aluminum K bikes will get pin holes along the bottom seam. Gas left in the carbs for years, just get a rebuild kit and do it first to eliminate a big stumbling block getting it running. O rings will be shot, gaskets shrunk, etc. Fuel line probably leaking.

    Spark

    Battery with a full charge, connections not corroded, pull the plugs to see if they're glazed over from burning oil,,or rusted which mean water got in the cylinders. Front cover off (battery disconnected first) to see if the points, stator, and/or rotor are rusted. If engine starts but no charging, the last place anyone looks is behind the diode board where the 3 wire adaptor plugs in. Surprising number have this funny green corrosion and the metal connectors are mostly eaten away.

    Pull the gas tank and look in the headlight bucket. Main harness and handlebar connections. Big wads of electrical tape or those blue plastic quick connects - first question is why..then how bad is it?

    Just about anything rubber is a given for replacement..tires with the nubs still there but a build date of 4495 (in the shop right now), cables etc. Don't try to squeeze the front brake until you bleed the system especially when you take the brake resevoir cover off and it looks like coffee..old coffee. Squeeze first and good chance of moving that plunger against old fluid crud in the bore and you'll tear the seals. Power bleeding is best if possible..suck everything out.

    Then it's basics like spline lubes, wheel bearings, head bearings, etc.

    Up to you to determine how far down the rabbit hole you want to go...just to flip it, daily rider, or long term keeper?
    #20
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