Back on an Airhead - 1975 BMW R90/6

Discussion in 'Airheads' started by tete, Aug 27, 2012.

  1. tete

    tete clown shoes

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    im confused on how to run the fuel line. for example i have in line fuel filters. the kind that do not have a T to them do I need to run them off like that or can I simply run fuel line directly down to the filter then to the carb no "T" needed?

    thanks
  2. disston

    disston ShadeTreeExpert

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    The Tes are an extra piece, not part of the filter. The T is so you have a cross connection between the left and right fuel line. The T was part of the original set up for the bike. They will run fine if you don't have the T. Just run the petcocks to the carbs. Makes for a little confusion maybe when you are running out of gas. When the tank is low one side or the other can run out first.

    The fuel filters in the fuel line are after market pieces.
  3. tete

    tete clown shoes

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    ok so i got the carb, tank, petcocks on and working furl line and filter and everything ready to go.

    carbs ready I dont have a workin choke lever but i assume if the en-richer are is up that means the choke is in the ON position.

    I got enough oil flowin by turing it over so that the light went off. Finally as I tried to start it, ....

    nothing.

    So now im wondering if I need to adjust the carb screw closest to the jug. I uncrewed it by 3/4 of a turn which i thought was about right ... nothing...

    any suggestions?

    there is definitely spark.

    its starter is strong and the kill switch is in the proper position which is in the center - I assume ( not up or down.)

    please any input would be nice.
  4. disston

    disston ShadeTreeExpert

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    The enrichner levers up is start position.

    Two screws on the carbs. #1 is mixture, it is in it's little shroud, it goes into the carb, mixture screw is 1 turn out, I think. #2 carb screw is idle speed, it pushes up on a tab that is part of the lever connected to the butterfly shaft. This will hold the butterfly off the fully closed position a little. Set idle speed i turn in from where it first makes contact.

    These settings are approximate.

    To start bike have the throttle cranked open a little. Give it some gas. Maybe 1/4 to 1/3 turn.

    As soon as it starts you will probably be able to turn the enrichners down 1/2. They will come completely off after another minute. Also approximate info.
  5. tete

    tete clown shoes

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    yeah pretty much set up as suggested checked spark again. checked floats they are fine

    mmmm.

    i guess ill stop and think about this for a bit before proceeding. are any of the screw inside the carbs in float area supposed to be back out at all?

    it it OK to pull those plastic elbows off and see what going on in there. and try starting it like that until i figure out what is up?

    Update:

    I think I flooded it somehow initially. I got it started momentarily and then it died again. what might be somethings to check if its flooding?

    I'll take a break and come back in a bit and see whats up.
  6. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    The fuel lines should be run like this:

    [​IMG]

    Even though there is spark, the timing may be off. Give it a shot of ether starting fluid-- that helps on recalcitrant engines. Sometimes an engine that hasn't run for a while needs help.
  7. tete

    tete clown shoes

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    Okay went and this time it started. Pretty good overall except when I let go of the throttle it died and would not start again. .... Saga continues.

    I have my laptop out here with me and I'm constantly looking up stuff that maybe the culprit. When it did start it seem like it was pretty solid.

    That's why I thought I could let go of the throttle. Next time I hold it a bit open for a while to just get all the juices flowing.

    I put 10/40 oil in it for now which I plan on changing one I'm done dialing it in.

    How much should this thing take, ? as I've heard all kinds of stuff different from the manual.
  8. Kt-88

    Kt-88 I like everything.

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    Mine is finicky for the first eight seconds or so of running. I also had my mix screws about 1 1/2 turns out so maybe I'm screwing up there. On the bright side my rebuild kits for my brand new been sitting forever r90/5 haven't gotten here yet, so there's not a good o ring in either one, but it still runs quite well.

    What I mean to say is don't distress.
  9. disston

    disston ShadeTreeExpert

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    Inside the carb are two settings. ONE: is the float level. The seam of the float should be level with the main body of the carb. There is another method that has advantages especially for older floats, that is measuring the level of the fuel. The second stting inside the carbs is the needle height. TWO: needle is set on second notch.

    Those are generally the only things inside the carbs you mess with. There's one other thing that was attended to when the carbs were rebuilt, that is the fit of the butterfly in the throat. So you set the butterfly when you changed the O-ring and you set the needle on the second step. The only thing you should have any business messing with is the float adjustment.

    Try some starting fluid as Bill suggests. I know, I know, I don't like it on principle either but it sometimes helps.

    I checked the Bing book. The idle mixture screw is 1 turn out for initial setting. It may help to get this monster running to have them a little rich, even 1 and 1/2.

    After it starts and runs for a couple of mins one of the first things to check is timing for full advance with a timing light. And check idle at about 1000 rpm, full advance 3000 rpm. If the timing is off it will be hard to start.

    I just brought my bike home. I have to go back now and get the car. Bike had a broken wire in the harness for the booster. I was changing the points when I found the broken wire. I had the timing light with me but it ran good enough for the 4 miles home. Will check timing later and put the cover back on before I go to Laural, Md. Tomorrow.
  10. tete

    tete clown shoes

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    Ok got it started and took it for a spin. Ran OK considering. Starts really easy right now. I need to adjust idle however. Clunky tranny just like my old R65. As expected.

    Honesty I don't think we are far off currently. Maybe get the idle an carb set. I had spoken to a BMW mechanic thurs, an he suggested I have the needle set on the 3rd location. If 2nd is better that is easy enough to change. The butterflies sealed fine. The float seams to be fine as well.

    How much is the proper oil for this thing? Everyone seems to say a different amount.

    The tach literally just spins in location, like something from a circus. I will probably remove that entire assembly at some point. Speedo worked fine.

    I need to install my new cables as the ones on here are garbage. Also needs new springs for the carbs as these are sooooo stiff. Turning the throttle is a chore.

    So I need to address the timing so i need a timing gun. Do I need the best one or will a Harbpr freight chat age one get it done. As its closest to me.

    Please feel free to shoot me ANYTHING else I can address I plan on taking all this apart again soon and cleaning everything up better and adjusting a few things etc.

    Thanks again guys seriously
  11. Kt-88

    Kt-88 I like everything.

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    I got the cheapest timing light from sears. 15$? It's been fine and weatherproof for a few years now.

    My dipstick says 2L, but I really fill to the full line. Mine has an aftermarket sump cooler on it, so the manual isn't much help.

    I rode mine for a few days and discovered after the fact that the transmission didn't exactly have oil in it, just water. So, maybe drain and refill that.
  12. disston

    disston ShadeTreeExpert

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    Amount of oil depends on which oil pan you have. I don't really go by an amount, I go by the dipstick. I try not to fill it to the Max or Full line. I try not to let it reach the lowest or IL low line. I try to keep it in the middle of these two lines. It is really very common for Airheads to run best with the oil about 1/2 Low, in between the two lines.

    The dip stick is removed, wiped off and reinserted till the threads of the dip stick contact the top of the filler hole. Then remove to read.

    Most will stay more stable around the halfway mark but these engines always use a little oil so you do have to keep an eye on it. Since this machine is new to you you should check the oil every day.

    A cheap timing light with the clip on magnetic induction pick-up. It's the one that has a clamp arrangement to go on the spark plug wire. I thought the cheap Sears ones were $25 years ago. I have no idea what they are now. This is another tool you will need, so get it.
  13. Kt-88

    Kt-88 I like everything.

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    I got the cheapest timing light from sears. 15$? It's been fine and weatherproof for a few years now.

    My dipstick says 2L, but I really fill to the full line. Mine has an aftermarket sump cooler on it, so the manual isn't much help.

    I rode mine for a few days and discovered after the fact that the transmission didn't exactly have oil in it, just water. So, maybe drain and refill that.
  14. tete

    tete clown shoes

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    Harbor freight $14.99. Get err' done.
    [​IMG]

    Picked up this fancy coffee machine too!
    [​IMG]

    Gotta keep the miss's happy :)

    After ordering stuff left and right.
  15. tete

    tete clown shoes

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    I charged the bike overnight for the sake of not having to wear the battery down. I went outside this morning. Put some gas in it because it was empty and it started right up. I'm starting to feel pretty good about this bike now. Just need to start putting the pieces together and doing regular maintenance. Clean it and dial it in better. After the bike shut off I could not start it again. Im not sure why. Maybe I'm flooding it? Maybe the timing is still off.

    I will look up a tutorial on how to check timing. If anyone has any suggestions, of course they are welcomed.

    I want to change the cables, most particular the throttle cable as mine are not in good shape.

    I ordered the Ez pull throttle springs as mine are garbage and super stiff.

    I also need to see if my petcocks are sealing. They are not leaking per say, but when in off position Im not sure they are closing.

    What are my clues as to why I am flooding it? Where do You guys generally gap your plugs for hot weather if it makes a difference.

    My petcocks feel fine I think Im just starting to get paranoid.
  16. disston

    disston ShadeTreeExpert

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    Plugs are gapped the same all year I thought. 0.7mm or 0.025 in.

    Do you have your timing light yet? Hook the clips to the battery, red to Pos and black to Neg. The larger clamp goes around on of the spark plug wires. The rubber plug above the dip stick area is removed so you can see the flywheel. Start engine, aim timing light at timing hole and pull the trigger. The light should flash. They are not bright enough to use with direct sunlight on the engine, you need to be in the shade at least. At idle there should be three lines in the window. Timing should be on the middle line I think, maybe it's the bottom line. Make note. Then raise throttle, engine speed, and watch the timing mark change, the ignition is advancing with rpm increase. The round dot and the F mark should be in the window around 2500 rpm, sometimes sooner or later. Note at what rpm it is at full advance. Note if it goes above full advance. Adjust so the dot stays in window at full advance. This is adjusting timing with a timing light at full advance and is a better way to do this than static timing.

    Turn petcocks off, remove fuel hoses, allow all gas to run out of hoses, place cardboard under engine, go in house and watch TV for one hour. Then come outside and see if petcocks leaked.
  17. tete

    tete clown shoes

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    Yeah I got my timing light however I don't have a readable tach...lol.. mine just spins.

    I have no rubber plug in the timing hole/ window. I guess I should order one for rain etc..

    Im wondering why I start so easy some times and other times its so difficult. generally after its been sitting a while it will start really easy. After if shut it down it gives me trouble. unless I wait and hour or so.

    How would I know if its being flooded?

    wouldn't the carbs leak from somewhere? or show some sign?
  18. disston

    disston ShadeTreeExpert

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    You may have carb problems but this is still a new thing for you. You are still learning. You can't adjust the carbs or fix the carbs until the ignition and valves are correct.

    You don't have to have a tach to check the timing. You want to have the idle set at something less than 1000 rpm. Idle, you should know when this is right. You are sitting on the bike and it is idling at the light. When the light changes you go. That's idle. Aim the flashing light at the timing window and see if you can see the three lines. The bottom line should be lined up with the middle of the window. But if the three lines aren't exactly where we want them don't worry about it right now.

    Now raise the throttle slowly and watch the lines climb out of the window. Eventually the dot with a mark, F, will appear. This will be above idle by quit a bit but you will be able to hold the throttle here for a few seconds while you look, look now at the dot and the F mark, hold the throttle steady where they have climbed as high as they will, they should stop in the middle of the timing window and a little more throttle they don't go above the timing window. There should only be one mark that you are watching. If you get a double image it is a problem. Look for it but I would hope you don't have this issue. It's actually rare.

    You are looking for the full advance mark at approximately 2500 rpm. It will be at approximately 2500 rpm so don't worry about it. If the mark is above or below the window then adjust the points plate to center it. Sometimes it's actually easier to move the advance unit a little. They don't fit the D shape on the tip of the cam too tight and can be moved a couple of degrees.

    I hope this helps. What should happen eventually is that you understand what is happening. When that happens you won't need me anymore Grasshopper and you will be ready to enter Cafe Bike Nirvana. :evil

    Do you own a manual yet? Which one? You need a manual. Either the Clymers or the Haynes.
  19. Horsehockey

    Horsehockey A GPS? Huh?

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    Charlie-
    I think this is when you're supposed to snap your fingers to bring the subject out of his trance-like condition.
  20. tete

    tete clown shoes

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    I have the Clymers Manual. It does a good job when you know what you are looking at.

    OK so I got the bike to start more easily now. I adjusted the screw closest to the jug to about 3/4 turn out.

    My petcocks are fine, no leak.

    I have it idling now. I'm just not sure how high. I doubt its much over 1000.

    I have it starting pretty easy now. Just turn the key, push button and its firing right up. All I did was adjust the mixture screw and then dialed in the idle screw the best I could. I believe the carbs are function much better now. I don't feel like there is a carb problem.

    Im going to have to make some choke pull / levers etc... as my choke unit was rubbish.

    As for the timing I will have a go at that relatively soon.

    When in neutral, and I turn the key, as most people do, three lights turn on.

    The Green, for neutral, Red, I think for charging and Amber for oil. sometimes the oil light is on other times it is not.

    After the bike is on the oil light turns off right away regardless. I checked the oil and its right smack in the middle.

    I check the oil by unscrewing the dip stick, wiping it down then re-inserting it by simply setting it on the threads and NOT screwing it in.

    I tok the bike around the block again. This time it felt much better. - Still massively different than my 73 Honda, and still different than my previous R65. I am really excited about getting it to this point . Like I could just hop on and ride it to work. But I won't. I have 3 little boys to keep me from doing anything that dumb.



    @disston, thanks again for walking me through all this.