HELP!!! Why won't it start?!

[roscowgo]

Check your killswitch too. I've had trouble starting mine when it was in the "Neener neener neener you dont get to ride" position.

[MontyCarlo]

Never said I wasn't a bike-moron

I do know where the battery is. I've even removed it, charged it, and put it back in [all in the bike-not-starting-period]. I knew I was gonna learn a lot about bikes, and I want to, I just didnt realize it would happen when I had to.

To try to answer a few at once:

Give me some specifics about your bike and I'll try to give you a plan to get it going. Make, model,cc, year.

1976 BMW R-75/6 (750cc boxer airhead twin)

I'll check the fuse system behind the headlight - I have a directional thats out anyway, and it's not the bulb (I already tried switching them, and still only the left side worked).

(make sure you turn the petcock back on).

Right, fuel on, as always - wait, do you mean it should be off when i'm trying to start the bike without the sparkplugs?

Now that you mention it, is it damaging to accidentally leave the choke on or petcocks on when youve parked the bike for a day? an hour?

Thanks again.

Leaving the petcocks on is OK unless you have worn floats or float needles in the carbs, which will cause you to leak fuel out of the float bowls. Leaving the choke on does nothing.

BMW twins should start and run even when they're not supposed to. The failure to start after a near tipover indicates a fuel issue to me.

Pull the spark plugs off the cylinders (PLEASE tell me you can find those on a BMW) and crank the engine for 10 seconds or so. Yes, turn the fuel OFF for this procedure. If the plugs are black and sooty replace them.

Turn the petcocks OFF if not already done so, and remove the float bowls at the bottom of the carbs. THey're held on by wire bale-tyep clips. Be prepared to spill some fuel. If there's no fuel in the float bowls, you've found your problem: clogged fuel lines or petcock screens, or just plain out of gas. If things look cruddy and the float/needle doesn't move smoothly up and down, spray some carb or brake cleaner in there. Clean the junk out of the float bowls (there will be junk on the bottom).

[woosta2]

Monty wins - though sadly* I had to figure it out myself - didnt get back into the site before I tinkered enough to fix it.

The plugs look both carbon and oil fouled. It looks like carbon flakes, but it wasn't dry. I think it was runnning too rich lately, so my plan is to replace the plugs, adjust my choke useage and check them now and then for condition. Maybe this means I get to try a valve adjustment soon.

Sparkplug test was positive (they do spark), so I checked the fuel valves - they work. Sparkplugs looked like a rich mixture was running through, so I checked the airfilter - it looks brand new. Previous owner must have replaced it recently. I opened up the carbs to make sure fuel was getting that far, and to empty them in case they were flooded. Fuel was in both (maybe 1/2 inch or so) and runs to both via the float gauge.

Put er back together and she started right up - mostly. Just the left engine and exhaust were warming up, though exhaust was coming out the right side. After a few minutes of running down the road, both sides were firing just fine. Except for a weak battery (and some directional wiring issues), it seems all is OK.

About the battery - should I replace it? If I was a normal rider, it'd be fine, but when I went out on my first road (non-parking lot) ride, I stalled it enough times that I had to push it home (the altenator is WEE (280w) and I ranout of starting juice). I do have a pretty short commute anyway - maybe I should replace the battery? Its that or keep charging it til I dont stall so much.

Thanks for the help, all. Seriously.


*=not really sadly, I learned a hell of a lot already. Hopefully i can keep that up without the emergencies.

[ofblong]

Now I am assuming these are just like cars. If your trip is less than 10 miles you are better of charging the battery on a charger 1x/week. 10 miles is where you can consider what was used to start your vehicle and to get to where your going has been replenished in the battery. I had a battery last me 9 years by doing this.

[dr_bar]

I had the same low charge problem on my 95 virago. It was diagnosed with a bad stator by some mechanical knuckle head but turned out to be a whole lot cheaper fix. All I did was just replace the Regulator/Rectifier with an after market jobber piece. Put it in a good location for cooling and away I went. Check your voltage at the battery while the bike is running. It should be between 13.5 and 14 volts to charge the battery. If it's not that high, then check the charging circuit.

[MontyCarlo]

Monty wins - though sadly* I had to figure it out myself - didnt get back into the site before I tinkered enough to fix it.

The plugs look both carbon and oil fouled. It looks like carbon flakes, but it wasn't dry. I think it was runnning too rich lately, so my plan is to replace the plugs, adjust my choke useage and check them now and then for condition. Maybe this means I get to try a valve adjustment soon.

Sparkplug test was positive (they do spark), so I checked the fuel valves - they work. Sparkplugs looked like a rich mixture was running through, so I checked the airfilter - it looks brand new. Previous owner must have replaced it recently. I opened up the carbs to make sure fuel was getting that far, and to empty them in case they were flooded. Fuel was in both (maybe 1/2 inch or so) and runs to both via the float gauge.

Put er back together and she started right up - mostly. Just the left engine and exhaust were warming up, though exhaust was coming out the right side. After a few minutes of running down the road, both sides were firing just fine. Except for a weak battery (and some directional wiring issues), it seems all is OK.

About the battery - should I replace it? If I was a normal rider, it'd be fine, but when I went out on my first road (non-parking lot) ride, I stalled it enough times that I had to push it home (the altenator is WEE (280w) and I ranout of starting juice). I do have a pretty short commute anyway - maybe I should replace the battery? Its that or keep charging it til I dont stall so much.

Thanks for the help, all. Seriously.


*=not really sadly, I learned a hell of a lot already. Hopefully i can keep that up without the emergencies.

First of all, if you're doing lots of short commute trips on your airhead you *must* invest in a small 1-1.5 amp trickle charger. The "smart" types, like the Battery Tender, are the best. Real charging doesn't kick in until 4,000 RPM on those bikes. Get in the habit of plugging it in nightly when you return home, and your battery will last much longer. Replacing the battery without keeping it charged won't do you any good...

Rich-running beemers and their bings are caused by one or two things: the floats and float needles are heavy or out of adjustment, and/or the needle/needle jet assembly is worn. Faulty float needles are easy to diagnose by the gasoline dripping on to your boot.

If the floats look brown or deep orange, it's probably time to replace them (they might be 30 years old!) They're cheap enough, usually around $14 each from the dealer. You can check their adjustment by pulling the float bowls and checking that fuel just starts to flow when the top of the float is parallel with the bottom of the carb. Heavy (stained) floats will still cause rich conditions even if in adjustment.

The needle/needle jet is a little harder to get to, but not much. If the floats are good but you still have a rich midrange, these are worn or out of adjustment.

The carbs are actually very very easy to disassemble and rebuild on that bike, and there's lots of writeups on the web that will guide you along. For about $100 you can go to your dealer and get a complete rebuild kit, new diaphragms, new floats, and new needles+jets. In other words, new carbs!

Search this forum for the $4 carb synchronizer, and you're good to go.

[TechTMW]

Holy Crap! An Airhead problem and I wasn't here to help

Well, Monty's advice is spot-on, especially in regards to the Floats! You may find this website beneficial, and there is also an airheads mailing list - check it out -

http://www.airheads.org/

http://www.airheads.org/content/view/21/46/