new R100/7 owner woes

hi im new here. i just bought an r100 /7, and am having some troubles with her right off the bat. i thought id post my symptoms before i go searching the forums, perhaps someone can throw me a lead on where to start problem-solving.

the bike hesitates on acceleration and idles very poorly [dies if you dont keep keep blipping throttle]. this morning i yanked out the spark plugs and sure enough the right side was toasty. left side was normal. replaced the right side spark plug, drove around and for a while it seemed to be ok. but then the hesitation came back after a few miles. limped home, looked at the plugs again, and the new right side one was completely black again.

im going to pick up a manual for the bike tommorow, as well as a set of new plugs, and i will search these forums in the meantime for a a hint as to what the culprit may be. i am a novice when it comes to mechanics, so if you explain something, talk to me like im four.

thanks in advance,
heres a pic of my sick bike:



regards, from wisconsin



edit: i should clarify what i mean by "hesitation" --> i start out in 1st gear and roll on the throttle, the bike will accelerate a little bit then just stutter or stop accelerating [as if almost it ran out of fuel - yes i checked the petcocks, no i wasnt out of fuel] then i keep rolling on the throttle it will accel a little bit and keep stuttering, shift into 2nd gear, try to roll onto the throttle, again, it will accel a slight bit, then just stutter, hesitate, accel a little, hesitate again. its like im telling the bike to "go go go!" and its saying "ok im going going, NO, ok going going, NO, going going going NO". [if that last sentence made sense to you, congratulations].

hope that helps

Absolutly always the first diagnostic step is to check valve clearances and correct if necessary.. It's pretty useless to proceed beyond this step.

Look in the float bowls at the cleanliness of the fuel. This is the very bottom portion of the carburetor, held on by a wire clip. It slides off. Turn off fuel first.

Older bikes often lose the lining (paint) in the fuel tank.

In any event, bike requires clean carbs to run smoothly.

Also, check compression. Must be similar both sides.

Dirty plugs are of course a symptom and not the disease.

Best bet is to join up with your local BMW club. There are usually guys willing to help

Contacts here
http://bmwmoa.org/about/clubs/clubs.htm
http://www.airheads.org/component/option,com_contact/catid,80/Itemid,43/

Things you need to do

1. Rebuild the carbs Chances are that the diaphrams are leaking and other parts may be deteriorated like the floats and O rings. They're easy to work on/ You can get the parts here: http://www.bingcarburetor.com/

2. It looks like you have a pre-electronic iginition model (I'm guessing due to the ATE caliper on the front wheel) Check/change the points and by all means,change the condensor and check the timing.

3. One of your coils may also be going south.

4. Also check the spark plug wires for leaks.

5. Check for air leaks around all the rubber sleeves connecting the carbs to the engine and airbox.

6. Check the cleanliness of the air filter.

7. As someone else said, check the valve clearances.

8. You also need a vacuum gauge of some type to balance the carbs.
Your problem is most likely the ignition (points/condensor/coil/spark plug wire) or rebuilding the carbs.

Please let us know how you make out.

Sounds like Carbs

My Buddy's R100RT had similar symptoms & it turned out that the carb diaphrams (in both carbs) were torn. It ran equally bad on both cylinders, but overall the thing was kinda balanced. A carb rebuild is not hard as the design engineers mad it difficult (but not impossible) to reassemble them incorrectly. Do the valves first, that is really easy.
http://www.airheads.org/content/view/182/49/
http://www.ibmwr.org/r-tech/airheads/carb_rebuild.shtml
Above are two links to a tech articles on rebuilding carbs. One from the internte BMW riders, and the other from the Airheads club. Both organizations are valuable resources.

Yours is a nice bike and you will be delighted with the way it runs once the bugs are sorted out. A service manual such as a Clymers is a very important addition to your library.
See ya

nhlcats,

My R75/6 had the same symptoms that your R100 has when I bought the bike.

The problem was that one of the choke cables was not letting the choke go all the way off when I returned the choke lever to the 'no choke' position.
The choke was staying partially on all the time. The immediate fix was to reach down to the carb and push the choke lever all the way down after the the bike was started and the choke was turned off. I did this every time I used the choke. The long term fix was to change the choke cables, the wire
was binding inside the cable housing do to old age and oxidation.

This is very easy to diagnose. Just reach down to the carb and push the choke lever on the carb down with the main choke lever in the 'off' position. If the carb choke lever your pushing on moves downward, even a little bit, you got lucky and found the problem!

By the way, is that good looking fairing a Parabellum Scout? Would like to have one of those on my /6. Bruce

Kent C.'s advice is absolutely correct, as usual. Always check the easy stuff first. If your bike has points, check the gap and re-adjust if necessary, then the timing. As the cam-follower wears down, the timing changes toward retard slightly, and the quality of the spark degrades from the working gap closing up slightly. The result is poor performance. There is a rubber plug on the side of the motor near the choke lever. It is the cover for the hole where the timing marks show. You will need to remove both plugs to release the motor compression. Then remove the front engine cover to access the points and the alternator. WARNING: it is necessary to dis-connect the battery before removing the front cover, otherwise it is nearly impossible to not arc the cover on the diode board when removing the cover. That is not good. I like to dis-connect the negative battery cable where it connects to the transmission to disable the electrics. Always isolate the battery before removing or replacing the front cover. You can then use an allen key in the bolt in the center of the alternator to turn the motor easily. There will be a series of marks on the flywheel under the rubber plug. Whe the S shows in the opening, that is the place where you want to set the point gap. The mechanical advance obstructs access to the point set and it is helpful to bend the blade of the feeler gauge to check the gap. If your bike has an electronic ignition, I will consider this to be a typing exercise. If you don't know, you ought to have a look.

A note on choke cables; This can be a challenging task. The first time I tried I spent 3 hours, consumed a 6 pack, and invented new combinations of curse words. Should you choose to attempt the choke cable change, you can e-mail or PM me for pointers.

Yeah, the choke lever mechanism is very 'elegant' and will baffle you if you
don't watch carefully when you take it apart. I remember marveling at what a clever device it was after figuring out how it went back together. Bruce

hey folks, here with an update.
thanks for all responces so quickly, i greatly appreciate that.

i ended up contacting the previous owner, the guy who sold me the bike. i told him about my troubles, and he said he wanted to look at the bike.
the outcome:

1] positive terminal on the battery was loose
2] idle was adjusted so bike no longer dies
3] right side plug changed

the bike stopped hesitating, and drives normal now [as of last night at least]. he also lent me his maintenence book until the one i ordered arrives, and said he'd be happy to look at the bike again if any more issues arise.

heres a pic of his 69' moto guzzi that he rolled up in:



on another note, i did check the right side choke setting, and indeed it was slightly on.

so hopefully this is the end of those troubles........... [famous last words?]

thanks again folks!

time to go ride

naturally, i spoke too soon.
yesterday i rode 70 miles with no problems.
then i went for an evening spin after that with a passanger.
now my tach sits at 0 rpm all the time, and the bike hesitates when trying to keep a constant velocity. that is, no longer hesitates on acceleration, acceleration is smooth and good, but when trying to keep a constant velocity, the bike stutters/hicups/hesitates.

Replace those spark plug caps with NGK. Replace the spark plug wires while you're at it. Get the high tension wire from a local cage speed shop and the caps from any dirtbike store.

I still think it's a good idea to check the valves, timing, compression, points if so equipped, and look for crud in the float bowls. The easy stuff that "don't cost nuthin'".
The instruments on 70's airheads are notoriously troublesome and I'm sure the tach is an entirely un-related issue. Good luck.

just replaced the plug wires and caps with NGK. bike runs well now, no hesitation during constant velocity.
tach is still at 0 all the time, but ill figure that out later.
there are no points on the bike, it has 2 coils with the electronic ignition.
i need to go get some more tools to check the other things listed [$$$].

nhlkats said:

tach is still at 0 all the time, but ill figure that out later.

Click to expand...

What year? Does it have an electronic tach or cable-driven mechanical?

77'. i believe its cable driven. i am going to take off the cable from the tach, start the motor, see if it spins. if it spins, im guessing the tach itself is malfunctioning. if it doesnt spin, ill know the problem is elsewhere.

nhlkats said:

77'. i believe its cable driven. i am going to take off the cable from the tach, start the motor, see if it spins. if it spins, im guessing the tach itself is malfunctioning. if it doesnt spin, ill know the problem is elsewhere.

Click to expand...

You're on top of it. While you're in there, withdraw the cable core and LIGHTLY grease it with some white lithium grease.

Hesitation at constant speed--often called surging--is classic symptom of torn carb diaphragm.

Diaphragms require replacement every two years and are nearly mandatory on a just-purchased bike.

On a constant velocity carb, your throttle cable does not control throttling, but rather controls vacuum, which in turn--via the diaphragm--actually lifts the slide and needle, further opening the main jet. Torn diaphragms do a poor job of responding to vacuum.

Electronic ignition?

Quote:
"there are no points on the bike, it has 2 coils with the electronic ignition."
___________________________________________________________

If the bike is a 1977, unless the ignition has been upgraded to an electronic one, it has points and a condensor.

lkchris said:

Hesitation at constant speed--often called surging--is classic symptom of torn carb diaphragm. Diaphragms require replacement every two years and are nearly mandatory on a just-purchased bike.

Click to expand...

Require replacement every two years?(!?!) I bought an R80G/S in 1981 and another in 1982. I sold them both in late 1997. I think I put a total of four diaphragms in both bikes in sixteen years.

flash412 said:

I think I put a total of four diaphragms in both bikes in sixteen years.

Click to expand...

Exception.

It's Bing's recommendation.

I've run them longer than two years for sure.

Nevertheless, the symptom described here is torn diaphragm.

Yes, they're $17 each, but BMW motorcycling is an expensive hobby.

scjack said:

unless the ignition has been upgraded to an electronic one

Click to expand...

correct