Airhead Carb 'flooding' ??

[XPLRN]

As stated in a prior post I'm looking at the purchase of a 1985-87 R80. A bike I was checking out was represented by the seller as having a 'tendency' to be hard starting when shut down hot. He mentioned that it was a "characteristic" of the BMW's airhead design by having the carbs so close to the head that the head/cylinder heat would cause 'vapor lock'?? or somehow 'flood' the carbs ??

I'd like to hear from folks with1985-87 R80's in particular as to whether your bike has problems with re-starting after having been shut down hot??

The seller mentioned that if he shut the petcocks off it wasn't a problem. However that seems a bit rediculous to have to do everytime and certainly wear intensive on the petcocks.

Could this be a 'bad'??(how does one tell??) float problem?? The seller did say that he'd put new diaphrams and O-rings??in the carbs and had set the float level.

Thanks in advance for any carb advise/experiences you can tell me about. I'm 99% certain of purchase of this bike, just wanting to know about the carb situation and how to factor that into the price.

Happy 'XPLRN'

[Craig Porter]

This is probably no big deal. I'm certainly no expert, but here's my take: Experienced airhead riders automatically turn off the petcocks as they're getting off the bike; they'll take a lot of wear and tear and it prevents this 'flooding' that the Bing carbs can exhibit should something bad stick open the needle jet(s). Nothing can ruin your day like coming back to the bike to find the entire contents of the gas tank pooling underneath the motor...

The 'hard starting' and 'flooding' could go hand in hand. My surmise, from having a similar problem last year on my '83 RS, is that one carb's needle jet, a rubber tipped jet pressed upward against its orifice by the carb floats, is buggered up, hardened by age, or perhaps has a piece of grit stuck to it. That prevents the floats from stopping flow at the optimum height, leading to overflow. Gas can then rise to the level to where it will come out of the overflow on the carb. Should that be plugged by age, etc., the gas could continue to rise until it finds a place to drip out.

Ok, so you go to start the bike in this condition. Say you've even turned off the petcocks to stop a minor drip. With the petcocks back on, you start the engine and it starts rough, seemingly running on only one cylinder (it is), which goes a on a bit then 'clears its throat' and starts running smoothly on both cylinders. I think what's happening there is that you've now run the overflowed gas out of the carb and gotten back to the float's ability to keep ahead of the gas flow _while_ the engine's running.

All this to say that you'd probably want to buy a Bing rebuild kit and replace all those itty bitty parts in both carbs, flushing it out to remove the pieces of grit and deteriorated o-rings, etc, that might be causing the problem. You'd want to evaluate the diaphrams in the carb tops, too. Bing sells a little book that explains all this stuff pretty well.

If you suspect that the gas tank is nasty inside this would be the time to clean the petcocks and flush out the tank, too. Some install inline gas filters above the carbs to prevent those little leak-causing chunks o'grit from reaching the carb's delicate innards. (Reminds me; I bought the filters and never installed them when I did all this to my carbs last winter -- Maybe I'll put them on today..)

Sorry, long answer. Short answer: I suspect if you do a carb kit you'll be fine for many miles down the road.

Craig
Dearborn, MI

1983 R100RS

[flash412]

Bing carb floats will "sink" over time. Replace them (and adjust float heights) and you may find that any hard statring is amazingly cured. (Probably wouldn't hurt to go through both carbs, replacing all the o-rings and gaskets just to thwart Father Time.)

[TZOLK]

There is a nifty fuel filter that comes on a 1999 Suzuki Bandit 600, probably later models as well. They have magnets in them so as to attract any metal particulates before they reach your carbs. I have them on my bike, R100PD and seem to do a fair job(like how can I tell?) I learned of these when I was a wrench at a japanese bike dealer...Suzuki Factory update class. They are inexpensive and probably effective. At least some examples they had of metal intrusion made them out to be.

Todd
Plymouth, MI

[XPLRN]

Thanks for the responses to my inquiry regarding airhead carb 'flooding' !!

I'm happy to mention that I did purchase my 1st BMW today; a 1987 R80 with 7350 miles on it . I flew back to Ohio this morning and now have 30 days(Ohio temporary motorcycle permit) to go visit my father(here in Ohio) and road trip back to Phoenix, AZ.

It should be a fun and interesting adventure as I'm trying to ride a "non-slab" route back across the country. Today I rode it about 70 miles to my friend's house in Michigan where I'll be getting "geared up" ready for the ride.

Regarding 'Craig Porter's response; Excellent info and explanation of your thoughts/knowledge of carb issues!! The nice thing is that this tank is super clean inside so I don't think there is any problems with contaminates currently. What I do detect is some in-balance in the carbs as it sorta shakes like a H-D right at idle. As soon as I slightly twist the throttle it smooths right out.

Regarding 'Flash 142's response; I'm curious as to the carb "sink" situation. Do the floats saturate over time or ??? Does the new blends of fuels cause deterioration of the floats?? I did go ahead and order the alcohol floats/float bowls kit from Bing Carburetors and it should be here tomorrow.

Regarding 'TZOLK's response; Those Suzuki gas fuel filters sound real neat!! You mentioned something about the 'Zuk factory traing school showing some examples of metal intrusion caught by the magnets inside the filter(s). Are the filters metal cans that they(Suzuki school) cut apart to show the working of the internals?? Do you have the Suzuki part number for them available and a guess-timate as to cost?? I'd much appreciate it and will go get some at the local 'Zuk store for backup on the trip back!

Thanks again and if anyone is located along this route out of Ohio; 30>224>24>54>136>24> into Kansas City, MO. and wants to see what I ended up with for my 'new' BMW ride just let me know........I'm also open to adventures off of my "non-slab" route if anyone has suggestions or ideas! :-) Please shoot me a e-mail at ' gonexplrn@yahoo.com ' if you have any thoughts/suggestions/potential roof over my head situation!! :-)

After Kanas City, MO I'm heading over to my friend's place in Manhatten, Kansas and don't really have any plans from there out to Phoenix.

Happy 'XPLRN' :bliss :bliss

[R100RS]

I never shut my petcock off and my carbs have never flooded since I replaced the original floats (about 5 years ago). Before that, they only flooded once or twice in the 2 years I owned the bike.

[flash412]

Originally posted by XPLRN I'm curious as to the carb "sink" situation. Do the floats saturate over time or ??? Does the new blends of fuels cause deterioration of the floats?? All I know is that the (older) floats discolor and become heavier, particularly when subjected to gasohol.

[TZOLK]

The part # for the filters are 15410-19E00. They are white and have a screen and magnet in each. During the seminar they had one cut open to show the metal particles stuck to it from the pumps. They are just over $9 on ronayres.com, just as a reference. They are not cheap but they do have that added advantage! Good luck with the new bike. Have fun on the journey to AZ!

Todd Zolkosky
Plymouth, MI

[Craig Porter]

Congrats on the new beemer! you're going to get to know that bike riding it all the way home to Phoenix.

Filters: Some have written on fuel flow being impeded by certain filters as high road speeds, leading to fuel starvation to the engine, which is why I'd double-check the flow of the Suzukis before relying on them. The magnetic aspect sounds really intriguing. Let us know if you try them. That's why I bought the ones offered by Bing -- you'd hope they'd sell one that'd be free-flowing enough for the bike's high speed gas demand.

Petcock(s): Mike, does the 88 RS have only one? With the two-petcock bikes like mine I'd rather turn off the gas each time than have the 1/year (average) spills you experienced pre-rebuild. It just takes one gas dump to ruin your day.. Maybe just paranoia creeping in...;)

Floats: I put in new floats when I rebuilt my carbs but opted out of the updated versions, which I've read can be fiddly to tune properly. Snobum (Bob Fleisher) who posts regularly on the Airheads list has cautioned against them if I recall correctly.

Idle sync: Sync the carbs at idle with the throttle stops (a very long screwdriver helps you reach both from one side of the bike.) Sync at higher revs with the cable-length adjust barrells. The bike must be totally warmed up for these adjustments to be accurate. I think I get close enough with my CarbStix mercury tool hooked to the vacuum takeoffs on the undersides of the carbs. I'm not sophisticated enough to understand how to factor in the carb mixture screw, so I set it at the recommended setting and limit the variables. Anyone able to help me understand that??

Craig
Dearborn, MI
1983 R100RS

[lkchris]

Hard hot starting is NOT a standard Airhead feature.

Your informant is mistaken.

All the replies for which you've given thanks describe out-of-tune situations.

I turn off petcocks only for overnight parking--no problems not doing so, say, at a lunch stop.

[kbasa]

Originally posted by lkchris
Hard hot starting is NOT a standard Airhead feature.

Your informant is mistaken.

All the replies for which you've given thanks describe out-of-tune situations.

I turn off petcocks only for overnight parking--no problems not doing so, say, at a lunch stop.

Don't forget to turn them on. It can lead to some interesting experiences in heavy traffic. :huh

[PeoriaMac]

Here's a cheap fix until you get home. Put cleanable fuel filters on both sides. I got mine at the local HD dealer.
First, check the floats by unsnapping the wires holding on the float bowls.
There you'll see the float bowls. (There's two, they are connected) With a container under a carb, turn on the gas. With the bowl hanging down, gas should flow easily. Now, push up the bowls slowly up. The gas should stop. If it doesn't, something is clogging the float pin.
So, turn off the gas. A pin with one serrated end holds the floats in place. Using needle nose pliers, gently pull the pin out, serrated end first. When the floats come off, the float needle will drop out. Examine for any obvious crud. Turn on the gas to flush out any crud inside the carb. Put things back in reverse order...float needle, floats, float pin (non-serrated end first) The float bowl, and finally the snap ring which holds the bowl to the bottom of the carb.
This really only takes a couple of minutes. My left carb would puke on my boot on a regular basis until I put on the filters.
You've bought a very low milage BMW, which means it sat a lot of the time. Float bowls will absorb gasoline eventually, which may be your problem. The other aspect is that gas tanks are lined by the factory with a red anti-corrosion coating. Such coatings (at least on my bike) will eventually start flaking about a decade or so. This is the stuff which can lodge between the float needle and its seat. Not to mention all the other crud which is in the bottom of gas station tanks...

Mac

[mrmaico]

I never have any problems with hard starting when hot on my 86 R80RT. I also always shut off my petcocks about 1/4 mile from home so that when my bike is just sitting in the garage the floats aren't sitting in much if any fuel. I'm not cetain that this will actually help with fuel saturation over the long term but I like to think it will help.

Barry

[XPLRN]

What a FUN evening! I was able to ride over to 'R80Guy's place last night as he lives about 18 miles from my friend's place in Michigan.

This was my first exposure to another R80/owner and it was a blast to chat BMW's AND now my engine doesn't vibrate like a H-D at idle. The idle issue always went away right off of idle but was pretty ruff just sitting there! So 'R80Guy' has a Twin-something electronic carb synch tool and I now have a VERY smooth idling R80!! My sincere thanks to 'R80Guy' for the great evening of BMW work, food and fun conversation about all things BMW related.

I ordered (thanks Charlie!! I'll try and stop by on my way out!)and received the new Bing twin float alcohol floats/float bowls. Thanks to a much appreciated loan from R80Guy I also have a Bing carb video to show me how to approach working on the carbs.

I am going to just ride the bike the way it is out to my buddy's house in Manhatten, Kansas to establish a average MPG reading pre-modified float setup. I'll do the float install in Manhatten and then see what happens from there with the MPG readings back to Phoenix.

Thanks for all the interesting responses!!

I'm still a bit 'confused' on how much of a problem the shutting off of the petcocks/float leakage is!!???? Seems like there is no "standard" procedure as responses with personal experiences certainly varied!!

I guess I'll just factor in all the info and see what happens!!
I am curious to know about the potential of the red anti-corrosion coating inside the tank flaking off......have many of you folks experienced that?? Mine looks good so far......low miles but still has 17 years of time to do what ever that stuff does!! :-)

I'm off for a quick evening ride to get some more time with the R80 and my friend I'm staying with!!

Happy 'XPLRN' :bliss :bliss

[PeoriaMac]

Well, I have for one had RFS in my tank. Jeeze, I'd hate to think I was the only one. Kinda like brown shoes in a world of tuxedos
((George Gobel))

Mac

[dentino]

An R80/7 that I had bought a few years ago ran fine for about 90 miles. It's mileage at that time was about 13,000 miles. It started running on one cylinder. The electrics were checked and a plug wire appeared to be conducting poorly. Replacement appeared to help but the symptom continued. Balancing the carbs was tried, that appeared to help but the symptom stayed. The carbs were rebuilt with new floats, seals and diaphrams. I drove it home 40 miles, seemed ok. The next morning, it went back to the one cylinder mode. Back to the carbs. One of pistons was stuck. This was a Bing flattop carb. The piston was disloged and then the piston and the cylinder were carefully rubbed out with very fine emmory cloth. After reassembly, the engine ran extremely well. Pulled RPM very well, no balks, hesitations or poor starts. From that experience, I'd recommend an emmory cloth rubdown of the piston and cylinder when rebuilding the Bing carbs or treating a carb problem.

[dentino]

One of common things I see on Airheads is the thumb size fuel filters between the tank petcock and the Bing fuel inlet. They may be ok, but I think this is a place where bigger is much better. With a small amout of sediment passing the petcock fuel screens above, these can easily plug. I've used the larger automotive filters - 1 inch diameter by 3 long, or the 2 1/2 diameter by 3 long. They are at all automotive shops and the chain discount stores. They hold several times the volume of fuel which adds to trip travel range, and have enough filter area to provide adaquate time for sediment to not affect flow. I've removed the petcock screens as they will accrue sediment and reduce the volume of fuel available at the bottom of the tank that can reach the petcock. I replace the German braided fuel line with U.S. rubber hose. The German braided line rubber dries and splits. Can't cause a fire on an airhead but it can be leaking and wasting fuel. Function and reliability are more important to me than original equipment esthetics. I like to reach the rally, and not be fixing stuff on the way.

[Mag00]

The fuel shutoff question is real simple. Just put yourself in the habit of turning them off before you dismount and turning them on after mounting. Practice reaching both valves while riding in a safe environment.

You could go 20 years without a problem, but on the 20 year and one day you could come out to a charcol pile. Just train yourself to turn them on and off and you won't ever explode your garage. Remember it only takes once and it's all over.

You can never know when it will act up. The cost of repairing the shutoff valves is far less than a new bike, garage, or life. Russian roulette is not something I want to play for kicks.

Enjoy the ride!

[flash412]

Originally posted by dentino One of common things I see on Airheads is the thumb size fuel filters between the tank petcock and the Bing fuel inlet. They may be ok, but I think this is a place where bigger is much better. You think wrong. Smaller is better in this application. LARGE fuel filters directly over hot cylinders on a hot day are MUCH more liable to vapor lock than tiny ones. Fuel doesn't stay in the tiny ones long enough to heat up enough to vapor lock.

"In theory there's no difference between theory and practice. But in practice, there is."

[XPLRN]

Thanks to all for the responses!! Some interesting ideas on fuel filters and the positioning of!! Also the carb slide surface 'issue' and the appropriate fix info was good to have filed away in the mental files!!

I'm just going to take off and ride west to AZ.......will deal with any RFS or whatever else might crop up along the way when it happens!! :dunno :brow

Happy 'XPLRN'!!:bliss :bliss