Intake, Exhaust, & Battery

[seannbrownn]

Hello all,

My first post here. Just finished (well, never finished) rebuilding a 1981 R100. See picture below. I have a few questions.. I know some of these have been discussed frequently. Hoping for some solid information to formulate my future plans for my airhead. First, my eventual goal is to make it a very simple and clean "cafe" style motorbike.

1. Intake. What are the benefits / drawbacks to switching to the cone style air filters? Is there any harm in swapping to the cone filters? Do they hold up as I ride my airhead 4-5 days a week. My bike is stored under a cover, and I would worry about them getting wet. My goal is to eliminate the black plastic air box. If the cone filters aren't practical, is there any compatibility with the older style metal airboxes? I would like to convert to either the cone filters or retrofit the older metal clam box. If the metal airbox is compatible what is entailed with swapping to it?

2. Exhaust. I'm familiar with harley type exhausts where the baffles come out easily without the need to remove any welds. Before I pull the exhaust apart is this possible with the stock BMW exhaust? would love to get a little more tone out of these pipes. I like the look of these and don't want to swap them out.

3.Battery. I have recently swapped to the AGM style battery that is much slimmer. I've done some research and saw that some are mounting the battery beneath the frame. What are your thoughts on this? are there any kits that allow you to keep the center stand as well? Also, are there any battery boxes specifically made for the slimmer battery? would like to clean up the look of the battery area.

Thank you. I hope the attachment works. Any help / direction is appreciated. Also, if anyone can point me in the right direction to find after market parts that would be appreciated. So far I've stumbled across boxer metal are there other sites that have similar airhead aftermarket parts?

[SteveD]

Hello all, Welcome.

My first post here. Just finished (well, never finished) rebuilding a 1981 R100. See picture below. I have a few questions.. I know some of these have been discussed frequently. Hoping for some solid information to formulate my future plans for my airhead. First, my eventual goal is to make it a very simple and clean "cafe" style motorbike.

1. Intake. What are the benefits / drawbacks to switching to the cone style air filters? More trouble than it's worth as the system works well enough as is. Plenty seem to do it though, so ... Is there any harm in swapping to the cone filters? Do they filter as well? The carb is only held on at the head by a hose clamp. Do they hold up as I ride my airhead 4-5 days a week. My bike is stored under a cover, and I would worry about them getting wet. My goal is to eliminate the black plastic air box. If the cone filters aren't practical, is there any compatibility with the older style metal airboxes? I would like to convert to either the cone filters or retrofit the older metal clam box. If the metal airbox is compatible what is entailed with swapping to it? They can be retrofitted. Would need to look at the engine breather and the round airfilter of course.

2. Exhaust. I'm familiar with harley type exhausts where the baffles come out easily without the need to remove any welds. Before I pull the exhaust apart is this possible with the stock BMW exhaust? would love to get a little more tone out of these pipes. I like the look of these and don't want to swap them out. Sell those and buy Hoskes.

3.Battery. I have recently swapped to the AGM style battery that is much slimmer. I've done some research and saw that some are mounting the battery beneath the frame. What are your thoughts on this? are there any kits that allow you to keep the center stand as well? Also, are there any battery boxes specifically made for the slimmer battery? would like to clean up the look of the battery area.

Thank you. I hope the attachment works. Any help / direction is appreciated. Also, if anyone can point me in the right direction to find after market parts that would be appreciated. So far I've stumbled across boxer metal are there other sites that have similar airhead aftermarket parts?

What sorta parts?

[hal]

Hi and welcome!

Podfilters are a bad idea for several reasons. The airhead setup with higher intake than the carbs give you better performance than any other solution. That's most of what I know about it, but try googleing it a bit and it will be clear for you.
I saw a tuned GS with pods that looked and ran fine, but there the builder had used plastic-tubing to mount the pods high, as in the end of the tubes you have there today, only the tubes where longer.

Hal

[khittner1]

If your new AGM battery is "much slimmer", I'm guessing that it's a 19amp battery, rather than the 28-30amp battery your bike used to have. BMW went with these smaller batteries starting in the mid-80s, so they're sometimes listed as compatible for all airheads. My '86 monoshock R80 came OE-equipped with this smaller-capacity battery; it quickly died in commuting use, and was replaced with the larger-capacity battery. If you've tweaked your charging system to charge at lower RPMs, and/or you religiously use a smart charger when the bike's parked, you'll get away with the smaller one. Otherwise, you probably want the 28amp battery. You'll have to go to lithium to get both small and powerful.

[Gibson]

I ran K&N cone filters, Mikuni VM34 carbs and Supertrapp mufflers on my 81 R65 commuter bike for 50k miles without issues. You will loose a bit of mid range and low end power, and maybe gain a bit on the very top. The stock filter / air box is better in the rain, and is tuned for the mid range speeds the R100's are typically run. I never had any real problems with the R65 because it benefited from a little more on top, and really didn't have a lot of grunt anyway. I rode in the rain many times without any problems. If you decide to do the pod filter thing, they need to be cleaned and oiled often and you will need to make a plate for the transmission top. Also they need to be short, or they will be in your foot space.
The stock air box is really better for these bikes because it is a finer filter and will give longer ring life, but these bikes last forever either way.

[Bamboo812]

Just a thought; the space created by using a thinner battery can be handy for putting extra stuff in a Tupperware container or a spare quart of oil...

[Ken in Oklahoma]

Just a thought; the space created by using a thinner battery can be handy for putting extra stuff in a Tupperware container or a spare quart of oil...

Hmmm, a spare quart of oil? Even in a square can I kinda doubt it would fit there. When I fit an AGM battery in one of my airheads I have a 3/4" thick piece of wood to take up space behind the battery. There is still some room in the front, but where I center the battery it seems to fit the top hold down clamp better.

Ken

[Bamboo812]

With a PC680 mounted to the rear in my R90/6, there is 2.5" space between the front of the battery and the airbox. Valvoline bottles are 2.5" thick...

[Ken in Oklahoma]

With a PC680 mounted to the rear in my R90/6, there is 2.5" space between the front of the battery and the airbox. Valvoline bottles are 2.5" thick...

Well, there you go. It looks like I was w-w-w-w-w-wrong!

That happened to me once before this time too. Of course I've been called wrong many more times than that, but you know how wrong other people can be and often are.

Ken

[khittner1]

Bamboo---How much oil are you burning or leaking that you want/need to carry an extra quart of oil onboard? I check and top off the oil level occasionally, but I don't carry an extra quart of oil, even on my 2-stroke Vespa.