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Topic-icon Vented lower fairing

  • 81RTBC
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4 days 5 hours ago #6607 by 81RTBC
Vented lower fairing was created by 81RTBC
I was talking to someone yesterday who has had a few old RT’s over the years, and he was saying I need to install a vent of some kind in my lower fairing to save the charging system from being “cooked”. He said he took the piece off and drilled six one inch holes in it with a hole saw. Has anyone installed a vent upgrade of this nature ? Or any other ideas ?
1981 R100RT

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4 days 2 hours ago - 4 days 1 hour ago #6608 by Wobbly
Replied by Wobbly on topic Vented lower fairing
I posted a similar version of this about a year ago and got zero responses. My research on the subject has continued, and I'm glad to share what I know. Some of it is "internet rumor" and some is factual, and not being a long-time BMW guy, I really don't know how to separate the 2.

First thing to keep in mind is this: Thermal issues are HIGHLY dependent upon where you live and ride. The ambients for Vermont are not the same as those in Arizona. Nor are the riding styles. By this I mean there are places out west you can hold the throttle open all day, whereas in the Blue Ridge Mnts where I ride, any heat gained on the way up the mountain is soon cast off as you use engine braking to descend the opposite side. So this is not a one-size-fits-all question and answer.

• Apparently, first year bikes did have some thermal issues in some North American locales. But you must also remember that there were also compression differences from year to year. Nothing makes more heat than high compression. Forty years on... it's a fairly safe bet the worst combinations of compression and fairing are now all dead and in the junk yard.

• The problem was not with the whole fairing, but solely with the front grille. And about 4 or 5 different interchangeable grille designs were made over the life of the Airhead product line. The safest grille to have looks like this...



I think there are 2 versions of this... with and without oil cooler.

• Next, it wasn't the entire charging system that overheated, it was only the diode board (aka "rectifier"). Air comes in the front engine cover bottom, and is allowed to flow over the alternator and the rectifier before going to the air filter. But, if you've read any of Snowbum's stuff you'll know that BMW went with a different rectifier vendor and the second design had thermal issues simply based on current flow. So was it the fairing or the rectifier at fault ??

But again, times have changed. Back in the late 70's / early 80's people regularly fitted 100W head lamp bulbs and then added 2 high wattage Halogen "driving lamps". Talk about your power hogs !! Today everyone fits LED bulbs and lights. These have 1/10 the current requirements. The alternator doesn't make electrical power for the fun of it. No! The alternator and rectifier make and process power because the electrical system demands it. If there is no demand, then there is no heat. So today's lamps simply have a lower demand, which simply means lower heat generation.


Bottom line is this... You can't simply point to a fairing and make blanket statements like "this will work , and that won't" or "you must do this". Especially today because times have changed....

1. Today's bad, low octane fuel simply won't support running high compression engines without advanced computers to control ignition timing, cam timing, and fuel mixtures. 99% of the remaining Airheads are moderate compression machines which generate only a moderate amount of engine heat.

2. If you are REALLY concerned, then the place to start is to convert your entire bike over to LED bulbs... starting with the biggest consumer... the headlamp bulb. Simply changing out a 65W H4 bulb for an LED H4 replacement will reduce the power requirements (and therefore heat) by over 68% !!!

3. If you do live/ride in a locale with high heat and low humidity, then look for one of the more open front grille designs and fit it. They are easy to find on Ebay for ~$45.

Hope this helps.

Don't hide 'em, Ride 'em !!
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Last edit: 4 days 1 hour ago by Wobbly.

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4 days 1 hour ago #6609 by 8166
Replied by 8166 on topic Vented lower fairing
I dimly recall replacing the non-louvered grill on my '81 RS with a louvered one. Bought the grill new from the dealer, along with some rattle can paint to match the metallic gray fairing. Not sure if either the grill or paint is available these days through the dealer, but any number of used parts sources will have them, and Holt Design in Athens, Ohio will sell you all the paint you want for a shockingly high price. It will match your factory paint job perfectly, however.

I don't recall the ventilated grill making much difference to my comfort in hot weather, either. That bike was hotter than a two dollar pistol in the summertime, and that was one of the main reasons I got rid of it. I can recall several times when the oil temperature got alarmingly high in rush hour traffic, so high I would pull over and let the bike cool before getting back on it. That was back in the day when I was bound and determined to fill up all the gauge holes in the fairing, so it had both cylinder head and oil temperature gauges. Seems like all they did was cause unnecessary worry.

As Wobbly correctly points out, the heat problem was mainly due to a poor diode board design. You can upgrade just the diode board if you like, but my recommendation would be to put one of the Emerald Island 600 Watt alternators in the bike. The kit comes complete with replacement diode board and voltage regulator in addition to new rotor and stator, and in in my experience has been highly reliable. There's on in my '95 RT right now, which incidentally came with the ventilated grill. I figure since it mainly gets ridden in the winter, when days are short and maximum demand is placed on the alternator by an electric jacket, heated grips, and big lights (they're LED but still draw significant amperage), the bike would use all the Watts the alternator can produce.

$.02,

Scot

8166 Scot Marburger, This email address is being protected from spambots. You need JavaScript enabled to view it.

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3 days 21 hours ago - 3 days 20 hours ago #6610 by Wobbly
Replied by Wobbly on topic Vented lower fairing

Wobbly wrote:



I think there are 2 versions of this... with and without oil cooler.


Yep !




There's an oil cooler version for sale in AirBazaar...
airheads.org/airmarket/for-sale-parts/4-...er-for-rs-rt-fairing

Don't hide 'em, Ride 'em !!
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Last edit: 3 days 20 hours ago by Wobbly.

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2 days 18 hours ago #6612 by 81RTBC
Replied by 81RTBC on topic Vented lower fairing
Thanks for the input , I certainly won’t be drilling holes in the fairing .

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