ADVrider

Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 09-08-2010, 04:35 PM   #1
Nortryder OP
n00b
 
Joined: Sep 2010
Oddometer: 2
More mid range for R100?

It's probably been covered before but I can't find it. I have a 1984 R100RT in S clothing. It's pretty much stock and I'd like to get some of that shoulder dislocating mid range acceleration. I've seen interesting stuff on 336 cams etc but that seems to be more top end. I live in the wilds of northern VT and we don't have any roads long enough or straight enough for top end.
Nortryder is offline   Reply With Quote
Old 09-08-2010, 05:38 PM   #2
nella
Gnarly Adventurer
 
nella's Avatar
 
Joined: Apr 2010
Location: Raleigh, NC
Oddometer: 405
Quote:
Originally Posted by Nortryder

snip/

I'd like to get some of that shoulder dislocating mid range acceleration.

snip/

Me too!

But I think we both started with the wrong bike to realistically achieve that. I think you should just go for arm-straightening mid-range acceleration and be happy, I am. Spend the money you save on a road trip.

If you really want to mod, look at some of the recent threads on cylinder and pistons swaps. Luftmeister made a turbo kit. Krauser made 4 valve heads. SanJose BMW makes a 1050 kit, an Israeli company makes a piston kit. Motobins sells performance parts in England. Some years R100 have better cylinder heads.

Enjoy the ride!
__________________
Scott
nella is offline   Reply With Quote
Old 09-08-2010, 05:45 PM   #3
zenben
all roads are one
 
zenben's Avatar
 
Joined: Feb 2007
Location: Portland Oregon
Oddometer: 596
Smaller valves, carbs, and more restrictive exhaust keep the torque curve down in the low and mids.
Wide open everything can generally only be driven wide open with good results.
I've built them both ways, and mild tuning is always nicer to drive all around.
zenben is offline   Reply With Quote
Old 09-08-2010, 07:33 PM   #4
bmwrench
Beastly Adventurer
 
Joined: Nov 2006
Oddometer: 1,915
Boost the compression-your 84 is set at 8.2:1. You can get a small C.R. increase via head milling, which will also tighten the squish area, do a really good valve job, clean up the ports and push the ignition timing ahead a bit.

And/or, install a 1050 kit. It won't last as long as the Nikasil cylinders, but it is a lot of fun.

You might also consider a shorter rear drive ratio. The stock R100RT ratio is 2.91:1. A 3.20 will really make it scoot. This is probably the biggest bang for the buck.
bmwrench is offline   Reply With Quote
Old 09-08-2010, 07:40 PM   #5
east high
Studly Adventurer
 
east high's Avatar
 
Joined: Oct 2009
Location: Portland, Oregon
Oddometer: 937
Mikuni conversion?
__________________
'71 r75/5
east high is offline   Reply With Quote
Old 09-08-2010, 07:55 PM   #6
ericrat
Beastly Adventurer
 
Joined: May 2007
Location: Cincinnati, OH
Oddometer: 1,087
Swap Final Drives

I don't think the 336 cam is going to help much at mid-range. The increased duration is more of a bennefit at high RPM. zenben is right about smaller valves, but this is exspensive to do and to reverse.

Which final drive do you have? I am guessing an 11/33 or 11/32. Those are long legged highway gears. I would try something in the 3.3 to 3.5 range, perhaps a 37/11 maybe from an R80. Should be plenty of those around and it is an easy swap.

I can help you with calculation to show speed/rpm at various gearing if you would like. Also, the 11/33 final drives are very desirable if you want to sell it later.

Oh, you said should dislocating, well hunt around for the highest numeric ratio you can find, or buy a faster bike.

Good luck,

Eric

Eric
ericrat is offline   Reply With Quote
Old 09-08-2010, 08:05 PM   #7
Hawk Medicine
Coyote's Brother
 
Joined: Jun 2008
Location: NOR CAL
Oddometer: 3,303
The Lufty turbo really didn't work that well (But could probably be made to work if you have an engineering degree.). Keauser heads were selling for about $3000 per set five years ago, they're delicate, can tricky to setup and are currently unobtanium. Haven't seen a set for sale in ages. The Sam Jose kit has issues with extended use....

Probably the best bets would be to either spring for one of the Siebenrock 1050 or 1070 kits or stay at 1000cc and build a high compression engine. Any of these methods will deliver higher performance but since youre after torque,
dollar-for-dollar, I'd go with the Siebenrock 1070 with some nice big carbs.

Don't forget that somewheres along the line youre going to need better suspension and a stiffer frame too.
__________________
Hawkdude

Hate rots the pocket that carries it.
Hawk Medicine is offline   Reply With Quote
Old 09-09-2010, 01:57 AM   #8
nella
Gnarly Adventurer
 
nella's Avatar
 
Joined: Apr 2010
Location: Raleigh, NC
Oddometer: 405
I was not really serious about the turbo kit or the Krauser heads, but just trying to make the point that any significant performance changes in these bikes is generally an expensive endeavor and that the original poster's goal of "shoulder dislocating mid range" is not that realistic.

Mikunis were mentioned above. I have TM's on my R100 and think they improve throttle response but didnt seem to impact mid-range torque in any noticeable way.
__________________
Scott
nella is offline   Reply With Quote
Old 09-09-2010, 02:26 AM   #9
Plaka
Brevis illi vita est
 
Joined: Jun 2010
Oddometer: 4,573
Quote:
Originally Posted by Nortryder
It's probably been covered before but I can't find it. I have a 1984 R100RT in S clothing. It's pretty much stock and I'd like to get some of that shoulder dislocating mid range acceleration. I've seen interesting stuff on 336 cams etc but that seems to be more top end. I live in the wilds of northern VT and we don't have any roads long enough or straight enough for top end.
The simplest things are to up the compression (and buy more expensive gas) and/or drop the rear end ratio.

The Mikuni's will give a snappier response--but you always end up wanting more.

For the cost of the big displacement kits you can pick up a 75,000 mile K100 and get it all out of your system. The thing has a gear indicator on the dash because very often you can't tell where you are. Serious torque. Or there are ton of other inexpensive jap bikes that will do the same or better.

Straining shoulder ligaments isn't what airheads are about. As soon as you start trying you spend a lot and don't get what a real performance bike will do while losing the best virtues of the Airhead. Tune the Airhead for smoothness, reliability and very long legs. Then get an RD350 or 400 for those midlife moments.
Plaka is offline   Reply With Quote
Old 09-09-2010, 05:23 AM   #10
SprintSix
Gnarly Adventurer
 
Joined: Dec 2009
Location: Ohio
Oddometer: 151
1981 r100rt. I got very noticable mid range improvement from 34mm mikuni round slides. Stock for me is 40mm bings. More power across the band as well. At a guess I'd say a pumper would be even better. Compared to stock it had the arm yanking power you describe. No other mods. Long winded +1 to smaller carbs.
SprintSix is offline   Reply With Quote
Old 09-09-2010, 05:29 AM   #11
Cogswell
Spudly Adventurer
 
Cogswell's Avatar
 
Joined: Jan 2005
Location: Riding with my pal Richard Cranium
Oddometer: 3,887
Quote:
Originally Posted by Plaka

Straining shoulder ligaments isn't what airheads are about. As soon as you start trying you spend a lot and don't get what a real performance bike will do while losing the best virtues of the Airhead. Tune the Airhead for smoothness, reliability and very long legs. Then get an RD350 or 400 for those midlife moments.
I'll have to agree.

I bought my airhead knowing what it was, it's limitations, and capabilities. It is fun to get on periodically and just plain enjoy for what it is. It does not do any one thing spectacularly, but it does a little bit of everything well.
I have other bikes to suit the other riding needs I have when that time arises.

Mike
__________________
Cogswell Rides To Big Bend
See my airhead project here
Time Warp Vintage Motorcycle Club
The good thing is, your damn motor can't read. If it says oil on the container, it's pretty much OK to dump in there.... ED.
Cogswell is offline   Reply With Quote
Old 09-10-2010, 07:57 PM   #12
ericrat
Beastly Adventurer
 
Joined: May 2007
Location: Cincinnati, OH
Oddometer: 1,087
Check your PM

Quote:
Originally Posted by Nortryder
It's pretty much stock and I'd like to get some of that shoulder dislocating mid range acceleration.
Check your PM.
ericrat is offline   Reply With Quote
Old 11-24-2010, 10:49 PM   #13
beemercafe
Cafe-racer
 
Joined: Nov 2010
Location: Australia
Oddometer: 4
R65ls mikuni conversion

I have just fitted 34mm Mikuni round slide carbs to my R65LS cafe racer and am looking for a base in the jet sizes for tuning

Any information would be gratefully accepted
beemercafe is offline   Reply With Quote
Old 11-25-2010, 12:08 AM   #14
supershaft
because I can
 
Joined: Sep 2010
Location: San Francisco Bay area
Oddometer: 8,050
Quote:
Originally Posted by Nortryder
It's probably been covered before but I can't find it. I have a 1984 R100RT in S clothing. It's pretty much stock and I'd like to get some of that shoulder dislocating mid range acceleration. I've seen interesting stuff on 336 cams etc but that seems to be more top end. I live in the wilds of northern VT and we don't have any roads long enough or straight enough for top end.
336's have no midrange? I guess that false rumor got started back before they advanced the timing? When I installed my 336 three different mechanics and the owner of the BMW dealership where I worked at were all telling me that my bike wouldn't idle below 2000rpm and that it would have NO bottom end and midrange. All those warnings were all 110% BS! Right after I installed the cam I rode over the mountains to a BMW rally. A fairly local guru with a very popular BMW website that pops up by the time you type BM into your computer listened to my bike and declared to all that were listening that in fact it was not a 336 cam I had just installed. He said it idled too smoothly! My girlfriend and I got a good laugh out of that! We just got through hauling ass over Donner Pass and we were both stoked about all the extra pull with almost NO down shifting where before the same highway with exactly the same two up for camping load would take rowing the gear box from third to fifth back and forth constantly and we still weren't going as fast! (I usually go over that pass in the mid 80's mph and it is usually through a lot of traffic.) If you are a below 2500rpm engine chugger, you won't like a 336. Other than that, they get you WAY more midrange and top end.

IMO, 980cc's IS a big bore kit. Basically, your 1000cc beemer is a hogged out 750! BMW stopped hogging her out at 980cc for good reasons. I don't recommend big bore kits. They do run great for a short while!

I would and have started more than a couple of times with a 336. Clean up the ports, raise the compression, put some Dellorto's on and JET them and I have had some very happy customers. I got a lot more midrange out of my setup and I didn't raise my stock 8.7:1 CR. SO many airheads are modified ass backwards with marginal results. No one changes the cam and that is where the big diff comes from! Big bore kits often turn into oil pumps. I can't tell if they pump more oil out the exhaust or through the gaskets! Big bore kit alone? Ride a 750 and then ride a 800. It's a tiny bit bigger diff than that! That is before the power falls off due to corrugated cylinder walls. That's my $.02.

Happy Thanksgiving inmates!

supershaft screwed with this post 11-25-2010 at 12:45 AM
supershaft is offline   Reply With Quote
Old 11-25-2010, 12:39 AM   #15
supershaft
because I can
 
Joined: Sep 2010
Location: San Francisco Bay area
Oddometer: 8,050
Quote:
Originally Posted by zenben
Smaller valves, carbs, and more restrictive exhaust keep the torque curve down in the low and mids.
Wide open everything can generally only be driven wide open with good results.
I've built them both ways, and mild tuning is always nicer to drive all around.
Were you setting them up to pull one of those plows made for a two wheel drive Rokon?? I have never felt the need to tune one that way. I have used bigger carbs, bigger valves, and opened exhaust and got way more midrange down to just below 3000rpm. I don't chug my bikes with much of a load at all below that anyway. They don't like it no matter how they are tuned.

Man, now you got me thinking about two wheel drive Rokons. I want an old one with a Continental I think two stroke. Two strokes won't dry sump when you are climbing that tree!! I figured that out mowing lawns!
supershaft is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 12:06 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014