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, 05:35 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, 06:38 PM   #2
nella
Gnarly Adventurer
 
nella's Avatar
 
Joined: Apr 2010
Location: Raleigh, NC
Oddometer: 403
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, 06:45 PM   #3
zenben
all roads are one
 
zenben's Avatar
 
Joined: Feb 2007
Location: Portland Oregon
Oddometer: 595
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, 08:33 PM   #4
bmwrench
Beastly Adventurer
 
Joined: Nov 2006
Oddometer: 2,036
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, 08:40 PM   #5
east high
Studly Adventurer
 
east high's Avatar
 
Joined: Oct 2009
Location: Portland, Oregon
Oddometer: 944
Mikuni conversion?
__________________
'71 r75/5
east high is offline   Reply With Quote
Old 09-08-2010, 09:05 PM   #6
Hawk Medicine
Coyote's Brother
 
Joined: Jun 2008
Location: NOR CAL
Oddometer: 3,301
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 11-09-2011, 03:36 PM   #7
Sniper X
De Oppresso Liber
 
Sniper X's Avatar
 
Joined: Jul 2006
Location: Central New Mexico, 7420ft above sea level
Oddometer: 33,308
Quote:
Originally Posted by east high View Post
mikuni conversion?
bingo!
__________________
" The people who cast the votes decide nothing. The people who count the votes decide everything."
Straight Out Da Trailah!
Sniper X is offline   Reply With Quote
Old 11-10-2011, 06:37 AM   #8
DoktorT
BigBrowedNeandereer
 
DoktorT's Avatar
 
Joined: Apr 2009
Location: Chewelah, WA
Oddometer: 1,143
Quote:
Originally Posted by bmwrench View Post
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.
I put the 3.2 in my 79 RS and just love it. Much better in low gears around town and can still do the ton all day long. Just much more usable for real use in all gears. With the 2.91, 5th gear is useless at less than 75mph or so. I did this so I could pull a trailer and it works super for that, but love it solo much better than the tall gears.

As to fuel mileage, no change at all with the lower gears. The engine may be turning faster, but the better torque makes up for it. I get 48 to 49.5 mpg long range on the road typically at speed limit plus 5. That drops about 3 to 4 mpg when towing the Bushtec with some 300lbs gross load. I run it 300rpm higher than solo. The only time I got just over 50 is when I maintained 3rd anfd 4th gears at 50 to 65mph for a full tank or more. Less wind resistance at lower speeds is just lots more efficient.

I had a new 76 R90/6/S years ago. Just right at 50 was typical. Recorded 53 once on a group ride all day in 2nd and 3rd on mountain twisties.

Both machines are maintained stock and precisely tuned and balanced. The S fairing is worth a mile or two per gallon. The RS is better still. 45mpg rule of thumb is good for a bare 100/7.

Like so many things Supershaft says, it's just his customers get poor efficientcy due to his by guess and by golly seat of the pants ideas. If he knew how to tune them properly, they would get the same results. Maybe as well that his clients tend to be heavy on the throttle in high gear. Cafe types trying to keep up with the riceburners. That would explain the 10mpg waste of fuel and danger to the public general and falling off the bike for a few weeks of physicians interests. How many times has he screwed the pooch? At least 5 times before this recent shunt. Are you going to take the advice of someone who thinks broked bones are required from time to time if you know how to ride or wrench Airheads?? I would want anyone who demonstrably cannot ride in a safe manner to keep his hands and tools off my Airhead, thank you. Stupid procedures yield stupid results.

DoktorT screwed with this post 11-10-2011 at 07:21 AM
DoktorT is offline   Reply With Quote
Old 09-08-2010, 08:55 PM   #9
ericrat
Beastly Adventurer
 
Joined: May 2007
Location: Cincinnati, OH
Oddometer: 1,150
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 11-25-2010, 01:39 AM   #10
supershaft
because I can
 
Joined: Sep 2010
Location: San Francisco Bay area
Oddometer: 8,792
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
Old 11-25-2010, 06:26 AM   #11
2xdisco
Gnarly Adventurer
 
Joined: Dec 2007
Location: WNC western NC
Oddometer: 220
i have experience with these models. dual-plug the bike while doing this eather shave the heads or add HC pistons(better).... have the bike timed and tuned proper!.. i have found that most shops do not know how to do this right.... they do it ok but miss out on the total potential of the motor.... with it timed right. the motor will pull so hard from 1500-5500 that u actually have to hang on. after 5k the bike will accelerate extremely fast. this way u can leave everything else stock , exhaust, 40 bings, ect.... this mod will also increase fuel millage.. i have this same set up on a r100rs/s i get 45-50mpg at 75+ loaded. HP with this done right, will put u in the 75HP range. and torque will be lowered due to the retardation of the timing and a widening of the advance range...
__________________
BMW R80 G/S PD 1000cc kit and heads to match
84 r65ls(hers)
78 r100rs euro- for sale
98 vtr1000 superhawk (fun)sold
2xdisco is offline   Reply With Quote
Old 11-25-2010, 11:53 AM   #12
supershaft
because I can
 
Joined: Sep 2010
Location: San Francisco Bay area
Oddometer: 8,792
Quote:
Originally Posted by 2xdisco
i have experience with these models. dual-plug the bike while doing this eather shave the heads or add HC pistons(better).... have the bike timed and tuned proper!.. i have found that most shops do not know how to do this right.... they do it ok but miss out on the total potential of the motor.... with it timed right. the motor will pull so hard from 1500-5500 that u actually have to hang on. after 5k the bike will accelerate extremely fast. this way u can leave everything else stock , exhaust, 40 bings, ect.... this mod will also increase fuel millage.. i have this same set up on a r100rs/s i get 45-50mpg at 75+ loaded. HP with this done right, will put u in the 75HP range. and torque will be lowered due to the retardation of the timing and a widening of the advance range...
75hp at the rear wheel from dual plugging alone? Even at the crank would be a miracle! I wouldn't count on that happening twice here on planet Earth.

Dual plugging? I am all for it. Remember that I didn't raise my compression? It's because I wouldn't raise my own compression without first dual plugging and I opted out. Besides, my boss and a bunch of mechanics I worked with the last time I had my heads off said that you HAD to raise the CR if you put in a 336. Wrong! For 1000cc, my 8.7 is about as high a CR as I would run single plugged. It runs on regular just fine when it isn't too hot and when it is hot it needs premium to keep from pinging. That's about as close as you can get to the highest CR doable IMO.

I have seen F'ed up machining on a lot of dual plugged heads. Usually the plug is way off center and if it is off center towards the exhaust seat too much, the head will crack between the spark plug hole and the exhaust seat. I have seen a lot with Fed' up threads right out of the shop too. I have seen some that have had coil inserts installed right out of the shop because the first attempt at cutting the threads was a fiasco!

I have seen even more dual plugged setups timed wrong. There are two schools of thought on this subject. One works WAY better than the other. Oak and Snowbum on on the wrong side of THAT fence.
supershaft is offline   Reply With Quote
Old 11-26-2010, 10:06 PM   #13
Ron In Buffalo
Adventurer
 
Ron In Buffalo's Avatar
 
Joined: Oct 2004
Location: Buffalo, NY
Oddometer: 67
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.
I agree w/ this guy I have a 1977 r100/7 w/ 32 mm carbs and smaller valves and give riders on the rs/s/rt fits up to 100 mph. Then after that point their hp wins. Bit if you are after more torque less id more. Ron
__________________
1999 Triumph Tiger & 1998 K1200RS
Ron In Buffalo is offline   Reply With Quote
Old 09-09-2010, 03:26 AM   #14
Plaka
Brevis illi vita est
 
Joined: Jun 2010
Oddometer: 4,581
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, 06:23 AM   #15
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
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 05:43 AM.


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