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Throttle screws; friction & anti-friction devices.
>> Originally published as: Snowbum gets OFF and RUNNING! <<
A different viewpoint?
For BMW Motorcycles (also useful for other motorcycles)

copyright 2019, R. Fleischer
https://bmwmotorcycletech.info/throttlescrews,etc.htm
8

Are throttle screws (throttle locks) a good or bad idea?  Useful?  What about ThrottleRests & similar devices?

Many motorcyclists use a throttle lock or friction device, or the stock BMW special friction screw (available on/for most models) to ease right-hand forces while on the road for long distances, particularly where the throttle is not being constantly moved.  You'd not likely use one in constant twisties.   Many of us use them for tune-up purposes, etc.   I have used all sorts of these devices & even have a pet conversion method that is 'different' .....an anti-friction, reverse spring method, described herein.

For Airheads after the /5, less strong carburetor return springs are now available from many dealerships & independents. These  help reduce wear on the throttle gears, reduce hand effort, and result in less tiring throttle use.  These lighter springs were not available in 1985, when the incident in this story happened, but would not have made any difference in the outcome.  Some of us did, back then, make lighter springs, but there was nothing, AFAIK, available commercially.  There WERE reverse spring devices for the throttle itself. There have been two of of the reverse spring devices sold commercially in years past ....one was called the Twist Assist ....it did the same thing as my modification, just different methods of attaching & adjusting.

Today one can purchase the simple, inexpensive, ThrottleRest (other fairly similar devices are sold under other names), and these are OK items (I love them).  Some friction devices besides what I describe are available too... but MAY not do the same thing as my reverse-wound spring method, which does NOT upset carb sync if set for very light throttle action.  ONE of the secrets of using these friction devices; ....or, just using the stock bars without any such devices, ...is to have leave a V between thumb & forefinger & not have too strong a thumb grip on the bar twist.  In some situations, as on dirt, trying to manipulate a throttle ever so gently, one might put the thumb over onto the metal of the assembly, as a 'steadying rest'.    Devices like the ThrottleRest do NOT decrease actual total throttle turning force needed, as my reverse spring device did, but they spread the forces over your palm including the immediate area behind the thumb.  I like them, as I noted, and used them on most of my bikes.  They are safe to use, providing you never get your sleeve cuff trapped, etc.

While I am not against friction screws, friction clamps, & reverse springs, and I still use them (although at less friction settings!) .....be aware that they are potentially dangerous in a get-off.  Be aware of all the ramifications ....!  .....SO...

 ....here, in this article ....I will relate my own involvement, especially with the knurled BMW friction lock screw, etc., and add some information about some, not all, types of devices.   There are some old sayings about things best left unsaid here; but, not everything that is made, even by the Factory, is totally safe, no matter what.    Examples are the early side-stands, and the later ones that automatically fold up.
 

This particular 'adventure' happened in 1985, on my near new 1983 R100RT (purchased new, I took it out of the crate, at my dealership, in 1985).  This fun & games is likely to be forever in my memory.  Even today I crookedly smile (the wry pinched look) when I think of it.  Luckily for me ...& my motorcycle ...it turned out OK  ....YOU might not be so lucky.

I not only had the stock BMW friction screw lightly tightened to where it was adding some quite modest but still noticeable friction (although not enough 'on its own' to hold the throttle for any period of time);  but, .....I had another device I had dreamed-up, made, and installed.  Just a throttle lock or use of just the friction screw WILL, if a bit too much is used, have the SAME effect in one characteristic: ...the throttle will NOT return to the idle position on its own, when your hand is removed from the throttle, or not quickly.

The bottom line for this article is:  If one uses any sort of anti-friction or friction device at all, the use of only a small amount of the friction screw or other device is preferable, in my opinion, so as to allow the throttle to return to idle, even if slowly.

There ARE solid reasons to use a LOT of friction, such as when synchronizing carburetors or doing alternator testing, etc.


When I purchased this bike it had 4 factory test miles on it.  Within a few hundred miles or so I had made up & installed a reverse spring device. This moderately strong coil-spring was several inches in length, inserted into the right side of the handlebar. The bar tubing, not the throttle tube, was drilled & a roll pin installed by strong press-friction into that bar tubing, so it would not move out of position.   The spring left eye end fit over the roll-tube during the roll tube's installation.  The spring's other end, the right-side end, was fastened to an adjustable screw/nut/large washers, that clamped onto the END of the original closed-end throttle rubber grip. Thus I could actually have a considerable amount of the turning friction forces eliminated ...that is .... the spring could be 'anti-wound-adjusted' for almost any amount of 'help'.   It was possible to adjust it so much that the throttle went wide open if you took your hand off it.  I never used it like that.  The effect was adjustable and worked better than our later type of aftermarket lower force carburetor return springs.  These days we have bar end weights that control friction, and are a bit more convenient than the BMW friction screw, but none of these devices did what my anti-rotation spring did.  I still consider it a neat-o device.  Those with weak hands may well love to make one. It is far nicer in operation than the Twist Assist. It is even better than lighter springs ...although I like both.  One of the palm pressure point spreading devices is a really nice thing to add.

Some throttle forces come from friction in the cables & the throttle assembly (& the T adapter if you have one, as this bike did), but a considerable amount are from the springs at the carburetors.   BMW used a nylon-like substance to line the inside of all of the cables after the very first /5 (originally unlined), & the exact date, models, serials, that various models got lined cables is UNKNOWN to me.  Lined cables are NOT to be oiled.

The same throttle friction & other devices, can be used on other BMW models, such as the Classic K bikes ....which have a different sort of return spring setup, but, AFAIK, NO factory or aftermarket throttle device is a true anti-spring, anti-effort, except the type that I made up for myself.

Today you can purchase aftermarket 'lighter tension' throttle springs for all but the earliest (/5) era Airheads.  The friction & spring action is severe in the old /5 models which have the return springs OVER the cable ends at the carbs.  The  /5 can be modified for smoother and less force throttles, by eliminating the springs over the cables, making up something that operates like the later carburetor levers & springs ...without changing the carb tops ....with some work.   These are side-notes, just for your information; & have nothing to do with me and my bike in this story.

One question, as far as this true story goes, is the same, whether the knurled nut is used for friction, or a locking device lever, or my anti-spring device, or any combination ....and that is "will the throttle return to idle if your right hand is removed from the throttle".


In the early days of my riding with this type of setup, I did not give enough thought to safety. It never occurred to me that the friction screw, or my anti-spring; or, both together, could cause any problem in light tension use.   NOT THINKING about changes versus consequences can have nasty effects.  Not thinking about the factory friction screw device is easy to do, after all, it is 'factory'.  Note that the SAME results could have occurred with just the stock ...or aftermarket friction devices ...or my anti-friction device.


In 1985, on the first of September, amidst a serious bout of Very-Early-Cabin-Fever, I made a 10 minute decision & less than an hour later I had packed-up, shut down the house, & jumped on the bike wearing my white leather racing suit! ...etc.

I headed for Oak and Tiger's (Orlando and Carol Oakleshen) home in the Chicago area, to annoy him, and to probably annoy his wife Tiger (Carol) even more.  I had/have, over the years, annoyed Oak a very considerable amount, and probably also annoyed Tiger (no "probably's" about that!).

Not exactly a short day-ride from Lake Tahoe, California. Nope, it was 1960+ miles.  Many miles at 'Warp 9', mostly Highway 80, super-slab. Got an $5 'energy' violation in Nevada for using too much fuel ....think I was at Warp 9.9 at that moment.  I hit warp 10 for stretches.  A G/S at WOT joined me for a short while in Nevada, and he tried to keep up with me ...he also got a "energy violation".  I paid the $5 fee later (no record of it made by the Authorities to DMV, assuming you paid).  Best speeding citation, ever!  Yep, Nevada, ....not the only State that hated the Fed's 55 mph speed limit back then.

Once in Chicago; after being greeted by Tiger at their door (with some unmentionable words)....and, me thereupon pestering my put-upon hosts, we eventually all left, Oak & wife Carol (Tiger) on his bike, pulling their camping trailer; me on my R100RT.  We were off to attend the Land Of Lincoln Rally.  I made a photo of the back of my T-shirt for you....yep, still have the shirt:



On the way to that Rally, it was raining cats, dogs, & elephants.  There was a LOT of standing water on the roads; rather excessively so in some places that did not drain well (is there a reason country roads in that State have no crowns???).  We were on Sauk Trail, as Oak remembered (R.I.P, Oak) some of these details better than I did.  We were mostly doing a goodly rate of speed.  I was not comfortable at those speeds on very wet, even flooded roads, but did it anyway.  Mistake #1.

There was the quite rare country traffic signal.  One in particular I will not be forgetting.

Oak & Tiger made it through 'my' traffic signal, it had been green for them.  They were a fair amount in front of me, and going like the dickens, even with that fairly large camping trailer behind their R100T.  I was more cautious.  I am sure I was thinking of my tire tread depths, & I NEVER ride in deep heavy rain, NORMALLY, at over 40 mph, to avoid aquaplaning.  I began to slow for that ONE & ONLY traffic light in the middle of nowhere, which was shining bright red.

As I was slowing down, I probably used a tad too much front and/or rear brake, considering the 1-1/2 to 2 INCHES of standing water on the road. I became an aquaplaning missile, a "tire-friction-deprived-passenger, no longer a rider". The bike & I came to a reasonably square & probably close to a full stop ....at the proper stopping place for a red light  ....  >>> FOR A MICRO-INSTANT.

NO excuses, really.   I was traveling at a high rate of speed, trying to catch up to Oak & Tiger ...who were barreling along pulling their TimeOut Camper trailer at their usual ...ah ...rate.    At the traffic signal ...THEY made it through, ...well ahead of me ...when it was green;   ...I did NOT.   Well, I made it half way through  ...sort-of.

There was an interesting fishtailing half-wiggle of VERY substantial amount. Dirt riding techniques were not sufficient planned-for ahead of time.  They don't help much with aquaplaning anyway.   The seat, having inches of standing water on it, had some fun & games with my butt, which was sitting in a substantial pool of water (and NOT off the seat, with me standing on the pegs, as things should have been ...>>>besides the way beyond 40 mph I should NOT have been doing).  Mistakes #2++.

The bike continued into the intersection withOUT me!
I shall explain that ........

As the bike left me,... or, I left the bike ....well, we got a divorce ....>>>I was on my feet ....running. Something about all the water on the road, me wearing boots, the deep water on the seat, wet grips ...ETC.  ...all nice and slippery...

...off the bike I went ....(AND ...another thing ...I was NOT, at that moment, TRYING to run....but I WAS RUNNING).

I had simply separated from the bike at a modest speed (real divorces should be so fast?), STANDING UPRIGHT.  To this day I am unsure of how that happened.   I suspect the bike fell and slipped to the left, well on its side, and I simply was left on my right foot, then both feet.  I wish I had a video of this.

CRAZILY UPRIGHT, my big boots were additionally acting like skis on the standing water.   In fact, I was 'running' FAR FASTER than a 4 minute mile.   That's what it seemed like.  I possibly looked like a certain floppy-eared Disney character, flapping my feet, dance-like...??   Have YOU ever skied on your motorcycle boots?  It could be a hoot ...if it was done on purpose.   yeah.   riiiiiiight!

This went on for about 20 or so feet (feet:  pun intended). My boots were skiing AND moving to and fro, & I was UPRIGHT!   I had never skied in motorcycle boots before!  (nor since!).  I can honestly state that those biker-style engineer's boots, which I still have (nostalgically worn-out) ...did a great job being mini-skis.

The bike had also decided it was time to prepare a Special Edition of Evening News Divorce ....its own fun and games, ...no lawyers needed ...all just for me, ...& any onlookers (none at that moment).

The motorcycle, ...having proceeded somewhat angularly into the intersection, ....began turning left doughnuts in a fairly tight diameter circle.  The diameter of that circle was probably close to the length of the bike.  The bike was spinning, a bit tightly, somewhat on the left cylinder but mostly on the left rear saddlebag.

The throttle was not about to reduce to idle by itself. Definitely Mistake #3+++....maybe mistake #4+, because I had been ignoring the somewhat squared-off rear tire from the slab miles and speeds from California to Chicago. I think the bike had a nearly new Metz ME88 on it, can't remember, but in less than 2000 miles the constant high speeds on paved roads...etc.
A squared-off rear tire is VERY conducive to a bike becoming unstable.  Another little helping of something or other, besides my gross mistake of excessive speed for conditions.  https://bmwmotorcycletech.info/instability.htm

This is all hilarious NOW, if being related, animatedly, at some campground fire pit, with a brewski or two, or tumbler of Lagavulin with friends, .....but the bike was spinning like a top, although much slower; but it seemed rather fast at the time to ME. The left side of the rear tire, which had hardly been used on this super-slab journey trip across the USA, had enough grippy tread ... & had enough friction in the deep water and surface of the road, with little touching the road but a bit of the left saddlebag and the left cylinder head, so that was enough to keep the bike moving. The bike was moving in a rather tight circle ...which appeared too fast for me to jump in & use any KILL switch (inactivated anyway, due to the tall tank bag, ...I had bypassed the kill switch!!) ....or, for me to reduce the throttle.  At least it looked that way.   I had no intention (at first), in having over 600+ pounds of bike & gear ....slam into me.

There was no side traffic within sight, but, after a minute or tad more, but seemed like several minutes ....a sports car arrived from the left & stopped.  The driver got out. We are both laughing, & also trying to figure a way to stop the damned spinning bike. We began by running in a circle in the same direction as the bike, with decreasing radii as we ran.    With the large amount of standing water on the road ...& the rain ...this was hilarious; let alone hard to do without slipping and falling ....although I wasn't laughing much at the time. I only wish I had a video of this. The motorcycle slowed ...but only slightly  ...after numerous turns and finally I caught up with it just enough & I cast to the winds (well, water) any thoughts of physical injury....and......jumped onto the pile of moving bike, to shut off the engine with the key.  The jumping onto it made the bike dig in a bit more, and the rear tire lost its purchase onto the road, ...well...'nough said....but... at the same time I managed to turn the ignition key off.   The damage to the bike was hardly noticeable due to all that water acting like a lubricant, just some quite minor rubbing marks.  I personally had no physical damage (my ego suffered....a couple of barleys, much later, at the campsite, did wonders for the ego...and my flapping mouth).

I refuse to get into 'crash bars' controversies, the RT had none, & I am not sure what would have happened if it did have them ....the bike MIGHT have not spun, or it might have flipped. I learned my....(or A) .... lesson (well, maybe not!).

I still use friction devices. Not using the reverse spring goody I made, although I had it on a later RT.   I now use only light settings, so there is always decent throttle shutoff return forces.  I NEVER set the friction high enough to hold the throttle completely for any length of time if I let go of the throttle ....UNLESS in a shop situation for some tuning or other purpose.

Oh, ....I did catch up with Oak and Carol ...and proceeded to the rally.  


BMW offers its own friction device. It is a special screw, all-metal (except for nylon-like friction tip), threaded 8mm x 0.75 mm (there ARE some 10 mm ones), with a 'sort-of' captive spring.   The primary usage was originally for setting the throttle, for such as adjusting the carburetors; but a secondary purpose was to relieve some right hand stress.   It has been, over the years, on various models at various times.  Sometimes the throttle assembly was not drilled and tapped with threads, or not drilled at all.  There are some variances, and the part number for the knurled screw with its spring and plastic tip (the knurled screw has a nylon or similar hard plastic tip, which works nicely against the throttle tube), is:
K bikes and R80R and R100R:  32-72-1-454-414.
Rest of the Airheads:  32-72-1-230-874.  Shorter than the above one.

The blanking plug was 32-72-1-236-605, probably fits all of those bikes (?).  You may find a blanking plug on your bike, you can remove and install one of these friction screws.


Schneiders, inc., used to have a product called a Flip-a-lever.  This item was fairly popular, many years ago.  They could even drill your throttle housing if yours was not factory drilled, ... etc.   The old address was Schneider's Inc.  43B Mullan Rd. West; Superior, MT  59872, and they had a website long ago.   Schneider was, I think, sued out of business by someone who used a different Schneider kit ....to convert the automatic retracting side-stand to 'not automatic', and had an accident.  Schneider sort of became a hermit after that, so I was told.

There are numerous sources for various types of throttle levers or friction devices or other effort reducing contraptions, from most (?) BMW dealerships & most Independents, etc.   Your BMW dealership or independent may well have a number of types in stock, besides the BMW version.

I LIKE the Throttle Rest (the name I give to all of the palm-rest type products, which are similar but not exactly the same), a simple piece of plastic, it makes for considerably less effort on my hand. These simple devices work pretty well, although some may slip some on some types of grips without putting a layer of tape underneath. These are, of course, not friction modifying devices. I use them on all my BMW bikes.   There was some sort of lawsuit over patent rights (?) of these products, Throttle Rest versus Crampbuster. I don't remember the details ...but I think it is the same company now (??), two websites:  http://throttlerocker.com/            http://www.crampbuster.com/.   Check these products out on the Internet, as they are different in fitment, size, usage.

Another such palm-rest device is/was the Wrist Rest, from WolfTrax, etc.   I think the WolfTrax folks that made the Wrist Rest have disappeared.

Friction device, non-stock:
Throttlemeister.   Have substantial weight, fit both ends of the handlebars (friction adjusting for right side); look fancy, cost $$$, and can work well on reducing vibration, and are easily adjustable for friction amounts.  I have a set on my K1100LT.  I tend to forget which way to turn them to change the friction amount, you probably won't.  These are NOT wrist/palm rests; I also have one of those.     (414) 464-6060, FAX (414) 464-9423; www.throttlemeister.com; Marker Machine, Inc.  5240 N. 124th St. Milwaukee, WI 53225.  These also can replace the stock BMW weighted bar ends on those models using them.

Lighter tension/force carburetor springs:
Lighter carburetor springs are available ....they are not the same for 32 and 40 mm carburetors. Check with your dealership; or, Ted Porter's Beemershop in California, etc.  There is a type 606 for the 32 mm carburetors that have 3 digit model numbers; a type 908 for the earlier 2 digit 32 mm types, and a type 312 for the 40 mm carbs.


ADDENDUM:

On this same trip trip in the greater Chicago area, Oak & I refueled with what must have been left-over Winter gasoline blend.   My R100RT was not carbureting too well.  Oak's K100 (yes, Oak had Airheads but ALSO had a K100 at that time) had boiling fuel in the fuel tank, & was acting up a lot. I suspect he needed to add reflective insulation to the underside of the fuel tank, as later K bikes had, although that is not all that is needed.

On the way back from that Rally (at Starved Rock State Park), we returned by a different route, which Oak remembered as Beecher Peotone Road.  We raced a storm back to Oak & Tigers house. It was bright, sunny, & QUITE hot.   Oak remembered the sky being painted in two colors, & towards the East, clear blue, towards the West, pitch black ....SOLID BLACK.   So, Easterly we went, at a VERY high rate of speed indeed, racing that storm ....to I-57, then North to Monee, then back roads to Oak's....& quickly into the garage...

.....& then, .....the storm hit.  We never had time to get into the house ....we were, as Oak says, 'trapped' in the garage until the storm passed.  We missed being in that deluge by seconds.


rev:
2005 through 12/10/2016:  Updated to exact information on the Land Of Lincoln Rally, roads traveled, weather, etc., in the sections on me in Illinois, & spinning in the road, and returning to Oak's house.  Minor typos & clarifications in other areas. Update QR, language button, Ad-Sense, remove script for language button, update for smaller displays, add photo off off my Land 'O Lincoln rally shirt, etc.
05/03/2018:  Reduce excessive html, colors, fonts.  Clean up layout.  Change a few things to past tense, due to Oak's death.
01/23/2019:  Slight update and again, typos, on 04/20/2019.
06/19/2019:  Two minor corrections.

Copyright 2019, R. Fleischer

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Last check/edit: Monday, July 22, 2019