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

copyright, 2013, R. Fleischer
http://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 friction screw (available on or 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 later herein. 

For Airheads after the /5, less strong carburetor return springs are now available from many dealerships & independent's that help reduce wear on the throttle gears & require less hand effort, and this results in throttle use being less tiring.  These lighter springs were not available in 1985, when the incident in this story happened to me, but it probably 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 good items, and I really do like these products.  ONE of the secrets of using these ....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 fact, 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.

While I have nothing 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 with the knurled BMW friction lock screw, ETC., and add some information about some, not all, types of devices.

This particular 'adventure' happened in 1985, on my near new 1983 R100RT (purchased new, out of the crate, in 1985).  This fun & games is likely to be forever be in my memory.  Even today I crookedly smile when I think of it.  Luckily for me ...& my motorcycle ....it turned out OK. 

I not only had the stock BMW friction screw lightly tightened to where it was adding some noticeable friction (although not enough 'on its own' to hold the throttle for any lengthy 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 ...the throttle will NOT return to the idle position on its own, when your hand is removed from the throttle.  

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 reasons to use a LOT of friction, such as when adjusting carburetors.


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 special reverse spring device. This 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 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.

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 that various models got lined cables is UNKNOWN to me, they were phased-in, IMO & 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. 

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.

The effect, as far as this 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.


In the early days of my riding with this type of setup, I never ever gave any thought to safety. It never occurred to me that the friction screw, or my anti-spring, 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 would have ocurred 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 & a 20 minute packing-up, & jumped on the bike, wearing my white leather racing suit! ...etc. 

I headed for Oak and Tiger's home in the Chicago area, to annoy him, and to probably annoy his wife Tiger (Carol) even more.  I 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.  An R80G/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.  Yep, Nevada, not the only State that hated the Fed's 55 mph speed limit back then.

Once in Chicago; pestering my put-upon hosts, we 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:



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, as Oak remembers some of these details better than I do, on Sauk Trail, mostly doing a goodly rate of speed.  I was not comfortable at those speeds on very wet streets, but ....did it anyway.  Mistake #1.

There was the quite rare traffic signal.  One in particular I remember.  Oak & Tiger made it through 'my' traffic signal.  This was pretty much in the boonies.  They were a fair amount in front of me, and going like the dickens, with that fairly large camping trailer behind them.  I was more cautious.  California riders seldom need to know what rain is, & 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.

As I slowed for the ONE & ONLY traffic light in the middle of nowhere, which was shining bright red at ME (on the only vehicle within sight) ..... I probably used a tad too much front and rear brake for the 1-1/2 or 2 inches of standing water on the road.  Maybe. 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.

I became an aquaplaning missile, a "tire-friction-deprived-passenger, no longer a rider". The bike & I came to a reasonably square & nearly a full stop .... at the proper place for the red light    >>> FOR AN MICRO-INSTANT.  

There was a interesting fishtailing 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 it 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 can only wish I had a video of 'my happening'.

CRAZILY UPRIGHT, my boots were 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 maybe 30 feet. 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...did a great job being mini skis.

The bike had also decided it was time to prepare a special edition of fun and games ...all just for me, ...& any onlookers (none at that moment).

The motorcycle, ...having proceeded into the intersection, ....began turning left doughnuts in a tight diameter circle.  The diameter of that circle was probably about the same as the length of the bike.   The bike was spinning, tightly, on the left cylinder and 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 and mostly not very curvy roads. A squared-off rear tire is VERY conducive to the bike being unstable.
http://bmwmotorcycletech.info/instability.htm

This is hilarious NOW, but the bike was spinning like a top, although slower; but it seemed rather fast to ME. The side of the rear tire, which had hardly been used on this super-slab journey trip across the USA, had lots of grippy tread ... & had enough purchase on the wet road to keep the bike moving. The bike was moving in a rather tight circle ...too fast for me to jump in & use the kill switch (inactivated anyway, due to the tall tank bag, I had bypassed the kill switch).... or 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 (?), but seemed like minuteS ....A sports car arrived from the left & stopped.  It's 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; although I wasn't laughing at the time. I only wish I had movies of this. Finally I caught up just enough & I jumped onto the pile of moving bike, to shut off the engine.   The damage to the bike was hardly noticeable ...due to all that water acting like a lubricant.  I had no damage. Pride?  Knowledge? Habits?  I refuse to get into 'crash bars' controversies, the RT had none of those, & I am not sure what would have happened if it did have them ....the bike MIGHT have flipped.  

I learned my 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 use only light settings.  I guess I have not truly learned all my lessons here, but I rationalize it by leaving SOME return force. 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.


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 or not drilled and tapped for them.  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.



http://www.schneidersinc.com/flip_a_lever.htmTHAT link has not been good for a very long time.  I am showing it here for reference, and to help you understand what I am talking about, if this item is unfamiliar to you.   Schneider use to make the fairly popular adjustable lever type ....and they could drill your housing if yours is not drilled, ETC.   Schneider's Inc.  43B Mullan Rd. West; Superior, MT  59872   http://www.schneidersinc.com.   The link is also NG, listed here for reference. 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.  He sort of became a hermit after that.

There are, however, other sources for various types of these throttle levers or other effort reducing contraptions, most BMW dealerships & most Independents, etc.   Your BMW dealership or independent may well have a number of types in stock.

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. More than two companies make these sorts of things, and you often find them at BMW dealerships, etc.

I use them on all my BMW bikes.   There was some sort of lawsuit over 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 type unit is the Wrist Rest, from WolfTrax, etc.   I think the WolfTrax folks that made the Wrist Rest have disappeared.


Friction devices, non-stock:
Throttlemeister.   Have substantial weight, fit both ends of the handlebars (friction for right side); look fancy, cost lots more, 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 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.


MORE FUN:

On this same trip trip to/from the 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.

BTW....the 'Land of Lincoln BMW Rally' was nice, small, great group.  

On the way back from that Rally (Starved Rock State Park), we went by a different route, which Oak remembers as Beecher Peotone Road.  We raced a storm back to Oak & Tigers house. It was bright, sunny, & QUITE hot.   Oak remembers 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.  Never got rained on; we missed that deluge at Oak and Tiger's home by seconds.


rev:
2005 through 12/102016:  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.

Copyright, 2013, R. Fleischer

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Last check/edit: Saturday, December 10, 2016