Throttle Control

[The General]

Mother`s day here in oz and I thought I`d get a little closer to her. (She passed away some years ago). So I took FJ3 (ex-klavdy`s) on her maiden thrash through the Kenilworth Twisties and up the Obi Obi race track. 
Now I have been Generalising her a bit over the last coupla months but still got the old square tyre on the back and the triangular one on the front. (Waiting on a delivery of Roadsmart II`s).
When I`m on  FJ1 or FJ2  (clip- on standard bars) we are a Smooth precision team, (for an old bloke) in unison and comfortable near the edge of Newtonian law, particularly in regards ta throttle control, downshifting under pressure etc. (but with allowances for old technologies in the tyre & suspension departments).
However, FJ3 has motocross type Bars (Ritner front end) and as a result a little 5mm slack before throttle response. I figured eventually my body responses would adjust to what I would describe as a snatchey throttle feeling (not good in tha 6000 to 8000 rpm range thru twisties) and we`d be in Unison in no time. - but it just doesn`t happen???.   ..... Made sure chain was adjusted to minimum slack, carbs professionall synched, throttle cables lubed (maybe too slippery?) and adjusted. In the old days (cough, cough splutter) we`d modify the shape of the throttle spindle for quicker and less hand movement between half throttle and full, while having more control (and more wrist movement...no comebacks please) in the first half of the throttle response.
I`m sure I woulda kept that ducati in my sights this mornin if i had smoother transition and FJ1 & 2 throttle control. (I know clutch position can help) - Anyone else experienced this? What`s the fix?  or is it all in my mind. 

[Arnie]

Doug,

If there's slack in the throttle cables, there are adjusters under the tank, just over the head before they connect to the bank of carbs.  Make sure you leave a little bit of free movement, ~2mm at the grip is generally fine. You might want to check that Rittner hasn't put a quick action throttle on it.

I'd be cautious about "professional carb sync'ing" too.  Just because they charge you money doesn't mean they actually do anything, or do it right.  If you do it yourself, you'll know its right.

Cheers,
Arnie

[Pat Conlon]

Hey Doug, here in the states we have a company called Motion Pro where we can get different throttle controls based on our needs.... Here is a article from their tech page:

Tech
Throttles and Throttle Kits

posted Dec 31, 2007
Tags: Reference, How To     All Article Tags
At Motion Pro, we never refer to our throttles by fractional names (1/4-turn, 1/2-turn or other any other "turns"). How far a throttle fractionally turns is a function of the throttle's "rate" (how much cable inner wire the throttle's drum or cam reels in, versus how far in degrees the tube must be turned to reel it in) and the carbs/throttle bodies travel (how much cable inner wire must be reeled in to fully open the carb(s) or throttle body/bodies.
As an example, our fastest throttle, the Vortex, has a rate of 1.90 (the maximum number of degrees turned divided by the maximum travel in mm, 95º/50mm of wire travel). Since it has a maximum of 95º to turn, it will never be much more than a 1/4-turn throttle but in any application requiring less than 50mm of travel, it will be less than 1/4-turn to fully open. If only 25mm of travel is required, it will be about a 1/8-turn throttle. The opposite of the Vortex is our CR Pro; our slowest single pull throttle. It has a rate of 2.93, the result of a maximum of 170º turn and 58mm of travel. The rule of rates is simple; the smaller the value of the rate, the faster the throttle will open the carb.
Since we do not know the travel of your carb(s) or throttle body(ies), we will not quote a fractional turn. With careful measurement you can determine the approximate fractional turn required by a given carb and throttle by removing your existing throttle from your existing cable. Carefully measure the exposed inner wire (in millimeters) between the last fitting on the housing (the cap, elbow fitting, or threaded adjuster) and the wire end fitting (usually a ball or barrel). Do not include the wire end fitting in the measurement, only the exposed wire. Write down the measurement, it is your present "throttle free length". Now pull the inner wire until the carb is fully open against the stop and repeat the measurement. Subtract the throttle free length from the measurement you have just taken; this figure is the carb's "travel". Refer to the "rate" of the throttle you are considering. Multiply your carb's "travel" by the "rate" of the throttle. The result is the approximate number of degrees the throttle will turn to fully open the carb(s).
Notes: Do not consider any single-pull throttle (only one cable used) to replace any push / pull throttle (one pull cable and one return cable). WE WILL NOT build a custom cable to operate a push / pull carb with a single-pull throttle (including ATV thumb throttles). To fully open your carb, the throttle's maximum travel must be greater than or equal to the carb's travel or the carb will not fully open.
In most cases, your present cable will not work with a throttle of a different rate. Even if the rates are similar, differences in internal design usually require a different free length (the amount of cable inner wire required to reach from the end of the cables housing and housing end fittings to the connection point on the throttle tube's drum or cam). We calculate free length as a total figure, both the carb's required free length and the throttle's required free length are combined to determine the correct cable free length. This, in addition to the varied types of required housing end fittings, is the same reason you may require a special cable when you change your carb to a different size or type.
Part Number    Throttle    Max Twist    Rate    Max Travel    Free Travel    Replacement Throttle Tube
01-0054    Vortex    95º    1.90    50    601   01-0082
01-0053    CR Pro    170º    2.93    58    45   01-0087
01-0056    CR Comp    190º    2.35    81    50   01-0088
01-0057    TURBO (Std.)    120º    2.30    52    902   01-0089
     TURBO (w/ Opt. Tube)    150º    2.00    75    902   01-0072
01-0060    Magura 314 mx    95º    1.90    50    70     
     Magura 314 enduro    105º    2.10    50    70     
01-0058    Push/Pull Black    165º    3.67    45    T20/50I   01-0052
01-0059    Push/Pull Chrome    165º    3.67    45    T20/50I   01-0052
01-0073    Straight Push/Pull    109º    3.00    36    T34/49I   01-0090


1F/L measured thru TH-1245, for use with 01-0024 add 10mm.
2F/L measured from cap.
Rate = Twistº / mm Travel Max travel is measured in millimeters (mm)

[The General]

Doug,

If there's slack in the throttle cables, there are adjusters under the tank, just over the head before they connect to the bank of carbs.  Make sure you leave a little bit of free movement, ~2mm at the grip is generally fine. You might want to check that Rittner hasn't put a quick action throttle on it.

I'd be cautious about "professional carb sync'ing" too.  Just because they charge you money doesn't mean they actually do anything, or do it right.  If you do it yourself, you'll know its right.

Cheers,
Arnie

Thanks mate. Good thoughts. The throttle itself was my next "point of call" and will adjust cables a fraction more to your suggestion (while observing all linkages and full lock movements). Might even try a throttle swap/purchase next weekend. Then will look at longer cables maybe. (Then some protection Bars).
It`s a strange sensation - like when ya march with ya arms synched to the same side as ya feet - it feels wrong, - though all tha right actions are there. ........hmmm, - maybe it is in the mind - this one has always been suspect.

[The General]

Thanks Pat - Very interesting facts. (a subject I haven`t seen in such detail before). Sounds like a weekend of interesting measurements coming up. 

[oz.fj]

Hey Doug
For future reference, I've got a Morgan carb tune pro you can borrow
it's a piece of cake to sync the carbs (i didn't even need my hammer)


Darran