Forum miłośników motocykli KTM

lukaszd7

znalazłem tez taki link moze ktos to testował:http://www.enduro-adventure.com/new/index.php?option=com_content&view=article&id=239:modyfikacja-pompki-przyspieszajcej-keihin-fcr&catid=37:poradniki&Itemid=234

hacker33

Chyba większość z nas ma/miała taką modyfikacje w swoim FCR.
Normalna rzecz, nie odnotowałem jakiś negatywnych zjawisk tego zabiegu.

lukaszd7

bo u mnie musibyc słaba ta spreznka bo bez niej to lipa jezdzic.. ale tez tak jak w linku polecacie tą srubke wykrecic???

grzegorzszw

Pompka przyspieszacza jest po to aby przy otwieraniu przepustnicy mieszanka nie była zbyt uboga (wstrzykuje się dodatkowe paliwo). Producenci nie wiedząc jak będzie ktoś operował gazem stosują uniwersalne nastawy pompki. Niestety o ile sprawdzają się one przy płynnym dodawaniu gazu to już przy agresywnym niestety nie. I tu zaczyna się cały tuning, chodzi o to aby zwykle zmniejszyć ilość zastrzyku (np. zakładając większą dyszę przelewową - leak jet) i skrócić czas wstrzykiwania paliwa (np. zakładając o-ring lub drucik). Jest jeszcze kilka metod w zależności od modelu/roku motocykla/gaźnika.

Tutaj chyba wszystko jest najlepiej opisane (a sprawdzając kolejne linki możemy się dowiedzieć jeszcze więcej). Treść pochodzi z KTMTalk, autor Dave Hopkins:

ACCELERATOR PUMP SET UP 101
(For the Kehein FCR Carb)
Note do to the complexity of the accelerator pump I have broken this into two sections, Carb Set Up 101 and Accelerator Pump Set Up 101

First lets understand the basics, a carburetor works on the principle of air flow siphoning gas as it passes the needle & jets. At idle the air flows thru a very restricted area adjacent to the jets. When you twist the throttle quickly at low RPM the air flow is suddenly moved from right at the jets to spread over a big area, same amount of air spread over a larger area, vacuum decreases and air speed at the jets decreases too the point that fuel siphoning stops, no fuel equals Bwaaaaaa!

To supply fuel from the “twist” until vacuum is restored the manufactures have several options;
1: Smaller carburetor.
This keeps the air flow close to the jets, makes a bike work nice in low speed maneuvering but kills top end power!
2: Fuel injection.
Fuel injection, it does not rely on the siphoning effect. Like it or not its coming as;
A) As they are not vacuum dependant they can use a bigger throttle body thus Rev higher equals more power, and
B) Once the R&D work is done and you turn up production volume it may cost less to produce than a carburetor.
3: Constant Velocity (CV) Carb:
A “CV” carb is an excellent deal, you whack the throttle open (or think you did) but a vacuum controlled deal keeps it only part open until the engine is revved up enough to use it. Common on street bikes, to put one on your KTM you would have to cut a notch out of your knee to get the space and get stronger springs as it would add several pounds. Not suited well for a “race bike”.
4: An accelerator pump:
This is the route most of the state of the art off road bikes have until we have FI, this provides a little shot of fuel to fill in during that moment of lag in vacuum. Problem is, how much gas? Earlier designs squirted gas “while” the throttle was being moved, once the movement of the throttle stopped the squirt stopped. That was a bit to brief and left many a car or MC pre-igniting (Pinging) for a moment after the “twist”. This Pinging can lead to a piston failure! The common setup on the Kehein carb is set to squirt for 3 seconds after the twist. This is not necessarily wrong, just a compromise setting chosen by the manufacturer. What we need the AC pump to do is bridge the gap from the “twist” to the engine being revved up a bit, lets just guess that 3,000RPM will be enough to get the air flowing sufficient to get the siphon effect underway again, while a big twist at low RPM can make the engine “fall on its face” even once past that point a heavy load on the engine the engine could be experiencing a lean spot that can lead to pre-ignition.

We could debate names all day but in my definitions:
A: A “Lean Bog” is when lack of vacuum to maintain the siphon effect has caused the engine to run out of gas before the RPM got up to where the siphon thru the jets can take over. The AC pumps job is to bridge this gap, and
B: A “Throttle Stall” is when too aggressive of an AC pump floods the engine.

The area in between is the Happy Zone we all strive for, the manufacturer does not know how your going to use your bike but they do know, not enough AC pump can cause pinging/piston failure, too much AC pump causes a bog, which is worse? So they have to seek a compromise combo on the AC pump.

Most off road riders are using relatively low gears, this together with wheel spin gets the RPM “up” quickly!

Example 1:
You have left camp on asphalt headed for the trails, riding pretty mellow, think your being easy on the bike, exit a corner at say 1,500 RPM in 5th gear, you roll on a little bit of throttle and the engine slowly builds momentum so its 3 or 4 seconds before the engine gets back to 3,000RPM. What would happen here is without squirt of the AC pump the engine would be very lean yet with a fair amount of load on it, several seconds of that “easy treatment” may even be melting away a small bit of the piston. By designing an AC pump that continues squirting for say 3 seconds that lean spot is patched over by this “squirt”!
Example 2:
A bit down the road you turn onto a trail of delicious loamy soil, you whack the throttle open and the rear tire breaks loose, the RPM jumps almost instantly into its happy zone, say to 5,000RPM and while the phun meter heads up yet the engine seams just a kinda hang there a couple seconds, then takes off! What is happening here is when the RPM jumped up the air flow thru the carb drew in all the fuel the engine needed for its proper fuel air mixture thru the jets! Yet at the same time it was being supplemented by the AC pumps squirt. Combined the two fuel supplies and the fuel air mixture was overly rich, that “rich” mixture burns slower than a correct fuel air mixture and the engine feel just a bit lazy.
Example 3:
Your on your shinny new Orange bike and leading your buddy who rides this wrasspy old “faded other color” bike, you enter a corner with this MX track like berm, your leaned over maybe 70 degrees and you whack the throttle open anticipating roosting old blue or whatever, you anticipate “Rriiiiippp” but hear “Bwaaaaaaaa”, engine dies, 70 degree lean angle becomes 90, phun meter collapses. Old blue’s owner gives you some squidly look. What happened here is your AC pump was set for example 1 and basically flooded the engine!

These “High Performance Engines” have a carburetor that is big for its size so they do not maintain vacuum when wide open so it needs that AC pump squirt to fill the gap of the "lean bog". Often the AC pump is set up too aggressive and floods the engine, the “throttle stall”.

Kehein was very clever in this design as it squirts during the twist AND for some predetermined amount of time after! First and foremost your pump needs to be working!
Check for
A: Function! It must squirt when you twist
B: Start of squirt! It must squirt as quickly as the slide starts moving up but should not splatter on the back of the slide!
C: Duration! The duration is the amount of time is continues to squirt after the twist!
Start of the squirt;

On the 03 and newer models there is a screw on the right side of the carb that adjust the start of the squirt, when correct the squirt does not hit the slide, the slide should lift and the squirt follow just under it. The following link gives you a good starting point:
[link widoczny dla zalogowanych]

Duration of the squirt:
Most bikes as a compromise are being supplied with the AC pump set to squirt for 3 seconds after you twist. If your riding is strictly off road the bike can be more responsive by shortening that duration! Do Not reduce this squirt duration on any bike that is used in high traction riding such as Dual Sport! You can’t have it all and trying to make one of those bikes respond like a moto crosser would make it deathly lean when you gently rolled on a little throttle on asphalt!

You have to judge how long of squirt time you need! That is tied to how low or high of gears you use, wheel spin, gearing, size of bike etc. If you are a very passive rider, roll on the power gently and seldom spin a tire the factory 3 second setting may be prefect. However most off road riders are geared down for the woods and ride aggressively so the low gearing and wheel spin will have the RPM up in about a second, thus they want a 1 second squirt time.

Pay close attention, test to follow! The way the AC pump works is very clever in that the throttle activates a link pushes a spring that pushes a second link (you gotta look at it) that allows the second arm to be delayed, the delay is caused by the fuel pressure in the pump circuit! To illustrate, visualize yourself draining a hot water bottle full of water, you toss it into the sink, pop the cap off and press on it. What happens parallels when you twist the throttle, the throttle door that controls air is allowed to open right up but the hands pushing on the water bottle takes some period of time for the water to squirt out!
On the carburetor this creates a squirt that in stock setup is for about 3 seconds after you twist, we can reduce the squirt by blocking the pumps movement OR by leaking off some of the fuel pressure! Like draining the water bottle we can vary how long it takes with pressure, or by stopping the push! Stopping the push on the diaphragm is achieved by a mechanical stop, a bit like tossing a rock into that water bottle so you can’t squeeze all the water out:

WHAT THE “NUMBERED” MOD/ADJUSTMENT’S DOES IS ADJUST THE FUEL VOLUME BY STOPPING THE AC PUMP CIRCUIT PUMP DIAPHRAGM BEFORE ITS TRAVEL IS COMPLETED.

1: Honda Mod: Kehein makes a series of different AC Pump diaphragms with a post on the bottom to stop the diaphragm just as the rock did in the hot water bottle. Basically the longer rivet thru the middle that stops its travel, the shorter the squirt. My recollection is that there are 4 lengths available? The KTM comes with the shortest post, longest squirt Honda Part #16021-MEB-771 or Yamaha part # 5JG-14940-19, is the opposite. Longest post, shortest squirt. The best part is this works on all years of the Kehein FCR carb, is a simple, no brainer, minimal talent required just change the diaphragm, ignore a couple other pieces that comes with it and a bargain at under $20.

2: BK Mod: For ’03-05 only, you drill & tap a hole, install a screw & spring to make an adjustable stop called the “BK mod” (Brian Kenny). The link to its instructions are near the bottom of this page. For the bikes that it works on this is my choice because its almost free and fully adjustable.

2.A: For the ‘00-02 bike you do the same thing by bending a tang on the side of the carb, it is like a small fork and you need to bring the tips closer together, then recheck. For a pic go to JDs web site photo gallery, currently it is page 3 (but that may changes as more photos are put on the site?) [link widoczny dla zalogowanych] look for photo titled Pinched_Linkage.jpg

3: Taffy mod: This involves a wheel spacer from some model airplane that is slipped over the rod of the AC pump, while this is perfectly viable and I believe works only on 03 & newer, I have no further info.

4: I have also heard of gluing a valve adjustment shim into the bottom of the AC pump cover, someone even did this with a button.

5: And threading a hole in the cover and putting in a set screw adjustable stop! I like this with the exception of fear of gas leaks.

6: There is an AC pump cover called a P-38 that also restricts the pump travel.

WHAT THE BELOW “LETTERED” MOD/ADJUSTMENTS DO IS ADJUST THE FUEL PRESSURE IN THE AC PUMP CIRCUIT.

A: “Leak Jet”: As the AC pump is pumping more fuel than we know what to do with another way to reduce the squirt is via a metered leak back to the float bowl! Most of the bikes other than KTM have a “leak jet” in the float bowl, up thru 05 KTM did not have the hole machined for it, rumor has it that some 06’s do?? If not you can by a bowl from JD that is machined for the jet. Common jet sizes are in the 50 to 80 range. What this “leak” does is reduce the fuel pressure of the squirt! As the duration of the squirt is tied to the volume of fuel pressurized under the diaphragm adding a leak quickens the draining of that chamber. Thus adding a leak has two effects:
1: The duration is shortened somewhat like that of mods 1-5 above, and
2: As the fuel pressure in the AC pump circuit is decreased the initial hit of the squirt is weaker!
BACK TO THAT WATER BOTTLE, ADDING A LEAK JET IS LIKE HAVING A SECOND NOZZLE ON THE OTHER END OF THE BOTTLE (ONE END GOES TO ENGINE, THE OTHER END GOES BACK TO THE BOWL.)

B: Wire Mod: Credit for this trick goes to Redbeard. I want to tell you how cool it is but have not tried it so I will leave you in his hands if you want to try this route. His site (below) has a host of photos that you can refer to regardless of what route you elect to take. This involves safety wire to effectively tie the two linkage pieces together. I am still not on the same page as this as now the AC pump is moving the same speed as the throttle. This can only be done with the pump diaphragm that allows full travel AND can only work with a substantial sized “leak jet”. Object is it hits the pump harder then the big leak jet bleeds off excess to get back to some normal duration of squirt. Notes; He shows an optional way of doing the same with an Oring rather than the wire. In this application the Oring is solidly tying the two links together.

C: ORing Mod: Credit for this twist goes to JD as a modification of Redbeards mod. This involves taking the same Oring as shown in Redbeards site above (an ID about 5/16th inch and OD about 7/16th inch) and installing it as shown on his site but setting the linkage and the squirt duration in a conventional manor.
Many paragraphs back I said there would be a test! And described how one arm pushed on another with a spring, well this ties the two pieces together with a bit of elasticity which increases the pressure of the spring, thus increasing the fuel pressure of the pump for its initial hit! This yields a higher volume initial hit, then the pressure tapers off. I personally watched & rode/tested a KTM525 and it brought this bike to life! It worked very well in conjunction with a limited travel diaphragm of mod #1! With this setup as with stock when you open the throttle the first arm gets ahead of the second arm! This is what creates the "duration of squirt!"

D: Quick Shot: This does the opposite, it increases the squirt. Its purpose appears to be for some bike (that I have not met) that needs a stronger squirt than original. For the rest of us I see no value in the piece, I have heard that some have benefited from its instructions on setting the start of the squirt which are free here so just take the $94 you just saved and send to me:>)

Dave’s way: As we learn more about this I am leaning more toward tailoring the squirt to the size of the engine! We are all learning but my thoughts at this time.

250SXF Has trouble using the full volume of fuel of the pump, is easily flooded when stalled and at least in a trail application favors a softer hit of the pump (reduced fuel pressure) AND the reduced duration. Thus my recommendation is BOTH mods “#1” and “A”. Side benefit, this will help if not cure the hard starting when hot problems we see at the MX races.

350-450 is happy with just “#1” or “#2” if 03-05 and “#C” is worth trying.

525 and bigger responds very well to a bit more fuel on the initial twist and less duration, thus I am favoring both mod “#1” or #2 if 03-06 and “#C”!

Street, Dual Sport who have 100% traction need the full 3 seconds. Too short of duration can hurt your engine when riding mellow. If pre 06 you might try Mod #2 as its adjustable and tinker with it out on the road? Listen carfully for pinging and run as long of duration as you can without bogging.
Motard or Ice racers may have the 100% traction but are less likely to gently roll on the throttle, more apt to be revved up all the time? So I suspect a short duration is fine?

Some resources
Setting the start of the squirt [link widoczny dla zalogowanych]
Redbeard’s Instructions: [link widoczny dla zalogowanych]
BK Mod Instructions: [link widoczny dla zalogowanych]
BK Mod Instructions: [link widoczny dla zalogowanych]
BK Mod Instructions: [link widoczny dla zalogowanych]
Diagrams/parts: [link widoczny dla zalogowanych]
Diagrams/parts: [link widoczny dla zalogowanych]
Fuel Screws [link widoczny dla zalogowanych]
Fuel Screws [link widoczny dla zalogowanych]
Fuel Screws [link widoczny dla zalogowanych]
Tech [link widoczny dla zalogowanych]
Tech [link widoczny dla zalogowanych]
Slide Plate [link widoczny dla zalogowanych]
Jet kits, float bowls etc. [link widoczny dla zalogowanych] jdjetting.com

Also see Carb Set Up 101

Dave “DJH” Hopkins

lukaszd7

a co sadzicie o tym? [link widoczny dla zalogowanych]