accelerator pump adjusting

[GT @ oh.]

Has anyone attemted to fix their stumble by adjusting this rod as suggested.....sounds complicated as far as the whole procedure goes...... with getting the exhaust gases right and other technical stuff.... but I was thinking about playing around with it....unless you all think its best not to....... without doing the whole 9 yards.

[Walt_M.]

I have experience only with my '83. When I put it back on the road 5 yrs ago, I did not have a rebuild kit and the accel pump did not seem to have much oomph. I did not have a lot to go by so I increased the stroke enough to get a nice strong flow and it has run great ever since. I don't remember how much I turned it but it was probably over 1 full turn.

[QBS]

I have never messed with the acell. pump stroke setting on my '83.  However, I do have a slight off idle stumble that can be quite annoying.  Lengthening the stoke sounds like an excellent idea to try out.  Since the pump is only functioning when the throttle is being opened, I would think that messing around with trying to get the air/fuel ratio right would be an exercise in major frustration.

My plan would be to establish which way the activation mechanism needs to be adjusted to lengthen the pump stroke.  Then, lengthen the stroke in small increments followed by road testing.  When the off idle stumble is eliminated, declare victory.

[Night Vision]

there is a plethora of possibilities regarding the stumble....

assuming the carbs are spotless  ::) and assuming you have stock air/pipes/jets.....

the first thing you need to determine is whether it's a lean stumble

                                                                  or a rich stumble

an easy way to determine this is:

IF you have a vaccum flapper... adjust the dashpot (unscrew and slide forward) so that the flapper door is about 1/8" open and not touching the rubber stopper when the top of the air box is "right side up" .. deceiving because you think you have it... and then turn it over, it's not 1/8"


if your stumble is less.... then you are rich and have a rich stumble
if the stumble is worse.... then what you did was make it leaner and therefore you have a lean stumble

remember.. the flapper opens upon carb vaccum draw.... regardless if you have a vacc assisted flapper or regular flapper

once you determine what type of stumble you have... (most likely a lean stumble) then you need to make adjustments

if you're lean... try fattening up the air pilot screws.... adding weight to the flapper door (slow it down) perhaps mess with the accel pump rod...

if you have a rich stumble... adjust the flapper door to open quicker (see above) and/or lean out the pilot screws

so far... I've gotten out 96.8% of the stumble on two V's with both types of flappers using weights and pilot adjustments...

this third one  :-\  isn't quite a stumble... more of a blurble on fast acelleration.... so now I may look at adjusting the pump rod shorter because I put it at 60mm? like the other two... and just maybe I'm FAT  :D

[Lucky]

I'm fighting a stumble & cold lean problem.  i KNOW my carbs are spotless. i've had them out & apart 3 times in the last month.  they look like they just came out of the dip inside. every passage has been blown out with compressed air. they are clean!

i've messed with all the adjustments ( no they aren't far out of whack) my YICS is sealed, even capped off makes no difference.
no water in the gas either.

cut back my wires 1/4"

seems to be mainly ft cyl, i might swap caps/ plugs f & r

cannot locate any sort of vacuume leak.  might cap off the accelerator control valve vacuume line...(internal leak?)

i'm now in the middle of testing the ignition. i made a tool to test the coils: adjustable spark jump. 6mm is pass/fail according to OEM manual.

the rear cyl has great spark, need to pull the fairing lower to test the ft coil.

i've allways suspected the pick-up coils too...

i did a valve adjustment 5 years ago, might be time to do it again..ugggh!

Yes QBS, connectors at p/u coils & pickup coils are clean & shiny (as are all electrical components)

i got worse last month & i found the YICS shot. swaped that out & it helped some.   somehow i don't thing running lean from that would have burned an exhaust valve.. hope not...

did i miss anthing?

--Lucky

[joevacc]

Hey Lucky,

My bike did the same thing out of the blue...  Was running perfect absolutely no hesitation at all. Then it hesitated around 4000 rpm.  I tested everything.  I was with jasonm and he said that I should open my air box flap.  I had tested my dash pot, it worked, no vacuum leaks whatsoever.  I adjusted the flap to within an inch of it's life.  No go - still hesitation.   I opened that flap about half way and that did the trick!

Now it is against my better judgment to put things out of whack and call it a fix...  But the thing is running perfect again.

I would love to know what has changed to "all of a sudden" make the bike hesitate like that.  Something is making that flap open slower now?  Why did it go from good to bad from one ride to the next?

I would love to figure it out...

Good luck,  I hope that your TCI unit is not acting up.

[h2olawyer]

Why did it go from good to bad from one ride to the next?

It's a Vision.   ;D ;)

H₂O

[Night Vision]

Why did it go from good to bad from one ride to the next?

It's a Vision.   ;D ;)

H₂O

'zactly...

my brother: "my Vision is running like a 750!!!!!!!"

me: "not to worry... that'll change"   ::) :D ;)

[Night Vision]

I'm fighting a stumble & cold lean problem.  i KNOW my carbs are spotless. i've had them out & apart 3 times in the last month.  they look like they just came out of the dip inside. every passage has been blown out with compressed air. they are clean!

did i miss anthing?

--Lucky

you've got 83 carbs... correct? Jason went up a size on the pilot fuel jets .... from 50 -52 IIRC

[Rick G]

My YIKS box was sealed too, it was one of the first ones I did. I used JB weld and now 6 years later its leaking I only did one that way, I like three bond  better. I corked the ports up , I'm still trying to find out whats causing the idle to wander all of the place.

[joevacc]

my brother: "my Vision is running like a 750!!!!!!!"

Which one?? ?? ??

[Night Vision]

my brother: "my Vision is running like a 750!!!!!!!"

Which one?? ?? ??

his..... like a 1980 KZ750 Twin
mine runs like a 675 when it gets a wild hair up it's ass.

[supervision]

 I just noticed a problem going on on my front carb. The connection of the throttle shaft has become lose.  When you first pickup the speed off idel, the front carb is getting a delayed reaction, as their is a bunch of play to take up.  Oh well, if it's not one thing, it's five others!!   

[motoracer8]

Ok, one more time, accelerator pump adjustment. You want .25cc, thats 1/4cc, per complete throttle opening, check each nozzle with the float bowls full and set to the correct level. I have some small viles made for that job. But can modify a small drug store syringe to measure with. Several of the Vision carbs I have messed with squirt too much fuel whitch produces a rich bog, you also want to make shure the nozzles squirt fuel right at the throttle plate edge. Make shure that they flow fuel, and squirt straight, like a water pistol. Here is another tip and this best done with carbs off, dropping small parts in the engine can spoil your day. Take the accelerator pump nozzles off, under the nozzles you will find a small weight, and a ball, remove these parts, fill the bowls with fuel, or carb cleaner and operate the throttle make shure fuel flows from the ports, if not check the pump valves, and diaphram. If it pumps fuel replace the ball, then the weight then the nozzle in that order. After It's running at operating temp, set the CO to 2.5 to 3%. If you can't do this take it to some one who can. If the low speed adjustments are done right there will be no off idle flat spots. Good luck.

  Ken G.

[GT @ oh.]

That is the technical.... involved stuff..... I was refering to.....I am not smart enough to get into all that .....wish I were.....and most mechanic here wont even touch it.... but ...I hope I found one who will... we'll see.

[jasonm.]

FYI, lengthening the accel rod has it's limits. If you go too far you DELAY the point at which the squirt happens. If you have stumble off idle...rod is too long. I set mine so it squirts immediately as the throttle is opened. Meaning it seems to squirt at the most minute slightest opening from being closed. Accel rod is 57 or58mm. No off idle stumble. For those with 4500rpm stumble(hiccup). The accel pump will not fix this. As you should still have some stroke left at that rpm to squirt gas.  As my throttle is barley opened at speeds below 60mph. Guess that's why I get 50mpg. I weigh almost 200#. My 52.5 pilots gave more midrange on my '83, no stumbles anywhere. My '82 had great midrange due to those stock 60 pilots. When tuned right on...The 82s should have great midrange pull.

[GT @ oh.]

Mine stumbles at most rpms...... if throttle is cranked open quickly but worse at off idle.... better in mid range....and I'm still not able to get rpms up past 8-9000 ....but good news is the mechanic i got refered to just called me..... and is willing to work on it next week..... or next...... and if he can do to mine what he did for my friends GPZ.... I should be all set....heres hopeing..... I'll probably get him to do the brakes, fork seals, fluid and tapered bearing while he has it....then that is it for a while..... knock on wood.....he seems reasonably priced and knowledgable....he actually use to work at the dealer where I bought it 20+ yrs ago.....what a coincidence....I'll let you all know how it goes.

[jefferson]

Something to check when your bike won't rev is the carb vent lines. If they are gone or not hooked up or even run to the wrong place it can cause an overly rich condition which will kill the revs. The vent lines should be run into the hole in the boxed in frame section right behind the rear cylinder. If the vent lines aren't there you will need to use some thin wall tubing as there isn't alot of room for anything else.

Jeff

[jasonm.]

HAS everyone SEALED their air boxes?  This is a poorly made box. The rubber intakes have a lot of play. This alone can make a big difference. BUT you must clean the parts completely(brake clean) and seal with Permatex ULTRA black($5) or Suzuki sealer($20). This makes the air go where it should . Just one caution. You will need to put the airbox on the carbs for the sealer the seal in the proper(running) position.

[Lucky]

Something to check when your bike won't rev is the carb vent lines. If they are gone or not hooked up or even run to the wrong place it can cause an overly rich condition which will kill the revs. The vent lines should be run into the hole in the boxed in frame section right behind the rear cylinder. If the vent lines aren't there you will need to use some thin wall tubing as there isn't alot of room for anything else.

Jeff

i just don't see this as being any sort of issue. i pulled the dead lines the same day i got my first Vision, never saw another one that anyone had bothered to replace them, and never had a problem due to them being absent...