VM26 carbs with Accelerator pump-Won't idle down.

And carb assembly showing accelerator pump.

[Click on image to enlarge view]

With history given so far, would suggest first test running with the new oem advancer unit installed, before again tearing into the carbs (which may already be okay in light of all the previous bench work on them).

And while test running, could also perform vacuum sync to determine best idle rpm performance available with new advancer absent another carb teardown.

Good Luck!

P.S. Reminder (probably not needed :lol: ) -- When installing the new oem advancer, be certain to re-time so F mark aligns with permanent case mark at idle rpm.

Well, since I don't know how to cut and paste from a manual or Kaw parts fiche, I guess I had best defer to Mr. Patton on carb issues in the future. bwhahaha

K, This may be inappropriate but has hosed me once or twice, Plummens' illustrations show a restictor sleeve/needle locator, atop needle nozzle. usually they extend into carb throat and are visable w/slide raised. they sometimes dissapear when un-attended, their absence allowing fuel flow thru needle/main ckt. with erratic overtones, a quick check.G

I can't thank all of enough!!! I got lots to look at this weekend and the Super Bowl!!!
I've come the conclusion that if I don't get the problem fixed this weekend I'm removing the carbs, and contacting WireGeorge about rebuilding them.
I can't wait to get started on the dragbike again....All I have to do is for wide open throttle, SOOOOOOOOOOO much easier.....

Thanks again,
Buzz

i'm with you brother i'm notching my frame for some extra chain clearance tomorrow and can't wait to get in some passes first chance this spring.

UPDATE!!!

Well it's always the obvious, isn't it!!!

When I started to work on the carbs on Sunday I decided to check the easy stuff first.

The first thing I did was to start the bike to warm it up. After the warm-up I blipped the throttle a few times. The idle down problem was even worst than before.

I decided to check the throttle pully spring first. I reached under the tank and put my thumb on the top of the throttle pully. I blipped the throttle and at the same time I put thumb pressure on the top of the throttle pully.

The engine went straight to idle!

I repeated this proceedure a few more times and sure enough with just a little pressure from my thumb on the top of the throttle pully the engine idled down perfectly everytime I blipped the throttle.

I didn't get a chance to determine exactly what the fix is but I guess either the throttle pully spring is weak or maybe some binding in the carb linkage or throttle pully area.

Anyway...knowing what I know now I can fix this.

My heart felt appreciation to all of you for your comments, help and suggestions. It's reasurring to know that that all of you are out there and willing to help a poor soul...


Thank you all..

Buzz

KruZer wrote:

... decided to check the throttle pully spring first. I reached under the tank and put my thumb on the top of the throttle pully. I blipped the throttle and at the same time I put thumb pressure on the top of the throttle pully. The engine went straight to idle! I repeated this proceedure a few more times and sure enough with just a little pressure from my thumb on the top of the throttle pully the engine idled down perfectly everytime I blipped the throttle. I didn't get a chance to determine exactly what the fix is but I guess either the throttle pully spring is weak or maybe some binding in the carb linkage or throttle pully area. Anyyway...knowing what I know now I can fix this....

Glad to hear the problem's being resolved.

While at it, would check out - - -

"Correct" throttle cables (outter length and inner length).

Assure throttle cables are themselves in good condition without any bent spots, as well as being lubed inside, and unfrayed inner cable freely moving both ways, tip to tip.

Adjusted to assure sufficient slack in both throttle cables. Look for slight slack at carb fitting when throttle is closed and moved minutely back and forth without raising the slides.

Assure throttle cables are routed without binding or kinks.


On my Z1 (with 29 smoothbores) and KZ900, the single carb return springs are stout enough to make Godzilla proud. Before resorting to the friction throttle grip lock, I used to ride without the spring, or substitute a weaker hardware store spring in its place. If the single return spring strength is anything close to the smoothbores or KZ900 return springs, when closed, there's no danger imo of the throttles bouncing up due to vibration overcoming the spring pressure.

With single return spring carbs, when adjusted correctly, the return cable should pull the carb throttle slides fully closed without any spring and without any help from human fingers. Am guessing the carbs at hand are similar in this respect.

Good Luck!

EDIT -- Edited to clarify that the return springs being referred to are the later model single springs (as shown in the above posted diagram), and not the oem Z1 springs that wrap around the throttle shaft.

Thanks.

I check the items you mentioned and probably replace the throttle cables just as a caution.

In case my pully spring is stretched I think I'll purchase a new Throttle Pully spring from Bike Bandit ($44.00 ouch!).

I should have time in a couple of weeks to get the parts and get everything checked out.

I give you another update in a week or two.

Thanks again!!!
Buzz

KruZer wrote:

...In case my pully spring is stretched I think I'll purchase a new Throttle Pully spring from Bike Bandit ($44.00 ouch!)....

These return springs are imo overly substantial (guessing liability concerns), and thinking it would be rare to find one that won't fully close due to having been too far overstretched.

On the Z1 and KZ900, the return springs, when installed, are already in stretch mode and pulling hard even when the throttle's fully closed.

With properly functioning cables and correct slack, it should require very little spring pressure pull to hold the slides closed.

Just trying to help save that $44.

Good Luck!

Well.......So maybe this should have mentioned this information in my inital question....

To be honest I only run a single throttle cable on the bike. I know it's not a good idea but I have a semi-good reason.

The bike has inch and quarter handle bars. the bars taper down to one inch on the ends so I have to have one inch grips and throttle housing. The only grips I could find that I liked for the one inch bars were made by Performance Machine. The grips are billet and the throttle housing only accommidates a single pull throttle cable.

I have ran single pull cables on VM33 smoothbores on the dragstrip before and never had an issue with the idle so I didn't even consider the lack of a push-pull throttle as an issue.

Anyway, I'll replace the spring with a new one and make sure nothing else in the linkage is binding.

I'll let you know how it turns out.

Thanks,

Buzz

KruZer wrote:

... only run a single throttle cable on the bike... have ran single pull cables on VM33 smoothbores on the dragstrip before and never had an issue with the idle so I didn't even consider the lack of a push-pull throttle as an issue...Anyway, I'll replace the spring with a new one and make sure nothing else in the linkage is binding....

didn't even consider the lack of a push-pull throttle as an issue-- I agree 100%, and imo it still isn't an issue.

Not so long ago, single "pull" throttle cables were all we ever had and served us well. If a carb failed to close, we could switch off the ignition or hit the kill switch.

Imo the single opening cable isn't causing the issue in this case (slides not wanting to stay completely closed and having to use finger pressure to hold them down). The 2nd closing cable is imo only a safety measure to close the throttle in event the return spring fails.

If the existing fitted return spring is already in stretch mode enough to pull the slides closed when the cable is not attached to the carb, it should continue to do so when a correct good properly routed cable is attached, with proper slack, and nothing else in the linkage is binding. Same as an old Amal slide carb with the relatively weak internal return spring.

Not necessarily recommending against a new spring, just don't suspect the existing spring is at fault unless it has been somehow damaged so as not to be already in stretch mode when fitted with the carb slides down.

Good Luck!