RPM drops on Petrol even carburetor & Butterfly repaired Cultus VXR

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mahmad83 (mahmad83) 2011-07-16 12:09:58 +0500 #1

Dear All,

I had the issue of non stable RPM, after servicing of Carburetor and Butterfly, Issue is still there, When I give race to car, and RPM goes to 5-7K, then immediately after lifting race, RPM goes to zero, and car shutdown.

I have no clue what is issue. Please respond asap.

fahadwizz (fahadwizz) 2011-07-16 12:30:54 +0500 #2

I hope u also replaced your accelerator cable.

schehxad (schehxad) 2011-07-16 12:34:00 +0500 #3

check for vaccum advancer pipe is it there in between distributor and carburetor

Xulfiqar (Xulfiqar) 2011-07-16 12:58:27 +0500 #4

carburettor dash pot is inoperative - its there to hold the throttle open at abt 1600 rpm for about 1 second before gently releasing it.

Its the vacuum diaphragm on the carb with a little plastic piece in it - that plastic piece is the device that slowly bleeds vacuum. If connected backwards it wont work and if not connected at all the dashpot effect will not work and you will suffer from what you are posting.

mahmad83 (mahmad83) 2011-07-16 14:33:02 +0500 #5

Mech has not replaced the Accelerator cable, I have check the plastic point on carb, it is connected. The cable is coming from body side, and when accelerator is released it goes backward (towards body).

Please help

Xulfiqar (Xulfiqar) 2011-07-16 23:18:53 +0500 #6

check operation of the dashpot - the dashpot should release the throttle (butterfly slowly - theres an adjustement screw on it also to fine tune the "holding" rpm. What you are describing is dashpot not working

mahmad83 (mahmad83) 2011-07-17 04:24:54 +0500 #7

Dear Zulfiqar,

Mech did the adjustment, but mostly it is working stable, even I lift the race from 6-7K RPM, it goes to 1K RPM (also when applying brake).

But 2/10, its behavior is same (Car goes down) due to RPM drops quickly to zero.

Also can u give a favours, to tell me any good mechanic so that I can go there, and also can u share contact number, I will call u for this issue.

Regards
Ahmad

mahmad83 (mahmad83) 2011-07-17 14:39:18 +0500 #8

What about other members?

Please help me in this regard.

isi0000 (isi0000) 2011-07-17 16:44:20 +0500 #9

@poster what if u start the car and leave it idle......is it shutdown???
u drive the car and it shut down as u break to zero, is it???
if so then it may b the issue of slow jet(in language of mechanics) requires cleaning

mahmad83 (mahmad83) 2011-07-18 03:05:51 +0500 #10

Yes, you are right. When I apply the brake s, it goes down.
Also when I release the accelerator while RPM is 6-7K, 2/10 times it goes down.

Please help

Xulfiqar (Xulfiqar) 2011-07-18 12:36:14 +0500 #11

leaky brake booster diaphragm or vacuum pipe to booster, remove pipe from manifold and plug the port - start engine and play around with the throttle - if its stable you have found your fault.

kazmi_muzammil (kazmi_muzammil) 2011-07-23 01:28:47 +0500 #12

I don't think so it's the leaky diaphragm..

Dear iv'e been through the same problem myself. I had a carby cultus back an 2003 one. Belonged to my Cousin who left it in Lahore with me so i kept it for about 2 years with me before selling it...

Now i also encountered the same issue. We did all we could to resolve the issue, from butterflies to aeroplanes..

What i found out was, i got the valve unit taken out.... Had a fight with my mech so serious i was gonna kill him because he wasn't agreeing.

We poured petrol in it, what we found was that the valves were leaking as petrol leaked out from the edges of few valves. Now why did i come to that conclusion....

Its simple, the car was driven on total gas when my cousin gave it to me, Gas is dry, has less moisture, it ruined the edges of the valves causing compression to leak out immediately and form also immediately... My car refused to pass the 80km/h speed limit as well and the car would eventually die down as soon as i pressed the pedal..

So if you want first get the brake diaphragm checked as adviced by a pakwheel member expert.. But if that doesn't work ( and i think it will not), the issue is leaky valve and i suggest u get them replaced after checking with petrol as i told you...

Take out the unit pour petrol into it, and look at the edges of valves if you see petrol leaking out from them...

Here is a sample picture of the valves im talking about..

kazmi_muzammil (kazmi_muzammil) 2011-07-23 01:31:13 +0500 #13

Do let us know once uve resolved the issue out.

Hyder99 (Hyder99) 2011-07-23 16:45:12 +0500 #14

Weak Fuel pump which is usually in fuel tank nothing else..!!

mahmad83 (mahmad83) 2011-07-24 08:48:14 +0500 #15

I got checked the fuel pump, it is working fine. Mech told that run the car on fuel for around 700 KM so that butterfly start work smoothly.

isi0000 (isi0000) 2011-07-24 10:27:11 +0500 #16

you may also check the slow jet for any foreign particles or blockage.....

mahmad83 (mahmad83) 2011-08-12 10:01:56 +0500 #17

Mech replaced the fuel jet, but same issue. Issue is more on while Car is on Petrol.

Any help.

Xulfiqar (Xulfiqar) 2011-08-12 12:35:34 +0500 #18

if the dashpot is OK, and you have got solid vacuum in the inlet manifold then only one thing comes to mind - the carburettor float height is either incorrect, or the needle valve is sticking, or may also be a choked fuel filter too.

tjcivilian (tjcivilian) 2011-08-12 12:48:00 +0500 #19

dude u r in real trouble... u have to replace ur carburator with another one. Once I had faced same peoblem in my 2003 cultus.

mahmad83 (mahmad83) 2011-08-12 15:06:15 +0500 #20

I checked with another mechanic, he told me that Butterfly and its road is little bit tight, so that when you press race, the RPM stuck when you apply brakes after some drive, they goes back ( around 1K RPM). Lets see..

can you tell me Urdu name of Dashpot, so that I can share the same with mechanic?