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Sticky slide and/or butterfly valve can do that. Try cleaning/get cleaned the whole carb. And mileage seems slightly low for average conditions. How's your riding habit and conditions by the way? And also tell us the odo reading.

First check your throttle cable. Its may go junk from inside lubricate it, see it it not stucking anywhere and its freely moving, also lubricate the throttle comp and bar/handle. Do this things and it will get fine for sure.

could be a vacuum leak as well. Check that the carb fits well w/o any gaps on to the inlet manifold.

Thanks !

+1-Honda_CBF-
check throttle cable engagement by turning the handle left and right.....if rpm increases then its the throttle cable or else it might be the butterfly spring or the slide in the carb

There is no effect on RPM when handle is moved left or right. What is Butterfly valve?? Got the carb cleaned in last service but still the problem persisted.
About my riding habits, I commute daily abt 35kms, speeds between 65 to 75 on Highway with no sudden harsh accelerations. The ODO reads 33000.

http://www.xbhp.com/talkies/attachme...g-dsc03403.jpg that golden colored thing is called butterfly valve, also known throttle valve. its the thing which is controlled by accelerator.


you sure carb was well cleaned, specially slide and the butterfly/throttle valve? also, mileage is low, should give at least 45-50kmpl.

For the most part, the main things that cause high idle revs are air leaks, low fuel levels, and spark advance. I'm guessing its happening because of lean mix (may be carb's tuned lean or clogged pet cock/fuel line, or may be crack somewhere in airbox/intake manifold connection to carb and airbox)

damaged diaphragm can also do this as it can lean the mix.

Troubleshooting question:

since when its been happening? Is engine heat increased since then?

Thanks for your reply. I'm not sure if the carb was cleaned as I left the bike with mechanic & he told me that fuel tank & carburetor has to be cleaned as there is some water inside & bike was not starting. I'll make sure to get the carb checked again & cleaned in front of me.
Mileage in range of 45-50 has bean a dream since a very long time.
This has been happening since 3 weeks. Regarding engine heat I could not say if it is increased as it used to heat up a lot earlier also.

re-tighten the clamps on both sides of the carb and see if that makes any difference also check the connecting tube of intake manifold and air filter for any cuts and cracks....replace if found damaged......then check idle screw spring for malfunctioning....these things can be done by yourself.....next proceed for carb thorough cleaning (including butterfly/slide)....do check the choke.....it just cant be ignored.....next get the timing and tappets set....

As far as i know, pulsar 150 doesn't used butterfly valve in carburetor, its has a slider


When u pull the throttle, the slider moves upward allowing more air/fuel mixture. And this cannot be stuck because a spring pushes it down and so the throttle moves back/close when u leave it. All the carburetor have working springs which allows the throttle to move back immediately when u leave.
So if a throttle cable get jammed, it makes the difficult for the spring to move the slider down. Hence, higher rpm.
So therefore, i'm telling u to first lubricate your cable.
Buy a injection form medical chop. Inject kerosene first to clean it. After dry lubricate it.

On the other hand, your carburetor air/fuel ratio is not correct.
Your rpm increase sudden when the engine is warm? right?
That means your engine is running too lean, and therefore, your ideal screw is not responding. Your rpm is not decreasing even when u r losing the screw all out.

So get it adjust first, your both rpm and mileage problem will solve here.

@-paul-ofcourse pulsars have butterfly valve as well as slide (atleast in my p150 ug3 ) recently done carb. cleaning myself....the pic you posted seems to be of splendor i guess, which has a slide directly operated by throttle cable....whereas in pulsars' carb the slide is operated by intake suction and throttle cable operates the butterfly valve...

^ yeah, cv carb's slide depends on engine vacuum for movement. Throttle valve is controlled by accelerator. And it can get stuck when not so clean. Causing the stated problem. I had the same problem, when cruising down the highway, if i press clutch and leave the throttle, RPMS used to get stuck at 3-3.5k rpms. (this used to happen only on highways while at higher speeds) When checked the carb, slide was lazy to move up/down so cleaned it (actually the whole carb as it was opened) and voila! problem solved.. BTW, cleaning throttle cable won't hurt anything for sure and can help