[km120]

My M800 has done 1.35k on the odo and has variations in the RPM. When the A/c is turned on, the engine turns off within few seconds if the accelerator is not hit. No help of good idling. I regularly face jerks at lower rpm. I have got my 35k service done yesterday at MASS and later told to get prepared for a carb overhaul. Can anyone kindly explain what is carb overhaul and what are the parts one needs to take care during the process. Is it necessary to go for a engine overhaul too. Can i consider any kind of customization for improving performance. I am not doing by myself .The estimation is give for 2k. I thank all the members for their valuable contribution to TEAM-BHP.

[anupmathur]

Km120, first off: Has the AC and idling issue been solved? There is a relay, called FICD IIRC, that increases engine idling speed on AC being turned on. Has this been changed?
Are you still having a problem with slow speeds and jerky movements?

Carb overhaul is basically a cleanup of the carb. It is dismantled and all parts cleaned. The jet or jets, tiny orifices, are checked for wear and renewed if required. The butterfly flap valve is checked for wear and replaced if needed.
At 1.35 lakh kms it is possible that no replacements are needed. If you cannot personally be present to check, you'll be told they require renewal.
Carb overhaul is a delicate job and certainly not for heavy handed mechanics!

[esteem_lover]

Carb overhaul for a M-800 should not cost 2k, should be around 1k and should be done by someone who is expert in carbs. Make sure they do not overcharge you, since the cost of a new carb should be around 4 to 4.5k.

[adheesh]

Carb Overhaul would cost maximum Rs. 150 at a local garage and 500 at MASS with packing and gaskets extra (Rs.100 or so). If your car stalls after turning the A/C on see if the vaccum operated throttle opener with AC vaccum pump is present and working fine. This increases the cars idling speed when the A/C is turned on to prevent engine stalling. Also check for choked PCV valve ( below the perpendicular thick tube at is attached to the tappet cover).

Regards,
Adheesh Parelkar

[km120]

Originally Posted by anupmathur

I got that done twice using the Engine Analyser (EA). Initially they were set to 1000 rpm and when ac is turned on it drops to 800 rpm. The second time it has been set to 1200 rpm, but there is lot of variation '+' or '-' 80-100 rpm in both the cases.

There is a relay, called FICD IIRC, that increases engine idling speed on AC being turned on. Has this been changed?

I guess it was adjusted during the EA under the air filter after removing it.

Are you still having a problem with slow speeds and jerky movements?

Yesterday after the tuning i had less engine drops. But I didn't check for long time with AC on. I'll check it today.

The jet or jets, tiny orifices, are checked for wear and renewed if required.

Ten days ago I had problem of severe engine drops and taken the car to MASS. They finalized it as jet clog and cleaned the 2 jets. There was no problem thereafter with sever drops . After the 35k service I was told for carb ovehaul as future job. Later I realized that these variations in rpm are due to the low carb performance during the second EA. The car makes frequent trips to Bangalore - Mysore. So I don't want to take chances and planning for the job getting done immediately.
[/quote]

Originally Posted by esteem_lover

Carb overhaul for a M-800 should not cost 2k, should be around 1k and should be done by someone who is expert in carbs. Make sure they do not overcharge you, since the cost of a new carb should be around 4 to 4.5k.

esteem_lover: I am taking car back to the service center tomorrow and let all know what wud be its estimation.

Originally Posted by adheesh

Carb Overhaul would cost maximum Rs. 150 at a local garage and 500 at MASS with packing and gaskets extra (Rs.100 or so). If your car stalls after turning the A/C on see if the vaccum operated throttle opener with AC vaccum pump is present and working fine. This increases the cars idling speed when the A/C is turned on to prevent engine stalling. Also check for choked PCV valve ( below the perpendicular thick tube at is attached to the tappet cover).

Adheesh I’ll make a point to check about what ever you asked me to, but I believe the problem is with carb .

[adheesh]

Adheesh I’ll make a point to check about what ever you asked me to, but I believe the problem is with carb

The vaccum operated throttle opner is a part of the carburetor itself.