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Old 14th October 2008, 11:23   #1
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Default Carb 800, loss of power at higher gears

Hi All,

Have been driving a '92 carb 800 for the last couple of years and and am facing a peculiar problem. The car drives very smooth and have no serious issues with her. Only thing is that while the accelaration upto 4th gear is smooth and quick,once i shift from 3rd to 4th i feel the lack of power and the same rate of accelaration is not maintained which makes me actually down shift to third if i want to do some quick overtaking on the highway or on an open stretch of road.

Any suggestions on what the problem could be and what i could do about it
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Old 14th October 2008, 12:07   #2
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i think at higher RPMs your car gets out of breath. check the carb tuning, ask an expert to set the air-fuel ratio.
also get the car serviced. clean the carb. ask the service centre guys to dismantle the carb and clean it thoroughly and not just spray the cleaning liquid from outside.

Last edited by amit_mechengg : 14th October 2008 at 12:18.
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Old 14th October 2008, 12:10   #3
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Check the air fuel ratio checked as amit said and also check if the secondary butterfly is opening or no.
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Old 14th October 2008, 13:23   #4
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Quote:
Originally Posted by humyum View Post
Check the air fuel ratio checked as amit said and also check if the secondary butterfly is opening or no.
I second this, I think this might be the problem.
There is a vacuum thingy that actuates the secondary stage in the carb.
  • Clean the air filter
  • Clean the plugs
  • Check the Secondary stage (Usually you can feel this if you keep the pedal pinned in 2'nd gear and the car will not go as its supposed to)
  • If you feel this only happens in high rpm you might want to check the timing too.
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Old 14th October 2008, 16:20   #5
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Dear Perez - hello to you and welcome to the forum - please note that the Maruti 800 engine runs on a double barrel Mikuni carburettor. Essentially this means that there are 2 throttle valves in the carburettor. The primary throttle is connected to the accelerator pedal and actuates when you operate the pedal. The secondary throttle is connected to a diaphragm which is actuated by intake manifold vacuum (there is no mechanical connection to the throttle valve). It is designed to operate only if the primary throttle is open to more than a certain angle (around 75%). As the cars run in the city traffic most of the time, average speeds are low and there is very less chance of the secondary throttle valve actually opening. This prolonged "non-use of the secondary throttle" even when you use the car regularly results in jamming of this throttle due to the presence of gum in the fuel (take a spoonful of petrol in your hand, let it rub between your fingers and then let it evaporate. Then bring your fingers together and release them. You will find your fingers sticky. That's gum in the fuel). How do you find out if this has happened? Remove the air cleaner, operate the primary throttle physically from the carburettor and then try to operate the secondary throttle. If it is jammed, it will not operate at all. DO NOT FORCE IT TO OPERATE, THE THROTTLE PLATE WILL BEND, ONCE BENT IT CANNOT BE SET RIGHT. The remedy is to remove the carburettor from the car, dismantle it completely, clean it with a good carburettor cleaner, wash it in petrol, de-gum the throttle plate to make it operate smoothly and reassemble it with all new gaskets. Then assemble it on the car and operate the engine, checking for smooth operation.

Other reasons for loss of power are incorrect valve gap setting (correct setting is 0.15 mm / 6 thou for intake and 0.175 mm / 7 thou for exhaust valves with the engine dead cold), incorrect dwell angle (correct angle is 52 degrees), incorrect gnition timing (correct setting is 7 degrees BTDC with vacuum advance connected), incorrect grade or gap of spark plugs (correct plugs are Japanese make NGK BP5ES only, the correct gap is 0.9 mm / 36 thou), loss of tension of the timing belt due to normal life cycle inspite of auto tensioner, choked air cleaner element (use only genuine Purolator make air cleaner element), incorrect grade or excessive level of engine oil (use 15W40 engine oil, please buy from a good petrol pump, thereby you protect yourself from suspected adulteration), choked exhaust system muffler (use original equipment exhaust system only, aftermarket parts play havoc with back pressure), blocked fuel return path (check for kinked fuel lines in front of the rear left tyre), excessive fuel pump pressure, slipping clutch (if found slipping, please buy and use original equipment Japanese Daikin clutch assembly - do not use Asco), incorrect or worn out tyres (Bridgestone give good coefficient of rolling resistance and decent life), scored wheel bearings (use SKF earings) etc.

Hope it clarifies. Please post some photographs of the car's engine compartment, which will help me in further diagnosis. Please PM me if you need more information on positive changes that can be made to the carburettor to obtain brisk performance without undue effect on fuel economy.

Best regards,

Behram Dhabhar

Last edited by DHABHAR.BEHRAM : 14th October 2008 at 16:22. Reason: add info
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Old 14th October 2008, 17:51   #6
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Quote:
Originally Posted by DHABHAR.BEHRAM View Post
Dear Perez - hello to you and welcome to the forum - please note that the Maruti 800 engine runs on a double barrel Mikuni carburettor.

Best regards,

Behram Dhabhar
Have a question to ask you when I see you more logical than emotional. Hint- it is linked to this thread.
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Old 14th October 2008, 21:36   #7
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get the engined tuned and spark plugs cleaned
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Old 20th October 2008, 11:38   #8
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Thanks all for the suggestions.

Behram sir, have PM'd you a detail description of the issue. Would really appreciate a response on that.

Thanks again.

Perez
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Old 20th October 2008, 13:56   #9
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Could it have anything to do with worn/damaged Diaphragm?
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Old 1st October 2009, 21:23   #10
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Default Loud Squealing noise accompained with loss in power

Hi,
Decided to post here instead of staring a new thread.My '97 800 (carb) almost stopped in traffic tonight as i was driving home.

The car was in second gear when it started to squeal really loudly typically the kind of squeal you get to here when the fan belts loose only along with the noise i found the car was hesitating to accelerate.

I have a tachometer and i noticed that the needle was just hovering around < 2000 rpm mark even as i was stepping on the gas.As the sqealing got louder i started to drive towards the left of the road so as to stop and inspect but just as i moved over to the shoulder of the road i found the engine had freed up again and the squealing had stopped and i was able to proceed again home.

Now i have some pending issues with the car.
a)Brakes need overhaul (have noticed fade recently)
b)Carb needs overhaul (as suggested by my mechanic at my last tune up)

Could the above problem could be due to the above problems listed.Also i had recently changed my timing belt .

Any suggestions are welcome to help diagnose the problem.

Thanks
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Old 22nd May 2012, 10:33   #11
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Default re: Carb 800, loss of power at higher gears

Can you post me some instructions of how to dismantle and assamble the carb of my maruti 800 MK1 ( 1991 ) as it needs cleaning. Diagrams are appreciated.
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Old 24th May 2012, 00:25   #12
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Default Re: Carb 800, loss of power at higher gears

Quote:
Originally Posted by techkarl View Post
Can you post me some instructions of how to dismantle and assamble the carb of my maruti 800 MK1 ( 1991 ) as it needs cleaning. Diagrams are appreciated.
this shall help:
http://www.team-bhp.com/forum/techni...uti-800-a.html
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Old 24th May 2012, 02:20   #13
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Default Re: Carb 800, loss of power at higher gears

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Originally Posted by infotech58 View Post
Thanks for your reply. I have read the instructions given in that post but i am glad if I can get clear diagrams with perhaps some settings, etc.

Help please, i appreciate if you can help.
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Old 24th May 2012, 05:26   #14
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Default Re: Carb 800, loss of power at higher gears

Quote:
Originally Posted by techkarl View Post
Thanks for your reply. I have read the instructions given in that post but i am glad if I can get clear diagrams with perhaps some settings, etc.

Help please, i appreciate if you can help.
Link of maruti 800 sevice book.

https://skydrive.live.com/redir?resi...N3hNPjguNx4KqQ

I am not sure this is for your old car.
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Old 24th May 2012, 11:43   #15
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Default Re: Carb 800, loss of power at higher gears

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Originally Posted by knob View Post
Link of maruti 800 sevice book.

https://skydrive.live.com/redir?resid=4BCE72C650DB1F66!215&authkey=!AN3hNPjg uNx4KqQ

I am not sure this is for your old car.
Thank you for this manual, The carburetor looks like mine, but mine is mikuniu not solex. Can they be the same ?
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