Tune 4G15 Carburetor

[Iroshw]

Hi guys,

I have Mitsubishi C62A (known as ASP Model 1991). It has 4G15 engine and very powerful. But I'm not happy with the fuel efficiency of this car. And there is a black smoke as well. I just surf the new and found this car does 14km/1ltr (average). But my one is doing nearly 8km/1ltr (without AC).

I was searching a solution through net since I'm really really tired with garages. I took my vehicle to a lot of place to solve this issue. But so far no good result.

I found some instructions from a forum. This is about tuning the engine (4G15). Please check this and let me know your feedback since I'm going to try this on Saturday .

1) Warm up engine first(run 5-10 mins)
2)Shut off engine
3) Back out on the idle speed screw until it justt doesn't touch the throttle linkage. Then screw it in back about 11 turns (what this does mean actually?)
4) Screw in the A/F mixture screw until it stops(do not force tighten)
5) Screw out the A/F mixture screw 2 full turns
6) Start the damn car. It will run like its choking. As long as it's running it's ok.
7) Now turn in the A/F screw until engine dies. If this happens, turn out the A.F screw half turn at a time to bring it back. (try to start the car of coz) (what this does mean?)
8)Continue to turn out the A/F screw at half turns every 3 seconds. Engine will pick up speed. Continue to screw out until the point engine runs worse. When that happens screw back in half turn every 3 secs to the point engine runs smoothest.(do this by ear or watch engine vibration) (what this does mean?)
9) Now set the idle speed. Go on the air conditioner. Watch the tachometer. Turn in the idle speed screw until rpm is around 900 to 1000 rpm.
10) Now it's ready to rumble..

black smoke also caused by KO piston ring (what this does mean?).. check the compression

Guys, please let me know your feedback, is it ok if I follow this to tune my engine? Only problem is my AC is not working. So will it be a problem for me to follow these steps since it says that I need AC to be on during the process. Please advise.

Will this help to get a good fuel efficiency and stop black smoke?

[The Don]

Not clear as to why your carburetor needs to be replaced because the piston is damaged. I'm pretty sure you get the piston as a part of the (genuine) carburetor repair kit.

What is the piston in a carb? I've never come accross that term... is it called something else too?

[Rumesh88]

What is the piston in a carb? I've never come accross that term... is it called something else too?

Davy was referring to the suction piston of a variable venturi carb.

[The Don]

Davy was referring to the suction piston of a variable venturi carb.

Shows how much I know about carbs. Just reading up about it now!

[kusalk]

yes it is the piston in the variable ventury.

An small portion of the rod connected to the piston has been cut away. This piston and the rod have to be purchased separately. Mr. Dhammika’s advise was to check the prices of a complete carb before go for piston replacement.

The carb sometimes get flooded. Also cannot adjust the fuel control screw (the bottom one). This could be due to the above reason.

After correcting the vacuum lines, I feel a difference and also the cold start not too bad now. Can you guys suggest me a place to look for a reconditioned carb??

[Davy]

What is the piston in a carb? I've never come accross that term... is it called something else too?

Davy was referring to the suction piston of a variable venturi carb.

Rumesh is right. I was indeed referring to the suction piston. I distinctly remember it being part of the carb repair kit.

yes it is the piston in the variable ventury.

An small portion of the rod connected to the piston has been cut away. This piston and the rod have to be purchased separately. Mr. Dhammikas advise was to check the prices of a complete carb before go for piston replacement.

The carb sometimes get flooded. Also cannot adjust the fuel control screw (the bottom one). This could be due to the above reason.

After correcting the vacuum lines, I feel a difference and also the cold start not too bad now. Can you guys suggest me a place to look for a reconditioned carb??

If I were you, I'd still look into the possibility of repairing the carb using a genuine repair kit. The carburetor you'll be buying will probably be a used one and God knows what issues it will have. Edited February 27, 2015 by Davy

[The Don]

yes it is the piston in the variable ventury.

An small portion of the rod connected to the piston has been cut away. This piston and the rod have to be purchased separately. Mr. Dhammika’s advise was to check the prices of a complete carb before go for piston replacement.

The carb sometimes get flooded. Also cannot adjust the fuel control screw (the bottom one). This could be due to the above reason.

After correcting the vacuum lines, I feel a difference and also the cold start not too bad now. Can you guys suggest me a place to look for a reconditioned carb??

Places like Engine watte in Panchikawatte will have old carbs and this was a very popular one and was used in proton cars as well.

In a Sri Lankan context Mr Fernandos advice might be correct, but I think you should still look into the cost of the original rebuild kit and the piston and rod as Davy has advised. I did note that the kits I've seen does not have the piston and rod, but just the float and float pin which I assume isn't the same thing. You should try to source a Mitsubishi or Proton original (as Proton uses the exact Aisan carb, not a malaysian alternative) not an after market kit for best results.

But if an old carb is cheaper than the kit and you find one in good condition, perhaps it might be a better buy though you need to be prepared to rebuild that too (hence might end up needing the kit)

[PerfMad]

Rumesh is right. I was indeed referring to the suction piston. I distinctly remember it being part of the carb repair kit.

If I were you, I'd still look into the possibility of repairing the carb using a genuine repair kit. The carburetor you'll be buying will probably be a used one and God knows what issues it will have.

Hi All,

I'm a newcomer to this replying (recently created an account), though i was following all most all the interesting threads on AL. With regards to this discussion, well I also have a Mitsubishi lancer CB1 (carb) model. And recently did a full carb tune-up since my car was not doing really well on fuel. I thought it may be due to the BEAT silence i fixed one month ago.. Anyhow I wanted to repair my carb, like my garage baas advised we need to buy a repair kit and do the rebuild. But after spending few hours at panchikawatta, he called me and said that, he couldnt find repair kits.. Therefore let's remove and clean all the parts..After the tuneup my car seems to have a good pulling power + less carbon deposits on the muffler (compared to earlier)... Well I will let you all know the consumption very soon..

In addition, i believe both CB's and CK's have same carb model.

Note: As per baas these carbs are called bothal carbs, where most says after removing it gives lot of troubles (that's the rumor)..

[Rumesh88]

Hi All,

I'm a newcomer to this replying (recently created an account), though i was following all most all the interesting threads on AL. With regards to this discussion, well I also have a Mitsubishi lancer CB1 (carb) model. And recently did a full carb tune-up since my car was not doing really well on fuel. I thought it may be due to the BEAT silence i fixed one month ago.. Anyhow I wanted to repair my carb, like my garage baas advised we need to buy a repair kit and do the rebuild. But after spending few hours at panchikawatta, he called me and said that, he couldnt find repair kits.. Therefore let's remove and clean all the parts..After the tuneup my car seems to have a good pulling power + less carbon deposits on the muffler (compared to earlier)... Well I will let you all know the consumption very soon..

In addition, i believe both CB's and CK's have same carb model.

Note: As per baas these carbs are called bothal carbs, where most says after removing it gives lot of troubles (that's the rumor)..

The carb in your car is the subject of this thread. In fact these carbs have a bad reputation and are known to give trouble not because of their bad design or inferior quality of parts etc but the way they are handled in the hands of our mechanics. Since there is a moving part directly on the air passage these carbs are a bit more vulnerable to effect of dust and gunk that gather inside compared to more common fixed venturi carbs. All what is required is to carefully remove the suction piston along with the needle and clean them. Particularly the needle should be handled carefully when inserting back to make sure that the it does not damage the valve seating. Also the piston move on a teflon coated linear bearing. This coating should be very carefully cleaned.

[Splat]

Before adjusting the carb - Clean spark plugs and adjust the gap with a gaping gauge tool refer to the maintenance manual for the gap, (you can also check on-line). check spark plug cables and make sure that they fasten well to the plugs and distributor. Also check the air cleaner and make sure there are no air leaks. Just some simple steps to begin with.

[Splat]

I use a vacuum gauge unit that make the tuning job a lot simple and stress free. Unfortunately tuning vacuum gauges are not available in Sri Lanka. I'm just lucky my Dad had one.

[The Don]

Before adjusting the carb - Clean spark plugs and adjust the gap with a gaping gauge tool refer to the maintenance manual for the gap, (you can also check on-line). check spark plug cables and make sure that they fasten well to the plugs and distributor. Also check the air cleaner and make sure there are no air leaks. Just some simple steps to begin with.

Read up, the issue has been investigated and triaged down to the carburettor.

[PerfMad]

Hi kusalk

What the fuel consumption after carb tuneup ?? Mine just turned out to be 8kmpl in city with AC from 6.5kmpl... went to garage and he said have to check the spark plugs and all ..

And how much did it cost to do a tuneup from Mr. Dammika ?? how much did it cost you ? and also can you send me his contact no as well??

Guys,

what is the average fuel consumption of a CB1 ? I don't no whether this is cz of the beat barrel i installed recently.. hmmm I need to increase this upto 9--10 somehow... or worst case scenario have to remove the BEAT silencer

Edited March 9, 2015 by PerfMad

[hrm]

Hi kusalk

What the fuel consumption after carb tuneup ?? Mine just turned out to be 8kmpl in city with AC from 6.5kmpl... went to garage and he said have to check the spark plugs and all ..

And how much did it cost to do a tuneup from Mr. Dammika ?? how much did it cost you ? and also can you send me his contact no as well??

Guys,

what is the average fuel consumption of a CB1 ? I don't no whether this is cz of the beat barrel i installed recently.. hmmm I need to increase this upto 9--10 somehow... or worst case scenario have to remove the BEAT silencer

My CB2 did around 8-9 KMPL in city limits with AC. Outstation it's about 12 - 13.

Edited March 9, 2015 by hrm

[PerfMad]

My CB2 did around 8-9 KMPL in city limits with AC. Outstation it's about 12 - 13.

@hrm - then i think no point of chasing this to increase further but anyhow I'll be most probably going on this weekend to check spark plugs and all are in good condition.. I think that's all i can do with related to this...

[hrm]

@hrm - then i think no point of chasing this to increase further but anyhow I'll be most probably going on this weekend to check spark plugs and all are in good condition.. I think that's all i can do with related to this...

You can give a try and see as I never paid much attention to it until I sold the car, As these are Carbs, anyways FC is bit high at least in city traffic (mine being 1500cc). Enhancements might improve long distance figures I suppose.

[The Don]

My EFI manual 4G92 engined Mirage does 8-10 on city. To be honest to get beyond those figures you need to adjust your driving style and avoid a bit of traffic.

[PerfMad]

@hrm & @The Don- hmmm.. i think I'll give one last shot..will be going to garage on this saturday to sort this out most probably..im having a doubt is it because of the silencer... but removing that will be my last option.. because daily i go close to 10KM so my plan is to limit it to 1liter

To be honest im really careful on throttle unless someone pissed me off hehe and that's why im thinking that it should do atleast 10..

does anybody has a beat silencer installed on their vehicles ? fuel figures change after the beat silencer ? any ideas / experience ?

[The Don]

@hrm & @The Don- hmmm.. i think I'll give one last shot..will be going to garage on this saturday to sort this out most probably..im having a doubt is it because of the silencer... but removing that will be my last option.. because daily i go close to 10KM so my plan is to limit it to 1liter

To be honest im really careful on throttle unless someone pissed me off hehe and that's why im thinking that it should do atleast 10..

does anybody has a beat silencer installed on their vehicles ? fuel figures change after the beat silencer ? any ideas / experience ?

So called beat silencers when not properly designed might reduce fuel economy by reducing back pressure beyond optimum levels. If you wanted fuel efficiency you should have kept the car stock.

[PerfMad]

So called beat silencers when not properly designed might reduce fuel economy by reducing back pressure beyond optimum levels. If you wanted fuel efficiency you should have kept the car stock.

@the Don- initially i thought if it makes like 1kmpl difference..that would be fine..not sure whether it has affected even..cz early days i only used this on weekends..so didnt measure the consumption much... but now since i use it daily only this issue came up..hmmm if this im unable to increase it, then sadly i have to remove the beat and fit my stock silencer again

[Davy]

@the Don- initially i thought if it makes like 1kmpl difference..that would be fine..not sure whether it has affected even..cz early days i only used this on weekends..so didnt measure the consumption much... but now since i use it daily only this issue came up..hmmm if this im unable to increase it, then sadly i have to remove the beat and fit my stock silencer again

If you still have the stock silencer with you, and if you really want the quoted figures, my opinion is that you should switch back to the old one. Carburetor engines are known to consume a lot more fuel when incompatible/poorly designed exhausts are installed.

[kusalk]

Hi kusalk

What the fuel consumption after carb tuneup ?? Mine just turned out to be 8kmpl in city with AC from 6.5kmpl... went to garage and he said have to check the spark plugs and all ..

And how much did it cost to do a tuneup from Mr. Dammika ?? how much did it cost you ? and also can you send me his contact no as well??

Guys,

what is the average fuel consumption of a CB1 ? I don't no whether this is cz of the beat barrel i installed recently.. hmmm I need to increase this upto 9--10 somehow... or worst case scenario have to remove the BEAT silencer

Hi,

Sorry for being late to reply

Mr. Damika Fernando 011-2694223

Get an appointment before going.

He didn't repair the carb, but he corrected the vacuum lines and checked ignition. Also he did some tuning to reduce the CO emmision, because my carb cannot be tuened properly under this condition. He introduced me a person in Gampaha to do the repair. I showed him the car today and he told me that the rod of the choke has been come out and not working. Also it has a problem in the rod connected to the piston as i mentioned earlier.

I'll update you when the repair bigins

[PerfMad]

Hi,

Sorry for being late to reply

Mr. Damika Fernando 011-2694223

Get an appointment before going.

He didn't repair the carb, but he corrected the vacuum lines and checked ignition. Also he did some tuning to reduce the CO emmision, because my carb cannot be tuened properly under this condition. He introduced me a person in Gampaha to do the repair. I showed him the car today and he told me that the rod of the choke has been come out and not working. Also it has a problem in the rod connected to the piston as i mentioned earlier.

I'll update you when the repair bigins

Thanks Kusal.. I just showed mine to my bass... And he checked the spark plugs and found out that only 1 was working well.. other 3, the distance of the tip was too closed (that's what he said) and then he aligned those and cleaned the tip of all 4 plugs and did some fuel adjustments as well.. And asked me to come back after doing 50KM's... So after doing 50Km today itself, i went to show him and he removed the spark plugs to check, and those seems to be cleaned... He asked me to pump full tank again and recheck the consumption.. As per him, now fuel figures should increase... Hope this would do.. I really don't wanna remove my BEAT silencer ... Will update you all once i figure out the fuel figures..

And Kusal, Please do update us on your repair as well

Cheers....

Edited March 14, 2015 by PerfMad

[Gihanmj]

Hi all,,

i have CB 1 1995 model car. it is also consist with bothal type carb. when overtaking or driving on a mountain way it is knocking. this is occur when the accelerator pushing a certain depth. power is low. i feel that. one mechanic told me to replace distributor. but i m not satisfying with this answer, if anyone knows or feel the problem please help me to solve it  

[Rumesh88]

On 9/2/2016 at 5:02 PM, Gihanmj said:

Hi all,,

i have CB 1 1995 model car. it is also consist with bothal type carb. when overtaking or driving on a mountain way it is knocking. this is occur when the accelerator pushing a certain depth. power is low. i feel that. one mechanic told me to replace distributor. but i m not satisfying with this answer, if anyone knows or feel the problem please help me to solve it  

I assume that by "knocking" you meant a hesitation or a "miss" in the engine not the pinging (or kara kara noise) sound you get when your ignition timing is too advanced. Please correct me if my assumption is wrong.

First get the all spark plugs, plug wires, air cleaner (replaced if necessary) and all the vacuum lines checked. If possible get the ignition timing checked too. If you narrow the problem down to a fuel starvation issue from the carb then find someone who is really familiar with dismantling and reassembling a "bothal carb" . If you carefully read the previous posts in this thread you will understand why. To me it looks like either your fuel level inside the carb is low or the carb piston gets stuck at some position. How about your last Eco readings at idle and 2500 RPM?

[Danny1997]

I have a Lancer CB2 1995 which also has an issue with the carb

The fuel comsumption is very high and only does like 7km/L

The carb had never been tuned or serviced

Current mileage is around 160,000 km

Any reasonable and a qualified mechanic whom i can consult ?