Query Approved

Thank you !!!

20 kmpl is too low considering a good condition RX will give 40kmpl.Please tell about the engine condition and last engine overhaul.How is the performance?Is the air screw on carburettor adjusted recently?

My friend's RX 100 has a G-flute in silencer and he says it increases mileage.

Hi Habin,

Engine condition is good, I am not sure when was the last engine Overhaul(bought it few months ago), but the fitness is upto 23-Sep-2015(Vehicle was bought in 1991).
Performance has been good but I haven't really driven a lot.
The carburetor was recently clean and the float pin replaced to fix the fuel leak issue. Not sure if the air screw was messed up. Kindly advice on how to check te air screw(its that thing at the bottom of the carburettor which has a spring?)

Sounds to me like its a Carb tuning issue. Get it tuned and revert back.

Oh, are you sure ??

Because this guy seemed to know what he was doing, so I am not sure if that will help.

With regards to Air screw, could someone suggest how should it(normally) ??

Prakash:- Remove the spark plug with help of spanner and check the plug color. What is it like? Can you post some picture?

Also, AFR (Air Fuel Ratio) screw needs to be adjusted. Take a screw driver (Minus/Flat head), turn clockwise to completely close (do not over tight). That position is 'Rich', now, you'll need to turn anti-clockwise slowly about 1-1/4 turns. That's more or less ideally the optimum position. After running some odo, you adjust accordingly.

To check the mileage, follow reserve to reserve to get the reading.

Thanks Sriram, I will try to tune it as suggested, though I must say it has been done 3-4 times already. Kindly advise if it is 1 to 1 and 1/4 turns ??

I have been checking the Reserve - Reserve ratio all the time, that is how I know the mileage is gone down. I have been filling it up either 1-2 ltr every time and then check it...that is Why I know it is 20kmpl if not less

Sriram - as Prakash says that he'd had the float pin changed, there could be an issue with the float level adjustment. If the fuel level in the float bowl is too high, it will result in a rich running engine irrespective of the idling AFR screw adjustment. Of course it will show with a dark brown or blackish plug. But the plug reading is valid only for an engine that's been run for an appreciable distance at normal or high speeds and has the 2T oil premixed in the correct ratio. Low speed high gear operation will show up as a dark plug.

If I remember correct, for the stock RX carb the fuel level in the float chamber should be 21mm above the chamber's lowest spot. An easy way of checking this in an appox manner would be to hold the fuel drain pipe upright next to the float chamber and unscrew the fuel drain screw at the bottom of the float bowl. Fuel will flow out into the pipe and rise till the level at which it is in the float bowl. Check if it is about 6-8mm below the float bowl edge. Any higher means that the level is high. I hope they still have those metal tangs on the float through which one can adjust the fuel level.

Could someone confirm the value for float level?? I might get it tuned and check.

I also believe that the carburettor fitted is of RX 135 and not RX 100

I guess I was right with my hunch



That's a page from the RX 100 workshop manual.

Thanks, You were able to find it

Btw, the carburater fixed is that of RS 135, so should it be the same(21mm) ??

Will replacing RX 135 carburetor to RX 100 affect my mileage or performance ?

Should be more or less the same. I am not as familiar with the 135 set-up as with the '100.

As for replacing the carb, I don't think you need to go that far. The 135 carb can be set up properly to give you good economy too. I guess anywhere between 30-35 kmpl should be pretty good.

So just so I understand clearly, the float level should be around 21mm. I have attached an image just to confirm if that is the float level...Kindly confirm