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Virtual Mechanic

Car and bike questions? We have the answers

My stock Yamaha RX135's top speed is 95 kph with 45 kpl in the city and 60 kpl on the highway. I have now altered the rear sprocket from 34 teeth to 30 teeth and mileage is up to 68 kpl and top speed to 100 kph. How can I further increase top speed and maximum power without changing the silencer? Also what is the air screw setting for better top-end and mileage? Will it affect performance and engine life?

R Chandra Kumar, via e-mail

The results you have achieved by the sprocket change should be more than you can expect. Trying for a further improvement will mean extensive modifications to the powerplant which would involve quite a bit of expense. The air screw settings do not affect top-end performance, so let the standard settings remain.

I own a Wagon-R which has a problem right from the first service. Whenever the accelerator pedal is depressed 90 percent, the engine starts knocking only between 3000-4000 rpm. This happens in second and third gear. Maruti engineers have seen the car but say that all MPFI cars will knock at some rpm or the other and blame the quality of fuel. Is this correct? Also, after the third service, average has dropped to around 8.5 from 10-11 kpl.

Rahul K, via e-mail

The quality of fuel is important for proper engine performance. Try changing to a different fuel outlet and see whether things improve. Failing this, you need to find a dealer who will look into the problem without trying to evade the issue.

Whenever my Honda City 1.5 EXi goes over a bump, there is a sound from the left front tyre as if it is bouncing up and down rapidly. The suspension has been checked and the dealer says there is nothing wrong. But the inner side of the left front tyre has worn out more compared to the rest of the tyres. Please advice.

Vir Kumar, via e-mail

Obviously, the camber on the side where the tyre is wearing out is not correct and the sound that you mention is probably due to a weak damper or a problem with the strut, if the suspension bushes are not at fault. Get the alignment checked and replace whatever parts may be necessary.

By changing the gear ratios and final drive ratio of the current engine spec Palio 1.6, what can be the maximum true speed achieved, with the tacho indicating just over 6500 rpm, running in fifth gear? Also how capable is the engine of sustaining and surviving such modifications? I attempt upshifts only at max revs in any given gear. If the Accent GTX's standard 185/60 Potenzas are used on Palio 1.6's standard alloys, how will it affect the car's handling and at what cost of ride comfort? Also how will this change affect suspension and steering response?

Neil, via e-mail

Without knowing exactly what ratios your Palio 1.6 is running on, it is impossible to predict what the performance will be. Having said that, it is no easy task to swap ratios and it is rare to better the manufacturer's values by indiscriminate changes. Also, it is almost impossible for an engine to spin to maximum rpm in fifth gear. Changing to other than standard sizes of wheels and tyres will always affect certain handling and steering characteristics. Predicting results is only possible if some actual tests are performed.

Write in with your queries to wheels@thehindu.co.in

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