Re: Discover 125 ST - Huge vibrations and low mileage


How many kms you have clocked till date, leaning of the mixture will improve mileage but not by a huge margin plus the engine will suffer, engine will heat up faster consume engine oil, will start vibrating and you gonna feel the vibes all over the bike, if this is an ASC mechanic then write to bajaj's consumer office of your problem.

Re: Discover 125 ST - Huge vibrations and low mileage

[MENTION=60617]ShantanuD[/MENTION].
I see everytime you are facing the same problem.
Vibrations depend on various factors starting from bad adulterated fuel, bad engine oil, poorly maintained bike.
Try switching to other busiest fuel station. Make it permanent if good.

So please share your maintenance history of bike from day 1.
Kms clocked now?
X service at xxxx kms.?
Oil changes? Which oil?
How many times is carburetor attended?
Chain cleaning and adjust? Check free rotation of wheels?
Tappets adjust till now?
Any special attention in services?
Any parts replaced?

Just share this information. It will help many of us to diagnose your problem.

Re: Discover 125 ST - Huge vibrations and low mileage

[MENTION=49419]kusmaker[/MENTION]: Total Km:~8200 and no this is not ASC mechanic [MENTION=7141]lokesh[/MENTION]:
I always fill from a very popular and busy petrol pump. Their record is clean.

Now about your questions
1. Maintenance history:
Only first free service was done in bajaj ASC. They did such horrible work that I never gave bike to them again. I took my bike for servicing a mechanic i knew for years. Till 2nd and 3rd servicing bike was fine. No vibes however mileage was never great. 48-52kmpl. After 4th servicing things started going downhill. Thereafter I took my bike twice to that mechanic he tried a lot, then gave up. Then I took the bike to another mechanic who is quite experienced. He changed damaged air filter and bike was never that smoother. After 2 weeks of buttery smoothness engine started vibrating again although not too much. Mileage was between 40-45. My previous post tells what happened afterwards. Now after another visit to him bike vibrates tremendously, pickup is drastically reduced although mileage seems to have improved

2. Total Kms: ~8200

3. Total 5 servicings done

4. Oil changed 4 times: Initially Motul, now running on shell advance

5. Carburetor cleaning: maybe thrice

6. Chain cleaning: every service. Free rotation: rear wheel seems like a bit jammed. But i checked another 2 discover 125st and they also showed same thing.

7. I have no idea what a tappet is

8. no special attention

9. air filter replaced

Re: Discover 125 ST - Huge vibrations and low mileage

I think the vibrations are just because of improper maintenance.

Follow all these checkpoints below. I am quite sure this will solve your problems:

1. The rear wheel should rotate freely. If not the chain needs to be adjusted. The chain slackness should be 1-1.5 inches. An over- tightened chain will cause vibrations and make chain sprockets to wear out faster. If chain is dirty get it cleaned, lubed and adjusted.

2.: Change oil to motul 5100 15w50
Replace oil filter with original one.

3. Ask your mechanic to remove spark plugs. Take photos from a good autofocus camera in proper light and post it here. This will tell the condition of engine and carburetor tuning. Because a lean or rich tuned carb will also cause vibrations. Refit them without cleaning or tempering.

4. Check the clutch free play. Adjust play to atleast 2-3mm.

5. Get airfilter cleaned and get checked for any loose nut bolds because of vibrations.


Most of the mechanics are expert in over tightening the chain and reducing the clutch free play to nil.

Btw No mechanic will use feeler gauge for adjusting tappets/ valve clearances. So I recommended not to do it now.

Re: Discover 125 ST - Huge vibrations and low mileage



Most of the times engine gives vibrations due to insufficient amount of fuel or due to incorrect A/F ratio, so feeding the engine with right amount of fuel is the most important thing, the leaner the mixture more the engine vibrates, changing the engine oil won't help untill this mixing ratio is corrected, get your carburetor tuned properly and post the pictures of the spark plug.

Re: Discover 125 ST - Huge vibrations and low mileage

But then mileage starts to suck bad. Right now I am getting somewhere near 50. If I tune it to even the neutral setting mileage will dip below 45. I am in a soup really.

Re: Discover 125 ST - Huge vibrations and low mileage

All right you are getting mileage of 50 but on what account, engine is vibrating and you aren't enjoying it either, if your bike is fine tuned you will get good mileage plus riding pleasure, incorrect A/F mixture adjustments have these characterstics
Poor overall performance
Rattling sounds from the clutch and vibrations.
Engine tends to stall easily
Erratic acceleration
Poor fuel economy
Misfires and/or backfires
check your low speed running jet and main jet.

Re: Discover 125 ST - Huge vibrations and low mileage

1) The above tips are spot on, a big cause of vibrations in pulsar's like mine(135 ls) and your is a dry chain. Never apply grease to the exposed o ring chain, use sae 90 oil to lube it after cleaning it with diesel or kerosine, you may also use a motul chain lube spray and spray it between the chain links same goes for the oil. Maintaining proper chain slack is ver imp. Trust me a tightened and dry chain produces a lot of vibes than we think. Keep lubing it every 500 kms and more frequently during rain.Let the bike sit for half an hour after lubing.

2) make sure your clutch is properly set, it should not remain partially engaged when you pull in the clutch lever, there should not be too much or too little play, adjust the clutch properly from both ends.

3) use motul semi synthetic oil according to grade appropriate for your bike.works best for my bike.

Rest depends on your carb tune and valves clearance +engine foundation(which you have already checked.)+timing chain ( if the engine is making abnormal ticking sound.).


Also the handle bars get vibes is your handle is over tightened, the handle should fall to either side on slightest tap in either direction. put your bike on main stand and check it.

Re: Discover 125 ST - Huge vibrations and low mileage

Thanks for the help guys. However even before this tuning my bike used to give me 45kmpl. I will get the chain cleaned. Ran out of option now, I will be giving bike to bajaj ASC nearby. See if they can do something

Re: Discover 125 ST - Huge vibrations and low mileage

@kusmaker
Thanks for your help.
I gave the bike to Bajaj ASC reluctantly because my mechanic said there is nothing more he could do. Surprisingly they did a good job. Vibrations are reduced a great deal. But there remains another problem.
When one releases the accelerator without depressing clutch, speed begins to drop slowly. This speed decrease is less when bike is in highest gear. i.e speed stays almost constant. In my bike's case speed drops like crazy even at highest gear. It feels like brakes are being applied. Speed drops by 10 kph in 5-6 seconds. I rode many other bikes, this isn't the same in them. In lower gears this is even more prominent. In 1st and 2nd gear when i release accelerator, even gradually, there is a violent jerk and speed drops suddenly.
Because of this I have to depress clutch every single time whenever there is some traffic on the road. This causes immense pain in my left palm. Also my bike doesn't go past 60 easily, it takes a lot of time and I have to twist accelerator really hard.

It all feels like there is something that is causing restriction to the movement of either rear wheel or some internal gears or stuff like that. This might as well be the reason for abysmal mileage I get i.e not more than 50 kmpl. Is this really a problem or just how this bike is?

P.s I have checked rotation of wheels. It's not the case of over-tightened break, chain is with proper slack and lubed up well enough