Q. Is Discover 125 suitable for long ride like 400 KMs if maintained properly?

Absolutely yes in my personal experience on Bajaj Discover 125 2018 November model. Did above 24000 kms. * Use Motul 7100 20W50 instead if Bajaj oil and replace in every 5000 kms.* Upgrade to decent tubeless tyres.* Keep the bike serviced properly in every 5000 KMS in bajaj service center or any other good service center that do all the regular maintenance and checkups as like the authorised service center. Discover demands regular and complete maintanace in adequate intervals as skipping them makes the bike louder all over the body and crazy jerky feel.* Use WD 40 to lubricate hinges, handlebar switches, electronic modules and also can be used as chain cleaner(not necessary as kerosene can do the same job in less expenses)* Use EP140 grade gear oil to lubrucate chain and repeat in every 500 to 600 kms . It is cheaper than chain lubes and can last long too. My chain still performs like brand new even after 24000 kms.* I usually maintain 45-55 kmph as going above that speed makes the bike feel stressed and I am not a fast rider. * Use a well padded seat cover because riding with stock seats can give backpain which makes us stop very often. *

I own a bajaj discover 100 (4 gear). I went on a ride of 510 kms.. which i was able to complete in almost close to 10 hours. To be very honest, i did not used any tips n tricks, all i did was: 1. Got my bike washed 2 days before drive. 2. Checked for any loose screws and nuts. 3. Got my oil changed, but i used bajaj 10w50 instead of company recommended 10w30. Used old oil for lubricating the chain, tyre rotating point.. break and break springs. 4. I didnt tried dhoom machale... And drove on a constant speed @65-70 kmph. On this speed i drove for almost 100kmph before taking any stoppage. I didnt stopped in between. i took around 5 to 5, 20 mins each; break in the whole journey. So you do not need any special preparation as such.. all you need is patience and not try to run fast. Choose a cruise speed and follow that, even if you can go fast

Yes bro. These days 125cc bikes comes with disk brakes and tubeless tyres. If the tyre conditions are good, go for a long trip but give some 15-20 mins rest after every 200 kms.