you sure? old, dirty car engine oil can be used? I have some 20w40(used) oil

ok bro, I'm waiting..
BTW, when one should change fork oil?

Yup. Sad. Though it had nasty flash point. I remember those guys in that repair shop keep it inside a large steel locker. I used to think it was trade secret of some sort... Since I grew along with those kids in my neighborhood, they used to be generous to lend me some.

@Honda_CBF: Just hold on until Saturday till I get my report card for this. . Its going to be 1 week and I have got almost all the conditions that Indian roads can throw. Rain/Sun/Dirt/Potholes are covered. The only one missing is harsh riding and speed bumps, which I will do tomorrow . Looks like I m the only guy (in this thread) riding with this concoction.

Yes I use Diesel to clean Self and tools after a work. Kerosene cleans ,but the stink also sticks to your hand for long .Aviation kerosene/petrol is no longer available outside now..

Alternatively, you can go for all time favorite DIESEL. Very good cleaner, leaves very less residue except for good smooth waxy coating (beneficial). I have used that for cleaning chain/bearings/cables/ and my hands after messing it up with ol' black grease.

My all time favorite was aviation kerosene. I m not sure of its authenticity, but I used to get it in old Bisleri bottle from a mechanic. He used that as cleaning agent in his "Premium" service package. . But, boy oh boy, cleaning with it was a magical experience.

@Prince: Given the steep price, I would suggest mere kerosene would suffice (the ones that we get from PDS or Paint shops). If possible, try white kerosene, significantly better than the blue one (cause unknown).

Don't petrol use like that bro; it's carcinogenic , flamable , low-flashpoint ,makes toxic fumes and getting pricey now . Once I was tinkering inside a Maruti Zen bonnet , pulled the fuel line to check if the fuel-pump was working . It was , and it spilled some petrol inside there , then I selfed it and the whole engine compartment burst into flames with a big bang . Scary day ! now I am a lots more careful around petrol. Kerosene is an excellent high-flashpoint govt subsidised cutting solvent . The dirt in there is hardened sometimes from long neglect . You may need to poke/scrape it with something long like a straightened shirt hanger or a bottle brush etc . Older bikes had a drain-bolt at the bottom of the fork .. sigh .. not anymore nowadays .

and how to clean the settled dirt in fork bottom.....by petrol or somethiing?

Sorry , for late reply .. was slogging out all day . It is dreadfully hot and humid in kolkata today . Had to ride around in that burning noon sun too .
Yes , that horrible thud sound of your fork bottoming out ... happens to me too often .. kolkata city roads are no better . Yes , you can try out a 10w30 , no harm in it . Also remember , you don't even need a motorcycle specific ( jaso MA etc ) oil for this purpose , some leftover car oil would do fine , isn't it ? .
@psr'jee - most of the time I see mechanics keep new seals on the garage floor etc before fitting and fit them like that with dirt & sand or use screwdrivers etc to poke and drive them in . Oil seals damaged like this will fail early anyway , forks or elsewhere . I mean I am not sure how a little extra oil would cause a leakage , it is unlikely . Possibly you had a coincidence ? I have had leakage from good branded fork oils and standard volumes too .. just like that . Also while replacing the oil , don't forget to clean out the gunk that settles in the bottom , mechanics ignore that and there is a lot of it there sometimes .

Awesome thread guys.. Keep experimenting..
I also want my front to be stiff a little, because i ride on the india's worst road may be world's.. Its with lots of big fat potholes & speed breakers, my front forks use their full travel length almost all the time. It gives a thud noise when forks bottoms out. After reading all this I feel using 10w30 oil is good for me. So, what's your suggestion guys?
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No issues....even the normal Fork oil becomes black within a few months..just like the HH engine oil . I used to change it every year,and so never faced any problem. After the regular fork oil had become easily available switched to it...

@PSR: Good ol' days of 2T. I remember my old mechanic using 2T oil to lubricate my dad's TVS XT fork arms and then slopping loads of grease on it. He used to add (5 mL) that oil in cylinder whenever we used to take it to him for service. I have seen 2T oil becoming rancid after prolonged exposure to atmosphere. I lived very near to sea coast (Chennai), and have seen it darkening as time progresses, didn't this cause you any issue PSR ?

Ten years back i had tried 2T oil in fork with very good results.....I had always found that filling fork oil a little extra leads to early oil seal leakage,and filling to the spec with a slightly thick..10W30 or ATF/Power steering oil, gives better balanced drive .....
Mr. Pinaki your advise on this ?

Yes , a little more oil in there will stiffen it up too . The standard seals should be able to handle 20-50ml extra easily , since there is much air space in there already , I mean it's not like that there is no space to contain the extra oil that the seals shall be stresed anyway . The stiffening is not by the extra oil itself . By adding more oil , you reduce that air gap inside it to alter it's hydraulic property .
I am not that much of an fork oil tester , and I am just 58kgs , so I don't know whats best , but since it's not that expensive a deal to try out a few different fork configs with just oils ( atleast way cheaper & simpler than experimenting with K&Ns & jetting etc ), you can experiment and find out what works best for you . A good mechanic should have an better idea from experience .

So pinaki , what is the best forkoil for a stiffer ride.
BTW I hear adding 10-15ml extra oil make ride stiffer. What about the oil seals, ? will the hold up ??

LOL psr'jee
( sorry mods for sms lingo )