complete bombshell overhaul guide

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complete bombshell overhaul guide

This is a discussion on complete bombshell overhaul guide within the CRF50 forums, part of the General Talk category; hey guys i found a quick mod to get 7" travel out of your bombshells, along with a mod for stiffer spring preload and the ...

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    baconaddict's Avatar

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    complete bombshell overhaul guide

    hey guys i found a quick mod to get 7" travel out of your bombshells, along with a mod for stiffer spring preload and the gas to oil cartrige conversion.



    ill start with the 7" travel and preload mod.



    remove the fork tubes from the bike and loosen the top cap on the spring leg (left side) fork.







    then pull the little rubbet thingy off the top and pull the upper and lower appart, careful there is a little bit of fork oil in there.







    the fork should now look like this







    next tighten the axle down and step on it so the fork doesnt rotate







    next, uncsrew the silver fork cap on the top of the lower and pull the guts out. youll see a yellow runner bushing between the cap and the spring, cut 3/4 inch off that bushing so it looks like the picture below.







    my fork tube actually unscrewed from the bottom part of the fork so thats why the pix dont look right. but this will work the same with the top cap. reinsert the spring and slide the cap back on. you should still have 3/4 inches of preload. the spring has enough to take 9" of compression, so with 7" of that in the travel and 3/4" of that in preload, you now have 1 1/4" of preload to play arround with.







    i found a 1" deep big nut and a thin washer to take up the 1 1/4" of preload left.







    just throw a quick wrap of tape on it to hold it in place when you drop it back in and reasemble everything.







    once its assembled drop a splash of fork oil in through the top cap for the oil bath and voila you now have 1 more inch of travel and your forks are now stiffer. now onto the valve leg for the oil dampening conversion.







    first off get yourself a 22mm wrench and loosed the top cap off.







    once you get the top cap loosened you need to take it off the rod, youll most likely need ot throw it in a vise like this.







    once the top is off itll look like this







    pull the upper off the lower.







    then clamp down the axle in the bottom again and unscrew the cartrege out of the lower







    ok heres the tricky part. once you have the cartrige out stick a #4 metric allen dowh the top of the rod and unscrew the rebound adjuster, pull it out. it looks like a foot long carb needle. be careful it is under pressure and will spit everywhere. once the rebound adjuster is out, cut a watterbottle in half, then stab a hole in the cap just big enough to jam the shaft into it. press that onto the shaft and put some tape at the bottom if you dont want fork oil to go everywhere. next, get yourself a clamp that will firmly grab the shaft but wont scratch it and clamp that about 7 1/2 inches up from the seal. you are now setup to bleed it. it will look like this







    now you need a buddy for this next step, fill up the half of the waterbottle up about 3/4 of the way with fork oil. (i used 20wt) then slowly cycle the shaft up and down a couple times then press down the shaft untill the clamp hits the seal, it will have filled itself up with fluid, now continue to hold it down while your buddy drops in the long rebound needle and screws that back in all the way tight. once its tight you can release it, take the bottle off, whipe it down, then reasemble. remember, when your holding it down, keep it held down or it wont work. and the tip of the shaft must always be submerged in fork oil when filling and tightening or it wont work either. and dont forget to put a splash of fork oil in through the top to keep the oil bath seals all buttery.





    well there you have it, a complete fork overhaul and upgrade for free. you no longer have a mushy pogostick for a fork. you have a fork with 7" of travel and rebound adjustment that actually works now.

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    zwieblekopf's Avatar

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    Re: complete bombshell overhaul guide

    Nice tutorial. This should work the same for Red Baron G1 forks too.

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    Re: complete bombshell overhaul guide

    thanks man, and idk ive never messed with any g1's

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    themountain's Avatar

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    Re: complete bombshell overhaul guide

    hahaha...nice tutorial...the forks look eeexactly like my DNM downhill forks on the MTB inside...sweet now I have a manual for them ...thanks

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    Re: complete bombshell overhaul guide

    Ultra front ends are different though right? What is benefit of oil over nitrogen? Also don't you need a little preload or is 3/4" enough? I've never messed with suspension. Seems like a very easy and userfriendly tutorial u posted tho.

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    Re: complete bombshell overhaul guide

    internally they should be the same, its just bombshell stopped production so they have someone else producing it. the preload is if you want it to be stiffer. and nitrogen doesnt expand or contract unless its in extreame weather so it stays consistant, fork oil dries out over time and needs to be replaced, i think they did it for longterm ease of maintenence. and thanks =)

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    Re: complete bombshell overhaul guide

    now that i look at it, its unnessisary to take the cartrige out of the leg, you can do the bleed with it still in and save the trouble of taking it out

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    Re: complete bombshell overhaul guide

    the big question...how does she ride? compared to stock bombs?

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    Re: complete bombshell overhaul guide

    well working the valve leg up and down with gas was ok, once i did the oil swap i cranked up the rebound all the way and i pushed down the fork then pulled up on it pretty hard and fast and it was fighting me the whole time so i know the valving is waay better, as far as the spring its noticable stiffer. havent gotten to ride it on any terrain yet, other than off a curb haha. ill update you guys once i take it to the track.

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    Re: complete bombshell overhaul guide

    finally got it to the track, world of difference

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    Re: complete bombshell overhaul guide

    hmmm im liking the stiffer spring idea since I just stunt mine and dont really ride tracks or jumps....and from what was said when I talked to Sano a lot is different between ultras and the old bombshells...the materials that the lowers are made from, the way they mount and bolt the axel on and a few other things...

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    Re: complete bombshell overhaul guide

    so for the spring and preload part...is that the fork leg with or w/out the little red rebound adjuster?? i really need my ultra's stiffer for my weight and am going to try this little method you used here.



    thanks,

    tyler

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    Re: complete bombshell overhaul guide

    spring and preload are in the left side. the leg WITHOUT the rebound knob.

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    Re: complete bombshell overhaul guide

    ok cool thanks hopefully this will work for my ultras as i believe they are close to the same internally as the bombshells were.

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    Re: complete bombshell overhaul guide

    murkin, be sure to post on if this works on the ultras or not please. im picking up a crf50 with some ultras on it this weekend and the fork seals are leaking and need to be rebuilt.

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