Rebuilding MKII Hydraulic Forks

) Cupermcnewbster ( /

Ok, so I want to give the hydraulic magnum forks another shot, so I'm going to do it up right and rebuild them. I've basically got 2 good sets, except the main tubes are bent on one, but all other internals are perfect.

Something strange to note; the '78 (not sure of 79) have beefier springs within than the '80 forks. I found this a bit odd, but I prefer the extra spring rate so I'm going to use the older springs.

All the seals, etc look good.

The manual recommends 4oz of 20-30 motor oil. What have others used. I'm looking for maximum awesomeness.

Also, someone once told me you can adjust the lower springs to alter the dampening. There are 2 lower springs, the short one inside the tube and he longer one outside. Does flipping them make any difference?

Check out these springs:

Re: Rebuilding MKII Hydraulic Forks

You're photographing this and putting it on the Wiki, right? :D

Re: Rebuilding MKII Hydraulic Forks

you should have asked mr you know who about fork set ups. i think he just recomends using more or less oil.

Re: Rebuilding MKII Hydraulic Forks

zack, i dont know if dude gets on this board that often, but this guy john (?) from rhode island came to bombourbon with a maxi-height brown magnum. he was however, running the mkII hydraulic forks. he said something about how he switched the order of the bottom springs and in turn lowered them to maxi height...

Re: Rebuilding MKII Hydraulic Forks

nice! maxi length hydraulics would be awesome. i've got some mkII forks i was going to sell to get maxi ebrs, but i'd definitely rock the mkII's if i could lower them. let's keep this updated. anyone know this john dude?

Re: Rebuilding MKII Hydraulic Forks

) Cupermcnewbster ( /

Just take them apart and try switching the springs. I put some heavy weight oil in, but its not so great. I think a thinner oil would lead to more dampening.

You can see the difference in the smaller springs, so putting the shortest one on the bottom would in effect lower what the pistons sit on by about an inch or so. If that didn't do enough you could easily cut the main spring.

If someone has a triple tree from a bent set of tubes, I'll buy it then lower them myself.

Re: Rebuilding MKII Hydraulic Forks

When I rebuild my magnum forks I switched the bottom springs. It definitely lowered them. I didn't put more oil in because some of the seals where missing but this winter I am going to fix that.

The forks compress really well but they uncompress so fast and hard. You don't really notice this as long as your front wheel stays on the ground. The only time it bothers me is if I try to do something like do a little wheelie or manual off of a curb. When the front wheel comes off the ground it feels like the forks are bottoming out hard but in the opposite direction. It's pretty jarring to your hands. I am hoping that oil will help smooth this out.

I am not sure if this is explained well. If anyone is confused let me know.

I would definitely recommend switching those springs. Do keep in mind that when you do this that the studs that stick out the bottom of the fork will need to be cut down a little or they will get in the way of bolting your wheel on.

I don't know if I would Cut the main spring. If you did it would definitely sit lower to the ground with weight on it but when you picked the front end up I think the forks would just slid back to normal length.

Honestly I haven't had those forks apart for a while now so I don't remember every detail. I just mentioned things that I did remember. Good luck guys.

-John

Re: Rebuilding MKII Hydraulic Forks

John, I think the jarring sensation is described well enough. Anyone who rides a Magnum with hydro forks should know what this is all about. I've never been bothered by it, but does altering the springs intensify this effect? And are you suggesting that additional / different oil should, in turn, reduce the effect?

And can anyone verify if cutting the main spring would make the forks slide back out to original length when lifted?

Re: Rebuilding MKII Hydraulic Forks

i was so poor this year i ran my minarelli hydraulics all year on spare brake fluid. haha.

Re: Rebuilding MKII Hydraulic Forks

thanks for the info.i was going to lower mine but now i am not because i dont want the jaring affect.

by the way my hydrolics are smooth even when u pull a wheelie

Re: Rebuilding MKII Hydraulic Forks

Charles Cole (OFMC) /

Most professional motorcycle road race teams spend 80 percent of their time trying to get the suspension dialed in. Mainly the front. ( they have PLENTY of power) That should tell you a lot. I wish I had a set of the forks you are talking about, because I'll bet I could figure out how to make them work good. Rider weight is BIG factor, however, I haven't seen different weight springs for Mopeds. Since you guys didn't put a lot of pix in this thread, there wasn't enough info to SEE what could be done. More things can be done to forks than most people realize.

Re: Rebuilding MKII Hydraulic Forks

i'm doing this right now. i just need to know what size the oil seals are that go in the top of the bottom tubes. i couldn't find it in the service manual, anyone know?

Re: Rebuilding MKII Hydraulic Forks

) Cupermcnewbster ( /

unfortunately I didn't replace my seals when I "rebuilt" them. I did add a sweet round, aluminum spacer to stiffen up the springs though.

Re: Rebuilding MKII Hydraulic Forks

bummer, anyone else?

what are your thoughts on the forks post-spacer?

Re: Rebuilding MKII Hydraulic Forks

) Cupermcnewbster ( /

The spacer is so awesome, way stiffer, but not too much. I think my springs were worn and soft, so this helped make it feel more like a new pair.

Re: Rebuilding MKII Hydraulic Forks

what are the dimensions on that spacer?

Re: Rebuilding MKII Hydraulic Forks

Charles Cole (OFMC) /

I just found a set of magnum hydro forks. They should be here in a week or so. I'll be tearing them apart to see what makes them tick. I doubt that the valving will facilitate a way to adjust rebound damping, never the less I will try. Usually some damping orifices are brazed shut, with the final adjustment by using different weight fork oils does the trick. I have done many for setting up road racing bikes. Much can be learned about setting up our mopeds by seeing what our bigger bros do. I have worked with Dave Moss on several occasions. He's known by everyone on road race circuits, mainly in the west, but regularly works with pro teams at Daytona every year. Check out his suspension tuning videos on youtube. I'll be posting my findings when I'm done.

Re: Rebuilding MKII Hydraulic Forks

Can't wait to hear back about this!

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