99 750 Suspension Improvements?

[Sgt_H]

Hi all,  The budget for bike parts is slim right now (no Ohlins  ), but I'm looking for ways to improve my suspension performance.  I bought the bike used with few records so I have no idea if/when the front fork oil was changed, so that is high on the list.  Is there anything I can do on a tight budget while I have the forks apart to make improvements?  I've seen threads on springs and valves but I don't know what either of those would run pricewise.  Is changing the oil the best I can do without serious outlays of cash?

Is there anything that can be done with the stock rear shock?

Thanks

[bigiain]

How slim's "slim"?

New springs will run a couple of hundred or less, and _will_ be worthwhile.

There's not a lot else you can do to these forks anyway - Brad Black's advice is "put 0.9 springs and 10wt oil in, that's as good as they'll get".

If the oil's _old_ old, just replacing it will help, but you'll likely still be a little undersprung (unless you're well under 200lbs).

big

[Sgt_H]

Well, the wife wouldn't like it but I could probably swing a couple hundred.  I did just spend $300 on an exhaust though. 

Eh, give it a month and I'll be able to justify it.  I'm 185 pounds now, but I'm hoping to get closer to 200 over the summer.  I know close to nothing about suspension.  Do you think that .9 springs are right for someone in the 190-200 puond range?

Is there anything that can be done for the rear? Or will that just have to wait until next year when I can replace it?

Thanks for the help bigiain

[bigiain]

Well, the wife wouldn't like it but I could probably swing a couple hundred.  I did just spend $300 on an exhaust though. 

Eh, give it a month and I'll be able to justify it.  I'm 185 pounds now, but I'm hoping to get closer to 200 over the summer.  I know close to nothing about suspension.  Do you think that .9 springs are right for someone in the 190-200 puond range?

Is there anything that can be done for the rear? Or will that just have to wait until next year when I can replace it?

Here you go, Racetech will sell you a pair of springs for $110 here.

Their spring rate calculator (linked off that page) suggests you probably should go for .85kg/mm for street riding. They'll sell you the right rate rear spring for $110 as well, and a revalve kit for the boge shock for $190 (though you'll need to get a properly set up shock place to fit that to your shock, that's not a home job for most of us, you need ~200psi worth of nitrogen to regas it...)

big

[Speeddog]

Don't go by RaceTech's calculator for rear springs, it's goofy.

0.85 is a little on the light side for you at 185, especially if you're targeting 200 for summer.
Depends how you ride and how bad the roads are too.

[Sgt_H]

Here you go, Racetech will sell you a pair of springs for $110 here.

Awesome, thanks for the link.  That makes this much more doable.

Don't go by RaceTech's calculator for rear springs, it's goofy.

I put in 200 punds and it still gave me .856.  What would you recommend?  .9?

[ducpainter]

Awesome, thanks for the link.  That makes this much more doable.

I put in 200 punds and it still gave me .856.  What would you recommend?  .9?

I would.

I have .85 in my bike and I'm 175.

Springs sag over time.

[Speeddog]

Just to clarify:

RaceTech calculator for front springs seems to be pretty good.

RaceTech calculator for rear springs seems to be fuxored.

[Sgt_H]

Just to clarify:

RaceTech calculator for front springs seems to be pretty good.

RaceTech calculator for rear springs seems to be fuxored.

Question for you on the rear...  The Racetech page says this, "Ideal Rider Weight for the Stock Spring  230 lbs or 105 kg" and gives me a recommendation of an 8.5 kg spring, with stock being 9.4.  I think the rear is already kind of soft but it's telling me to go softer.  Is there another calculator out there?  What would everyone else recommend for a 190-200 pound rider?

[Speeddog]

That confirms it's still fuxored. 

About 10 kg/mm should be good for ya.

[ducpainter]

That confirms it's still fuxored. 

About 10 kg/mm should be good for ya.

I'm 175 in street clothes and that's what I have.

[Speeddog]

I'm 175 in street clothes and that's what I have.

Dangit. My mistake, chart was for geared weight. 
Thanks, DP.

So 200# rider, with no gear, 10.5 kg/mm.

Just to clarify for the future if the OP's info gets lost, this is for the early '851' style hoop suspension.

[Sgt_H]

Thanks for the help guys. I think I'll have a nearly new bike, or at least new feeling bike, by the end of the year.   

[Privateer]

front springs are my next bike part I'd like to fix (04 620).  I'm about 215 out of the shower, and the racetech calc gives me this:
FRONT FORK SPRINGS
Recommended Fork Spring Rate for Street: 0.878 kg/mm (use closest available)

which would be either of these
RT FRK SPR 35.5x33.5x270 .85kg
RT FRK SPR 35.5x33.5x270 .90kg

I'm thinking I should bo with the .90?  Any opinions to the contrary?  I ride 100% street. 


thanks
Andy

[Speeddog]

At 215, I'm thinking you'll need more than a .90.

Lemme check my charts on monday, shoot me a PM if I forget.