Topic: progressive fork springs - too soft? Switch to cartridges ?

[greenjeans]

1970 CB750K (now an 836)

New seals in the forks, new fork tubes, new 15w fork oil and brand new progressive springs.   Geared up, I'm 230lbs.   I have some new IKON shocks on the back, coupled with a beefy aluminum swinger from MotoGPwerks.  The rear of the bike feels great.  A little stiff even.  However, the front is just too soft for my liking.  Too soft.  Soft to the point that I do not like the way it feel when braking into a corner.  It seems to "dive" too much as compared to all of the other CB750s I've owned.  I just can't seem to get used to it.
It actually sags a good 1/2" - 3/4" without me on the bike.  With me on it, it sags over an inch.  The bike is lighter than stock by about 30 pounds. 
I talked to the manufacturer of the springs and they suggested more oil, which I tried.  No noticeable change.   I think I may be just too heavy.
I have not bottomed the forks out yet.  I only have about 350 miles on it.

So...  I am now considering some emulators or some actual cartridges.  I have no experience with either.   Bang for the buck is a consideration, but since this is MY keeper bike, I don't mind spending a little coin on it.   Suggestions, experience ?

[flybox1]

Fork tubes too long?
Preload spacers?

[slikwilli420]

Progressive springs are hard to tune with preload since you are likely to preload all the progressiveness out of them.

Your best bet is straight rate springs for your weight and emulators. That way you can separate the rebound and compression damping circuits where the spring only controls compression and the valve only controls rebound. It's substantially cheaper than adapting cartridges and will be very effective.

[754]

Heavier oil.. 10-15 bux.I wont say what brand..

[seanbarney41]

+1 slikwilli!, racetech springs and emulators with set up instructions from Matt Wiley (he is the vintage guru at racetech) totally transformed my cb750 into the best handling sohc4 I have ever rode...totally worth every cent.

Someone here will probably buy your Progressive springs...or just use 'em in a bike you don't plan to keep.

[Steve_K]

I like Race Tech emulators, too.  They work well, but I needed to fool with preload to get it perfect.  This is on Suzuki forks but they are similar to Honda's.
I have Progressive springs in my CB750 and they are ok for the way I ride it.  I am (ahem 230 lbs) and I needed more preload and 15 weight oil for them to work.

Steve

BTW, the Suzuki forks are on a GIXXER with a Penske shock and it has the best suspension I have ever had.

[HondaMan]

Maybe try air fork caps, or make some? All it takes is a couple of Schraeder valves threaded into the valve caps. I love mine, had them there since 1972. I run 0-3 PSI unloaded and up to 10 PSI when touring "heavy" with my wife and all the gear aboard (up to 600 lbs on some rides to SD!). It also greatly reduces oil weeping past the seals,  and great reduces nosedive during braking.

[greenjeans]

Maybe try air fork caps, or make some? All it takes is a couple of Schraeder valves threaded into the valve caps. I love mine, had them there since 1972. I run 0-3 PSI unloaded and up to 10 PSI when touring "heavy" with my wife and all the gear aboard (up to 600 lbs on some rides to SD!). It also greatly reduces oil weeping past the seals,  and great reduces nosedive during braking.

That's an easy cheap option before I drop the $$ on emulators.   I'll give it a shot this weekend.

[slikwilli420]

If you are trying to tune suspension, air is a bandaid only. It can add bounciness to forks and really only covers up some other issue. In Hondaman's case, he uses air to assist when changing the loads he puts on his bike. Emulators and the right straight rate spring are the proper method for tuning a sporting bike.

[Rookster]

The emulators don't work on the early style forks.  You need to adjust the preload spacers on the Progressives.  I weigh about the same as you and have Hagons on the back with Progressive springs in the front.  Mine don't dive too much on braking.  I used a 1" preload spacer.  The springs come with a spacer that is a shade over 1 1/4". 



Scott

[CBGhia]

I thought they had an adapter for the emulators to fix the early forks.   

Here is a nice thread on them http://forums.sohc4.net/index.php?topic=86371.0

I bought the Mikes XS emulators and while they are much better than stock, I am probably going to go with the racetech emulators eventually.

[PeWe]

My fork was a little bit too hard when I installed the progressive forks 1989. The spacers on top where too high.
I used shorter spacers when I restored the bike to 2014. I followed the progressive instruction about the oil level. 140mm from top with fork fully stretched and no springs in.

The fork is now on the softer side, but not too soft. I do not remember how much I have as a spacer. I think I used some thick washers only.
The top cap is very hard to mount with long spacer.

Rear IKON shocks, settings 2,2.

[Duanob]

Maybe try air fork caps, or make some? All it takes is a couple of Schraeder valves threaded into the valve caps. I love mine, had them there since 1972. I run 0-3 PSI unloaded and up to 10 PSI when touring "heavy" with my wife and all the gear aboard (up to 600 lbs on some rides to SD!).

Dang 600 lbs?

[scottly]

Soft to the point that I do not like the way it feel when braking into a corner.  It seems to "dive" too much as compared to all of the other CB750s I've owned.  I just can't seem to get used to it.
It actually sags a good 1/2" - 3/4" without me on the bike.  With me on it, it sags over an inch. 

You want a certain amount of static sag, generally 25-30% of the total suspension travel, so 1 1/2" should be about right. Wrap a ty-wrap around one fork tube, just snug enough that it is easily slid up the tube, but stays in place. Slide it down against the top of the fork leg, then do a hard stop using the front brake, and see how far the forks are actually compressing.

[greenjeans]

My fork tubes and lowers are actually off a later year model.   I'll try some preload spacers this weekend - my springs didn't come with any.

Still entertaining emulators and straight springs - RaceTech pretty much the consensus there ?

[seanbarney41]

The real advantage of race tech is that setup and tech Data is just a phone call or email away.  And yes they are more knowledgeable than you will need.

[nixon]

kinda too late now..but the linear springs i got from sonic were, and are, perfect.  reasonable $ also

 hopefully a longer spacer  gives you the feel you want..