Which fork springs do I have?

[RayJay]

The previous owner said the suspension was upgraded with Progressive units (rear has a Progressive 412 shock). Is there an easy way either externally or looking at the front springs to tell if they are Progressive units?

'95 K75RT

I'm looking to improve the ride and stance (I'm a big guy, 6'2", 240lbs, 34" inseam). The 412 shock is the lowered version and I have a lowered seat as well, all making for a very cramped ride. The front fork dive on braking does seem very excessive.

Plan:
Progressive front springs if they are not in there, Progressive 420 rear shock, and a standard height seat if I can find one.

[MichiganMike]

I don't think there is any external way to identify, and many of the K bikes have had Progressive Springs put in and then they get worn in with all the miles.
Many people experiment with different weight of fork oil and longer spacers etc.
My original spacers were metal and the Progressives were PVC.

On the seat, post an ad for a seat swap for someone with a stock seal and hardware. You will need the side panels etc. Usually more people will be looking for a low seat than the other way around.

One more comment, I am 6'3' and 220 with riding gear. I put 113K on a K75 with a custom low Corbin seat and put some really long days in on that bike. A custom seat can move you back too. I did have highway pegs that came on that bike. I currently have a RT with a Russell Day Long and that is a perfect fit for me.

[johnpeter]

I am looking back many years but I did replace Guzzi fork springs with P/S units.

The stock springs "might" be straight wound, that is, the space between the coils will be the same over the length of the spring. On the P/S springs the coil spacing will vary along the length of the spring. So the rising rate of the spring is progessive. :laugh

Drain and re-fill the forks so you KNOW what volume is in there. Then add oil to displace air volume because this will help stiffen fork reaction. http://www.ibmwr.org/ktech/fork-oil.shtml

I do believe my(new to me for 3 months) '91 K75S forks were filled to the non-sport volume of 330cc with prolly 10wt oil. I orderd BelRay 7wt and will be refilling to under the speced 280cc. Prolly start at 250cc, then if I feel the need to further stiffen the forks I'll just add more via plastic 50cc syringe. The S bikes have stiff stock springs. BMW specs 5wt fork oil. I am 6'@240#dressed and ride agressivly for a 61yo guy on a 70hp 510# bike.

[RayJay]

One more comment, I am 6'3' and 220 with riding gear. I put 113K on a K75 with a custom low Corbin seat and put some really long days in on that bike. A custom seat can move you back too. I did have highway pegs that came on that bike. I currently have a RT with a Russell Day Long and that is a perfect fit for me.

The seat I have is some sort of Corbin low solo seat (passenger section is just a flat platform of vinyl covered foam). I think if the cut out was an inch or so higher and and inch or so further back it would work. Right now my knees are against the fairing and bent too tight. I did post a want ad. I figure if all else fails, this winter I'll get it recut to fit better.

[RayJay]

Drain and re-fill the forks so you KNOW what volume is in there. Then add oil to displace air volume because this will help stiffen fork reaction. http://www.ibmwr.org/ktech/fork-oil.shtml

I do plan on re-doing the fork oil, just figured I'd check while in there. The ibmwr site has been a great source so far (headlight switch rebuild, throttle position switch for backfire, etc.).

[35634]

The seat I have is some sort of Corbin low solo seat I did post a want ad. I figure if all else fails, this winter I'll get it recut to fit better.
Did you try http://www.ibmwr.org/market/ ? I've had excellent results buying-selling-
trading there, and it is free (donations accepted)

[tommcgee]

The Progressive fork springs are definitely not going to help the dive. I had a set installed a week ago. On the other hand, they're better than the OEM springs that were replaced.

What this bike really needs is straight rate springs in the forks. I'm sending one of my old fork springs to Sonic Springs in Oklahoma to see if he can match it. I bought a set of 1Kg/mm fork springs for the DL650 Vstrom from him and they transformed the bike.

I also got a new BMW rear shock and the ride is very harsh (1995 K75) on all three spring compression settings. Haven't decided what to do about that yet. Any ideas?