The spring rate may not be ideal if they were originally sourced for a 550. It is easy to check by doing a part search on the Race Tech website.
since this is all second hand parts Im not sure what the spring rate is and I didnt adjust the valve just dropped it in as was.
how do i test spring rate?
I dunno...but it is kinda pointless to use all that nice stuff if the spring rate is incorrect. Realize that that there is nearly 100 pounds of weight difference between a 550 and a 750. If you can achieve the correct amount of static and live sag, by adjusting your pre-load, than the spring rate should work for you. I don't have the correct sag numbers. You are gonna have to do some research to find them. There is lot's of info on the Race Tech website, but it's kinda hard to use, and they won't give away all their secrets unless you buy something. The vintage department guy at Race Tech is a genius and super nice. He has been extremely helpful when I have questions. You can get his email off the website and he answers back usually within an hour during business hours.
Another thing...what year are your 750 fork internals? K1 and earlier are not damper rod forks. These forks use a sliding bushing to cover and uncover the dampening holes. Cartridge emulators can not be used with these forks, All you can do to improve these forks is correct rate springs and different weight oil.
According the website the spring rate out of factory were the same and the recommended spring rates by race tech to use were the same as well. I remember Kevin telling me he setup his bike for a heavier rider but I might be mistaken as we discussed it years ago...also under the impression that the difference in stock springs between 750 and 550 were the OD and that an upgraded straight rate spring for a 550 would be at minimum good enough for the 750.
I cant use the DVS set up sheet ( got all this used) butI have a blue 40lb. valve spring on my emulator but not sure how much preload it has set to it, still have to pull it out and remove all preload and try it otr turn by turn.
So all in all - from factory the spring rates are the same (unless I'm reading all that wrong) - when upgrading they suggest the same hardware - I'm assuming whats here should be within spec just not tuned properly for my bike.
Just wanna say even just dropping these things in and not being sure what the tuning is even set to, the ride is 100% improved already...adding 10 weight helped a lot as well.
There is a huge difference in handling, the bike tracks less with more control over it on poor condition roads, I've been playing with the oil weight and preload spacers only as of right now.
I also have the pictures of the 550 and 750 dampers next to one another just a few posts above that you can reference, they are basically the same.