Hey Carsten, I'm sorry I hadn't seen your post, I'm on holiday vacation right now and just checked in to post some pictures from a recent engine rebuild and saw your question. I always refer to the Racetech Spring calculator to find what springs I need for both the front and rear of my dirt bikes.
It says you need a 6.4KG spring rate for 100kg or 220 lbs. Racetech sells a replacement 6.4KG spring for the G450Xs Ohlins shock. They don't list a spring any heavier than that.
The following is the Racetech part number #SRSP #622864.
I'm a big boy too so I have the same spring on my factory reworked Ohlins shock that's laying on the shelf in my garage, that I used before I switched to a WP 5018 Trax Shock on my G450X.
I also have been busy on another project in the meantime and just started going on with my G450. Thanks for your Information so fare. I allready have checked the Racetech page, which is very informative. Meanwhile I came to the decision that I also have to pay particular attention to the Front, as it seems that I have to much play in the left fork rod, although the bike supposed to have just 50 houres on the clock. At the moment I'm not sure if the Marzocchi Fork is it worth getting reworked ore if I would better change to a WP ore a Kayaba Fork, similar to the variant you have described very detailed in this Forum. I think I will need some further support from the guys of this community during this project in foreseeable future.
Carsten, Feel free to ask anything G450 related that you want to. That's what we are here for.
The previous owner of my G450X was my local BMW dealer, 120 miles away in Tucson, Arizona. It was his personal G450 and he had both the factory Ohlins Shock and the 45mm Marzocchi forks on the bike reworked by "Dicks Racing Suspension Services" in Utah, here in the USA.
The valving set up was for hare scrambles/desert racing. Perfect for what I did with the bike myself.
The valving on both ends of the bike worked very well actually. No problems with deflection off of the rocks where I ride at all and these forks were known for deflecting off of rocks and tree roots with the factory valving.
However, I was maxed out at the stiffest (6.4 KG) rear spring available for the Ohlins shock and was also using the heaviest fork springs (.48kg), that I could find that were listed anywhere for the 45mm Marzocchi forks as well.
By the time I got all my riding gear on and hydration pack and tool belt etc. I was pushing 265+lbs. I had a few occasion where I was pushing the bike hard and caused it to bottom the bikes suspension out, but all in all the suspension worked very well.
I am a tinkerer, I like modifying things that I ride or drive, I never leave anything alone.
I was able to find a used WP 5018 Trax Shock for a good price ($600.00) with about 20 hours use and by swapping to the WP Trax shock I was able to have a much larger spring selection to pick from including all the KTM PDS progressive wound springs. So now I run a progressive wound rear spring on my Trax shock that is near equivalent to like a 7.2 KG spring rate at the end of its stroke and about the same as a 6.6KG to start off at the top of the stroke, So far no matter what I can throw at it, it won't bottom out, and it rides very plush indeed.
There's not a lot that needs to be actually said about the WP 4860 Open chamber forks once reworked with all of the Race Tech internals, Gold valves, mid valves, etc. and progressive front springs, They perform excellently and deliver more than what has ever been needed all the time and on this bike a set of these forks is an absolute game changer.
The is only 1 downside to having done this Fork swap on the bike when I'm riding it, for one the bike doesn't turn as far to the left or right against the fork stops anymore since running the 22mm KTM offset triple clamps (factory offset is 27mm). For the most part though, this fact has never really been much of a noticeable problem when riding the bike even if you get in a really slow speed sections when your feet are on the ground and you are trying to switch directions in the trees or to sharply steer the bike when going between rocks. Just muscle it through like you would any other bike using the clutch and some wheel spin.
I'm a big guy, I can still muscle it through either way. Besides that, I try to avoid areas like that anyway at nearly 62 years old. I have really only noticed that, because I knew how sharp it turned in the first place, Actually, all that being said, I really only think its a pain in the ass when sharply manuevering it around in the crowded garage.
I guess there is probably 1 other downside to having done a complete suspension swap on the bike, its sort of a trade off in improved suspension performance that over time becomes a downside, as well.
The WP suspension on the bike has made it to where I will never learn as much as I would like to know about adjusting the suspension set up on this bike since it works so well now, that I don't ever have to mess with the clickers anymore to see or feel what it may cause the bike to do, (good or bad), if I did.