Fat Boy Spring Info

[nitris223]

For those guys having trouble with spring / idler wheel clearance try part number 7042240-067 and 7042241-067. These are from a 2005 600/800 touring model .405 Dia 77 degree. The spring coil is 1/4" less in width then the RMK edge springs. The inner diameter is also a bit larger. To solve this larger diameter problem you need to get a 10"-12" piece of 1 1/4" ABS pipe and slide it over the existing spring sleeve. This takes up the slack and keeps the spring from twisting over to much under tension. Set on the middle spring adjuster setting the slep pops up to the max height and sags to 4 inches with my 230 pounds on the sled. The long tail on the spring is about 1/4" to 3/8" longer then the rmk springs which you can cut off or leave . I can't see any interferance on my RMK in which they could stab the track which was mentioned in some of the other post I have read.

RMK spring numbers are 7042068-067
7042069-067
7042079-067
7042080-067
7042081-067
7042082-067.

There is a spring kit part number available but as to what springs are in the box I have no Idea, I know they are .405's that's all. That number is 2900098

 

[MARV1]

Excellent, and these will work better than the .359" 47* that are still way too soft.

 

[MARV1]

You can only add so much preload to a way too soft spring setup.

 

[nitris223]

I think the .375/47 is still a viable spring for some riders. It just depends on their riding style. I rode a friends 800 RMK after he installed the .375's and I could still bottom the suspension out on the stiffest setting quite often. I run a long track here in the flatlands of Saskatchewan mostly because the trails get pounded out and I find the longer track bridges the bumps better. If I was only riding bottomless powder the lighter springs would be fine. They may be to stiff for sit down style of riding but I am standing most of the time so my legs are acting like a shock absorber also. Maybe today I can get out and test these .405's and see how they perform.

What I found strange was how fast the springs can go from good to bad in one ride. The week before the ride was still ok, but just ok and then the next weekend I was bottoming so much I believe I was 2 inches shorter by the time I got home. I did get 5 yrs out of the springs or 3000 miles so that's not bad I guess, I just wish someone made aftermarket springs . It seems as soon as the manufactures made square style torsion springs that was it for the after market crowd. If anyone knows of any round style torsion springs that work , please add to the post.

 

[MORSNO]

My fatboy springs will be ready for replacement after this year. I'm interested if finding out if we will be able to use the 2011 coilover set up and just get rid of the OE torsion spring set-up? Otherwise I'll be going with the .375/47 degree springs (running the .375/77 now).