Good tip! Yeah, I'd planned to test out the travel and bottoming point in this manner. I only installed a '98 RM spring on the DRZ400 shock check clearance everywhere (topped out, it's tight at the engine case swingarm mount area). I know an old Lectron Legacy era carb or maybe even H-Series won't clear the larger diameter spring, but a Lectron Billetron or Keihin PWK33/35 clears just fine.KDXGarage wrote: 06:32 pm Sep 29 2024 Just in case you didn't do it, take the spring off and run it from full extension to bottoming out to see how the mounts and linkage work when moving.
The max length for a shock upgrade is about 17.25" (438mm) without modifying the frame or machining a custom rocker linkage. Anything longer will mean spring preload needs backed off in order to compress the shock just to squeeze it down to the maximum installed lengrh of 438mm center to center.
Stock shock is roughly 16.75". That extra 1/2" length with the rocker brought back into it's highest leverage ratio point possible, a point which the stock length shock never sees, added about 1.5" of ride height at the top of the stroke, & at the largest leverage ratio advantage point of the rocker's swing, meaning more travel here near the top, but also more plush response initially. 117mm KLX pull rods should help correct things slightly, but I believe initially it will still be quite plush. I'll probably valve the face shim area a bit more firmly because of this.
My big concern here... I was afraid with a lot longer body, and reducing travel through shorter shafts or spacers to bring the overall fully extended length down to 17.25"/438mm-440mm roughly (worn linkage bearings here... #'s wont be EXACT), that I'd be decreasing the available amount of travel too much.
I just tested travel on the stock '02 DRZ400E shock, WITHOUT yet swapping in the intended shorter '01-'04 RM125 clevis, & I was right at 11.1" from topped out with just a paper thickness clearance between the rocker & the frame, to sitting on the rear end compressing the shock & foam bottom out bumper, which was great news!
So that was with 117.5mm of a available shaft travel from topped out, & with a 5.5mm shorter clevis, I'll end up with around 123mm of shaft travel.
123mm of shock travel = 11.54" total rear suspension travel with the DRZ400 or '98-'00 RM body & the '01-'04 RM clevis! (with lowering spacers to reduce overall length to 17.25"/438mm).
The rear end has more room for additional travel, but the shock body lengths limit it. I'd consider modifying the frame's upper shock mount if after a little more travel, as adding 5mm more shaft travel will bump it up to 12" rear suspension travel, extending it deeper in the stroke still without coming close to bottoming out the tire in the fender. This also would let me tilt the slightly larger diameter shock spring slightly away from the engine case swingarm pivot bolt area - which is touchy here as to clear when the suspension is topped out (closest), you need to make sure the coil spring is rotated so that the gap in the coils splits the swingarm pivot area. It's a close one. If bringing the upper shock eye back just a hair towards the airbox boot, that would clear up this tight fit.
This is a big relief here... Knowing that the stock DRZ400 shock will allow 11.1" wheel travel, & the '01 RM125 clevis swapped to the DRZ or 98-00 RM shock, with lowering spacers, will still achieve 11.54" travel.
