Really struggling

[Nighthawk016]

Hoping you guys can help me. I came off of a rm250 that I added a few things for woods riding, flywheel weight, regear, the normal stuff. Suspension wise, all I did on the rm is go through the forks, clean everything up, reassemble and set the rear sag.

I got myself a kdx, I've got 12-15hrs of ride time on it now. On the kdx ive jetted the carb, new top end, and had the suspension resprung for my weight. I have the sag set properly at right around 90mm. I was expecting the kdx to a night and day difference better than the rm, but I am struggling. My biggest positive is, I can do 25-30 miles of tight single track in the woods and im not beat to snot like the rm. However, I am not sure if its my riding style or what, but I am significantly slower on the kdx. Even with the rebuilt and resprung suspension, the whooped out sections, which are a big portion of my riding, are a huge struggle.

What I need to know is, do I need to change suspension settings, gearing, tires? Or maybe it's a skill issue and i need to completely change my riding style?

Any advice is appreciated.

[Chuck78]

I believe I'm at around 103mm suspension sag on the rear, as 95 was not enough, although I'm 160lbs and running a 5.0kg spring on one shock and a 4.9kg on the other, when I should be at a 4.7kg.

I was always under the impression that with around 300mm rear suspension travel, you needed 100mm sag, as 1/3 of your travel generally should be rider mounted rear sag on a long travel suspension setup. 90mm sag is a firmer ride, which I'd think would be mire suited to whoops, but perhaps not...??? Maybe KDXGarage or other can chime in on this. Valving setup us also a huge part to play in this issue, but the sag stood out to me as not enough. Proper spring rates are critical, perhaps your rear spring rate is not quite ideal?


For whoops, perhaps a CRF250X front end swap would suit you far better... Whoops vs tight singletracks are night and day difference, requiring different suspension settings, but a well built closed chamber KYB or Showa fork can be set up to give initial plushness while still having bottoming resistance.

Closed / Twin Chamber forks are best for aggressive race use and whoops etc, the RM had Showa Twin Chamber forks (or 01-04? were KYB?), but setup for, whoops will in fact tire you out on a 30 mile technical ride most definitely, while some open chamber KYB forks valved plush for technical singletracks will in fact allow uou to fo 35-75 mile days with a fair bit of technical terrain without wearing you out drastically.

It's a compromise, but I really feel the Showa Twin Chamber CRF250X forks set up for initial plushness but with bottoming resistance will be the best of both worlds for your exact terrain.

What areas do you ride?

Alternately, a 2005+ YZ250 2-stroke triple clamp with similar year 2005+ YZ125 fork legs could be valved very nicely as well for this purpose, but you'll need a generic chinese 28x47x15 upper steering stem bearing, as no name brand bearings are available for this non standard size.

EDIT - if you're heavier, the CRF450X or YZ250 2-stroke forks are better than my 250X / 125 2-stroke recommendations

[Nighthawk016]

I believe I'm at around 103mm suspension sag on the rear, as 95 was not enough, although I'm 160lbs and running a 5.0kg spring on one shock and a 4.9kg on the other, when I should be at a 4.7kg.

I was always under the impression that with around 300mm rear suspension travel, you needed 100mm sag, as 1/3 of your travel generally should be rider mounted rear sag on a long travel suspension setup. 90mm sag is a firmer ride, which I'd think would be mire suited to whoops, but perhaps not...??? Maybe KDXGarage or other can chime in on this. Valving setup us also a huge part to play in this issue, but the sag stood out to me as not enough. Proper spring rates are critical, perhaps your rear spring rate is not quite ideal?


For whoops, perhaps a CRF250X front end swap would suit you far better... Whoops vs tight singletracks are night and day difference, requiring different suspension settings, but a well built closed chamber KYB or Showa fork can be set up to give initial plushness while still having bottoming resistance.

Closed / Twin Chamber forks are best for aggressive race use and whoops etc, the RM had Showa Twin Chamber forks (or 01-04? were KYB?), but setup for, whoops will in fact tire you out on a 30 mile technical ride most definitely, while some open chamber KYB forks valved plush for technical singletracks will in fact allow uou to fo 35-75 mile days with a fair bit of technical terrain without wearing you out drastically.

It's a compromise, but I really feel the Showa Twin Chamber CRF250X forks set up for initial plushness but with bottoming resistance will be the best of both worlds for your exact terrain.

What areas do you ride?

Alternately, a 2005+ YZ250 2-stroke triple clamp with similar year 2005+ YZ125 fork legs could be valved very nicely as well for this purpose, but you'll need a generic chinese 28x47x15 upper steering stem bearing, as no name brand bearings are available for this non standard size.

The rm has 49mm showa twin chamber conventional forks, they are definitely something else. I'd like to stick to conventional forks if possible. I was considering xr400 forks. The rear of the bike felt really good, I didn't feel like I was getting bucked, but the forks felt like pogo sticks.
I ride mostly mid-michigan trails, evart, horseshoe, holton, and cedar creek. The first three are a mix of black dirt and sand, with some of the trails being heavily whooped out. Cedar creek is all sand, and basically all whoops.

This is definitely a start. Do you think I should seriously conside the kyb sss forks?

[Chuck78]

Sand requires fast riding... And whoops are often found in the Michigan sandy trail areas...

I actually have several sets of those 1998 RM 125 forks and one set of 250 forks.... Those are known as the best woods forks of all time to a faction of veteran trail riders.

I actually have a multi-page thread here on this forum dedicated to those forks and a hybrid shock that I built out of RM 125 parts from various years as well as a second one out of DRZ400 shock parts mixed with some RM parts...

Those forks are excellent.

Look up my Showa 49mm thread on here if you're curious, the triple clamps do not bolt right on, but with the steering stem swap and milling off that raised lower bearing seat as I have a picture of in the thread, you can swap them onto a KDX frame.

Finding a set of those that still has good chrome in the seal travel area can be difficult though, which is why I have so many sets of them... Every seller guaranteed that the chrome was good, but then most ended up having rust pits and chips...

The XR400R forks are nice but other than having adjustable rebound and less under hanging tube below the axle, and being a lot lighter, they're going to function the same as the KDX fork. In my opinion though, they are much better as a base due to the benefits mentioned. I wouldn't hesitate putting all the upgrades into those in the form of upgraded springs if needed, Race Tech Gold Valves, OEM bushings and SKF seals etc

A CRF250 2004 steering stem should press right into those after milling the raised step on the lower bearing seat

[SS109]

IMO, your sag is way off. 100mm is what Pro Circuit recommends as a baseline for the '95+ KDX chassis and I think I'm at 104-105mm with my modified setup. Static should be between 30-40mm.

Also, you say you ride a lot of whoops. The stock KDX forks suck for whoops and anything requiring speed over rough ground. They just flex too much and don't have the adjustment needed to make them work well. I'm a mid-pack B Racer and the stock forks would get me in trouble on a regular basis, due to flex, sending me off trail and sometimes crashing hard. Went to USD forks and have never looked back.

You know, I have never understood why people wouldn't want USD forks. There is a reason all race bikes use uSD forks and it's not just marketing. They are superior for numerous reasons. Conventionals just have too much flex unless you get into those Showa 49mm conventionals and then you still have to deal with the underhang which can get you hurt in ruts/rocks. Also, since they are so beefy the underhang risk is even greater on those than other thinner conventionals.

[Chuck78]

Conventionals just have too much flex unless you get into those Showa 49mm conventionals and then you still have to deal with the underhang which can get you hurt in ruts/rocks. Also, since they are so beefy the underhang risk is even greater on those than other thinner conventionals.

FYI the '96 Showa conventionals do have a fair amount of underhanging fork tube below the axle, but the '97-'98 Showa RM conventionals and the DR-Z400 49mm (but open chamber, no mid-valve) Showa conventionals both have a very minimal amount of underhanging tube pretty similar to 96-98 and 03-05 KX forks. Running a DRZ400 billet front rotor guard can smooth out that hang up point, and if you're at risk of bashing rocks, you need that anyways.

But all that said, the inverted CRF250X (or for heavy riders, CRF450X) forks 2004-2017 should swap right in with an All Balls 30x47x12 upper conversion bearing kit which includes a 3mm spacer since the frames are 15mm tall in the bearing pocket but the bearing is only 12mm tall. Or else YZ250 2-stroke triples (250 2-stroke has taller stem than 250F and 125 2-stroke) and YZ250 2-stroke or TZ125 2-stroke fork legs and a generic Chinese non-standard conversion bearing size off of AliExpress, Amazon, or eBay in 28x47x15. Valve them for initial plushness but with bottoming resistance in mind. Volume spacers will help with the bottoming resistance, if you can find a suspension company who makes those for the Showa 47mm USD forks.