Not Just for the KDX . . .

[Jeb]

I figure this is worth mentioning even if it's not for on a KDX.

More like an RM250. I got the bike for the power and the feel. But the power was a shade unruly so I smoothed it out with the heaviest flywheel Steahly had and that worked. Except it took away a little more of the "nervousness" than I ended up wanting. I like some of that snappy, twitchy feel. I was thinkin' of a lighter flywheel weight when I decided to try Ron's stuff.

38mm carb bored to 39mm with the divider plate and some slow-circuit magic. Asked for a leaner slide and one of those gold twisty thingys for fine tuning. And the cyl head went for revamping too. Some brand new Boyesen dual-staged (power) reeds to wrap up the package.

First rate customer service as always, shipped out New Year's Eve, back this past Friday afternoon.

Got a chance to ride it right before dark, in a light drizzle, been raining for days so it's yucky. Fired her up and rode it anyway.

BIG power. It's cold enough for things to tend lean so the jetting actually seems pretty darn good right off the bat. Still managed to get decent traction as long as I went gentle-like on the throttle, so I didn't tear up TOO much yard.

Decided to hit the service road (paved) and that gave me a taste of what the thing is like wide open - GOO-OOD GRAVY MAH-REEE!

I just might have gone too far!!

[fuzzy]

SWEET!!!! Been curious about that. Ski had inquired for his KX250, and RB didn't think it would do that much. Even more interesting w/ the 39mm bore as I'm a fan of a 36 on a 250. How is the slow paced, off idle performance (luggability)

[Jeb]

I'm not sure why the KX250 would be much different. After I noticed that Ron had the 38mm carbs on the "What's New" page on his website I emailed him to ask and the replies were positive.

I know where you're coming from on the smaller carb because that's where more low end comes from. I think the new KTMs, for example, have smaller carbs.

Saddle time with the changes thus far is literally a warm up and maybe 10 minutes ride time (it was literally dark when I pulled into the garage), but I see improvement everywhere. Throttle response and low end wasn't bad to begin with, frankly, and what I was looking for was some of that hit-the-throttle-hard hold-on-tight boom that was attenuated with a 13oz FWW (which I really needed for my type of riding). Guess I wanted to have my cake and eat it too, but I like the hit as long as it's predictable.

But the off-idle response was awesome. I had to close the A/S a little to get rid of a slight bog but afterwards it was just fine. Most of my back yard is sloped and at the very end or bottom it's a fairly steep drop (far too steep for a riding mower for example). So my tests were: 1) Start off in second going uphill - no sweat, only thing was throttle control so the back wheel didn't break loose. Next was the same in third, again no sweat. The bike lugs JUST FINE. 3) From a dead stop start at the bottom of the steep section in 2nd. The first time I thought I was going to stall and jabbed at the clutch and found myself on the back of the seat coming over the crest of the steep section on the back wheel, almost looped it. The second try I anticipated better and decided if it was going to stall I'd just let it but it DIDN'T, it just "WUHHHHHH" until it reached the top where the RPMs started coming back (and then there goes the front wheel again).

Then the wilder stuff 4) Get on the throttle coming uphill toward the house - I had to stop because the ground is too soft and I was tearing up the yard. 5) Get on flat ground with reasonable traction and open her up. I never REALLY got here wide open because the paved service road was wet and I didn't want to risk going down. I did manage to rip off 3 gears like it was nothing before I slowed down. VERY stout pull. I got full throttle once right at the end and I decided to wait until conditions were safer, the thing is freakin' scary.

Overall: improved low end, very luggable, controllable power (gotta mind that throttle though). I suppose that plate he puts in gives you the small-carb attribute. Mid-to-high power, what I sampled will remove whatever cavalier attitude I have while on this machine. Quicker revving, very race-bike-like, even with that heavy-ass flywheel on there. I was nervous-like when I got off the thing.

I can't wait to really ride this thing. Then I can actually tune the thing! Like powervalve, jetting, etc. I'll bet there's more to be had.

Yes I'm ecstatic, of course we've learned to expect no less from Ron's work. BTW I got the race gas shaped head, figured might as well go all the way!

[fuzzy]

Nice...

[Little Jeff]

Ron Did his magic to my '02KTM300 carb. He just bored it out and put the divider plate in it. Real nice power everywhere.
Little Jeff

[canyncarvr]

So....from the 11th to now (the 27th) is a LONG time.

What's new?

[Jeb]

Weather's been bad here, very cold and snotty or rainy. I couldn't take it anymore and rode it a little more this past Sunday evening. Cold enough not to want to go very fast, like your hands freeze if you pick up any speed.

Anyway, the power on this thing is REALLY stout. Remember the first time you rode your KDX after the mods and thought, "Wow"? Like that. If you've ridden a 250 before you have some idea of what they do. Amplify that.

From idle, in neutral, if I just barely crack the throttle - enough to move the slide even slightly - the RPMs start picking up. If I whack it open the RPMs respond more quickly. There's no telling what the thing would be like WITHOUT the flywheel weight, probably a bit on the insane side. Which means I'll have to at least try it some time.

After I ride it more and fool with the jetting and the powervalve setting I'll give more details but the weather has severely limited my riding, MUCH to my chagrin.

[canyncarvr]

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Weather's been bad here, very cold and snotty or rainy.

Yeah. Who wants to ride in that kind'a crap?



...wuss



I mean...you'd have to be stoopid to ride in bad weather!!



Not that there's any reason to get all frigid about it!

[2001kdx]

An interesting read Jeb. I too am suffering from the cold, I haven't wanted to mess with my bike, it's rarely above 35 here this time of year. Good to see Ron has improvement for our Zooks as well, although, to be quite honest, what I remeber from last fall, my RM needs no more outright power. With the Fatty pipe on, the low end is pretty decent, the mid-top is just so strong, I'm happy.

On a side note, the RM with a PC platinum 2 was less impressive. Much flatter top end, slightly weaker mid, but with stronger torque and power down low. I believe you're using the stock pipe..... I don't recommend upgrading. The stock pipe is... well, got a little bit of everything it seems. Revs out better than the PC plat 2, pull about as hard off the bottom as the Fatty.

Glad to see you like the defect over to the RM. I like mine a lot, but I have a strong feeling soon I'll be readying another bike for the upcoming season, a bike with 15 or so less horsepower, 20 or so lbs heavier, a slightly smaller rear wheel and an extra gear in the tranny..... Hell, might even have a tool bag ;)

[Jeb]

And I suppose that bike is green in color! Nuttin' wrong with that . . . why the switch?

[2001kdx]

Not exactly a switch, but an addition. Won't be selling the RM, it's too foolish. I'm looking at having one bike for track, one for trail. I would have liked to have the RM for Harescrambles, but a suspension revalve is already gonna cost a few hundred dollars, and the local craiglist has some KDX's for $700-900.

[saddletramp]

Two bikes is the only way to go. I can trail ride my CR but it's just not the same as the KDX. The CR is geared to tall for one thing and takes alot of clutch work when the trail gets rough. I know I can spend a bunch on mod's and stuff but it's much easier to have the KDX, for the money it's the best trail bike made.

[Jeb]

I really enjoyed the 220, but having ridden this RM I'd have to say there would be no point in going back in my most humble opinion. The power is something to respect but the nimbleness and braun make the bike.

But gosh it would be good to have two bikes! If I had a choice of a second one I'd go for a 525xc with one of those grandma auto-clutches - wouldn't be a hill I couldn't conquer.

Weather's warmed up considerably . . . won't be long before I give this thing a real whirl.

[Jeb]

Got a solid 3 hours on a local farm - fields, woods, trails, hills, with plenty of mud. Dropped the pilot a size.

The power with the mods - and with the flywheel weight - is very, very solid and unmistakably two-stroke but builds at a reasonable rate - if you don't get crazy with the throttle. It certainly wasn't lacking for power to begin with, but now it's so very stout.

Here's a perspective - the fellow that I was riding with today rides a KTM XC450, he's not a stranger to power, and he thought it was a bit much and said "I think it has more power than my 450". His words. He said it seemed "faster" than from before the mods.

I have to concur, but his observations were based on screaming it across some fields and something he didn't get to do was motor up one of the muddy hills, on the RM, we hit on his property to feel the bike's power as it pulled skyward. He did get the chance to HEAR it though.

The steepest hill was also the longest. Muddy enough that you were spinning as you went along, just tacky enough to get some bite if you were careful. It has some momentum-ruining twists, turns, roots . . . and the moisture.

I didn't make it all the way up the first time (totally operator error) but I had the biggest grin on my face because of what it did on the way up. LOW RPMs and enough clutch to keep it from stalling . . . and it kept on going. I actually lost my composure when I grabbed too much clutch and the RPMs soared and that's what started the stall (not to mention some of the saplings I tried to tear through ). But I knew I had what I was really hoping for.

It took a few shots because it was very much a difficult hill - for me - to climb. When I made it the RPMs never got above 4k or so. John was at the top of the hill (he made it look like child's play but he's quite good) and said he thought the bike was going to die the entire time!! 2nd gear all the way with stock gearing, and the powervalve is NOT open at those RPMs, I'm quite sure.

Sound familiar?

I am absolutely blown away. All of both the sizzle and grunt wrapped into one motor you'd ever probably really need. This bike always had the power to get up that hill but it would be much tougher, in my opinion, to get everything just right to make it.

This post isn't about an RM250, it's about a fellow that knows how to squeeze out that kind of performance out of a motor.

I'm convinced he could do the same for any motor that could within reason be conceivably modified in such a fashion.

[Jeb]

Rode again today for a few hours.

The power never gets too crazy - that's the flywheel weight - but gosh you better be holding on if you're twisting the throttle, especially if you've already got some RPMs going . . .

and SPOOGE!

Sound familiar!?

The RM250 has drain hoses the allow spooge to drain from the exhaust valve and subvalve. It was muddier today so I spent my time lugging it around in 2nd and 3rd. So the stuff was DRIPPING from one of the hoses. And, of course, coating the side of my yella fender was the spooge comin' out da pipe. Still, I'm wondering if I could drop the pilot another size (down to 42 right now) and start fiddling with the powervalve setting, maybe get it to open sooner.

[canyncarvr]

Keep fussin' with it! Sooner or later, you might get it to run as good as that tired out 'ol 220!

..kidding about that part..sort'a.

It does just show to go 'ya, though. Give a guy a bike..don't matter WHAT it is or HOW it runs..there's must gott'a be more!

[Jeb]

Went riding in the icy slop yesterday, a place called "RedBird", public land (national forest) in south-east Kentucky. Spent the better part of the day lugging it in 3rd with some clutch work to minimize slipping too much and it seemed to work. I followed a couple of racer-types around and did my best to keep up with them but they are quite simply better riders than I.

After half a "loop", about 35 miles, we stopped at a store and I threw in the towel - between one particular muddy, rutted hill (there were several but one in particular) and trying to keep up with them I was DONE. The last 5-6 miles or so I was so wore out that I started to get sloppy and found the RM to be not-so-forgiving, wishing I was on a KDX at that time. Nonetheless, the ability to lug around in 3rd on those sloppy trails was something that would have been very difficult pre-RB, no question.

I noticed that there was more spooge on the rear fender. I wiped it off best I could. In order NOT to go the other half of the loop I had to ride a two-laned paved country road about 17 miles or so back to the park ranger/parking area. When I got there, very relieved to be done, I noticed the NEW spooge paint job on the back fender. When I got home 3 hours later, having driven 3 hours through some heavy winds/rain and a bit of snow, I snapped this photo of the RM in the garage.

Guess I need a black back fender

[canyncarvr]

What's the back of your hemet look like? Hhhmmmm?

No sense wiping it off. Not during a ride, anyway. It'll just grow back!!

[Jeb]

There's a little on the back of my chest protector, jersey, etc. Makes me wonder what someone on a bike behind me would end up with.

The mods really made a difference for the conditions encountered.

Of course there's more to be had, I just know it, so I've got a few differently profiled needles coming to see what that more might be. When I'm slowly rolling on the throttle things tend to be a bit crackly at midrange (not so, however, when under load where the engine note is smooth and the pull is stout). Gotta try more slack on the powervalve tension so it opens up earlier to see what that does, too. On deceleration with no load the bike runs uneven-like, almost sounds like someone stuck a potato (potato? potatoe?) in my stinger. But open that throttle and the kick is so THERE.

I did some searches to see who else out there has the mods and so far not too much. The Gas Gas crowd likes Ron's stuff, though.

An FMF Gnarly or Dynoport "Big Volume" pipe may be on the horizon.

Maybe some Northern Californian with a KX250 will give the mods a whirl.

[fuzzy]

Nice reports. Different needle may be the ticket. IMO I'd me more inclined to think having the PV open later would be more desireable. That's where your low-end is coming from (PV Closed). I've often been curious as to how I'd like a 250 with the PV permananetly shut.