Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Discussion for swapping a KDX motor in a MX frame...
EasyE#528
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Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

So I have been spending a fair amount of my winter layoff time glued to the computer "Researching" my potential path to a KDX/MX hybrid. After much thought and consideration this is what I am leaning towards a 2005-2008 RM250 chassis with a KDX stuffed inside of it. Or even crazier yet a 2010 up RMZ250 af chassis. Now hear me out I am basing this conclusion off my personal riding style and experience thats what is so cool about the whole hybrid concept is building something one off. I realize the RM thing has been done before but I have yet to see one I am really impressed by maybe there is good reason for this but I would like to believe it could be perfected upon. My reason for choosing the Suzuki is I have always been a fan of the nimble quick turning chassis it tends to suite my riding style in both woods and MX I dont mind sacrificing some stability on the straits for better turning this is where I tend to make up most my time anyways. I am sure I will stir the pot here but I just havent ever been a huge fan of the KX chassis and I am having trouble finding the heart to build one based on it just because its green and says Kawasaki. I realize a build on the KX will be much more straight forward but I feel the overall process will be similar. I also am aware I could save myself some heartache and money by just using a RM250 and adding a gnarly pipe and fywheel weight along with tuning the suspension but that just doesnt sound like as much fun. I personally have never had a reason to have a 250 twostroke or 450 four stroke being 160 ibs soaking wet, I have rode most all of them and none of them I ever cared much for unless they were de-tuned. This is why I feel the 200 just might be the perfect displacement for me, I love my KTM 150sx its the most fun I have ever had on a bike but in competitive situations there are times I am at a disadvantage against mainly fourstrokes due to the 150's lack of bottom end. I am excited to see what kind of feedback I get from the guys on the forum let me know what you think?!?! I just might be crazy enough to go through with this!
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by doctord23 »

I believe that the 05-06 RMZ250 chassis is identical to the 04-05 KXF250. I'm pretty sure they are the same bike except for plastics. So if you like yellow better than green, go with the RMZ.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Ffryno13 »

Kawasaki built the frames for 04-05kxf and 04-06rmz250 which is oddly close to the kx125s. Suzuki built the motors. 06 and newer were their own frames and motors.
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Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

Thanks guys, I am aware of the 04 and 05 RMZ/KX collaboration I thought I stated in my post I am only interested in 05-08 RM250 or a 2010 and up aluminum frame hybrid using RMZ chassis.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Tyl3r »

I believe one of the big issues that people don't want to deal with on those bikes is the fact that it has one center down tube (don't know the correct name for that frame tube), and the 05 and earlier KX frames has 2 down tubes. With the one center down tube, it ends up landing right in the way of your exhaust port on the head, making it impossible to mount the pipe unless you do some major mods to the frame. I know of at least one current build where this is being done. Major mods like that are out of my realm, so I didn't even consider that as an option when looking for a roller for mine. If you aren't a fan of the KX chassis, I have seen a couple of KTM's with the 2 down tubes with KDX motors in them.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

Tyl3r wrote:I believe one of the big issues that people don't want to deal with on those bikes is the fact that it has one center down tube (don't know the correct name for that frame tube), and the 05 and earlier KX frames has 2 down tubes. With the one center down tube, it ends up landing right in the way of your exhaust port on the head, making it impossible to mount the pipe unless you do some major mods to the frame. I know of at least one current build where this is being done. Major mods like that are out of my realm, so I didn't even consider that as an option when looking for a roller for mine. If you aren't a fan of the KX chassis, I have seen a couple of KTM's with the 2 down tubes with KDX motors in them.
I think your right that is what scares allot of people away rightfully so, but at the same time its not all that complicated of a thing to do I think its just going to take more time and of course a little more money. Not sure why I keep gravitating back towards doing an aluminum frame maybe cuz I always tend to want to do something different which gets me into trouble sometimes haha... I have a friend who owns a boat shop and they weld aluminum all the time thats what their entire boats are made of, I also know a few logging mechanics who are quite good at welding aluminum if I am lucky I might be able to get one of them to do the job relatively cheap I would just have to make a split downtube. The big issue seems to be finding a good roller suprisingly there arent very many in my area people around here seem to fix things rather than part them out. I quickly priced out buying all of the stuff to have a complete chassis off ebay and came out to be just over $2,500 just to have a rolling chassis granted theres allot of wiggle room in that.
The KTM idea would be cool thats what I am used to and I really think they have something going with their Chromoly frames and it would definately be cheaper than an aluminum build.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

Tyl3r wrote:I believe one of the big issues that people don't want to deal with on those bikes is the fact that it has one center down tube (don't know the correct name for that frame tube), and the 05 and earlier KX frames has 2 down tubes. With the one center down tube, it ends up landing right in the way of your exhaust port on the head, making it impossible to mount the pipe unless you do some major mods to the frame. I know of at least one current build where this is being done. Major mods like that are out of my realm, so I didn't even consider that as an option when looking for a roller for mine. If you aren't a fan of the KX chassis, I have seen a couple of KTM's with the 2 down tubes with KDX motors in them.

By the way do you have a link for the build you speak of?
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Tedh98 »

EasyE#528 wrote:By the way do you have a link for the build you speak of?
Probably this one: http://www.kdxrider.net/forums/viewtopi ... 11&t=18868
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Tyl3r »

thats the one. I was also thinking about this one http://www.kdxrider.net/forums/viewtopi ... 11&t=13656


off topic, but after reading through that thread again, I am wondering if using an RMZ air boot would with the KX airbox would be a good move for the 03-05 hybrids...the subframe/airbox look preeeeeeeety darn similar to my KX. He claims the carb slid right into the boot with no mods needed.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Ffryno13 »

The rmz250 boot at least the 04 is very tight. The carb also also bottoms out about 3mm too early. It works just depends on the level of finish your willing to accept
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Tedh98 »

Tyl3r wrote:thats the one. I was also thinking about this one http://www.kdxrider.net/forums/viewtopi ... 11&t=13656


off topic, but after reading through that thread again, I am wondering if using an RMZ air boot would with the KX airbox would be a good move for the 03-05 hybrids...the subframe/airbox look preeeeeeeety darn similar to my KX. He claims the carb slid right into the boot with no mods needed.
I thought of that back when that thread was active. Based on the pictures I found on eBay, the boot was such a different shape that I wasn't sure what impact it would have on the power delivery. It seems like most 4 stroke boots have a very pronounced and deliberate straight or tube shaped section. Whereas almost every 2 stroke boot I've ever seen has more of a funnel shape to it.

And ID of the RMZ boot right before it bolts to the carb looked much narrower than I would have liked.

This listing is a good example of what I was looking at several years ago: eBay RMZ boot. Especially that last picture of where the boot mates to the carb.

I ultimately figured that the designs were different for a reason and didn't want to take a chance and experiment and find out.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

Tyl3r wrote:thats the one. I was also thinking about this one http://www.kdxrider.net/forums/viewtopi ... 11&t=13656


off topic, but after reading through that thread again, I am wondering if using an RMZ air boot would with the KX airbox would be a good move for the 03-05 hybrids...the subframe/airbox look preeeeeeeety darn similar to my KX. He claims the carb slid right into the boot with no mods needed.
I have looked at this build too the guy did a pretty good job especially for being in a hurry it seemed like. I have found an 05 RMZ chassis on ebay for I think what was under $200 buy it now and a starting bid of like $80 came with sub frame/airbox, gas tank shrouds and footpegs I thought that was a steal.. almost enough to make me do the 1st gen RMZ build but not enough. Other than the added expense of aluminum and having someone Tig weld the frame the process would be the same for a newer RMZ.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Tedh98 »

For woods riding I would go with the steel frame.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Tyl3r »

I never realized the difference between the 2 and 4 stroke boots. Makes sense. Maybe the 4-stroke boot provides more air pressure, while the 2 stroke allows for volume? I'm glad you said that though, I was thinking about buying one and trying it out.

I'd also rather stick with a steel frame for the woods. From everything that I see and read, I believe the aluminum frames are more rigid, which is more responsive and better for MX. The steel frames are less rigid and have some "flex" to them (not sure what all benefits that would provide). Thinking about it, KTM's are supposedly the best new trail bikes you can buy, all of those woods bikes are steel frames. Must be for a good reason.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

Tyl3r wrote:I never realized the difference between the 2 and 4 stroke boots. Makes sense. Maybe the 4-stroke boot provides more air pressure, while the 2 stroke allows for volume? I'm glad you said that though, I was thinking about buying one and trying it out.

I'd also rather stick with a steel frame for the woods. From everything that I see and read, I believe the aluminum frames are more rigid, which is more responsive and better for MX. The steel frames are less rigid and have some "flex" to them (not sure what all benefits that would provide). Thinking about it, KTM's are supposedly the best new trail bikes you can buy, all of those woods bikes are steel frames. Must be for a good reason.
I think you guys are probably right about the steel frames I find it hard to imagine though that the majority of amatuer riders can actually feel the difference more so than the changes in suspension. I do use Motocross Action Magazine as a source of allot of my information I think their bike tests are unbiased and although they focus on MX allot of it correlates to trails. I remember reading in their tests of some of the aluminum frame YZ's and they also mentioned wishing they would handle like the old steel frames even for MX.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

I stayed up late last night reading a thread over in Vital MX where a guy put a KTM SX in a RMZ chassis very good build, I read the entire thing to try and get a feel of what I would be up against. Reading through the thread was a bit of a reality check, I wasnt thinking that a guy would have to modify the radiators to fit with the new motor and lots of other little things that add up. It seems totally doable but is it worth it? Probably not. I have good friends with the right skills that could help me put it together but then I realized it wouldnt really be my build so much then I would be essentially having multiple people build the bike for me ha. It was then I realized I could build on the steel frame and still have something completely original I dont need the headache of an aluminum frame just for the "wow" factor. Sorry it took me so long to come around hahaa.

I originally was thinking I would build a bike from scratch buing parts off ebay but now I kinda feel like it would be best to get a bike that I could atleast ride around a little to test out the chassis so I would have a more edjucated idea of what changes I wanted to make. Problem is I am having a hard time finding a good deal on a KX gonna keep lookin though and I have found a few RM 250's if I did decide to go that route.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Tedh98 »

Buying complete bikes is the way to go. You'll use more parts off the KDX than you realize.

A RM250 would work, but the KDX engine will look "more at home" in a RM125 chassis.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by Jaguar »

what kinda riding you want to do with it?
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

Tedh98 wrote:Buying complete bikes is the way to go. You'll use more parts off the KDX than you realize.

A RM250 would work, but the KDX engine will look "more at home" in a RM125 chassis.
Do you think it will fit? I havent looked into it but I was just assuming it wouldnt fit in the RM125 chassis with the external tank unlike the KX. I know my 2000 RM125 the tank comes way down and hugs right against the cylinder but maybe the newer ones are different.
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Re: Call me crazy but.. Suzuki RM250/RMZ kdx abomination

Post by EasyE#528 »

Jaguar wrote:what kinda riding you want to do with it?
I want to build a purpose built woods bike for the tight technical single track I ride in my area and plan to use it for cross country and harescramble type races also, would like to do some endurocross for something different I have done a couple but was horribly un prepared haha. The more I look into the KDX200 powerplant however I feel like there is some potential for it to be a good Motocross bike in the MX chassis so we'll see.. Right now I want a woods weapon though.
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