74 RD350 - Anything more than 2 strokes is a waste

Re: 74 RD250 - Anything more than 2 strokes is a waste

I did a little more demolition today. Removed the battery tray, air filter mount, and all of the other mounting tabs. I was also able to slide off the rear hoop with a mix of cutting, grinding, and air chisel to keep the existing frame rails in place.

Re: 74 RD250 - Anything more than 2 strokes is a waste

I put a 2008 EX250 swinger on my DS7 but put it right side up and used the alloy wheels. It worked out pretty good. If you do the shock on top, make sure that you have room for the air filter. I got all of the bits and parts for the conversion cheap also but when I went back and added all of the items that went along with it, it didn't seem cheap anymore.
You'll need an offset sprocket also if you go with the newer wheels but make sure you get a 520 since the 530(depending on amount of offset) will hit the clutch actuator.

Re: 74 RD250 - Anything more than 2 strokes is a waste

It's been a while so I figured I owed you guys an update. I've been in and out of interest with the bike as well as having spent last week at the Amateur National MX Championship in TN.

I got the engine and trans completely torn down and inspected. I found a nice layer of what I'd call "extra cut lapping compound" between the two inner crank bearings, which, after feeling the bearings rotate, is the insides of said bearings grinding there way apart. So the crank is junk. HVC Cycle sells a rebuilt crank for $400, which seems to be a fair price. I'll likely go that route unless one of you fine gentlemen chime in with a good crank for sale (PM me). My only concern is that HVC Cycle seems to offer 2 options - one for the 350/R5 and one for the 250/DS7 - do you guys know what the difference is?

I also scored a set of GSXR750 forks/triples off ebay for cheap. I spent some time yesterday determining how thick of shim needs to go under the lower bearing as well as grinding/sanding off the steering stops, ignition switch hole, and casting marks.
I'm going to keep pushing forward with mocking up the front end and work my way to the rear suspension.

Also, I'm really struggling to come find ideas on what hubs/wheels to use. I'd like to run dual front rotors on a set of spoked wheels, but I can't think of any stock to start from. I've been shying away from an MX style setup but may have to go that route. I"m guessing I'll be after something 18x2.15 for front/rear rims.

As always, I'm open for any feedback or advice. Thanks for the help.

Re: 74 RD250 - Anything more than 2 strokes is a waste

Did you race loretta's or were you there with a rider?

Re: 74 RD250 - Anything more than 2 strokes is a waste

I'm going to be watching this build until I see smoke...

Hey a cool option on the front wheel set up is use Cognito Moto's GSRX spoked replacement hub.
Uses all the stock bearings, bolts directly to the fork you already have,
and you can lace it to a 17"or 18", or what ever you prefer.
I recently started dealing with them, and the service and quality is top notch!

Re: 74 RD250 - Anything more than 2 strokes is a waste

clem said:

Did you race loretta's or were you there with a rider?

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I didn't race - I met up with my buddy from NY that used to race pro. I had traveled to the nationals with him from 2007-2009 to wrench so we got the band back together for one more show.

Re: 74 RD250 - Anything more than 2 strokes is a waste

Cool man. If you still need that manual I can send it to you when I get to work tomorrow

Re: 74 RD250 - Anything more than 2 strokes is a waste

After traveling back to NY last weekend for the Unadilla MX national, I ended up getting super sick and stuck on the couch for 5 straight days. I finally felt a little better today and got out to my garage. I put the GSXR750 front end on the RD, which was straight forward. Now, the issues are finding a set of wheels, brakes, and wheel bearings to adapt the front axle to a wheelset. I'm still trying to run a spoked wheel, but that's going to set me back $1000. I really like the Ninja 250 setups that Clem and some others have run, but I'd have a hell of a time adapting a 43mm wheel bearing bore to a 25mm OD front axle. Do any of you know of a resource for wheel specs? Any ideas on what the RD400 Mag wheel bearing bore is? XS650? I'm probably going to pull the front wheel off my moto bike to see what the wheel bearings in that are, and work from there to determine what supermoto wheels could be adapted. I know that the Cognito hubs are a perfect solution. The $300 price tag (which is fair) has me reluctant to pull the trigger just yet.

The other thing I did was finally make a decision on what to do with the rear suspension. I think the smartest monoshock think to do is to graft in the EX250 linkage. My EX500 shock is of no use now, so I'll try to find a good GSXR rear shock.
I ended up ordering a second swinger with linkage, rear axle, and chain adjusters earlier, which turned out to be much cheaper than sourcing the linkage, axle, and chain adjusters separately. A few other guys have completed this swap and much of the issues have been worked out. I feel like a bit of a dirtbag riding on the coattails of some of your guys hardwork, but hey, that's what these forums are for right?

Re: 74 RD250 - Anything more than 2 strokes is a waste

Spoked wheel and front axle issues may be resolved. Rear axle issues forthcoming...

Stay tuned...

Re: 74 RD250 - Anything more than 2 strokes is a waste

Well, I wouldn't be upset about riding any coat tails but since you got to go to loretta's and Unadilla I can help but be a little pissed. All jokes aside, the spokes will look rad. It sucks for us down South since they cut Gatorback and most recently Freestone. I'm hoping they bring something back to the Southeast next year.

Re: 74 RD250 - Anything more than 2 strokes is a waste

clem said:

Well, I wouldn't be upset about riding any coat tails but since you got to go to loretta's and Unadilla I can help but be a little pissed. All jokes aside, the spokes will look rad. It sucks for us down South since they cut Gatorback and most recently Freestone. I'm hoping they bring something back to the Southeast next year.

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Should I mention that Muddy Creek is 75 minutes away and I hit up Budds Creek as well this summer? I made the trip from central NY to the Freestone national back in 2009. I found out that 26 hours each way is the absolute limit for a moto trip.

Re: 74 RD250 - Anything more than 2 strokes is a waste

You had to rub it in! I'd like to go to either Millville or Red Bud at least once in my lifetime.

Re: 74 RD250 - Anything more than 2 strokes is a waste

I got to get in on this too, I live 25 miles from Glen Helen and have ridden there many times! Been blasted on the track by all the top riders

Re: 74 RD250 - Anything more than 2 strokes is a waste

I'm pretty pumped up about this project again. I was able to score a set of supermoto wheels for the RD for a killer price. Excel rims laced to excel pro wheels with the modular sprocket carrier design. I'm probably going to grab the hardware necessary to throw them on my KX250 as well.

The F and R use 25x47x12 wheel bearings so I have a large number of options. The front slides right over the 25mm GSXR front axle - just need to measure up and machine some collars. The rear may be a bit trickier getting the drive sprockets to line up, but we'll cross that bridge when we get to it.

I'm really happy I held out to find some spoked wheels. I had my finger on the trigger ready to grab a set of RD400 mags off ebay over the weekend. I also went to the steel shop today to get what I needed to gusset the frame, add a lower linkage mount and an upper shock mount to the frame, and enough 20ga to hack away at a seat/cowel. Hopefully I can really get the momentum going now that I have some parts to work with.

Re: 74 RD250 - Anything more than 2 strokes is a waste

johnu said:

I got to get in on this too, I live 25 miles from Glen Helen and have ridden there many times! Been blasted on the track by all the top riders

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It's pretty cool to be on the same track with those guys and see their speed and lines first hand. Some of my favorite racing memories are being lapped in collegeboy and +25 motos...

Re: 74 RD250 - Anything more than 2 strokes is a waste

jchek779 said:

It's pretty cool to be on the same track with those guys and see their speed and lines first hand. Some of my favorite racing memories are being lapped in collegeboy and +25 motos...

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Nothing like having Josh Grant or Mike Alessi Jump over you ( Also ridden supermoto with Nicky Hayden, Bostrom Bros and Max Biaggi (

The bike is looking great btw. I like your choice for the swingarm.

Re: 74 RD250 - Anything more than 2 strokes is a waste

The closest that I got was Tyler, Tx Swan MX Pro challenge. They would always get a few local pro's like Robbie Reynard, Kevin Windham, Andrew Short and Trey Canard. That track should have had the National way before Freestone but that's a matter of money I'm sure. Heck, I rode alot of the tracks that Windham rode growing up but was never there on the same day. It might have been better that way I wouldn't get my feelings hurt as bad. Lol

Re: 74 RD250 - Anything more than 2 strokes is a waste

I made some progress over the weekend on the bike. I was able to tack weld the Ninja frame-side linkage mount and start gusseting the frame. I'm by no means done, but want to get everything dialed in and in position. Then I'll box in that mount on the frame.
I need to widen the pull rods out in order to accomodate the shock spring and am in the process of removing material from the lower shock clevis to fit over the linkage shock mount. A coworker had a tig welder sitting in his apt without a 230V outlet, so he's letting me "store" it in my shop.

My next steps are to relocate the rear frame uprights to where I want them, and start with the upper shock mount. Any ideas on how to decide on ride height? I'm planning to get the wheels on the bike and use my trans jack to figure out how high the bike should sit - I'm open to learning a thing or two about bike setup if anyone has a recommendation.

Re: 74 RD250 - Anything more than 2 strokes is a waste

Check out the rocker arm/bellcrank position on the Ninja 250.

Re: 74 RD250 - Anything more than 2 strokes is a waste

clem said:

Check out the rocker arm/bellcrank position on the Ninja 250.

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Clem, for whatever reason, today was the first time that picture of the Ninja 250 linkage showed up on my screen. I'm a little bit surprised that the frame side link is in the position it is....Anyway - A girl I work with rides a 250 Ninja, I asked her to measure the static angle of the swingarm from horizontal. It'll give me a starting point. I'm only tack welding things in place for the time being. I'll probably put the swingarm/suspension through the full travel range to get an idea of where my rake/trail curve is, linkage ratio, and rear wheel travel.