I told myself I was just going to ride the bike this Summer. Next thing I know I'm buying an SRX600 swing arm from WeBike. Here we go again
To be brief, I'm going to install an SRX600 swing arm (looks very similar to a Radian) and run FZR600 rear wheel with associated caliper and bracket. Same as a TZR 250 as I understand.
For the front end, and for sourcing simplicity, I'm thinking a full FZR 600 front end is the ticket. I imagine I can source the bearings and spacers from AllBalls in order to make that work.
I read the fork swap sticky, but it was heavy emphasis on GSXR 600 front end, mixed with a few USD conversion notes, and some case splitting advice for good measure :vroom:
I believe Mark had an FZR600 front end on an RD some years ago. I'd like to know if anyone has converted their front end to FZR600, and I'm curious to hear your thoughts about that process. I'd love to see pictures, but I'm unsure if this platform allows that as a "commenter." This would allow me to run FZR600 wheels front and rear, which is the look I am after. Thanks in advance gents
I'm sorry that I don't have specific advice, but it sounds like an excellent idea! :thumbs:
i still have it. the stem is the right size but too long. swap the rd/fzr stem, mod the steering stops and its good. the forks stick up about 2" thru the tree. however, theres a year or 2 fjr 600 fork tube that swaps in thats shorter. i have those in mine but can not remember the year
also, i have a narrowed at pivot fzr400r aluimum rear swingarm, modded to take twin shocks. i know, blasphemous but.. dont care. its 4" longer than an rd arm.
Ahh good to know. Pressing a new stem is probably the safer option. I debated on an 85 RZ swing arm (steel) and welding shock mounts, and shaving the pivot tube. As I understand, the SRX swing arm is near plug and play.
Couldn't I counteract the length of the FZR tubes by extending the rear shocks, to maintain some sense of geometry? While I understand rake and trail, my head starts to spin when it comes to mixing parts for a different frame.
Quote from: m in sc on June 02, 2026, 10:28:49 PMalso, i have a narrowed at pivot fzr400r aluimum rear swingarm, modded to take twin shocks. i know, blasphemous but.. dont care. its 4" longer than an rd arm.
I wanna see what this looks like. I think that's awesome.
some but then its like an adventure tourer . however, it gives a good place to mount clipons.
I have a fzr front end in my RD as well. I stuck with spokes. It's an easy conversion and well worth it.
Damn, Mark! You spent a little time piecing that one together! I have seen a picture of this bike somewhere. Only other water cooled conversion I've seen was by a guy on FB on the west coast. Is there a build thread for this bike? I'd love to dig into that.
Chris, did you also press an RD stem into the FZR lower triple? Seems like there is an extra inch or so on the FZR stem.
lol. you probably saw robakuns r5cw an lc motor , id guess. sweet bike, mines an aircooled w an lc topend. i mean, its been around in various forms sine 2004. this is the final, there was a full build thread on the old site, i think i did an abridged one here in haus of projects
It was most definitely an RD bottom end. I remember talking to him about the electric water pump. Now it's bugging the shit out of me. I know I took screenshots damnit!
ah yeah ive seen pics of that. there's an adapter plate i think to run the banshee cyls. pretty gnarly setup. at that point, id look for a banshee lower end...
Ive done an elec water pump conversion as well, was pretty easy, pumps hanging off the front loer frame tube. ths was 16 yrs ago, this was the original lc topend on my bike, i had scott clough port the next set, (which i still have) and the latest set is from John ritter and it is just sick! lol. theres some old pics and how i did it below. fwiw this is a totally different bike than the white one.
this was wayyyyy back. . fwiw, you can get an lc top end, bolt on to an aircooled at webike. i know it says rz, buts these are nikasil coated rd350 lc cyls, i have actually held a set of these in my hands, nice quality https://japan.webike.net/products/25625106.html
You're right, I did ask him about the banshee top end, and he did fabricate an adapter plate.
Surely you need custom work to the crank with different con-rods in order to make an LC top end work, right?
(I'm hoping you tell me it's much more involved so I don't buy more shit that I "dont" need.)
direct bolt on with longer studs. the long lower case atuds are long enough. you can use ac headbolts. the pipe flange is wider like an rd400. bolts on. that blue bike was a 75 250. widened the stockbpupe flange holes, added 1" length to end of headpipe at muffler and it flat out ripped. atuds and headbolts available at yambits. just sayyyiinn
Ok...so you're telling me, that if I were to pull the cylinders off my bike, I could throw on some LC cylinders & heads, and the only thing that I MIGHT have to change are bottom end studs?
Of course I'm not asking about plugs, radiator, timing, jetting, water pump, etc. Simply the act of taking and LC head, and sticking it on an RD bottom end.
No good can come of this.....
We've gotten way off course, but I like it.
the longer lower case studs are what i used to bolt the cyls on however.. that was 20 yrs ago. now..
https://yambits.co.uk/rd350lc-cylinder-head-stud-p-84147.html
ac head bolts will work buuutt...
https://yambits.co.uk/rd350lc-cylinder-head-nut-p-77342.html
I stuck with the FZR stem but I shortened it. I converted to tapered rollers to accommodate.
Nobody tell him about TZ cylinders; he's in enough trouble already :lol:
the 250 ones not great on the street. 700 ones however... but... imho not worth it comparatively
Quote from: sav0r (CL MotoTech) on June 03, 2026, 11:19:18 PMI stuck with the FZR stem but I shortened it. I converted to tapered rollers to accommodate.
Thanks, Chris. I have tapered roller bearings with the stock stem currently. Looks like those same bearings will work for the FZR stem (25mm top 30mm bottom). Looking forward to getting parts in hand.
well. sort of. the taper on the stem gets wider before the bearing can seat. so you need to shorten, replace, or space it. you'll see when you have them both in your hand. i turned mine down on a lathe but still spaced the bottom beating race up on the stem a bit. i still have the fzr stem in, but if i were to do it again id swap it out w an rd one
700 you say??? :devil:
I feel like I could probably buy an RZ engine for what that would cost. Although, its TZ cylinders would be a better conversation piece.
I thought my dirt bike buddies were motorcycle nut jobs....until I ran across vintage 2T guys...
one 700 cyl is 350cc so...
Chris & Mark, if anyone else who's done it. Can you guys share some pictures of your FZR converted front ends? I'm most curious about how far the forks are above the top clamp. I'm also interested in the clip-on situation, or if you used stock (FZR) clip ons.
Rusty, grimy treasure from today's haul
heres a pic from 2013 . you can see how far the forks were over the top tree. with astock tree its even more, i made that one and it doesnt drop like an fzr one does stock. yes, you could put the clip ons on top. 2nd pic shows the stock fzr tree w clipons above it. this was from like 08 0r 09.
I run mine very much the same as Mark, specifically his second photo with the FZR upper looks nearly identical to how I run mine. It would be cool to machine a plate style upper triple, could drop the clip ons some but still have them high-ish. Maybe I will do that once we get through the race in July.
Cognito Moto has RD400 conversion stems for various front ends. ...triple trees etc. Seems to be a primary focus for them along with hub conversions.
A bit pricey IMO, but billet parts usually are. 350/400 steering head dimensions are the same so the stems should be interchangeable. From my limited discussions with them they have the information to match basically any stem/tree or hub combination for custom orders and a flat rate custom stem price.
https://cognitomoto.com/search?q=Yamaha+RD+400+fork+conversion+parts&options%5Bprefix%5D=last.
IR8D8R
Thanks guys. I appreciate the feedback/pictures. In my mind, I envision the finished product looking like the second picture. I have a left clip on, just need to source the throttle side.
I have a spare RD stem. As Mark suggested, I'm going to have the FZR stem press out of the triple, and the RD stem pressed into the FZR triple.
I believe all I need is new set of RD tapered bearings and it should be plug and play with the RD stem pressed into the FZR triple. Swing arm is next on the hit list
you'll just need to mill in the sides, an thrn countersink the bearing in the arm a bit. i dont remember the actual dimensions but 6mm rings a bell...?
I look forward to pulling it apart. It's an SRX 600 swing arm. Rough measurements between the stock pivot tube with bronze bushings, and the SRX pivot tube, it's so damn close. Hopefully digging in within the next few days.
Did someone mention TZ top ends on air cooled cases? Back in the day, TZ cases used to wear out and replacements were not always available, so racers took to modifying RD cases to take the TZ crank arrangement. Others bougt TZ top ends and fitted them to RD bottom ends.
This is a set of RD cases with a TZ crank and water pump with RD400 transmission and 40900 (64mm bore) top end with bigger reeds. 40970/40971 66.25 TZ750 C/D/E top ends also drop straight an to an Air cooled bottom end.
I forgot how to insert and image. I'll be right back as soon as I work that out.
I worked it out :whistle: