1975 Yamaha RD350 fork swap

[4schizzle]

Good Morning all!

New to the forum.  Have been looking at old posts but can seem to find exactly what I'm looking for to help with my new addition. 

I recently bought a 75 RD350 without a front end.  I am looking to build a dirt track racer and was wondering what fork swap would be the easiest/best to do on an RD.  I want to run a 19" spoked front wheel and have been searching the forum. 

I don't need a front brake.

From what i have learned from the forum and others.

R6 pre inverted is a common swap.

97-00 GSXR600 will also work. 

I was on all balls racing fork conversion website:
https://www.allballsracing.com/forkconversion/

And determined that both the RD and GSXR have:
TOP bearing : ID 25   OD 48  WIDTH 13
BOTTEM bearing: ID 30  OD 48   WIDTH 12   

I also know that the GSXR has a 25mm front axle which would allow me to use the front wheel i was looking at using.

Was wonder what fork swaps have been done and what work is required to complete the swap. 

Thanks again,

[85RZwade]

I can tell you that I am putting a '97 GSX-R600 front end on my '75 RD350 and bought those bearings from All Balls. The bearing kit came with two spacers and a dust seal; it's too early to say for sure, but it appears to be plug-n-play. Steering stops will need to be modified, but everything else appears to be falling into place.

[4schizzle]

Thanks 85RZwade.  I read your post on here.  I was also talking to a guy that has an RD250 dirt tracker.  He has 2006/2007 GSXR 600 upside down front forks on his RD and he also said that the conversation was basically bolt on.  He stated that he did have to make some spacers for the top as the stem is longer.  I want to go with the 1997 due to the 25mm axle. 

[rodneya]

When I put USD forks on my 73 I just used 2 RD bottom stem bearings and made 2 spacers out of the old bearings that came with the new stem.I make new steering stops, but Cognito Moto makes a sweet adjustable set. new ignition switch and instrument brackets and add a magnetic pickup for my digital speedo as there is no cable drive in my setup.

Why do you want to run a 19"front?

[4schizzle]

rodneya,

They only sell dirt track racing tires in 19 inch.  However you could go with an 18 and run a dunlop k180, but i like the look of 19's front and rear.  What USD forks did you use?

[m in sc]

i used an fzr600 one, same stem as an r6. i also used spacers on mien to make it work way years ago though. have you considered ktm forks? some if the indian guys have used them i think.

[rodneya]

rodneya,

They only sell dirt track racing tires in 19 inch.  However you could go with an 18 and run a dunlop k180, but i like the look of 19's front and rear.  What USD forks did you use?

07 GSXR 600 / 750 forks with a spoked hub from Cognito Moto. Currently 18", but probably going to switch to 17" next year when my other project is finished.

[4schizzle]

i used an fzr600 one, same stem as an r6. i also used spacers on mien to make it work way years ago though. have you considered ktm forks? some if the indian guys have used them i think.

m in sc.  Are you talking about the current indian twins using ktm forks?  which ktm fork are they using in the indian?  off a dirt bike or one of their street models? 

Just another question.  The rd 400 swingarm is longer correct?  Does anyone know how much longer than a 350 swingarm? 

Or are there any good swingarm swaps? 

I am also planning on running a 19 on the rear and from talking to another guy the 350 swingarm needs to be extended at least an inch. 

[m in sc]

400 swingarm is an inch longer.

the ktm forks ive seen used are 390/200/125 duke forks on the indian rd's(radjoot). I had a 390, the forks would be great for an 'offroad' version of an rd. I man, anything can be made to work just depends on the fabrication ability. 

[4schizzle]

400 swingarm is an inch longer.

the ktm forks ive seen used are 390/200/125 duke forks on the indian rd's(radjoot). I had a 390, the forks would be great for an 'offroad' version of an rd. I man, anything can be made to work just depends on the fabrication ability.

That makes sense now.  I was thinking the new Indian twins.  I'm an offroad 2 stroke guy but new to the street bike 2smokes.  What you said is true, you can make anything work if you have the ability. 

That really helps knowing the 400 is an inch longer.  Thanks

Well i got the 97 GSXR fork off a friend and the bearings are ordered so we can see how this goes.

I read on economy cycle that when you switch the steering head from conical to tapered rollers the outer races are a little higher.   

Thanks again for all the help. 

[4schizzle]

rodneya,

They only sell dirt track racing tires in 19 inch.  However you could go with an 18 and run a dunlop k180, but i like the look of 19's front and rear.  What USD forks did you use?

07 GSXR 600 / 750 forks with a spoked hub from Cognito Moto. Currently 18", but probably going to switch to 17" next year when my other project is finished.

rodneya,

I see that both 07 and 97 GSXR steering head bearing are the same size.  upper: 30-48-12 lower: 30-48-12.  So you used the RD conical bearings on the top and bottom.  I am going to check out Cognito Moto.  Thanks again.   

[4schizzle]

Next i need to split the cases and get it running.  Do i need a tool to split the cases.  I have the tool for a yz 125/250. Do i need to make a new post for this?

Thanks again all!

[rodneya]

Top and bottom split cases, so no special tools necessary. Just patience cause they can sometimes be stuck together pretty well.

[m in sc]

make sure you pull the bearing retainer plate off behind the clutch basket before you split the cases.  .02

[Striker1423]

oh gawd Mark no kidding, one good pry and you'd need case halves.... gives me the heeby jeebies.

I alway's link to this for the first time motor rebuilds, cause it really helped me.
https://www.aircooledrdclub.com/smf/index.php?topic=25398.0