RC8 parts on RC390?

[psych0hans]

Will rc8 fork stactions and internals fit in the rc390? Any guesses? I'm getting some at a reasonable price but don't want to risk it without knowing anything about it. I still have to buy my 390, but this is a mod I know I want to do. Thanks guys.

 

[Ryanthegreat1]

I think the are the same length and diameter but support dual brake rotors and probably bigger axle.

 

[psych0hans]

I think the are the same length and diameter but support dual brake rotors and probably bigger axle.

Thats actually exactly what I'm looking for. I hope to eventually find a new rim which will accept dual rotors. Also, this way I can use 100mm brembo brakes. Thanks for your reply.

 

[Treachery]

Wouldn't it be massively oversprung and overdamped? Plus it would seem to add a bunch of extra weight to the wheel. I don't mean to p** in your Wheaties, but short of all the parts being free, that swap sounds counter-productive.

 

[mr-fabricator]

I looked into this myself and the front will physicaly fit but it will be all wrong , and when youve spent more money with rebuilds it will still be way out . For cool factor and steady.street only u would be ok but i personally wouldnt take it to the track . Wheel to big making geometry and balance heavy , twin brembos are complete overkill and i think once u start with one thing it will affect another

Its a pitty as like i said i realy wanted to do it myself but it will never work.in reality .

Their is a post where someone put a gsxr600 front end on , a closer match than a rc8 and after 1 test run was taken of , just felt wrong .

Springs and oil front end , new shock or rebuild the stock rear . Thats where to put your money .

 

[psych0hans]

Hi guys, thanks a bunch for your replies. I've already pulled the trigger on the kit and hope to get it soon. I totally understand where you guys are coming from and yes, dual 100mm brembo brakes on a 390cc single which weighs much as the hair on my head, is totally overkill. Here is my thinking, and while it may not be justified, I wanna see how it pans out. The guys who did the gsxr swap altered too many things at the same time.

1) Steering Geometry
2) Front tire width
3) Front tire weight
4) Front rim weight
5) Added weight of the new rotor/caliper
6) And obviously, the Dampening of the forks.

What I plan on doing is : -
1) Change just the fork stactions, Internals, brake caliper and master cylinder keeping everything else stock.
2) Get the Internals sorted out.
3) Eventually look for a replacement wheel with dual rotors, but keeping the stock tire profile.

Why do I want Dual Rotors? Because I'm pretty much obsessed with them, absolutely no other reason. They look fabulous and give the "Big Bike" look which I can't afford right now... Wish me luck...

p.s. I still need to buy my bike... lol Negotiating with someone to sell me one for approximately 2400$ Only done 800miles too... (It's about $3,800 new here)
p.p.s. This will eventually be a track bike, but initially just a street bike.
p.p.p.s If you think that I have no idea about what I'm doing and that I'm just a blubbering idiot who just wants to mess around with things for the sake of it..... You wouldn't be too far from the truth...

 

[mr-fabricator]

Dude , your bike , your money and your time , one thing i will say and that is we , the members of this forum will be right behind you every step .

Innovate , dont imitate

Anything we can do to help just post the question .

Very best of luck and looking forward to progress.

 

[psych0hans]

Dude , your bike , your money and your time , one thing i will say and that is we , the members of this forum will be right behind you every step .

Innovate , dont imitate

Anything we can do to help just post the question .

Very best of luck and looking forward to progress.

You, Sir, are the BOSS! Thank you for the encouragement.

 

[RoninJames]

so suspension noob question here:
do rc8 preload adjusters fit our forks?
we are springs while i assume the rc8 is cartridge right?
im guessing preload adjusters would still help compress the springs a bit to dial in the front better?

again, suspension noob so forgive my ignorance... trying to learn.

 

[Fasteddy]

What I plan on doing is : -
1) Change just the fork stactions, Internals, brake caliper and master cylinder keeping everything else stock.
2) Get the Internals sorted out.
3) Eventually look for a replacement wheel with dual rotors, but keeping the stock tire profile.

You will probably be looking for the wheel sooner then later, Huge difference in axle diameter and mounting method. I just had to buy the wheel you will need for another project bike current price is $850USD, If you can find one used grab it! on the plus side I measured, and the triple trees seem to be the same distance apart.

 

[psych0hans]

Thanks for your reply Eddy. I have access to a proper machining shop, so if it's a matter of turning bushes etc... I can always have it done. I don't think I can afford the RC8R rims, so I'm not entirely sure what I'm going to do... lol I'll just cross each bridge as it comes I guess... Thanks for your insight tho. Here is a link to what I'm buying. 2012 KTM RC8 RC8R Fork Spring and Cartridge | eBay

 

[psych0hans]

What wheel did you buy?

 

[Fasteddy]

What wheel did you buy?

Stock front for 2007 990 SuperDuke, same as RC8 and 990 SuperMoto. I had a chance to get an RC8 wheel on Ebay a bit cheaper but did not realize they were same part.
FRONT WHEEL CPL. BLACK 07 - 6100900104430

 

[psych0hans]

Do you guys know what's the difference between the Duke and the RC forks? I believe the travel is different, but anything else? I don't want to mess up my bike trying to do the mods I want, so I was planing on buying a set of used Duke forks and modding them with the RC8 Parts and only swapping them over when it's ready. Any suggestions? I'm getting the duke front end for a pretty decent price.

 

[b0Xcrash]

p.s. I still need to buy my bike... lol Negotiating with someone to sell me one for approximately 2400$ Only done 800miles too... (It's about $3,800 new here)

Very nice, where do you live?
New at dealership here is $5200 or so.

Not that I am going to swoop in or anything, you got dibs on whatever you found, where ever you are anyway....but that would be ideal price used.
I have been looking, but expect not to find a good used one for at least a couple of years.

Dual rotors would be pretty nice, but yeah the added unsprung weight of an additional rotor is like gaining 50+ pounds elsewhere on the bike(then caliper and pads also adds to the front).
But I agree it would look awesome and give it that big bike look.

For me I think a good wave rotor or maybe go up a little larger(of course want to keep down unsprung weight myself, go larger as long as weight is the same or less). Then for master cylinder, brembo or similar(maybe AP, not sure who else is making them these days) radial master cylinder and upgrading the calipers is going to be to be plenty on the front brakes myself.

For me going dual rotors and calipers is going to be weight added I would want to reduce, but I totally support finding the limits of what can be done or cannot be done without re-engineering the entire bike

 

[psych0hans]

Hi, I'm from Bombay, India, so the bikes are much cheaper here than everywhere else, being as they are manufactured here. It's about 3800$ OTD I believe. I'm going to do this bit by bit, so I can evaluate each mod as I go. The first will be the forks and the caliper and the rest will follow. Not sure if I will land up doing the dual disk mod, but I would definitely love to. The current parts I have ordered are the R6 shock and the RC8 stactions + internals. Should be here in 1-2 weeks. Bike I'm buying tomorrow if all goes well. My dad is doing the deal, as the bike is in a different city close to where he is right now.

Very nice, where do you live?
New at dealership here is $5200 or so.

Not that I am going to swoop in or anything, you got dibs on whatever you found, where ever you are anyway....but that would be ideal price used.
I have been looking, but expect not to find a good used one for at least a couple of years.

Dual rotors would be pretty nice, but yeah the added unsprung weight of an additional rotor is like gaining 50+ pounds elsewhere on the bike(then caliper and pads also adds to the front).
But I agree it would look awesome and give it that big bike look.

For me I think a good wave rotor or maybe go up a little larger(of course want to keep down unsprung weight myself, go larger as long as weight is the same or less). Then for master cylinder, brembo or similar(maybe AP, not sure who else is making them these days) radial master cylinder and upgrading the calipers is going to be to be plenty on the front brakes myself.

For me going dual rotors and calipers is going to be weight added I would want to reduce, but I totally support finding the limits of what can be done or cannot be done without re-engineering the entire bike

 

[b0Xcrash]

Hi, I'm from Bombay, India, so the bikes are much cheaper here than everywhere else, being as they are manufactured here. It's about 3800$ OTD I believe. I'm going to do this bit by bit, so I can evaluate each mod as I go. The first will be the forks and the caliper and the rest will follow. Not sure if I will land up doing the dual disk mod, but I would definitely love to. The current parts I have ordered are the R6 shock and the RC8 stactions + internals. Should be here in 1-2 weeks. Bike I'm buying tomorrow if all goes well. My dad is doing the deal, as the bike is in a different city close to where he is right now.

Ahh very nice, and yeah that makes sense. Good luck with the deal!
Makes me wish I still had close friends or family in the Navy.....buy one cheap and have them bring it back on a ship for me

Yeah I have a couple of R6 shocks laying around, looks like hopefully that might be a good cheap way to upgrade the rear shock. Granted for me at about 145-150lbs on the heavy side, the stock would probably be fine, still nice to have adjustments though

 

[psych0hans]

I was wondering, if the valving in the RC8 internals is too stiff for the RC390, would using lower weight oil make up for the difference? Like maybe using 2.5 or 3 weight oil instead of 5?

 

[psych0hans]

Finally got my parts !!! The only issue is it's missing the compression adjustment screws which are supposed to be on the fork lowers... Any suggestions?

 

[jokerio]

I looked into this myself and the front will physicaly fit but it will be all wrong , and when youve spent more money with rebuilds it will still be way out ……. wouldnt take it to the track ……... but it will never work.in reality …… Springs and oil front end, Thats where to put your money .

1. Wrong ! Check-out my thread…. http://www.rc390-forum.com/forum/wheels-tires-and-suspension/673-fitting-rc8-forks-390-a.html

on the plus side I measured, and the triple trees seem to be the same distance apart.

2. Sort of wrong,... The distance in width of the forks are different, closer together on the 390...