Would this be legal for 500 Twins?

[aminalmutha]

Would an EX500 engine stuffed into a '91 GSX-R 750 chassis be legal for 500 twins? Has anyone done this? Just wondering.

 

[kneedrag]

Yes it's legal because it's a Formula class. Meaning no restrictions other than twin cylinder & 500cc.

 

[Mick-e]

I saw a bike like this on e-bay awhile back.
Wouldn't that chassis be awfully heavy for that little engine?

 

[aminalmutha]

I kinda figured, but just wanted to make sure. I've been trying to figure out what people run in 500 Twins, and from what I can tell, the EX500 is pretty popular.

I have a '91 GSX-R 750 that already has upgraded forks, Ohlins shock, braided steel brake lines, etc. It would be too new for the Dinosaur class and would be simply uncompetetive in 750 Production. Besides, I don't think I'd want to run in a class that quick. The motor can be used in other projects I have, so it wouldn't be a waste (long story).

Just thinking out loud. It needs some things and is basically a project bike, but I just thought "what if...".

Anyone know of anyone who's done anything like this, or is it a completely dumb idea?

 

[joe]

I saw that bike too, and while it looked "interesting" I doubt the weight differential would be appreciated by the rider trying to make the most out of a 50 something HP engine...

And, if you were going to do all that why not just find a GS frame and some old forks and swingarm and work a project that way.

But yeah, it would be legal, and as long as you had fun, who cares (Sonny's got an GS engine in an old GSXR chassis, doesn't he?).

Oh, and dude, if you need a full chassis and suspesnsion, I'm selling mine with pretty much everything minus engine and the stuff directly attached to it. Just toss in your engine/exhaust/carbs (mine are kinda for sale too)/wiring, and go.

pm me if you're interested.

thanks

 

[aminalmutha]

Wouldn't that chassis be awfully heavy for that little engine?

I have no idea. I think the GSX-R motor is a significant factor in why older Gixxers are heavy, so maybe a smaller motor would drop some weight?

 

[joe]

fuck it, I say build it and come play. We're already the circus race with us, formula singles, and vitange. Another monster wouldn't hurt.

 

[Zerox]

Wouldn't that chassis be awfully heavy for that little engine?

An aluminum-framed GSXR750 vs. a steel-framed EX500, how much is the weight difference?

IIRC I saw an EX500 engine in a ZX-7 chassis, in one of the U.S. bike mags a few years ago.

 

[aminalmutha]

Heheh... alrighty. :teeth I've got lots of projects right now, but that is a potential one; just puttin' my feelers out. Just didn't wanna go thru all the work, show up and get :wtf :| :laughing or worse, a "yeah, yer gonna have to take that somewhere else". I figured it might be a fun project and I'd have a fun bike that wasn't too fast yet too slow if ya know what I mean (with the GSX-R motor, that is... the late model bikes would run rings around me).

I'm not ready to buy anything for this potential monster quite yet, but I'll letcha all know when I am. Thanks for the input.

 

[Zerox]

(with the GSX-R motor, that is... the late model bikes would run rings around me).

At Buttonwillow and Thunderhill you'll be hurting, but at Sears you might have something for a few of the new 750s with your '91 (depends on the rider....what else is new). Just for giggles I compared my best lap on my '87 750 at the last race with the 750 Superbike field, the GeezerGixxer was faster than 13 of the modern bikes.

Having a faster best lap doesn't guarantee you'll finish ahead of someone with a slower best lap, racing doesn't work that way. I was going to race 750SB at Sears but my tires were torched.

I raced 750SB at Buttonwillow, I was gridded 2nd to last and finished --2nd to last-- but I had a nice battle with a group of 3-4 riders all the way til the last lap. I plan on racing 750SB at Thunderhill, I'll get stomped but it's valuable practice for my main race.

Keep in mind that if you want to race 750 Production you'll need to retain the OEM airbox, carbs and exhaust.

 

[aminalmutha]

I figured a good rider could keep a newer machine in sight, if not outright beat some of 'em, but for a new racer (which I would be; I don't plan on simply jumping in feet first, mind you; at least a track school and some track days would be in order prior to that) the speeds may simply be a bit over my head. I'd rather not even be tempted. Not to say 500 Twins would be slow, by any means, I'm sure I'll get thoroughly smoked there, too, but I'm guessing the pace is a little slower than 750 Proddy.

Just cuz I can hose my neighbor squid and his buddies on the latest 600s (hell, I even smoke 'em on my Concours :teeth ), I doubt means I'll be taking home trophies any time soon. I just don't want to be a danger to myself or others and I figured 500 Twins would be a bit more sane to start in than 750 Proddy.

Besides, my hopped up '91 motor might be a lot of fun in my soon-to-be-cafe'd GS750. :shhh :teeth

 

[Mick-e]

(Sonny's got an GS engine in an old GSXR chassis, doesn't he?).

Sonny's bikes is GS500 with all the gsxr 750 stuff attached. It's pretty heavy for a stock engine.
You're right the big 750's go faster than the little 500's, but those damn littlw twins still go fast enough to scare the shit out of you (well me at least). Maybe it's becasue the frame flexes like a wet sponge? If that's the case maybe a big aluminum chassis isn't a bad idea.

 

[christofu]

fuck it, I say build it and come play. We're already the circus race with us, formula singles, and vitange. Another monster wouldn't hurt.

:mad :mad

I keep telling you! My nose is only red when I'm racing because I'm DRUNK, not because I'm a CLOWN.

Pfft. Circus race. :clown

 

[joe]

Ha, when you take into account Chris' bike, Bobby's bike, and then the various level's of decaying EX500's about, it's not just the circus race, it's the three ringed, big top circus race!

And chris, I might just have something to come play with you next year on... Working at a KTM dealer has it's perks, I'll leave it at that.

 

[aminalmutha]

Thanks for the info. It's research time, now, along with trying to accomplish a few other projects before REALLY considering this one.

If it happens, it should be fun. :cool

 

[joe]

If that bike actually made it to the grid, with the bike that Bobby says he's gonna build, the bike that Patrick Aldinger apparently is building through Spears, and the Sv's get built up, the class really could be some fucking rocking times (not actualy laps times, but you know what I mean).

Us EX's might get left out in the cold, but hey, I don't see any reason we just can get in front and slow everyone else down!

We'll see as for now it appears there'll be two 70hp monsters on the grid next season (maybe a little less for Patrick), and who knows what Zoran will do the SV's (although if Jon wins the championship, as of now I think he's a lock, I don't see zoran pimping them out...).

You got anything mick?

 

[MrCrash]

IIRC I saw an EX500 engine in a ZX-7 chassis, in one of the U.S. bike mags a few years ago.

I think his name was Jamie Barkley. He ran it in a few AFM events in the mid 1990s. It was exceptionally clean, and pretty quick.

Sonny's bike is GS500 with all the gsxr 750 stuff attached. It's pretty heavy for a stock engine.

It was pretty quick with the modified 4-valve head though!

Hopefully the Aprilia 450 comes out to breathe new life in the class. The class has seen some interesting machines over the course of the years:

- The ZX-7 / EX500
- The AND EX500s
- The BRG GSEX
- The Gibson Trellis-framed EX500
- A couple of GS500s with chopped GSX-R 4-valve heads

If a new production bike like the Aprilia surfaced and the old creations that once ran at the front made their way back to the grid, that could be a pretty neat race

 

[joe]

have you heard something about the old creations we haven't mike?

 

[Mick-e]

damn, I was hoping not to spend any money on engine parts other than freshing up the head, but it looks like I might need to put the 1m over high comp pistons in if I'm going to just keep up with the front pack. I think most importantly though will be a front end change. These unadustable fzr600 forks that bottom out under braking are starting to really become a limiting factor.

Patrick's building a bike? That can't be good. He already wipps my ass on a bone stock ex. crap!

 

[fawndog]

aminalmutha,

I'm still learning the limits of this bike.

GSXR front/rear
GS 500 frame
I could use some more motor (stock)
It has a few one off and some adapted parts so I really really don't want to crash it for 8th or 9th.

I'd be interested in seeing the project. Hell I'd help.

:wtf With all the money in bikes we should have a class sponsor.