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Yamaha SR 500 track bike

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New to this forum. I want to build a track bike out of a 1980 SR 500. I don't want to race per se, at least until I can take some instruction and improve my skills, I just want to practice for a while. I want to build a classic, vintage, cafe racer style, one lunger, with the following mods: 10.5 to 1 pistons, ported head, 36 or 38mm Mikuni carb, after market tunable exhaust, oil cooler, cut down seat, clip on style bars, rear-sets, after market rear shocks, rear drum brake, spoked aluminum wheels front and rear and a stiffer front fork with drilled dual disc brakes and stainless braided lines. I think I've got everthing sourced except the front end. Would a FZR front end fit on a SR 500 frame? If so would XS 650 wheels fit the forks and the FZR brake discs, or could they be modified to fit? It's probably a long shot, but any help would be appreciated! Thanks! :D

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I would try and find a motorcycle wrecker in your area, and pay them a visit with a measuring tape handy. I would imagine the chances of finding someone on this forum who's fitted an FZR front end, XS650 wheels, and FZR discs would be pretty slim, but I could be wrong. :D I've been building/modifying bikes since I was about 13yo (i'm 39 now), and EVERY bike wreckers i've ever been to has been happy for me to measure things before purchasing them. Maybe drop around with a six pack :D

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Cool project -- pretty much the same as what I am doing (or have already done)

I am also looking into some sort of fork upgrade and have much the same question you do. I have seem pictures of SRs with more modern forks (even with inverted forks, although that seems a bit out of charactor, as well as overkill).

KEDO in Germany sells billet triple clamps in virtually all sizes, so if you cannot adapt the FZR (or other donor) triples to the SR steering head, that wouldseem to be an option -- leaving the question of adapting the XS650 hub.

I would think adapting the FZR brake disks to the XS650 hub could be a challenge, and dual disks of the more modern variety would probably be overkill as well. Even with old vintage grakes, most of the racers I raced with 25 years ago, opted for the single disk. With steel braided lines, good pads and careful bleeding, it is generally possible to get about as much braking as the tires would handle. Of course, modern tires do offer a lot more grip, so...

But personally, I would go with dual XS650 disks OR a single modern one. If you want a modern disk, I might suggest a modern hub as well -- something from Talon, like the supermotos use.

Have you decided what wheel sizes to run? I am currently running 18/19 because my wheels were built 25 years ago, but I am thinking of maybe 18s front and rear -- 17s don't comply with rules for some of the vintage racing classes I might run, and wouldn't look quite right, in my opinion. 18s seem like a reasonable compromise, and allow a lot more tire choices than the 19 front does.

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Better check with the rules of the sanctioning body, and / or the host track before you invest cash into the front end. At some Vintage races, the rules limit the size of the forks on Vintage bikes. On many Vintage bikes the rules limit fork size to 35mm, with an exception to the Yamaha SR/TT/XT of 36mm.

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I have done many suspension conversions and the fzr600 disc actually bolts on the xs hub, depending on what caliper you are going to use you may have to space your disc and or caliper. If you are interested i have a set of SRX forks with a sr500 stem in it. I have both wheels and all the stuff you need to bolt it on. You have to change the swing arm to a yamaha radian or srx (which is much stiffer anyway) the forks are36mm front wheel is 2.15x18" dual disc rear is 2.75x18" The whole set up is much lighter than the stock round anchors.Let me know if you are interested or have any swap ?s.

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Oh, and by the way if you do go with 17s you're really going to have to jack the bike up for ground clearance; the chain will rub on the swingarm. 18s with good rubber already drag pegs and pipes. Avon makes 18s that are like glue;most of the vintage guys use em(am22 &am23).

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True about dragging $hit.

Even with vintage Dunlop K81s in 18/19 diameter from 25+ years back, dragging the pipe and the pegs was a major problem on the track.

Relocating the pipe to either under the frame, or higher in a dirt-track style is highly recommended, as is higher, rear-set footpegs, for any track use, regardless of tire size (I learned this the hard way on my first day as a road racer)

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don't want to hijack the thread but i am thinking my sr500 to bonneville next year for the bub speed trials. the 500 production record is 114 mph. can the sr500 get anywhere near that?

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It depends on the rules (steamlining etc) My old tt500 streetracker would do 90 fairly easy just with a pipe an flatslide ( before the major mods) A well designed fairing would help more than motor mods. Air resistance increases exponentialy; you double the speed you quadruple the wind ressistance. Some fully faired race bikes in the 70s were hitting over 130 mph with only 50hp.

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the tricky part is what is production. i am waiting for the rule book so i can sort it out. even if i just go as fast as i can it is a lot of fun and not to expensive.

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I've been building/modifying bikes since I was about 13yo (i'm 39 now), and EVERY bike wreckers i've ever been to has been happy for me to measure things before purchasing them. Maybe drop around with a six pack :banghead:

I'm 15 now and thinking in a few years building a bike. Not from the ground up but finding some sort of harley sportster and modifying it. Did you build that bike in your avatar?

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I remember seeing a lot of cool SR/SRXs and the like on this web page:

clicky

Might be a good lead for some contacts who have done these sort of modifications.

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As far as the front end goes I have built a couple of different bikes one being a TT600 which is a couple of posts down from this one. Start with and try to stick with the stock steering stem. As I'm sure you know the steering stems are pressed into the lower triple clamp. With the TT600 I used a late model CR250 front end. I had to machine a small shim and press it in to the lower clamp because the hole in the clamp was slightly larger. But after that by using the stock stem I was able to use the stock races,bearings and the bearing cones. Also you are able to use the stock top nut and you already know the stem will be the right length. You will have to make sure you have fork clearance for turning radius and you might have to modify the steering stops on the frame so the forks don't hit the tank. Trust me anything can be done. You may just have to enlarge the holes in the clamps which would be easy. Inverted forks would be cool. Try to find a complete front end and adapt it.

Hope this helps,

Cliff

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Keep in mind that at our elevation, the power will be considerably down from near sea levels. Lots of Bonneville records seem unreasonably low compared to what people know their bikes (or cars) can run.

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Keep in mind that at our elevation, the power will be considerably down from near sea levels. Lots of Bonneville records seem unreasonably low compared to what people know their bikes (or cars) can run.

Hey Bob....what you doing over here? We'd probably get banned from the CE forum if they found out we frequent a dirt bike forum. At least you're talking about street bikes though.... :banghead:

Cheers,

Mac

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i understand the power loss at altitude. i have this sr500 that was a good friends bike who died and i am sure he would approve of this use as he was a racer himself. i was just curious if anybody here had experience making the sr500 run. it doesn't matter how fast it goes, i just want to tune it to run its best. i will get there with a handfull of sprockets and carb parts and my c/o meter and see how it goes.

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10-15 years ago I raced a modified SR500 in the Formula Singles class with the AFM. The guy I bought it from had finished fourth in class the previous year and sold it to me so he could buy a Woods Rotax. He never did as well on the Woods as he did on the SR500!

The SR500 had aftermarket shocks, tuned forks and a really tight steering dampener. Obviously it was stripped to nothing and the engine was punched to 540cc with a Megacycle cam, 38mm carb and streight thru exhaust. Crank was balanced and the valves done carefully. The builder put on sexy aluminum wheels and saw no difference in performance. The thing would run a season on one set of tires and traction was NEVER an issue. The bike was very competitive. It came with a box of sprockets to tweek for each track. When I bought it, the original wire wheels were on it. Stock seat and tank but clip on bars.

GO FOR IT!

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A good way to add horsepower is a "high port" conversion where the inlet port is modified to change it from being basically flat,(horizontal),to an angle of about 15 degrees-you have to be careful as the space is limited between the top of the carb and the frame.White Brothers used to do it,maybe they still offer the service,Stan Millard,"HP by Stan" ,and a place in France called VD Classics still does it-i'm sure they are all expensive though.Welding up portions of the combustion chamber to make what i think they call a hemi-spherical head to get a good squish area to improve combustion is also a good way apparently.A friend in Austria who races a SR 500 has the welded up chamber,a 10:1 Wiseco modified to suit the squish area,one of the milder Megacycle cams and i think he is running a 38mm carb,(possibly a flatslide Mikuni),a 49mm inlet valve and he is getting 49horses on the dyno which is impressive.

Anyone wanting to modify a motor should buy "Four Stroke Performance Tuning" available from Haines-it is an awesome book that will explain everything you could ever want to know and has a lot of useful formulae too.I am busy with a "Hot Street" project which is taking time as the pennies are short but i am doing the high port conversion,welding up the combustion chamber,have stroked the crank to 92mm,putting a 90mm Wiseco,hopefully a J2 cam by Johnson cams,(U.S.A.),which has a roller rocker setup which cuts out scuffing of the cam,a Carillo rod and a 38mm Mikuni kit which is ex White Brothers as well as 1.9" valve off a 350 Chevy which i modified by grinding down the stem to 8mm on a crankshaft grinder and shortened it to the right lenth and then machined the groove for the valve retainers-check out www.thumperstuff.com they have all sorts of useful stuff which is where you can get the rod and carb kit as well as Megacycle cams and so on. I have no intention of racing this bike but have always wanted to do an all out modification on one of these motors-this is my fourth XT and i have also had a SR as well-unfortunately not too many people are overly helpful i have noticed....so if i can be of any help i will be.

Good luck

Brandon

South Africa.

P.S. you can pretty much put just about any front end on your bike with a bit of measuring and sometimes a bit of modifying-another caliper off an XS650 is quite a common mod to make a double disc setup for front brakes.

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Hey Mac

I believe that I learned about this forum from a comment you made to someone on the CE forum!

Yeah, my SR is a street bike (set up as a street-tracker) but it does get lots of miles of use blasting on fire trails. Lots of fun sliding it around!

Some great information to be found over here.

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