1977 GT500 - to do list
This is a discussion on 1977 GT500 - to do list within the General forums, part of the Caferacer.net Forums category; Well, it's this time again, when one feels the need for another project.
so, manage to track down an unmolested 1977 GT500, it is the ...
1977 GT500 - to do list
Well, it's this time again, when one feels the need for another project.
so, manage to track down an unmolested 1977 GT500, it is the only one that is registered in the Israeli DMV and was sitting in someone's living room for the past 15 years.
the bike was not started for over 20 years, and beside the airbox and left battery cover, all parts are there (which is a great thing, an unmolested GT500 in israel, only in my wildest dreams)
so, i am trying to make a to-do list, and the goal is to make it "track worthy", so performance is everything.
would love to get your advice, here are the obvious (and not so obvious) things needed to be done -
- tires, the ones on it are dead, any recommendations for a good set?
- front fork oil seals, thinking about replacing the front to a different one, any suggestions?
- engine, since i dont know what is the history nor condition of the engine, i plan on taking it out of the frame and properly inspect its internals, where can i get parts for the GT500 such as seals, pistons, rings ect... ?
- rear suspension, original ones looks o.k... but i think i'll need to fork out the money for a nice set of hagons.
- chain and sprocket - replace with new ones.
- frame brace - i've read that adding a brace between the rear arm pivot point and the upper frame tube really helps the frame's rigidity, i have no problem tig welding the frame in order to brace it.
- wheels bearings, replace.
- steering bearing , replace (would prefer replacing the entire front)
- swingarm bearing/bushing - replace.
- and ofcourse - exhaust, will have to design and build a stainless steel expansion chambers for it, but i assume the expansion chambers should be designed according to the engine's porting.
any other things you think i need to address on the GT500? any weak spots or things to look out from when working on a GT500?
on a personal note, i am currently riding a 97 TL1000S, sold my cafe racer KZ400, have a yamaha XJ550 and a suzuki 84' GSX750ES (and a 1200cc bandit engine waiting to be installed into the frame) that is in the progress of injecting it using microsquirt.
I rode one for a while. Strange things, fast, smooth, long and flexy. I remember the rigid footpegs were too low and scraped. GT's aren't bad bikes, but they are a weird old fast tourer, and they don't handle bad, just loose and a little weird. Not really a sport bike, more a tourer. If you want a sport bike like an RD400, go find one, because you won't make one out of a GT500.
From memory, GT's have very little in common with the T, in parts interchangeability. Bear that in mind when hunting parts.
Fitting more rigid forks will only make the flexy old chassis even worse. Stress has to go somewhere.
You'll have a hard enough time keeping it running well stock, forget porting it as a hobby for the road. Two strokes used to be cheap to hot up and blow up all the time while learning, but parts used to be very cheap, now they are certainly not.
Forget chambers for road use, and forget stainless steel ones. Noisy peaky power is pretty useless on the road, and stainless is too hard to fabricate, modify and repair. Even guys I know who fabricate stainless as a job say it's difficult shit to work with. Stainless would most likely crack from vibration well before mild steel, as well. You have been looking at idiot build web sites, far too many times, now haven't you? Go find a stock airbox.
Bracing the centre of the frame is a good idea. Find one to copy on the net. The tubing only needs to be similar gauge to the stock tubing, it doesn't need to be the strongest tubing on the planet. Tubing compatibility is far more important than ultimate strength.
Danger, is my business."
Just for shits and giggles here's some pics of my buddies Titan during the build:
I don't have any pics of the finished bike.
It had a GT750 front end, some mystery engine work / porting and a set of pipes that he got made up in sections from some guy in the UK, then he got them shipped to Oz and got a local exhaust place to weld them up. Cost a small fortune, but Parker was happy.
The bike had no kickstart or side stand. It was push start only and he used to lean it against the house when he came over. It was a fun bike to ride.
Well, i think you got a few things wrong, but thank you for the reply (at least you replied).
the T and GT have a lot of interchangeable parts, especially engine wise.
the GT is a bit longer than the T, and adding the frame brace actually improves its handling (from what I've read, will post back after bracing it)
as i see it, a move rigid front, with braced frame and some weight reduction should turn the bike to a more agile bike that is a lot of fun riding.
As for the exhaust, again, i think you got it wrong... i fabricate all my exhaust out of stainless (car and bikes), it is a very nice material to work with as long as you know what you are doing (have a look below at the picture, this is the 4-2-1 exhaust i am building for my XJ550).
the expansion chambers will be o.k, even if it changes the torque curve to a more peaky one (that's what old two strokes are for). if built correctly, i dont see any reason for it to crack nor brake, its all a matter of stress relief and rubber mounts.
since the T and the GT chambers are exchangeable, i think i would be able to find one or two spare ones to use.
this bike can actually be track worthy, and i dont mind spending the time and money to get it there.
that is a good looking bike!!! i see frame brace, i see expansion chambers , i see different oil tank...
a lot of work went into that bike, one have to appreciate the effort put into it to get it to the track... that is what i am aiming for.
i am working on trying to establish a basic league/race/meeting for vintage bikes... maybe one day i will be able to actually race it here in Israel.
I doubt anyone ever raced bikes like TZ350's and RD250's with stainless chambers back in the day. Race chambers need a lot of maintenance, and stainless isn't as easy to repair and modify. Remember, they get dented, break, fall off and generally cause all kinds of hassles. From vibration and crash damage, for example.
I knew a guy who raced Titans years ago, strange I can't even think if his name now. He had dozens of sets of T race chambers hanging around his workshop. I think he had four or five race Titans all over the place. The bikes all looked like crusty shit, but went ok at the race track. But then again, he looked like crusty shit, but went well at the race track.
Danger, is my business."
I just found out the Titan racer guy I knew died a few years ago. So no luck in finding any race junk, porting specs, old chambers or chamber cone specs now.
Danger, is my business."
Too bad, it is always sad to loose good people with vast knowledge of these old bikes... perhaps someone here on CR.net could chime in from experience ...
That's a nice looking T/GT500 - not a lot of difference. Swarbrick chambers look good. They look like they are genuine Swarbricks and not JEMCO copies which are asymmetric. The frame braces are where they usually go and should help a lot. GT750 forks can be improved upon with Gold Valves and decent springs. RZ350 front fender has a steel bracket/brace built in, plus the aftermarket brace should stiffen things up at the front end.
Porting is easy on those but you will need a decent 90 degree porting tool and left hand burrs to work in the transfers. For track only use you could fit a self generating ignition such as FEMSA, MOTOPLAT, or modern PVL. Post pictures if you go ahead with it. Pipe and port designs are not rocket science but people who spend a lot of time working them out are not usually happy to give away their secrets. BIMOTION or MOTA or EngMod2T are useful tools.
Last edited by Teazer; 07-19-2015 at 08:57 AM.
Thanks for the info, very usefull... will check out the SW you recommended .
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