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Discussion Starter #1
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.

thanks.
Ravivos.
 

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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."
 

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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.
 

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Discussion Starter #4
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.
XJ550Exh.jpg
 

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Discussion Starter #5
hillsy,
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.
 

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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."
 

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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."
 

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Discussion Starter #8
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 ...
 

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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.
 

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Hey - how did I miss this one?

Absolutely first on the list - the Suzuki T/GT500 cannot be run on premix!!! Use the oil pump! You will need to drill the crankcase for oil flow if you want to go the premix route. Otherwise you will starve the crankshaft bearings.

The T500 and GT500 engines are practically the same. The GT has the PEI electronic ignition which required a different crank snout and different milling of the crankcases to fit the unit. Porting is milder than the early T500s but they did that around 1973 to distance the T500 from their new mid-sized triple the GT550. The GT500 also has a disc brake vs a drum on the T models. The tank is a GT750 unit and the seat pan and upholstery were changed to suit. This means the tank mount and seat mounts are different on the GT frame vs the T500 frame. Otherwise the frames and wheelbases are identical.

The GT500 can be run on the track without a battery as the PEI is a generating unit. You will need to disconnect the bulbs as the battery acts as a damper for them and you will burn out all of them with the battery out while running. The silver PEI controller boxes can burn out but the circuits have been mapped and they are not difficult to build. There's a good trouble shooting guide in the factory manual which you can download from here:

http://file.walagata.com/w/sundialmotosport/SuzukiT500.pdf

You should start with doing a pressure test on the engine to determine the shape of your crank seals. This will tell you if you need to split the engine open or not to have the crank rebuilt. You can build your own test set-up for about $25 or so. Let me know if you need details on this.

Seals are available. Here in the US three of the four seals are available along with the four o-rings needed. The right side crank seal has to be ordered from the UK. Not sure what your parts situation is like in Israel. Plus you will need someone that knows how to rebuild a two stroke crank.

Crank bearings and connecting rods have long been NLA from Suzuki. If you need the crank rebuilt and have to replace these items, they are available from Pete O'Dell in the UK:

TR500 Suzuki Specialist GT500, T500 Suzuki

Stainless chambers - really slip-on chambers like the old Allspeeds are available from Titan Performance in the UK. These seem to be good for street duty but you would want something that tucks in tighter like Swarbricks if you start racing your GT500:

www.classic2strokesuzuki.com - About us

Swarbrick Racing - Specialists in Competition Exhaust Systems - Lancashire - UK

The Swarbricks are in kit form and I do not know if he could supply you a stainless kit. They are excellent pipes when assembled by someone that knows what they are doing.

The T500/GT500 has a wide ratio gearbox which is not the best for racing duty. Nova Transmissions in the UK has both close ration gearbox kits as well as straight cut primary gears for the 500. It's all nicely made but expensive:

Nova Racing Motorcycle Transmissions/Gearboxes - Home

As for porting specifications, Muzza has his "old reliable" specifications that work well for someone starting out. In fact he has a full race prep section that may be of use to you:

Home of the Classic Suzuki Two Strokes Compendium T500 GT750 TR500 TR750
Suzuki 500 race preparation

And by the way, that's my GT500 race bike in my avatar.

Jim
 

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Discussion Starter #13
Hi Diamond,
Now that! is solid information! thanks...

As for the premix, i have read about it and will service and keep the oil pump.

As for not running battery, i will need to have working lights on the bike in order to make it street legal, otherwise i wont be able to ride it at all... is there a way to build a voltage limiter (high current zener diodes) that will act as a dumper and regulates the voltage?

i think i need to split the case anyway, since the engine was not started for over 15 years, and i really dont know what is the engine's internal condition. any thoughts on that? should i avoid splitting it and replacing the seals as i go?
can you further elaborate on the pressure test ?

thanks for the links, will surly check every one of them for information.
hopefully, i will be able to conclude the deal on Friday, as there was a small matter of ownership, but that got sorted out.

do you have any other pics or videos of the bike running? how is is in general? how is it on the track? do you like it?
thanks again.


Hi jcw,
the pipes are on the large side of things, but not too much... running some calculation, i got the ideal primaries at 30mm ID , ended up using 35mm ID, i know it is too big, and if the engine wont run properly with these pipes, i will have to ditch them and build a new set...
i enjoy the design and build, although very time consuming, i am trying to learn as much as possible as i go.
 

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here is everything you need to know to start to build a hot shit T500/GT500:

Suzuki 500 race preparation

some of it is a little out of date but you'll figure it our pretty quick.

Where is Diamondj to weigh in here with his vast suzuki knowledge.
 

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You could get a small gel cell 12 volt and use that as your voltage damper.

I had thought you were talking about racing this bike which would preclude a lighting system? Maybe you just meant track days?

To pressure test the engine, get a small hand pump for basketballs with a pressure gauge on it. Something like this:

Mini_hand_air_ball_pump_w_gauge.jpg
A set of spark plug non-foulers - these are made to raise a spark plug up out of the cylinder head. You want the shorter ones with a 14mm outer thread from an auto parts store... Like these:


eng114_pict00110.jpg

A long rubber tire valve stem - also from the auto parts store

Trim the edges of the valve stem seat with a pair of scissors, stick it into the female end of the non-fouler and seal it with JB Weld or Araldite or something similar. Once it dries, you replace a spark plug with the non-fouler/valve stem thing you made. You'll then need to remove the intake manifold and exhaust pipe on that cylinder and seal off the ports on that cylinder. I use pieces of scrap plexiglass from the local builder's supply with a thin layer of permatex that's the right size to seal the port and bolt holes drilled to match the bolts on the cylinders. Then I refit the intake manifold and the exhaust pipe collar minus the header pipe and run the bolts down until it's air tight. Attach your air pump to the valve stem/non-fouler that is screwed into your spark plug hole.

Pump up the cylinder to NO MORE THAN SIX LBS of air pressure. The rule of thumb is six PSI for six minutes. If it holds, your crank seals should be okay.

In regards to splitting the cases - if the crank seals are okay and the kick starter works (the pawls are not worn and in need of replacement) I would leave it alone for now.
 

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Send the crank to England and get someone who knows what they are doing, to check it out and rebuild it. Experience in a specific model is very useful.

XJ: The factories know what the I.D. should be for road bike exhaust headers. Bigger is rarely better. It usually just results in flat spots, surging and loss of torque.

Danger, is my business."
 

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Send the crank to England and get someone who knows what they are doing, to check it out and rebuild it. Experience in a specific model is very useful.

XJ: The factories know what the I.D. should be for road bike exhaust headers. Bigger is rarely better. It usually just results in flat spots, surging and loss of torque.
Danger, is my business."
Oh, only last week you said this....

[Yep, but the peak of British design and manufacturing prowess was 1955, and it's all been downhill from there. That is irrefutable./QUOTE]

I would say the OP may be better guided by Diamondj
 

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Oh, only last week you said this....

[Yep, but the peak of British design and manufacturing prowess was 1955, and it's all been downhill from there. That is irrefutable./QUOTE]

I would say the OP may be better guided by Diamondj

Getting a TS crank apart and pressing it back together isn't manufacturing. It's basically on the level of skilled tinkering. Like Napoleon said, the British are a nation of tinkerers. Tinker tailor. Hello soldier sailor.

On a brighter note, if you need any crank parts, they'll most likely have been manufactured in Taiwan. So no need to worry about quality.

I've done plenty of twin and triple TS crank rebuilds, it's pretty easy if you follow the correct steps. Just trying to do the first one without following the right procedures is just a nightmare.

Danger, is my business."
 

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Oh, only last week you said this....

[Yep, but the peak of British design and manufacturing prowess was 1955, and it's all been downhill from there. That is irrefutable./QUOTE]

I would say the OP may be better guided by Diamondj
What, Whit contradicting himself? Not here.:)

He could have his own forum and have discussions all day long. And never be wrong, or right.
 
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