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Discussion Starter · #1 ·
Hello to all, new here. I live in the States (Michigan,USA). I've been a 2T fan for long time and recently picked up my first 2T motorcycle. 1974 Suzuki GT750 all stock, in moderate condition, wanted to convert front suspension over to reverse mount forks and newer swing arm updated aluminum or magnesium wheels with rear disk brake. Not sure what front ends and rear ends are interchangeable with the ol'Suzuki. If any member could help me out that be a boost to my project. Long live the 2 strokes. 馃槉馃弽
 

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Keep in mind the effects a drastically different suspension will have on the frame... these old Japanese frames were not known for their rigidity and changing things too drastically will possibly ruin the handling.

Look into upgrading the forks with racetech springs and cartridge emulators. Otherwise take a look at what the guys racing these are running. That will give you a good idea of what works well.

I'm not sure what box options there are for swingarms, but you can always brace the existing one

As far as rear shocks, there's tons of good options; hagon, koni/ikon, ohlins... just depends on how deep your wallet is. The good ones all factor in your weight as a rider.
 

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Discussion Starter · #3 ·
Hello to all, new here. I live in the States (Michigan,USA). I've been a 2T fan for long time and recently picked up my first 2T motorcycle. 1974 Suzuki GT750 all stock, in moderate condition, wanted to convert front suspension over to reverse mount forks and newer swing arm updated aluminum or magnesium wheels with rear disk brake. Not sure what front ends and rear ends are interchangeable with the ol'Suzuki. If any member could help me out that be a boost to my project. Long live the 2 strokes. 馃槉馃弽
Purpose of this bike is for recreational riding. NOT a drag race or track race bike. Standard civil riding just want to upgrade the look. Lots of updated Buffalos on the web but they don't tell you what forks or swing arms they used in the changeover.
 

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I understand that. The suggestions I made will maximize the riding enjoyment you get from the bike.

If you're looking for purely cosmetic modifications, then I can't really help you.
 
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byron cox(ex cmr frames) will make you a nice frame kit, see tim voyer鈥檚 cmr/gt750. as front ends go - something off a late 70鈥檚 rg500. dymag wheels in 18鈥
 

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What they said (y) Personally I would mount Ohlins retro 43mm RSU forks on it with some nice yokes and wheel/brake upgrades. The rear would be equally expensive to improve. ? do you have about 6 grand to throw at it?
 

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In some other world, making the ultimate GT750 sounds like a great idea but in reality there are probably better ways to spend cash.

Simplest front end upgrade are a rebuild with new springs plus RaceTech, YSS or MikesXS emulators. USD forks are usually too short and can be lengthened with adapters. But then you really need a custom hub from Cognito or the wheel and brakes that came with the forks.

Conventional forks that would also work include Katana, early R6 and FZR400 but all bring complications in the braking area. Here's one solution to the brake issue using upgraded stock forks. https://pinkpossum.com/GT750/phattrakka2/p5brakes.htm

Wheels depend on how wild you cant to go. This bike has Suzuki GS wheels https://pinkpossum.com/GT750/Dunstall/details.htm GS rear wheels are often a smaller than GT diameter and require fatter tires to get similar rolling diameter.

At the back end GS750/1000 and 1100 swingarms are pretty much a bolt in set up and need appropriate spacers depending on which wheel you use.

There are enough GTs on the web with modern wheels and suspension and some are great and some not so much.

But start with getting and keeping the bike safe and reliable and have fun with it.
 

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Webike has a surprisingly little as far as these bikes go... kind of disappointing considering how stupidly popular the GT350 is in Japan
 

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Who was it who built that insane water Buffalo on here a few (10?) Years ago?

here:

 

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Anybody knows of a reputable person that's familiar to GT750 engine. Porting and polishing the cylinder block for me. Im located in Michigan, USA.
I know a mechanic familiar with the GT750 (Ian Taylor) ,but porting and polishing a 2-stroke cylinder block is an entirely different thing again. The GT750 and T500 were based on Suzuki 250 single cylinder engine design and parts (very reliable and under stressed engine design), so if you are looking to increase engine performance on the GT750 you would be wise to study what worked on the TS250 and particularly the T500 engines and apply similar modifications. The engines in that era are all of piston port design, so one of the more current tech ways to improve scavenging could be to add a reed valve block and modify the pistons. Short of that, there is a period correct article to be found here: T500 Port Widening Advice - Suzuki 2 Strokes showing port size modifications to the T500 which were historically proven successful on 500cc 2-stroke twin cylinder race bikes.

... note that it says right in the article, these modifications are for track use and Not recommended for street motorcycles.
 

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I have ported (we don't polish as such) many GT750 cylinders from mild to wild. The Phat Trakka made almost 80rear wheels HP on stock carbs, up from 50 stock. Depending on your pipe choice and intentions there are many different ways you can go.

With the head, you can go from machining "some" metal off and matching the bores and chambers, to welded and machined chambers or even replaceable inserts (domes).

They run OK up to about 100 rwhp on stock BS40 carbs and teh fastest street, stock looking GT750 that runs in the 10s has BS40 carbs.

For pipes you can spend 2 grand on excellent quality good power Jim Lomas pipes or Higgs in the UK or Jemco over here in the US. There are J&R and Bassani and other pipes like FPP available second hand from time to time. They are usually a bit beaten up but cheap and sometimes ridiculously expensive for some reason.
It all comes down to what you want to do and what you budget for the build.

But I am not the only person tuning these things. Doug Flannery in MI has done a few and hos motors are fast. All the usual suspects such as Scott Clough probably offer porting for them. They are a PIA to port.
 

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Discussion Starter · #13 ·
Thanks guys, will help me out on an engine build idea. Will look into the resources if there still in the business. Does anybody know what brand exhuast pipes are in the youtube video? suzuki gt750 two stroke b.m.r.racing - YouTube Scroll over to 2-minute mark and listen in. LOVE the sound 馃榿. Such music to the soul. The owner of this bike doesn't know themself either.
I wanted to get it up to around 80HP'ish. My fellow rider buddies have all these modern-day street bikes with stock 150HP+. I wanna keep up to them at least to the speed limits.
 

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.... I wanna keep up to them at least to the speed limits.
:unsure: I really don't think that will be a problem if you can ride any good, possibly twice the posted speed limit will be a stretch. Yours will be the ear splitting loud one laying down a blueish white contrail for the cops to follow.
If you put expansion chambers on it, that will increase power more then anything else you could do, I suspect you will be shopping for different carburetors soon afterwards. Simply running race fuel instead of regular pump gas would likely net you as much performance gain as the port polishing idea.
Good luck with your project :cool:
 

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80 rear wheel will need porting plus lift plate plus head and barrel machined to suit. Carbs are good to around 100 hp. Race fuel adds zero hp unless the compression is so high that timing had to be retarded. And as mentioned you will need pipes. Expansion chambers don't have to be too loud if the muffler is well designed. Best sound is from a 3 into 1 but they do not make the most power.
Bigger carbs are a PIA and require that they are lifted and downdraft because the right one will rest on the top of the crankcases and that doesn't work well. There are a couple of options for tilted inlet rubbers but the best way is to cut off the inlet stubs and weld them on at a better angle but that's not cheap either.
 

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Race fuel today is still lower octane then we use to buy at the pumps in the era that machine was produced. I'm finding it to work a whole lot better in my current 2-strokes even at 50% ratios, ymmv. The chamber in his video is minus the typical straight section through the middle fwiw

OP post photos when you can :cool: loved all the 1970's Suzuki' 2-strokes
 

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In all probability they are period Ocelot chambers or copies or copies of copies... Originals had single diameter headers but I have seen a pair of replicas with that 2 stage header design on a T500. They did not have a belly section at all for whatever reason.

Street gas in my day rarely exceeded 100 octane though I am sure that 101 was available somewhere back in the day.

We tested several race gas combos and on a low HP motor the difference was within the margin of error. I personally like U4.4 from VP which is 98 MON, 114 RON or 106 (R+M)/2. It costs 125 bucks for a 5 gallon pail and it's not really gasoline as we know it. More of a chemical cocktail. Typical drag race fuel is 116 octane. By comparison, the fuel we used in TZs was 100 octane and those things have a CR of around 15:1. VP sell a bunch of race fuels with less than 100 octane and in modern motors that's all fine.

A GT750 has a quiescent combustion chamber design, so no squish band at all and no squish so, low turbulence and low flame propagation rate combines with a propensity to detonate. A moderate increase in compression to say 165psi is OK on 98 octane but a squish head is always going to be better and they can be converted using domes or weld and machine.
 

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Every Sunoco station sold 104 octane at the pumps, my current model 2-stroke trials bike calls for 98 octane, pump gas ends at 93 octane around here now. I find Sunoco to be a little cheaper then VP up here, either brand is available, shipped right to my door at no extra charge thanks to W.O Stinson fuels (y)

... and you're right race fuel is closer to paint thinner then it is to modern pump gas which may contain water.
 
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