GT750 Red devil

I'm not a big thread poster but thought it might be fun or instructional, or maybe my ego needed a stroke.

So to cut to the chase. A few months ago I took the Phat Trakka to the drag strip and set a record. So I start thinking that maybe the "STOCK" class definition could be stretched a little. I was thinking that maybe it might be possible to replace some of the stock frame tubes with thin wall chrome moly tubing and save a few pounds.

Working on the basis that if those tubes are hidden under a tank or side cover, are they really chrome moly or are they just tubes with black paint and therefore "stock". So I called a buddy of mine who I know had a few spare frames that I could practice on. He had a better idea. If I were to buy all his project bikes, he'd GIVE me all the parts he had collected.

By now, you would think that I'd be a little more cautious. FREE bikes are the most expensive things on the planet. They are invariably pooched and all the parts that are missing are either non obtainable or ridiculously costly. So the three rollers weren't free but the price was still low and tempting and that portends to an impending event of foul financial play.

The truck had a slight misfire that was obviously water in the crappy ethanol laced pig swill that is sold as Gasoline today. Throw in a can of seafoam and a bottle of rubbing alcohol to absorb the moisture and all will be well. No worries mate. About 30 miles out and the misfire is getting worse, so I pull off the highway and eventually get turned around to head home.

It's just a misfire. Can't get much worse. I can nurse it home without too much drama.

OK. So that was just plain wrong. The miss got worse and worse and I eventually had the opportunity to work on my tan and chat to various state troupers, IDOT drivers and eventually a tow truck driver that dragged our sorry wreck back to our local hot shot auto shop.
Sitting at the side of the highway I noticed that I had stopped next to what they call Mile markers and this one was more like something out a Harry Potter story.



The next morning the shop called to say it was the distributor that was dying when it got hot and because it contained the coil (really!) and some other electronic module, they could get me one for just under 3oo bucks and fitted it would be around 60-700 bucks. WTF. So I drove it home and ordered one on ebay and fitted in an a couple of hours and all for less than $100. The dizzy arrived on Thursday and on Friday it was back on the road for a 600 mile round trip to pick up this pile of stuff.



And so my journey into poverty and dirty fingernails began again...............

Keep in mind that I had no good reason to have those three bikes on the trailer but they only needed carbs cleaned, air in the tires and new batteries. They used to run... It was last summer. No. Maybe the year before that but they ran OK. the gold 550 ran a little lumpy but that's just carbs or ignition. Turned out to be ignition alright. The ignition won't work if the bike won't run.

I decided to start with Goldilocks. Why "Goldilocks"? Of the three two stroke triples offered by Suzuki in the seventies, the 380 was too small, the 750 was often considered to be too large and the GT550 was just right.

I had no interest in a 550, so I thought I'd get it running and flip it, so it was first on the block.

The PO told me he bought it on a whim a "couple" of years ago and it ran a little rough but he never had time to clean out the carbs and set the timing. And that's all it needs. And a good wash to make it shine again.

So call me a doubting Thomas or a Reagan democrat. Trust but verify. So out came the compression tester. left side zero. Excuse me. what is wrong with this gauge? Try it in the middle pot. 131 PSI - pretty respectable for a bike that hasn't run in a couple of years. Right side, 127 PSI. Not too bad either. So let's check that left side again. Still zero.

So I removed the tester and placed my carefully calibrated thumb over the plug hole and kicked it over. No Phht sounds. No thumb blown off by the shear compressive force. Nothing. Nada. It's funny how the brain works. Nah. That can't be right. He said it used to run. :-(

After consulting with our cat and stopping for coffee, I slipped the borescope inside the plug hole and the truth became apparent. There was a dirty great hole in the piston. Oh dear. That is most unfortunate. I'm pretty sure those were the words that escaped form my mouth a millisecond later. Well that was the general thought at least. :

What had me fooled was that the motor spun over so well. No grinding sounds or tight spots. No sign of seizure or other malaise.



That's a problem alright. So I decided to remove the SRIS check valves to flush out the crankcase. Drip tray under the SRIS holes to collect any debris and solvent and oil. Into the bottom end went about half a pint of gasoline and just as fast it poured out of the left side of the motor.



That is not the way it is designed to work. I'm pretty sure of that. So off came the alternator rotor and low and behold, there was a problem - a seal with its heart torn out.

It looks like the center of the seal had stuck to the crank and when the OP fired it up, the center tore out of the outer. It happens, but it's uncommon to find one that dramatic. That's why people that buy old two strokes should always check them out carefully. At that stage I did a leakdown test on the center and right cylinders and they held zero pressure. Air could be heard escaping between cylinders and into the transmission.

I did rebuild the carbs and they were a mess of corrosion and white deposits and gas stains and who knows what else. After a few dips in the ultrasonic tank the internals started to become recognizable again. And as soon as the float bowl gaskets arrive, they can be bolted back together.

So the crank has to be rebuilt ( no surprise there, but hope springs eternal) and it needs new pistons and rings and gaskets and intake rubbers etc. Those parts arrived from japan pretty quickly, but I moved on to start on the next easy project - a shiny red GT750 that was being rebuilt by the PO and just needed carbs and it will be good to go. Right.....

The 550 is currently residing in a corner of the shop and offered itself up as a place to put parts out to dry, to hang coats on etc and now I'm working on port changes and thinking that a set of chambers and GSR600 wheels and a monoshock rear end might be just the things to spruce it up. They would work so well with that shiny new crank that it's asking Santa for Xmas. Hmm. 38hp stock. Maybe 80 or so at the rear wheel with 32mm GT750 carbs or flatslides and an electronic ignition...... I'll think about that. Might be fun. But first I have to get one bike finished and sold. That can't be too hard now can it? ???

Good to know, Teazer, that experience doesn't stop one from doing something dumb - rather that you recognize it earlier.

What we look for in life in general are patterns that make sense and when what we see or hear doesn't match the pattern we were expecting we have to determine which was wrong, the expectation or the perceived reality.

When that happens, we test to see which is correct. In my case, my come from place is to trust the OP but to verify that things are what they said and that leads to some interesting discoveries.

Further life lessons from this thread include the incredible ability of the human mind to rationalize.

This is a great thread so far. I'm gonna be watching it. Like you Teazer, I'm inclined to take PO's at their word, but with a sense of caution. I believe it is rare that they are literally speaking untruths, but more likely they don't know what they are actually talking about in the first place. In the case of Goldilocks, it's a hard sell though. If he said "it used to run", I guess he wasnt technically lying. I'm sure that at some point in history the bike did run. What year is it? I bet it ran that year. It sounds like once it ceased to run he parked it and thats when you came in.

But I believe that regardless of experiences like this, I have to maintain some modest level of trust in humanity. As for Goldilocks, she's a motorcycle, and you can trust that.

"Used to run" is a euphemism for it's dead now but at some point in the long distant past it used to run.

In this particular case, I believe that the PO believed that it ran OK, but actually has no idea how bad it was. He's a good guy but he's not a mechanic or an engineer. He's a good welder though and an upright guy. I have known him for years and he gave me the frame (with title) for my last GT750 - zero cost.

That's why I used the old Ronnie Reagan expression "trust but verify".

Golidlocks is a 72 and I'm sure it ran just fine back then and that's only 41 years ago. Almost seems like yesterday ;-)

Well, looking to see what else Pandora's box has in store for you haha!

When I get a few minutes I'll post some pics of the 550 carbs. A buddy of mine rode round on his CB900F yesterday and is interested in the 550 as a project as soon as he sells his DOHC 750. The 750 was his first big bike asnd has led him down a path to multiple bikes and full garage but an empty wallet. Funny how that works.

Bike number 2 is already completely stripped for a ground up rebuild - not so much a full restoration because I'm leaving the bodywork in its original paint. Pics to come.

If I wasn't trying busting ass and resources to get my 400f done I'd be interested in that 550!

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Ronnie,

That would break your heart, so don't go there. I love the 400F. Sweetest looking SOHC ever and they can be made to motor along quite fast, but a 550 has the potential to make substantially more HP than a 400F with the right modifications.

Make the 400 the best bike it can be and enjoy the journey and the ride. You know the old saying " I can resist anything . Except for temptation" That's me. Please resist....

Haha I hear ya, luckily I have some control! I am already stretched with my two bikes and a few boats... Haha!

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Subscribed.

I'm on board.

"Morbid curiosity" is the best way to describe why I am tagging along.... like slowing down to look at a car wreck.
But I know you'll pull this off. Glad you found that issue with the 550 and not the 750. Is that what's next?

Why the hell not?

I like the gt550, a buddy of mine had one, it was slower than my T500 but was very smooth and had a sweet sound. I am guessing that the engine could really be wakened up because Suzuki was conservative in porting with these guys. There is a lot of heavy components that can be removed and I bet you could knock 70 labs or so off of it. They are a lot rarer than the CB Cafés.

Finding the problem is the first step in fixing them. Bikes that drive me nuts are those that look like they should run and you slowly end up pulling the whole thing apart as you chase problems. My preference is to locate and identify the problem and then strip the motor and fix it properly the first time.

The Red 750 is already reduced to a pile of chain grease and flaky paint on the shop floor. There is not a single bolt or part left to be removed. Waiting on parts to arrive to start a rebuild. Motor first then frame and then add parts as they are finished.

CarbsAndCylinders said:

I like the gt550, a buddy of mine had one, it was slower than my T500 but was very smooth and had a sweet sound. I am guessing that the engine could really be wakened up because Suzuki was conservative in porting with these guys. There is a lot of heavy components that can be removed and I bet you could knock 70 labs or so off of it. They are a lot rarer than the CB Cafés.

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A buddy of ours decided to buy it to turn it into a STOCK class drag race bike. I'll guide him through the rebuild and have already worked out some porting changes to try. May even soak the carbs in a special growth hormone we developed in house to make the carbs bigger without anyone noticing. Starter can come off and pipes can be changed but it has to stay Stock but I figure they all came with carbon fiber fenders back in 72 didn't they? We can always grab a can of "chrome" paint. ;-)

Can you drill the shit out of it for stock class, put on alloy rims? Can you get your buddy a thighmaster?