Cafe Racer Forum banner
41 - 54 of 54 Posts

·
Registered
Joined
·
1,473 Posts
TR750 frame is nothing like a street GT750 frame, TR has rigidity through triangulation all the way from the steering head back to a much longer stronger square profile swingarm as you would find on a current model dirt bike.


another jalsteve bike photo (y)

edit: jalsteve has a video posted if you want to see how much smoke and noise you might expect
Amals? sweet
 

·
Registered
Joined
·
9,021 Posts
OP if you haven't found it already; there is one more huge problem you will encounter once you manage to extract more horses out of a GT750 engine: Suzuki 750 two stroke triple TR750 classic racing motorcycle flexi fliers As per the Suzuki factory techs all the way back to 1972 they determined the stock wet clutch can not handle the extra horses, the factory fix was to run the clutch dry, but to convert a GT750 engine to dry clutch operation you lose the kick starter. Unless you can figure out how to fit it with a greater number of thinner then original carbon fibre clutch plates, I think your dream of a GT750 street racer that will hang with 100+ horse sport bikes just evaporated.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #44 ·
Can anybody offer me any tips on which way is best to remove the cylinder block from the bottom end of the 1974 Suzuki GT750 engine. I've seen some say that remove the cylinder while engine still mounted in the bike frame. Also, that the cylinder removal is a real pain in the a*s. My engine is also locked up (5 degrees rotation maximum). Not sure if a piston is seized to the cylinder wall or not, I know will make much more difficult.
 

·
Registered
Joined
·
9,021 Posts
.... My engine is also locked up (5 degrees rotation maximum). Not sure if a piston is seized to the cylinder wall or not, I know will make much more difficult.
2-stroke has ports in the cylinder walls, if a piston ring or pieces of one catches on the edge of a port that would do it. If the piston was seized in the barrel you would see no rotation and yes the piston might be hard to extract from the barrel, even harder if there was zero rotation at the crank.
Have you pulled the exhaust and looked into the exhaust ports yet?
Photos of your project would be nice, without them we are flying blind here.
 

·
Registered
Joined
·
9,021 Posts
Endoscope was an expensive tool at one time, now they have become very affordable. That's the only tool you can use to view inside an engine without significantly taking it apart.
 

·
Registered
Joined
·
3,620 Posts
TR frames were somewhat different to street GT frames. GT frame is unbelievably heavy with cast engine mounts and very thick wall tube. It's also a bit soggy but handles well enough with a fork upgrade and better swingarm. TRs had normal round tube swingarms. Check out almost any GS series swingarm. They are lighter, longer and stiffer than the GT and the same width at the pivot but use needle roller bearings the same as any modern bike.

TL or GSXR swingarms can be fitted but require some modification. TL has a slightly larger pivot so the GT frame has to be reamed out on one side and a new thread cut on the other side. GSXR swinagrms use larger diameter swingarms and need to be sleeved. Anything is possible if you are inventive and handy with tools or know a shop that can do it for you.

Clutches are OK for 80HP. I ran one with early style fiber plates in it (they are weaker and more prone to breaking) and the owner manages to pull wheelies all day with that set up. Kevin Hutchinson has a drag bike GT750 making north of 150 hp on Nitrous with a wet clutch. He does use a lockup arrangement but up to about 100HP that's not really necessary.

I love that plated piston photo covered in carbon.

Block can be removed with motor in situ but if the crank is coming out anyway, pull the head and remove every part possible staring with clutch and alternator and points side cover and so on to reduce weight. Those blocks are always difficult to remove because as they lift, they pull on one side or the other and jam on all those studs. next problem is that water gets down past the sleeve nuts and the studs and barrels chemically stick together. And of course sometimes the pistons are rusted in the bores. Or more specifically the bores and rings are rusted and pistons may also corrode but that's less common.

5 degree rotation could be anything from a stuck piston to something in the bottom end. The only way to find out is to pull it apart step by step. Is it in gear by any chance?

Best way to get closer to your buddies is to lose weight, improve handling and brakes. here's one way to do the brakes https://pinkpossum.com/GT750/phattrakka2/p5brakes.htm

Expansion chambers save a huge amount of weight too. Replace the clocks with a single modern clock, fit a small battery and modern regulator/rectifier. Alloy rims are a nice way to upgrade looks, increase rim width and loose a little weight.

A few reed valve conversions exist but no kits on the market. The water cooled block makes everything more complicated than it has to be and converting to reeds doesn't add a lot until you get to very high power levels and need more transfer port area. Brett deStoop in Australia cast his own block with twin reed valves per cylinder and reportedly gets over 250hp out of his LSR motor. That's probably a wet clutch too.

Simplest ignition upgrade is Accent available from Uwe in Germany. Lots of other options but that's cost effective and they work well.

I would suggest you snd your bike here but I have two GT750s in teh shop already and another 2 waiting plus a complete T140 ground up restoration so you might be better to do what you can yourself. It will be a voyage of discovery and a great learning experience.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #50 ·
Teazer, thanks on the great info in last post. I will follow thru along with all the info in past postings on this topic page. Were abouts is your location if I were to consider dropping a GT off at your garage? I have 2 of these GT750's since finding out the one engine has the locked-up engine. Bought the other to do an engine swap just to be able to ride the bike asap besides Michigan winter season here now. Might consider restoring the other one to original. Both are '74's.
 

·
Registered
Joined
·
9,021 Posts
Anybody know if a 1978 Suzuki GS550 motorcycle swing arm and frnt/rear wheels fit the '74 GT750 chassis? Looking to upgrade to rear disc brake and aluminum rims....
I imagine they could be made to fit but that is not much of an upgrade, you are still shopping for 1st. generation 1 pot disc brakes with round pads.

Any steel rim with spokes can be fitted with an aluminum alloy rim upgrade.
 

·
Registered
Joined
·
3,620 Posts
Teazer, thanks on the great info in last post. I will follow thru along with all the info in past postings on this topic page. Were abouts is your location if I were to consider dropping a GT off at your garage? I have 2 of these GT750's since finding out the one engine has the locked-up engine. Bought the other to do an engine swap just to be able to ride the bike asap besides Michigan winter season here now. Might consider restoring the other one to original. Both are '74's.
Just north of Chicago near the WI border
 

·
Registered
Joined
·
3,620 Posts
Anybody know if a 1978 Suzuki GS550 motorcycle swing arm and frnt/rear wheels fit the '74 GT750 chassis? Looking to upgrade to rear disc brake and aluminum rims....
Fit a GS750 or 100 swingarm and a spoked rear disk brake wheel with aluminum rim. I have hub, disk and rim plus fresh spokes in stock. Sold the three swingarms. Might see if a box section can be made to fit.
 
41 - 54 of 54 Posts
Top