Messages

Looks like an ARD magneto.

Don't think that triple was designed to be ridden.  It's a show bike for sure. It will look great in someone's collection of overpriced cars.

That adapter is way more elegant than the three bolt one I used.

Not sure why an RZ needs a fan, but I just noticed that the hybrid has what looks like a brand new TZ water pump.  Mine are all ground down and scored after sliding up the road with a bike on top of them. 

Nice adaptation.  Did you weld up a boss on the side cover for it to sit on?  I had an adapter plate from a kart mounted TZ/RD hybrid that I used on our RD cases, TZ top end and wet clutch drag race motor.

Yea, I think I'm sticking to the trans I have. Fourth gear for the M series is a yeti. ................

And by some shear coincidence, the 8 valve GS750 has basically the same transmission with one or two better gears and a 16 valve 750 from say 82/83 has different dog design on the troublesome gears.  I ran a GS trans with GSX gears in one of my GTs and IIRC, those same GS and GSX gears will fit of a GT shaft with little or no machining required.

I am fitting a GSX1100 trans in my drag bike motor and apart from a couple of wider gears and longer shafts it is the same design as a GT but with updates. To fit that I needed to have bearings and shafts machined and a few other changes as well, but GSX transmissions are available.

Don't tell anyone.  It's a secret...

I'd stick with what you have rather than having two sets of parts that need work.  i have had a couple of sets built up with weld where a chain came loose and they both ended up fine.  Took a but of work to grind/sand them back to the correct profile but that's why we have winter....

They all look like that after a few years. I have seen worse come out of motors that shifted flawlessly. If you do decide to replace it, Nova in the UK have them but for the JKL transmission gear sets. M/A models had a different 5th gear set and late model A and B had different second and third gears. 

I have a list of all the gears and part numbers here from GT750L through GS1100 that I compiled when I was mixing and matching gears if you need any info on gears.

Not good but not as bad as it might have been.  That's typical on a motor that sat for a long time.  Sometimes they are like new but that's if the oil tank drains into the cases.

Looks like the alternator end seal spring failed and the seal allowed air and moisture in which caused the rusty end and rusty bearing.  I would ship as-is to Bill Bune Enterprises and have them order a set of seals and main bearings or order them yourself and ship the whole lot up there.

You could also try spinning the other mains and see if they sound crusty or spin smoothly.  Some may be OK, but if most sound gritty, I would recommend a complete set of bearings and seals.   

The rest of the motor and transmission don't look bad at all, but check second third and 4th dogs on the output shaft. Clutch shaft dogs are usually OK but check them anyway.

And while it's apart, rebuild the water pump.

edit: I just checked the video again and expect the right (left on your bench) big end to be rusty but you might be lucky.

71 will be fine.  That's what I order for stock or .5 o/s bores.  You have to check for clearance though to make sure the fire rings do not overlap the bores at any point. You may have to trim the bolt holes slightly to make it fit.

For my money, a Cometic head gasket is the only way to go.

Yes, a 72/73 motor typically comes with old style crank and rods and old style cases depending on how late in the production run it was manufactured.  Top ends have slightly different porting but on a stock bike the difference isn't huge and anything can be ported. 

Sounds more like they rust them to hide the fact that they are modified and are illegal.  What?  That rusty thing over there.  nah. Of course it's legal....

That is for the Australian market.....

That looks like it should be able to be cleaned up with a 0.5mm overbore. 

Some barrels are worse than others but they usually bore OK.  And order a head gasket from Cometic with say 72mm finished bore size and check to make sure it fits over the studs and does not overhang the bores.

An alternative is that you could buy that motor from Busa1300 and hope the bores are more central than yours.  And the crank may be better than yours so you could save on a set of rods and probably main bearings too.

What he said....

This is more common and can usually be cleaned up and used.

If you pull the outer bearings you have to be careful not to score the crank at the seal surface.  I usually send the whole crank.  Pulling bearings doesn't save any money and you risk damage.

The funny thing with these cranks is that they really don't wear out and that's probably a symptom of few miles relative to the ruggedness of the design.  What does destroy parts is rust.  If the balls or races are pitted, it will never run right and if the parts of the crank that the seals run on are rusty, then it will never seal.

BBE have called me a couple of times when rebuilding cranks for me to say, we need 2 replacement main bearings or a rod or a crank end because one or more parts are not good enough to put back in. But they can usually just clean the parts and pop them back in. Seals are always replaced, but bearings and rods, not so much. I have been very fortunate to inherit a few spare cranks and had a couple of other donated to the cause and I bought another one or two, so I have had cranks to use as donors, but quite a few contained zero usable parts and always rust was the cause.

What I would do in your case is to buy a set of seals from your local dealer or Cruizin and send them plus crank to BBE and ask them to strip clean inspect and build the crank.  If the bearings are shot https://www.cruzinimage.net/2018/06/06/72-77-suzuki-gt750-crankshaft-rebuild-kits-oil-seals-bearings/

You could send the crank to BBE and ask them what parts it needs and then purchase what you need.

I believe that is the set that Roy Gibson uses and Paul Miller sells, but that's speculation on my part. It's unlikely to need rods but will need rings or maybe pistons. Cruizin pistons are perfectly good enough to run on the street if the bores need to be freshened up. 

This is a bad example of rust under the outer crank seal.

Bill Bune Enterprises is essentially a machine shop that does great work at reasonable prices. They can source parts, but I usually send them pistons and crank seals.  And sometimes I have to send them straight cut primary gears and new conrod kits but that's another story.

I don't believe they do complete engine rebuilds. You could probably do the rebuild yourself.  It's quite a simple motor but as you can imagine it eats time like a hungry black hole gobbling up galaxies. The next issue with having someone else do a motor rebuild is that a complete motor weighs about 180 pounds and that means shipping on a pallet by truck or deliver it yourself. 

i recently drove to IN to pickup a GT750 for a rebuild but I think you are even further away IIRC.