GT750 won't idle on left cylinder.

[Striker1423]

Teazer, I would say it might have been antiseize? Seems a good spot as you said to get some basic work done.

Does Bill Bune do full motors? Not that I want to send it to him necessarily. It's just a complicated mess compared to the Yamaha, and my propensity to feel like everything was done right only to promptly mess something up is higher than average.

[busa1300]

Bill Bune did both my RZV cranks, and he bored my cylinders....beautiful work....very happy when I got the parts back.

[teazer]

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.

[Striker1423]

I'm in Southeast Michigan. I mean, don't get me wrong... I'll do the motor, just won't like it lol. But, I see Cruzinimage has full crank rebuild kits too. About $400 plus shipping. Would you run one?

[teazer]

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.

[teazer]

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.

[Striker1423]

Teazer, I know it needs at least the right rod as its pitted and rusted. I figured the cost for everything from BBE and Cruzin' for parts. Crank rebuild, top end and decking the head to be $1250 or so before shipping. Josh told me over the phone that Suzy parts are increasingly hard to find and that Cruzin' was my best bet anyhow. I'll just fill in the shipping to go directly to his shop so I'm not double posting parts.

I don't want to spend a bunch of extra cash, but I also wouldn't mind just getting it over with in a sense either. I'll probably ask for the old bearings back just if they're OK. If they're rusty or worn out, then no.

[Striker1423]

So the top end the cylinder bores are offset so bad, I don't think they would even take a fresh bore job. Best bet seems to either send it off to Bill Bune, or just go with the next best thing. The whole setup from the guy I know. Then just send that top end etc to BB.

This is... really bad haha.

[m in sc]

3mm overbore and sleeve it to a 900. 

[sav0r]

These head gaskets are notoriously bad. The heads too.

[teazer]

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.

[Striker1423]

I just received a 71mm cometic head gasket in the mail. 100 bucks. Will that still work, or am I playing with fire? I guess I can just use what comes in the gasket kit I ordered off Ebay... same one that was on it basically.

Engine seals, and bolt kit showed up. Guy on FB in Canada has a set of cases that are in good shape too. We'll see if he delivers on what he said he has. Almost got the cases to the separation point. Just need to see if all the bolts come out OK.

That motor is a 72 correct? Aren't they quite a bit different than what is on mine? Or are the engine cases the same?

[teazer]

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. 

[Striker1423]

Well, it came apart. It's bad haha.

[teazer]

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.