GT750 won't idle on left cylinder.

[teazer]

I have had no issues with CI parts.  I suspect that some of the cranks may have had rust pits where the seals run and that can ruin seals.  It's not unusual to have to ship two cranks to Anoka to get one good set of parts out of it.  Usually, minor pits and scratches can be polished out but if they are too deep, parts need to be replaced and use a bearing sleeve.

Bill Bune's team are familiar with our cranks and know what to do to ship back a good crank that should last for years.

Some people just don't like CI parts I guess.

[Striker1423]

Josh told me they'd do a more through assessment when he actually starts the work, but the cylinders look the way they do as they've been welded up and sanded down on both left and right cylinders, probably after a crash. Hard to tell on my end, but believable as the side cover has a huge welded crack that didn't get sanded down as nicely. He also said the bores looked normal to him... for a GT750. Although badly off-center it is far from untouchable. So... that's good I guess lol.

He stated there isn't any way to fix the exhaust holes where the sealing surface is non-existent. My welder might disagree, but he has yet to call me about the top engine case or side cover. This is the same it was when I had my snowmobile pipe over at his shop. Slow to do the work as he doesn't really make money on side jobs.

Will see how much is good, bad or otherwise on the crank hopefully next week? Josh didn't really give me a timeline.

[teazer]

Misplaced cylinder sleeves are common on GTs and some are a long way out. Some match the heads but on many there is some offset between bores and chambers.

https://pinkpossum.com/GT750/GT750head.htm

That's why Suzuki and aftermarket suppliers supply head gaskets with 76-77mm bores so they don't overhang the bores. My preference is to use COmetic head gaskets with say a 72mm finished bore and then gently open up the stud holes as needed to let the gasket move to the correct position.   

On a stock motor, oversized (stock) gaskets are rarely a problem but if compression is raised they tend to detonate in that area and blow out the fire ring.

Tell us more about the crash damage.  I don't remember that being mentioned before.

[Striker1423]

Well, the first inkling of damage I noticed was the right side charging cover looked kinda wonky on the bottom from rod scrape. I figured someone just smoothed out a few rash scratches until I took the motor apart and the cover had been cracked almost in half and welded back together.

Josh said the cylinders were welded and repaired due to a crash most likely. I didn't know exactly what he was talking about, but he thinks the outer exhausts were welded up which is why the gasket sealing surface is gone on both sides.

[teazer]

When the fall on that side, the cover usually falls apart.  It's wide and thin.  Nice casting work but zero strength when a big fat bike lies down on it.

What happens next can be more serious.  I have one in the shop that was crashed on that side and it not only destroyed the rotor, but managed to bend the crankshaft.  In this case, the end was out of round by about .065" and had to be replaced.  The rest of the crank was fine though and the outer crank wheel was still round and it was only the part outside the bearing that was tweaked.  If anything is wrong with yours, Josh and his team should be able to make it right.   

Welded barrels sounds more serious though and most unusual.  Damaged exhaust threads are common enough and usually can be repaired by opening them out and welding in fresh metal and then drill and tap back to size. But I guess if a crash was bad enough and ripped off the pipes, that could cause substantial damage around the exhaust port.

Did you have any pictures of that damage or welding repair?

[Striker1423]

https://www.2strokeworld.net/forum/index.php?topic=4581.msg38748#msg38748

I don't know if I agree with his sentiment on it, unless I'm just missing something...

[Striker1423]

So, just for S's and G's I ordered from Babbits a new temperature gauge for the GT750, figuring the thing was just showing it was in stock, but not actually... Well, it shipped! Lol, I guess now I get to see what a new gauge looks like!

[teazer]

I remember that picture but couldn't find it when I was looking the other day. 

That exhaust is a mess for sure.  The small pits are not an issue but it would be best to have that floor welded or machined to take a spacer to replace the damaged metal.

I doubt that damage is from a crash.  It looks to be eaten away by caustic soda or someone put an oxy torch in the port to burn off carbon.  Either way it should be repaired or replaced. if anyone can repair it it's probably Josh at Bill Bune Enetrprises.

[Striker1423]

I remember that picture but couldn't find it when I was looking the other day. 

That exhaust is a mess for sure.  The small pits are not an issue but it would be best to have that floor welded or machined to take a spacer to replace the damaged metal.

I doubt that damage is from a crash.  It looks to be eaten away by caustic soda or someone put an oxy torch in the port to burn off carbon.  Either way it should be repaired or replaced. if anyone can repair it it's probably Josh at Bill Bune Enetrprises.

Josh told me it's unfixable. I might just have to have my local guy attempt it if he will. The welder doesn't really take side jobs anymore.

[teazer]

It is fixable,  but will probably cost much more than finding a replacement cylinder.

[Striker1423]

Which was my only other thought. I doubt he has any extras laying around his shop though. And getting the right year, or later model cylinders might be hard.

[m in sc]

its def fixable, you just need a BIG welder to get it hot enough.

[teazer]

What year/model?  I might (long shot) have a set in my stash.

[teazer]

What year/model?  I might (long shot) have a set in my stash.

Would also need to pre-heat the block and probably cut away a lot of metal just to get in there. I would be more tempted to machine in and press in an insert and ignore the rest of the pits.

[Striker1423]

1975 M Model.