Pre-750 dirty gas/petcock/carb questions

[600toStart]

The first thing I noticed wrong with my new 750 was a broken petcock that leaked fuel on all settings.
I disassembled it to find this:
The shaft of the diaphram seems to be fused to the petcock housing because I cannot get it out and every part of it broke down to this.


There was A LOT of rust and dirt in the tank too. When I was pouring out gas from the petcock opening on the tank there was so much rusty nasty junk in the gas.

Upon removing the carbs I found this:


While cleaning the carbs I discovered one of the chokes was stuck. The other 3 slid in and out just fine.
I didn't drain the bowls yet or disassemble the carbs what so ever.
If these carbs work I'm not messing with them like I did with my 600's which are still disassembled because I need to replace all the rubber parts...

Freshly bathed carbs. I only cleaned the outside, the butterflies, and the walls on the outside of the butterfly plates.




You can see the two carbs on the left have discolored walls from the orange/white gunk that was all over them. I scrubbed the walls and butterflies with a maroon scrubber.


If you look closely you can see the needles on the 2 left carbs are all gunky too:




Here's the 600's petcock, it looks really nice:


So my main questions/concerns are these:
The guy I bought it from said the bike was sitting for at least a year outside not covered.
Is it safe to assume the leaking petcock contaminated the engine oil with nasty junk?
Do you think simply changing the oil will suffice or should I get some engine flush?
I'm planning to wash out the intakes of the cylinders then pull the spark plugs and crank the engine to shoot out any stuff in the cylinders.

[MickM]

Yes your oil has all the junk from the tank in it.
Do not try to sart it or turn it over.

Drain the oil out and look at it, remove the oil filter too.

Engine flush has to be sucked up into the oil pump.
So the engine has to be running.
I have used it on cars, not very successfully.
It may well destroy your wet clutch.

If the oil is really nasty you may want to remove the oil pan.
You should then be able to clean the oil pump pickup/strainer.


number 11 here:

http://fiche.ronayers.com/Index.cfm/Module/Main/TypeID/26/Type/Motorcycle/MakeID/2/Make/Suzuki/YearID/32/Year/1991/ModelID/6206/Model/GSX750F_KATANA/GroupID/252090/Group/OIL_PAN

New filter, clean oil.

Mick M.

[600toStart]

Thanks MickM!

The night I picked up the bike we tried starting it for like 5 minutes. It would kick over for a second at a time but wouldn't run because the choke lever wouldn't move. Good thing the contaminated oil only circulated while cranking. If that could be considered a good thing... it is compared to if I had been able to start it up... I probably would have gave it a good revving or two.

Could anyone confirm whether or not engine flush will mess up the wet clutch?

Guess I'm gonna have to drop the pan to be safe.

[Kreylyn]

It's not gunky gas you have to worry about at this point... it's water damage.

You have severe oxidization on all aluminum parts that was left with sitting water in them... Petcock, and carb bodies 3-4. In addition, it would appear that water also leaked into and sat in the the 3-4 chambers for the engine it's self causing some pretty major rust to occur. I'll pretty much bet that further leaked into the engine crank case, and the tranny/lower case may have some rust dmg as well.

My suggestion to not end up with a scrap motor and carbs (if they are not already to far gone) would be a complete tear down and rebuild of both motor and carbs.

If not, you may be it to run but it's life will be drastically reduced.

Krey

[600toStart]

You think a disassembly and good cleaning will be sufficient?
As opposed to a rebuild?

So, it may appear that the K&N filters let water in the carbs/engine.
That wouldn't have happened with the stock air box would it?

Is there anything to do to stop and clean the oxidation on the aluminum?

[Kreylyn]

You think a disassembly and good cleaning will be sufficient?
As opposed to a rebuild?

So, it may appear that the K&N filters let water in the carbs/engine.
That wouldn't have happened with the stock air box would it?

Is there anything to do to stop and clean the oxidation on the aluminum?

It depends on how damaged the engine is.

Simply put... oxidiation/rust is what is left when the base metal is consumed through the process. This means pitting, or worse... a serious reduction in the actual surface.

Now, if it's not too bad, then simple removing the rust/oxidization can help to put you back in mostly good working order. It will never be 100%, but depending on how well it's taken care of, you can get back close enough that the engine and parts will last you as long as you own the bike.

Pretend it's a sickness... and the only way to keep the bike from making it's self sick in the future, is to fully eradicate the sickness. If you don't, it will simply spread again. Rust will spread, like it's a virus almost.

The main areas of concern... rust/pitting in the cylinder walls, wear on the piston rings due to it, rust damaging the edges of the valves, so on. This is what I would suggest a tear down and clean. There are offerings that will neutralize the rust out there, like navel jelly. I think there is a new gallon jug liquid that is supposed to do the same thing. Just let it soak and the rust goes good bye.

Clean the rust off, oil the part to prevent it from coming back, and reassemble if the parts are not damaged. If it is damaged, then you may need to replace/repair.

For the carbs... If it's heavily oxidized, you may need to look at anodizing or polishing the parts to prevent it from coming back. Just brushing off the oxidization (white powdery stuff) leaves you with a surface that is very prone to just doign it again. Oils will wash off, especially if in contact with gas.

Krey

[600toStart]

So not only is one of the chokes stuck on one of the carbs but the whole black plastic thingy that bounces up and down on that same carb is also stuck in place. I hope that carb survives.

Btw, thanks for your input Krey.