Sourcing of 73 GT550 Carb Kits

[ukfan4sure]

Well I ordered the Keyster VM-0028 kits for my carbs and they were wrong. The bowl gasket was not the same. Can anyone point me to the correct carb kits I need?

I have the low hat version of the VM28, if I'm not mistaken.

[jabcb]

Best to not use carb kits unless you need to.

Look for a number stamped on the flat surface near the coke plunger — its the second part of the carb part number followed by a letter designating the cylinder (“L” / “M” “R”).
Suzuki sold five different versions of the early J/K carbs. The stamped number ranges from 34011 thru 34015.

Use your stamped number to make sure you are looking at the correct carbs. See:
https://www.partzilla.com/catalog/suzuk ... indy-gt550
https://www.oldjapanesebikes.com/mraxl_ ... /index.php

The pilot jet, main jet, needle valve & some other parts are standard Mikuni parts that are still available. You can save some $$$ by getting the standard parts.

[ukfan4sure]

Wow, thanks. This was getting frustrating. My Grace Lime metallic baby is going to come back to life hopefully!

[ukfan4sure]

I'm really starting to feel foolish... Mine are stamped 34012. All that in the references you mentioned are 13,14,15. I have the a parts manual laying out the Suzuki part numbers for 1973 (K), but that doesn't tell me if it applies to the 34012 carbs. These were carbs I picked up due to the fact mine were calcified in the bowls to the point I wasn't happy with them.

[jabcb]

The carbs on my GT550J cafe build are also 34012. Have the carbs apart & given them an initial cleaning. So I also have a lot of carb work to do.

I have a printed GT550J parts manual, which lists only the 34011 version. Might have printouts of the 34012 carb parts manual pages. Will take a look.

Over the summer I cleaned up a friend’s GT250M carbs that were awful. Total PITA! Going with clean used carbs can make a lot of sense if you can find them & they are in your budget.

Suzuki varied the GT550 jetting over the 6 years of production. Am definitely not a carb expert, so I can't provide much advice on what to go with. Comparing what is in the 34012 carbs & your original carbs is probably a good starting point.

[ukfan4sure]

Thanks.

[Vintageman]

I currently have a 73 GT550... some experience messing with these carbs.

The Needle Jet is obsolete and it is in the O-x size. Mine was stock O-5 and over the years I had purchased 2 sets of NOS O-6 for my bikes which work lovely on stock pipe or bike with chambers that come on (start boosting-increasing compression) at upper mid range RPM. Very good mpg and you can use the jet needle clip to compensate if needed.

When you get yours out look at number stamped on them. These can be eroded due to oxidation as the jet needle holding moisture upon them due to humidity for decades. Where the needle enter the needle jet, for a few mm, that precision machine barrel must be true and very smooth if not shiny inside. It can look a little pitted like the surface of the moon and bike will not run as good as it should. You need good light shined inside them and good eyes too inspect (Magnifying glass to see in there).

I think the jet needle stayed the same from 72-77 (check the above info others gave you to look this up). They are obsolete too. I acquired extra carbs and got some good ones that way. If yours are bad, maybe the Keyster kit is close enough. I always strive for stock ones. The Jet need can also erode and show wear rub marks.

If you have a lot of miles ,rub marks on the Jet needle usually means the needle jet has worn too.

For street riding pristine Jet needle and needle jets is critical.

All else I would use new available Mikuni items... forget if bowl gaskets is available still, but a lot of junk aftermarket out there and you at least want NOS.

The other items that fails soon after you put some miles is the crank. It is very unlikely there is no moisture damage, say for example in the big end rod eye, crank pin and even roller area. You can check the small end easily when you remove piston. The big end, if you look in the slot of rod with very good lighting you can partially inspect cage rollers and if you see any pits or rust stains on them you'll know. Only real way to know is to tear down. I think con rods are obsolete and some of the crank bearing too. Crank pins may still be available. NOS rod syou find usually have shelf damage due to rust inside eye... ask first... some say you can use a a KTM200 rod but its 1mm longer... raise jugs same amount... this stuff you will learn.


Pristine carb, good bottom end, fresh top end and the thing will run amazing and reliably.

[Vintageman]

I currently have a 73 GT550... some experience messing with these carbs.

The Needle Jet is obsolete and it is in the O-x size. Mine was stock O-5 and over the years I had purchased 2 sets of NOS O-6 for my bikes which work lovely on stock pipe or bike with chambers that come on (start boosting-increasing compression) at upper mid range RPM. Very good mpg and you can use the jet needle clip to compensate if needed.

When you get yours out look at number stamped on them. These Needle Jets can be eroded due to oxidation as the jet needle holding moisture upon them due to humidity for decades. Where the needle enters the needle jet, for a few mm, that precision machine barrel must be true and very smooth if not shiny inside. It can look a little pitted like the surface of the moon and bike will not run as good as it should. You need good light shined inside them and good eyes to inspect (Magnifying glass to see in there).

I think the jet needle stayed the same from 72-77 (check the above info others gave you to look this up). They are obsolete too. I acquired extra carbs and got some good ones that way. If yours are bad, maybe the Keyster kit is close enough. I always strive for stock ones. The Jet need can also erode and show wear rub marks.

If you have a lot of miles ,rub marks on the Jet needle usually means the needle jet has worn too.

For street riding pristine Jet needle and needle jets is critical.

All else I would use new available Mikuni items... forget if bowl gaskets is available still, but a lot of junk aftermarket out there and you at least want NOS.

The other items that fails soon after you put some miles is the crank. It is very unlikely there is no moisture damage, say for example in the big end rod eye, crank pin and even roller area. You can check the small end easily when you remove piston. The big end, if you look in the slot of rod with very good lighting you can partially inspect cage rollers and if you see any pits or rust stains on them you'll know. Only real way to know is to tear down. I think con rods are obsolete and some of the crank bearing too. Crank pins may still be available. NOS rod syou find usually have shelf damage due to rust inside eye... ask first... some say you can use a a KTM200 rod but its 1mm longer... raise jugs same amount... this stuff you will learn.


Pristine carb, good bottom end, fresh top end and the thing will run amazing and reliably.