Gs650 81 to 82 carbs interchangeable?

[Traycej]

I have an 81 Gs650 the #2 carb housing is cracked, I have a set of 82 Gs650 carbs am I able use the #2 carb on my 81 650 or will I need to find a new 81 carb?

I wasn’t able to find anything on 81 and 82 carb interchangeability, I appreciate any information or advice you all have, thanks.

[sacruickshank]

I have an 81 Gs650 the #2 carb housing is cracked, I have a set of 82 Gs650 carbs am I able use the #2 carb on my 81 650 or will I need to find a new 81 carb?

I wasn’t able to find anything on 81 and 82 carb interchangeability, I appreciate any information or advice you all have, thanks.

I expect it will be a easy swap since they all use the Mikuni BS32SS. I recently mated carbs 1&4 from an '81 with carbs 2&3 from an '83. They are not mounted on the bike yet for a test start (hopefully today), but I expect it will work fine.

This link provides info all the compatibility questions you may have

https://gsarchive.bwringer.com/bikecliff/images/carbspec_float_height.html

[Who Dat?]

Physically, the carbs are nearly identical. They actually have a different model number, but I could not find any differences in the carbs themselves.

The biggest thing you will have to watch for is if one of the sets is from a 650E, it will have different jetting. Just make sure the jets from the old carb are put into the new one and you should be fine.

[Nessism]

Partzilla can be used to check the PN's of the internal components.

[sacruickshank]

Physically, the carbs are nearly identical. They actually have a different model number, but I could not find any differences in the carbs themselves.

The biggest thing you will have to watch for is if one of the sets is from a 650E, it will have different jetting. Just make sure the jets from the old carb are put into the new one and you should be fine.

Speaking of jets for these carbs, how big of a difference will one size in the pilot air jet make? Specifically, going from #160 to #170 in 2 of the 4 carbs and assuming all other jets, filters, and exhaust are the factory parts. Asking purely for convenience of using parts on hand, not for any performance reason.

[phydeauxmutt]

A larger pilot air jet (170 vs. 160) will lean out the mixture that is formed with the pilot fuel jet. That will make the pilot mixture a bit leaner, it might require just a touch (1/8 turn?) more on the pilot screw to get the same overall mixture.

Probably not enough of a difference for mere mortals to notice, but at least make them all the same, if you can.

[sacruickshank]

A larger pilot air jet (170 vs. 160) will lean out the mixture that is formed with the pilot fuel jet. That will make the pilot mixture a bit leaner, it might require just a touch (1/8 turn?) more on the pilot screw to get the same overall mixture.

Probably not enough of a difference for mere mortals to notice, but at least make them all the same, if you can.

That's what I thought, thanks for the confirmation.

This carb rack will be far from perfect/factory since:
- #1 has aftermarket #170 pilot air jet and the outlet port beneath the mixture screw has been enlarged by previous owner. Fiddling with mixture screw definitely required, currently 1.5 turns
- #2 has factory #160 pilot air jet, but I couldn't get the mixture screw out. The passage is definitely clear, but I don't know the # of turns. Probably still at factory settings since I had to remove the factory seals.
- #3 has factory #160 pilot air jet and the mixture screw has been removed, cleaned, and replaced. Fully adjustable mixture screw currently at 2.5
- #4 has aftermarket #170 pilot air jet and the mixture screw has been removed, cleaned, and replaced. Fully adjustable mixture screw currently at 2.5

Like I said... far from perfect. Luckily this is a winter project and I'm still evaluating if the engine is any good. I'll need to check valve clearances after this first test start. Also, this is not my only bike, and riding season is still far way.