Carb Vacuum/fueling issues

[Steve]

There’s still two 1/4” lines that were on the carbs when I got them. Any idea where those are suppose to go

Ideally, all lines should be metric, so those 1/4" lines need to go in the trash bin.

Unfortunately, most hoses that you will find in the auto parts stores are thick-walled, reinforced hoses that will withstand the pressures in a fuel injection system. That makes them bulky and non-flexible, which is the main reason that I avoid them. Yeah, the proper stuff costs a bit more, but don't let the price scare you off too much. The fuel line is about $12 or so, but you get about 6 feet of it for that price, not just the few inches that it takes for your bike.

Fuel line is 7mm, which is in between 1/4" and 5/16", and the proper hose works SO much better.

In post #11 you appear to be pointing to the vaccum line that goes to the petcock. That is 4.5mm hose. If you don't want to splurge for the proper stuff, 3/16" hose is pretty close.

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[TPELL603]

Still working issues out. Had the carburetors off and cleaning them up and one of the studs broke for the float bowl mount. I ended up picking carbs off an 81 GS450L that ive taken apart and started cleaning. Ive got K&N PODS 48MM and EMGO mufflers on it so once i get these carburetors back on ill start the whole jetting process

[LAB3]

On my bone stock 450t those two lines are the float bowl overflow tubes, they route up over the carbs and sit on top of the airbox. Can't imagine an L model being that much different.

[TPELL603]

Getting there

On my bone stock 450t those two lines are the float bowl overflow tubes, they route up over the carbs and sit on top of the airbox. Can't imagine an L model being that much different.

Yup i finally figured out where everything goes as far as the fuel and vent lines go. I ended up tracing everything out on a similiar year GS450

Ive got the carbs clean and apart on a bench and i want to get a good base set of jets in there for my set up 48MM Pods and emgo free flow exhaust. Then i can start tuning them in.

Does anyone know anything about the dyno jets kits for these? The website only shows a jet kit for an 83 GS450.

Ive been doing alot of research on jetting for pods and a slip on emgo exhaust and multiple people have multiple opinions on it.

Just trying to nail down a solid plan for when i get these carbs back on.

[Steve]

On my bone stock 450t those two lines are the float bowl overflow tubes, they route up over the carbs and sit on top of the airbox. Can't imagine an L model being that much different.

You might want to re-examine your thinking there.
If they are "overflow" tubes, why don't they go DOWN, so they can drain any overflow?

Does anyone know anything about the dyno jets kits for these? The website only shows a jet kit for an 83 GS450.

I don't remember if the change was in '82 or '83, but the newer 450s had different carbs than the earlier ones. Since you are starting with '86 carbs, the '83 jet kit should work just fine.

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[TPELL603]

I broke the float post on my 86 carbs. I picked up older style 81 GS450 carbs that im rebuilding now so im not sure if the jet kit will work. It sounds to me like it wont. Ill just have to do more research on here and try and figure out what size jets i should start with. I was able to clean up my main jets enough to read them and theyre 115 and my pilot jet is 17.5. My 48MM pods and a non baffeled exhaust im guessing im going to make a 2-4 main jet jump and a 1-2 pilot jet jump. Other then the pods pods pods thread is there another thread more specific to 450s or the BS34 carbs and jetting?
Thanks

[Steve]

Did you by chance notice a difference in the shape of the bottom half of the carb?

I just went through the parts fiches for the 450 carbs. The '80-'82 carbs were the 'early' ones I mentioned earlier. They do, in fact, have a 17.5 pilot jet, along with a 115 main jet. Note that the bowl gasket has a large projection that almost divides the bowl in two.

Starting with the '83 carbs and going through '88 when the 450 ended, the bowls were basically an open rectangle inside, pretty much like the ones on all the four-cylinder bikes, and had a 45 pilot jet.

I don't like to offer suggestions for non-baffled bikes that are going to be on the street, so I will stop here.

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[TPELL603]

Yeah its an older style carburetor set up. They are quite different from the newer carbs on the GS450's. I was finishing up the welding on the mufflers last night and noticed that they do have baffles in them. I found a few people that restricted the pods to get the fuel mixture right with out jetting and haven't had issues at all. I contacted dyno jet and they dont make a kit for a carburetor this old only 83 and up.(My bikes an 86 but my carbs are 81). Thoughts on restricting the pods? Or do you think i should mess around with pilots and main jets. Im working on getting allen screws to replace the bowl screws so i can mess around with the jets without pulling the carbs every time. I just need to look up the screw size and pick up allen heads instead. Were coming into fall winter here in NH so ive got quite sometime to keep working at it and getting things situated.

[Steve]

There is no need to change the pilot jets.

As a starting point, try 125 mains, be prepared to fine-tune from there.

The parts fiche shows the part number for the screws as 02112-0412A.
That translates to a screw size of M4 x 12.

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[TPELL603]

Awesome. Thanks for the help! Ill order some screws and some jets today.

[LAB3]

You might want to re-examine your thinking there.
If they are "overflow" tubes, why don't they go DOWN, so they can drain any overflow?

No problem draining, everyone knows those tubes suck!

Should have said vent tubes, my mistake.

[TPELL603]

Hey Steve, Do you recommend a site for jets? I needed to order parts for another bike from JP Cycles and i ordered the jets for an 81 GS450. What i got were jets for a newer GS450 style carburetor. The jets head are too big and hit up against the threads on the float bowl drain plugs. JP Cycles says thats the correct part which clearly it isn't. Thanks

[Steve]

Jets R Us or JP Cycles.

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[TPELL603]

I ordered jets from JP but theyre not right. i think i need keihan main jets/pilots. I cant find 125 main jets for them anywhere. I just want to make sure im ordering the correct parts this time

[Steve]

Kehin carbs were not offered on any GS, only Mikuni. There are different styles for Mikuni, you will have to look a bit farther down the page.

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