Carb Vacuum/fueling issues

[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? :-k

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. :-k
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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[TPELL603]

I?ve looked and it only shows the fat head jets. There?s no way to tell because they use generic pictures.

 

[Steve]

Did you see THIS PAGE?

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[TPELL603]

ahh this is perfect thank you. i was looking under suzuki motorcycles and not this section. Thank you!!