1978 Yamaha XS400 full tune up

[arm]

Well, you do want the petcock to be able to shut off. My original vacuum petcock also went bad, but to be expected for 40+ year old seals. I tried a rebuild kit on it but it didn't work as there was some pitting in the metal inside thus I changed to a full manual petcock with off/on/reserve switching.
You also need the floats to be able to close off fuel entering the carbs or you could be running rich at the lower rpms and idle as fuel overfills the bowls. I bought new needles and seats and very carefully set the float levels to 26mm measured from the bowl gasket surface to the top most part of the float while holding the carbs upside down. You gently bend the needle tang on the float to adjust height. I also made sure each side of the float was 26mm by twisting them gently. I know it sucks to pull them back off, but dumping that much fuel is no good for the engine as it can wash the oil from the cylinders leading to excess ring wear or make it's way into the oil via the crankcase vent tube in the air filter boot, diluting the oil and then causing main and rod bearing wear.

Yeah i think id opt for the manual petcock just for the peace of mind that I actually shut it off

I watched a few videos on how to set float levels so I have an idea of what you mean by holding them upside down and adjusting the tang.

Do you have a link to where I can get these parts? I'm assuming you have the same BS34 carbs so it should be the same parts

 

[CaptChrome]

Any links to what manual petcock will fit on my bike? Is it a hard swap?

Here is one that should fit https://www.amazon.com/Carbman-Petc...6Y0B2&ref_=ast_sto_dp&tag=namespacebran129-20
Just check the distance between the mounting holes on your old one and make sure that they match the dimensions in the listing (the mounting hole spacing was make larger at some point in the manufacturing run of these bikes, I think 1978 was the first year of the wider spacing). Swapping it is a matter of loosening two JIS screws.

what happens to the vacuum line on my bike then? Do I just leave the vacuum line hanging

Remove the old vacuum hose and put a rubber cap over the nipple on the carb holder that the hose was attached to. If you don't cap the vacuum nipple, you will cause a lean mixture to the engine.

 

[arm]

Hey guys, so i been loking around for parts for the BS34 carb and since I'm in Canada a lot of sites charge around $80 - $100 for a few parts on the carb due to shipping and USD to CAD conversion.
I did find this though (Amazon link). I looked at the mentioned bikes and some have BS32 carbs but what I'm seeing is that the 1982 Yamaha XS400S Heritage has BS34 carbs which is the same as mine

The reviews are pretty solid, and this way, I could replace a good chunk of the carb's internals. What do you all think? Is it good to order?

 

[CaptChrome]

What do you all think? Is it good to order?

It is cheap. But, I would only use the gaskets, o-rings and the float needle/seat for putting the carbs back together and clean and reuse the original pilot, main and needle jets and the original jet needle. I especially don't trust the shape of that jet needle.

 

[arm]

It is cheap. But, I would only use the gaskets, o-rings and the float needle/seat for putting the carbs back together and clean and reuse the original pilot, main and needle jets and the original jet needle. I especially don't trust the shape of that jet needle.

yeah on second look it does look a bit off.

thanks so much for the response guys, really appreciate it, couldn't have gotten this far without the forum

I looked into some trusted sellers and found these options

Option 1:
carb kit
Floats (not sure if its needed though)
Reflector (bikes missing one )

Total: 86 USD (116 CAD)

Option 2:

Total: 103 USD (140 CAD)

Let me know what you guys think, i dont mind picking up new pilot jets considering one of mine is stuck in there but i think somone mentioned earlier that its fine to leave as is

 

[avemachina]

I'd go option 1. Any parts that aren't the same, just don't use. I'd get the new floats too--they sometimes develop pinholes, and that can cause flooding.

Something you can do as well if your jet needle seems to have stuck-on gunk and carb cleaner isn't doing the trick, is using a cleaner/polish like Brasso. I've found it's a great addition to elbow grease Just make sure you rinse thoroughly with soap and water after you use it.

 

[arm]

I'd go option 1. Any parts that aren't the same, just don't use. I'd get the new floats too--they sometimes develop pinholes, and that can cause flooding.

Something you can do as well if your jet needle seems to have stuck-on gunk and carb cleaner isn't doing the trick, is using a cleaner/polish like Brasso. I've found it's a great addition to elbow grease Just make sure you rinse thoroughly with soap and water after you use it.

Awesome will do!

anything else i should be worried about and adjusting in the carbs?

Like @tstidham mentioned the carbs should be able to form a seal and not overflow with gas so I reallyyyy wanna make sure that I get it right this time.

also I think you (@avemachina) mentioned that I should drill out that jet at some point, it looks like this carb kit comes with those jets so do you have any tips on extracting that jet without damaging the rest of the carb?

 

[avemachina]

I do! Pop over to the auto parts store and get yourself a screw extractor set. I got mine at NAPA, but I think they've got these at Princess Auto or Canadian Tire or whatever y'all have up there They look like this:

Sometimes the ends are spiralled, sometimes they're square, sometimes they're kind of a star shape. What you should be looking for is to confirm that you have one that's M3 or 7/64"-sized.

If you've never used these, here's how. The theory behind it is, you widen the stuck jet juuust enough for the extractor bit to get hammered in and create a "new" grab point in the softer brass. The extractor bit is left-handed, so as you twist in the "out" direction, the bit will go deeper into the stuck jet, and the jet itself will come out.

1) Drop a little bit of penetrating oil around the edges of the stuck jet.*
2) Use the little drill included with the kit, or whatever drill bit size is recommended for the extractor bit you'll be using (the packaging usually tells you), drill into the hole to widen it to the correct amount before using the extractor bit. Don't drill too deep! You only need to go maybe 25mm at most.
3) Take the corresponding extractor bit, position it vertically in the newly-widened hole, and hammer it into the stuck jet. It's in the right amount when it can stand up on its own inside the jet.
4) Grab an adjustable wrench or power drill or whatever you've got. Grasp the end of the extractor bit, apply some downward pressure, and start twisting counterclockwise to begin removing the jet. If the bit falls out, hammer it back in. If it's too loose, go up an extractor size. You've already destroyed the jet, so get the whole thing out!
5) When you've got the jet out, clean up the area you removed it from.

That's it!
*Optional, but recommended.