Ok. I'll take the carb out. As I do I'll send pics of the parts. Do you think I should replace them all? Or is it not worth it?
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Running rough
- Thread starter crybinsk
- Start date
Well, I'd see what you've got 1st. I usually do the typical "pipes and pods" mod to mine so I need larger jet sizes anyway, lol. Yes, these bikes require re-jetting for mods, but it's usually not much. If the P.O. installed really big jets then yes, you'll most likely need new smaller ones.
Well, the needle jet is correct but the others are too big. The P.O.probably installed a rebuild kit for the '76-'77 carbs because those are the size jets that come in them. They're wrong and are actually the stock sizes for the '78-'79 carbs, but those kits have been sold that way for years, lol. The 27.5 pilot is only one size larger than stock (#25) and may be OK if you lean the needles a step, which you will need to do for larger mains. The 135 main is too big. The biggest main I've been able to use in a '76-'77 carb set is a 132.5. This is with the typical "pods and pipes" mod. You have the pipes already so now you need to check your airbox and see what type of filters are in there. If they're the stock filter elements then you might want to switch to pods. If you're lucky though, the P.O. may have installed K&N airbox replacement elements. If he did then you're all set. Get 132.5 mains, lean the needles a step. and stick with the 27.5 pilots. That's if your needle is the stock 4M1 that is. You didn't give the needle number yet.
This is what K&N airbox replacement filter elements look like ......
Original filter elements are usually covered with a yellow foam .....
And this is the pod of choice, the all foam UNI. You would want the model #UP4200 for your carbs .....
This is what K&N airbox replacement filter elements look like ......
Original filter elements are usually covered with a yellow foam .....
And this is the pod of choice, the all foam UNI. You would want the model #UP4200 for your carbs .....
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I'm ordering the 4m1 needle and the 132.5 main. Should I get the 25 or stay with the 27.5 because of the pods and pipes? Also by step up you mean move it from 3 to 4 on the needle right?
I'm ordering the 4m1 needle and the 132.5 main. Should I get the 25 or stay with the 27.5 because of the pods and pipes? Also by step up you mean move it from 3 to 4 on the needle right?
No, you raise the clip (to slot #2) and that lowers (leans) the needle. You can get a slide/diaphragm assembly out with the carbs still in place, just take one of the tops off one of the carbs. I'd hold off on ordering the 4M1 needles because you might already have them.
Those are XS Performance pods. I tested some last summer and while they work OK, they don't flow quite as well as the UNIs.
Those are XS Performance pods. I tested some last summer and while they work OK, they don't flow quite as well as the UNIs.
I find it very helpful when talking about the needle, to just refer to the needle and not the clip.... which works opposite the needle.
When we say "raise the needle one slot to richen the mix"... then there's no ambiguity, we know exactly what we're doing.
But that's just me...
When we say "raise the needle one slot to richen the mix"... then there's no ambiguity, we know exactly what we're doing.
But that's just me...
Thanks. However the bike was running very rich before. You said before raise it to 4. Is it because I'm changing from 135 to 132.5 that it would need to move to 2? And should I keep the 27.5 or get the 25? I'll change the pods at the end of the season. I just want to get it road worthy right now
I don't recall telling you to raise the needle to #4. That would make it richer and you don't want or need that. You want to make it leaner, hence lowering the needle by moving the clip to slot #2.
The 3 circuits in your carbs overlap a little so changing one affects the one next to it. In the case of the midrange, it will affect both the lower part of the main and the upper part of the idle circuits .....
As you increase the main jet size, eventually the "bleed-over" into the upper midrange will make it too rich and cause stumbles and break-up under heavy or full throttle, say in the 4 to 5K range. To fix this you need to lean the needles a step (raise the clip to lower the needle). But changing the needle setting also affects the upper idle and the idle to midrange transition area, say from 2500 to 3500 RPMs. It can often create a flat spot there so to "fix" that, you increase the pilot jet one size.
So, I'd get 132.5 mains, keep the 27.5 pilots you have, and run 4M1 needles leaned one step (slot #2) from stock (slot #3).
The 3 circuits in your carbs overlap a little so changing one affects the one next to it. In the case of the midrange, it will affect both the lower part of the main and the upper part of the idle circuits .....
As you increase the main jet size, eventually the "bleed-over" into the upper midrange will make it too rich and cause stumbles and break-up under heavy or full throttle, say in the 4 to 5K range. To fix this you need to lean the needles a step (raise the clip to lower the needle). But changing the needle setting also affects the upper idle and the idle to midrange transition area, say from 2500 to 3500 RPMs. It can often create a flat spot there so to "fix" that, you increase the pilot jet one size.
So, I'd get 132.5 mains, keep the 27.5 pilots you have, and run 4M1 needles leaned one step (slot #2) from stock (slot #3).
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Yes, I just told you what raising the needle does, not to actually do it, lol.
And just a little note on your carb top screws. Yamaha used two different length screws, 4 longer ones for the inner screws that go through the butterfly shaped plate between the carbs, and 4 shorter ones on the outside. But they cheaped out here, they should have used 5 longer screws because the throttle cable bracket needs one too, lol. Looking at your carb pics in post #4, I see one long screw in the wrong spot (left carb outer rear). I would move that to the left front where the throttle cable bracket mounts.
Personally, I switch to stainless Allens. Here's a write-up I did with the required lengths .....
https://www.xs650.com/threads/carb-allen-screws.62686/
Personally, I switch to stainless Allens. Here's a write-up I did with the required lengths .....
https://www.xs650.com/threads/carb-allen-screws.62686/
Ok so I've started to take the carb off and noticed a few things. There is no rubber on the manifold and the only hose attached to the carburetor is the gas line. Is that right? Or am I into another issue. And shouldn't a hose be attacked to the top near the adjuster? Finally the only way I can see to remove this thing is to remove the manifold. There is zero wiggle room. I know I'm sounding stupid here and accept that. You have to start somewhere
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