So i decided to invest in the simple snapple bottle carb sync that bcbobbers posted and it actually came out awesome. However, As i was hooking this and that up..i noticed that the right vacuum hose that connects the carb to the petcock to pull fuel in doesn't work with this set up. In other words, as i hooked the tank up and had the tank connected to the fuel filter, there is no hose to go from the petcock to the carb to suck fuel. I tried one time leaving it on prime for one go around and nothing. Any ideas on if bcbobbers idea works with my set up? I have a 1980 yamaha xs400 special. Heres some pictures of what i did.
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Home made carb sync
- Thread starter xadmp
- Start date
I have looked in my local hardware stores where did you find the corks or stoppers for the ends of your bottles?
I went to lowes. Went to two different local hardware stores they pointed me to plumbing which has nothing at all. Go to Lowes or home depot and check the hardware aisles. Lowes had tool chest drawers that had plugs and anything misc items you ever wanted. Many sizes too.
brownv1
XS400 Enthusiast
Even with the vacuum line off you will get fuel on prime. If you don't your petcock is in need of maintenance. P.S. I just used the single tube with ATF fluid in it and worked great easier than bottles.
it does work on prime. the petcock is in fine condition. Just dont want to ruin my new oil i just put in the other day. How'd you do it with a single tube if you dont mind me asking?
He meant that he used a single tube in a U-shape. The traditional style manometer if you will. Fluid sits at the bottom of the "U" and the two open ends connect to the vacuum lines on the carb boots. If the carbs are in synch the fluid level will be even on each side of the U. He probably has a manual petcock or used prime.
So your problem is that you want to use the vacuum ("ON") position of your petcock? Well sir, that is very easy. All you need is a vacuum T fitting which can also be found at the hardware or auto parts store. Simply install the T fitting into one of the hoses in the bottle that DOESN'T (the dry line) suck up the fluid (one line sits in the fluid, the second sits high above it). You'll end up with a 3rd dry line going to the petcock.
So your problem is that you want to use the vacuum ("ON") position of your petcock? Well sir, that is very easy. All you need is a vacuum T fitting which can also be found at the hardware or auto parts store. Simply install the T fitting into one of the hoses in the bottle that DOESN'T (the dry line) suck up the fluid (one line sits in the fluid, the second sits high above it). You'll end up with a 3rd dry line going to the petcock.
Thanks guys ill have to give another try soon. It doesn't seem like it wants to stay on now since i tried syncing. Half choke idles nice but off it just shuts down. Had it running awesome, should have never messed with it 
But, i guess you can never have it easy all the time! Back to it this weekend.
But, i guess you can never have it easy all the time! Back to it this weekend.I took the carbs off and did ANOTHER thorough cleaning. My question is, the bike was running fine before i started trying to sync the carbs now it only runs on half or full choke? I have pods and open headers and ive looked at just about every post that has to do with carbs cuz i know this is the only thing stopping my bike from being a beast on the road. I forget who posted it but i found an awesome equation for jet sizes. I went half way and ordered 3 sizes up on my main but haven't looked into the pilots. I'm almost positive i need main jets to equal out the fuel and air. Should i order 2 main jets #140 or 145? what are your guys thoughts?
My bike is an 81 it had 135`s .They say buy at least 2 sets but I just went with 145`s and bump my pilots 1 size.Maybe I got lucky but it worked nicely.I still have to sync the carbs but I feel more power!
You haven't touched the pilot yet? If you're running a stock pilot you're too lean (only running on choke helps support that idea). I doubt you'll need to go larger than 3 sizes on the mains. Main jets also don't affect idle at all.
I went 2 sizes larger on my mains with pods and tiny free-flow mufflers. Larger mains were choking the bike during warmer weather.
I went 2 sizes larger on my mains with pods and tiny free-flow mufflers. Larger mains were choking the bike during warmer weather.
when it comes to the needle jets, whats the easiest way to diagnose if you need to go longer or shorter? I'm going to look into getting the next size pilot and ordered mains #145 and 150.AgreePeople tend to put way too big mains in there bikes when they should address the pilots and needle jet settings.
I'd post photos of the plugs on here for us to look at. Reading them can be tricky.
I left the emulsion needle stock (4th groove down from the top I believe); moving it around tended to cause problems. Raising the needle means the main jet opens sooner (you'll get a richer mid range). Lowering the needle means your main jet opens later (you get a leaner mid range). The best way to test the affect is to ride the bike; do a WOT pull from low rpms; if you're too rich (needle too high) your bike will be unresponsive; you'll experience lag or a delay in the mid range. If power and responsiveness suddenly increase at higher rpms you'll know for sure that your needle needs to be lowered.
Go 2 or 3 sizes up on the mains and 1 or 2 sizes up on the pilots.
Make sure your float height is good.
145 is moderately large; 150 is huge. What is your stock size again?
I left the emulsion needle stock (4th groove down from the top I believe); moving it around tended to cause problems. Raising the needle means the main jet opens sooner (you'll get a richer mid range). Lowering the needle means your main jet opens later (you get a leaner mid range). The best way to test the affect is to ride the bike; do a WOT pull from low rpms; if you're too rich (needle too high) your bike will be unresponsive; you'll experience lag or a delay in the mid range. If power and responsiveness suddenly increase at higher rpms you'll know for sure that your needle needs to be lowered.
Go 2 or 3 sizes up on the mains and 1 or 2 sizes up on the pilots.
Make sure your float height is good.
145 is moderately large; 150 is huge. What is your stock size again?
My jet needle doesnt have grooves like people have said (at least i haven't noticed them) I just ordered some pilots and the mains so when i get them in ill take some pictures of the carbs and the needles and what nots and show you guys my process.
This past carb breakdown i reset everything back to stock (carb wise) floats are at 27mm (let me know if i should be at 33, ive seen both but went with 27mm) and air screw to 3 1/2 turns out. soaked all the ins and outs as long with each jet.
After all this I'll have to try to configure my homemade sync device to work with my setup. Thanks for all the help.
With pods a lot of people make the mistake and not oil them. Using the proper filter oil makes a big difference in filtration of dirt and flow of air. Running them dry will cause issues with jetting and wear the top end of the engine out much faster and your valve seats. (More frequent valve adjustments) Just my 2-cents
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Never thought to oil them. Good point. Thanks!With pods a lot of people make the mistake and not oil them. Using the proper filter oil makes a big difference in filtration of dirt and flow of air. Running them dry will cause issues with jetting and wear the top end of the engine out much faster and your valve seats. (More frequent valve adjustments) Just my 2-cents
Another quick thought. Kind of a self diagnostic. If my bike runs and idles awesome on half choke and shuts right off on no choke, that has to mean not enough fuel correct? Which means just up the mains and the pilot for the most part? Just kinda on the go learning since im on my own with everything.
No and yes.
The mains do not affect idle. You just need to increase the pilot jet size or adjust the number of turns out on the mixture screws.
The pilots are responsible for idle and the first few thousand rpms, the emulsion needle starts to open in the mid range, the main jet is fully open at higher rpms.
The main jet and the needle position will affect the mid range, but the needle (in my experience) tends to have the greatest impact here.
Your main jet is going to have the greatest impact at high rpms with the throttle wide open.
The pilot jet contributes all the time (it never closes or turns off); it's just that its contribution becomes negligible once the throttle starts to open and lots of air comes in.
The mains do not affect idle. You just need to increase the pilot jet size or adjust the number of turns out on the mixture screws.
The pilots are responsible for idle and the first few thousand rpms, the emulsion needle starts to open in the mid range, the main jet is fully open at higher rpms.
The main jet and the needle position will affect the mid range, but the needle (in my experience) tends to have the greatest impact here.
Your main jet is going to have the greatest impact at high rpms with the throttle wide open.
The pilot jet contributes all the time (it never closes or turns off); it's just that its contribution becomes negligible once the throttle starts to open and lots of air comes in.
awesome thanks. I did see that diagram that shows what each jet does what that was incredibly helpful too. I guess I wanted the carbs for dummy's version from you guys
