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Carb sync?
- Thread starter junkshow
- Start date
section8joe
XS650 Addict
You don't pull the plug for a carb sync. You pull the plug to set the mixture screw. If you want to set the mixture screw you pull the plug and plug in a spare spark plug that grounds to the engine. If you don't ground the plug you can burn up the coil. If you want to sync the carbs you get the bike up to operating temp, hook up a manometer and adjust screw that links the carbs together.
You can build an adapter from an old spoke nipple and a inch of spoke. The spoke nipple threads on the spark plug. The inch of spoke threads into the nipple, hook the plug wire on the spoke. This lets you hook a short jumper from the spoke to ground. This kills one cylinder to adjust air mix scrws and sync the carbs. Better to hook the jumper from ground to the spoke. It hurts less that way.
Joe, have you read the repair manual on the early models, pre 76, they use the dead cylinder method for carb sync. They had no way to hook the manometer to the bikes. You used the idle speed screws on each separate carb.
In the 76-77 carbs there was a port you hooked screw in hose barbs to hook the manometer to.
The 78 and up had vaccum petcocks and you use the barbs in the carb holders to hook the manometer to.
The dead cylinder method could be used on the points bikes, up to 79 without hurting the coils by just unhooking a plug wire.
Leo
Joe, have you read the repair manual on the early models, pre 76, they use the dead cylinder method for carb sync. They had no way to hook the manometer to the bikes. You used the idle speed screws on each separate carb.
In the 76-77 carbs there was a port you hooked screw in hose barbs to hook the manometer to.
The 78 and up had vaccum petcocks and you use the barbs in the carb holders to hook the manometer to.
The dead cylinder method could be used on the points bikes, up to 79 without hurting the coils by just unhooking a plug wire.
Leo
section8joe
XS650 Addict
Whoops, yeah I did read that but since my bike was newer I just didn't pay much attention to it. Sorry Junkshow
Yes it's easy to think about these as all being just like the one you have. I have done that myself a few times. Usually some one sets me straight. Just passing it on.
Leo
Leo
Tanks for the replys fellas. I'm still a little nervous about disconecting a coil for fear of frying it. I might just reinstall my original coils for the carb sync, then put the ultimates back on.
You would think there would be an easier way.
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You would think there would be an easier way.
Posted via Mobile
pamcopete
Ride.Enjoy.Life is Simple
junkshow,
Unless the carbs are way out of sync you can just adjust the center sync screw to get the same sound out of each exhaust. Start by setting the mixture to factory turns even if it runs rough. I think a lot of people chase the mixture when the real problem is sync.
Adjust the idle speed with the left side throttle adjustment if the idle speed goes up or down when adjusting the center screw. The final test is to ride the bike and listen to see if the two exhausts sound the same when riding.
Ride. Enjoy. Life IS simple.
Unless the carbs are way out of sync you can just adjust the center sync screw to get the same sound out of each exhaust. Start by setting the mixture to factory turns even if it runs rough. I think a lot of people chase the mixture when the real problem is sync.
Adjust the idle speed with the left side throttle adjustment if the idle speed goes up or down when adjusting the center screw. The final test is to ride the bike and listen to see if the two exhausts sound the same when riding.
Ride. Enjoy. Life IS simple.
Thanks PamcoPete
I'm used to working in SOHC4's that are a PITA to adjust the carbs. I guess I was over thinking the carb sync. I've went over the carbs and set the air screws to factory spec, then worked on the idle. Now it sounds pretty good. It's tough to get it perfect without mufflers and pods/airbox.
That'll have to wait till I get back from Vegas next week. Maybe I'll win some $$$ to finish my build.
Posted via Mobile
I'm used to working in SOHC4's that are a PITA to adjust the carbs. I guess I was over thinking the carb sync. I've went over the carbs and set the air screws to factory spec, then worked on the idle. Now it sounds pretty good. It's tough to get it perfect without mufflers and pods/airbox.
That'll have to wait till I get back from Vegas next week. Maybe I'll win some $$$ to finish my build.
Posted via Mobile
This probably works better when there's no crossover pipe.
You have a true mixture or fuel regulating screw. On 99% of the carbs in this world, if the idle mixture screw is located between the slide and the motor, it is a true mixture or fuel regulating screw. If it's located between the slide and the air filter, it is an air screw. All stock 650 CV carbs have true mixture or fuel regulating screws. The aftermarket VMs and those God-awful Keihen clones have air screws.
A fuel regulating screw lets more fuel in as you open it more. It makes the idle mix richer. An air screw lets more air in as you open it more. It makes the idle mix leaner. The two types both adjust idle mix strength but in completely opposite ways. You need to know which type you have in order to know what it's doing when you adjust it.
A fuel regulating screw lets more fuel in as you open it more. It makes the idle mix richer. An air screw lets more air in as you open it more. It makes the idle mix leaner. The two types both adjust idle mix strength but in completely opposite ways. You need to know which type you have in order to know what it's doing when you adjust it.
