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Is a carb sync always necessary?


Oct 6, 2022
Manitoba Canada
2004 Yamaha RX Warrior
I own a new to me 2004 RX Warrior. At around 3000 RPM, I get some minor exhaust pop. Also, it does not seem to start well when very cold. I think a carb cleaning is in order. I have minor experience cleaning single carb engines (snowblower, dirt bike, etc.), but no multi carb engines. I have found numerous 'how to's' on this forum as well as others, all stating how easy it is to remove, clean, and then reassemble the carbs. However, very few state that a carb sync is necessary. My questions:
- is a carb sync always necessary?
- can I clean the carbs without removing them? ....if so, would this negate the requirement of syncing them?
- is a dirty/ clogged carb the likely cause of the exhaust pop?

Any and all advice is appreciated.
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The rule I always use when determining on whether or not to sync the carbs on my RX-1 was based upon how thorough of cleaing you do on the carbs. If you are just removing the cap off the top of the carb and the bottom float bowl and spraying with carb cleaner, then generally a re-sync is not necessarily. However, with the RX-1 and the small orifices on the jets used, I always disassemble the carb completely (ie. removing the jets, needle valve seat, etc) and this is where IMO a re-sync is needed. Just removing the carb rack also does not require a re-sync as the sync process involves adjusting the three adjustment screws between each carb. With that said and considering I still own one of those old school mercury MotionPro carb sync tools, I always got in the habit of disassembling and cleaning the carbs and the jets and then following up with the sync each year.
If you clean the carbs and still have difficulty getting a nice idle, that is a sign that you will need to sync the carbs.
It really just affects idle and has no effect on full throttle.
This is kinda old but for the archives.

Out of sync carbs and pilot screws cause throttle tip in issues such as stumbling. If you completely removed the carbs from one another you should probably resync them. If you simply remove the entire rack and just do a cleaning you shouldn't need to resync the carbs. Also make sure to keep all of the jets in the same carbs as well as counting the turns of the pilot screws and returning them to where they were. They may not all be exactly the same as the setting also depends on other conditions of each cylinder. If you don't count them the book says put them to 2 turns out. But I have done this and the mixture at 2 turns is pretty darn rich on my sled. 1 3/4 seems better and maybe 1 1/2 turns depending on temps and elevation.

Adjusting the pilot screws correctly is almost impossible. At least I've never figured out how to do it correctly and I've spent some time on it. The problem is accessing every screw once the carbs are installed and the engine is running... and hot. I've even bought the special gear drive screw driver and even extended pilot screws. I always walk away with torn up and burnt hands as the sled is supposed to be at full operating temps when you do this. Each individual cylinder is it's own puzzle due to clearance. In the end, it doesn't seem to matter all that much as long as all else is correct.

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