If you are having issues with your throttle or experiencing jumping RPMs at idle, you might need to sync your snowmobile’s carbs. This is a relatively straightforward DIY maintenance project that can improve your sled’s performance.
I’m Chaz, and I’m an avid snowmobiler. I’ve been working and wrenching on these machines since I was a kid. I have learned many skills that have proved helpful in the garage and on the trail. I’m not an expert mechanic, but I’m pretty handy when I need to be.
This post will show you how to sync snowmobile carbs and why you want to make sure they are synced up as part of your regular maintenance plan.
Stop staring at your engine, and let’s get started!
Table of Contents
- What are Carbs?
- Why Sync Snowmobile Carbs?
- How to Sync Snowmobile Carbs
- Stay In Sync
What are Carbs?
If you are an experienced snowmobile mechanic or any other type of mechanic, you can go ahead and skip this section. For everyone else, it’s good to know what carbs are and why you want to sync them to improve performance.
Carb is short for a carburetor. A carburetor is an important part of a non-fuel injected internal combustion engine. Carbs mix air and fuel in a set ratio that allows for combustions, which powers the rest of the engine.
The throttle is directly connected to the carb. When you ‘hit the throttle’ on your snowmobile, you are opening up the throttle valve to the carb to let in air and increase or decrease the rate of combustion.
On engines that have more than one cylinder, there will also be more than one carb. Most snowmobiles are either 2-stroke (2 cylinders) or 4-stroke (4 cylinders) engines and will have 2 or 4 carbs.
Why Sync Snowmobile Carbs?
Synced carbs are essential to proper engine performance. Since multiple carbs operate independently from one another, they can start to open at slightly different times.
This is normal and a result of constant use and steady motion. If you have been running your snowmobile hard and have never synched your carbs, it’s worth looking into.
Ideally, carbs would all work in unison, i.e., open and close at the same rate when the throttle is opened up. This creates the same amount of thrust in each cylinder and translates into reliable and powerful performance.
If they aren’t in sync, you can notice a loss of power as well as a vibration that seems irregular. You might see this issue right when you start up your engine. If your engine coughs or sputters, that’s a good sign you need to sync the carbs.
You might also notice a lack of power when you hit the throttle. That’s a much bigger issue than how the engine sounds and one of the biggest reasons to make sure all of your carbs are in sync.
How to Sync Snowmobile Carbs
You can purchase a synchronizing tool to help you with this process, but it’s not absolutely necessary. With a few basic tools that might be lying around your garage, you can also get things just as synced up as with the specialized tool.
1. Make sure your snowmobile is stable and secure
Before completing any maintenance task on your sled, you should always ensure that the machine is stable and secure. Try to park it on a flat surface (such as your garage floor), and if you have it on a lift, double-check to make sure it won’t slip while you are working on it.
2. Access engine and expose cylinders
You need to have clear access to the cylinders to adjust the carbs. Remove any side panels or any other body components so you can adjust everything easily. You can also remove the carbs from the engine block themselves for easier access.
3. Loosen the jam nut on the throttle cable and idle adjustment screw
Next, you’ll need to loosen both the jam nut on the throttle cable and the idle adjustment screw. This sets the valve settings back to ‘zero’ and allows you to begin the process to sync them all together.
Loosening both of these will allow the valve cover to slide down all the way over the bore opening. You need to make sure the idle adjustment screw is backed all the way off.
4. Use drill bits to set slide height
Using a drill bit of the same size as your slide specs will allow you to set the height without a specialized tool. Check the manual for the specific size and use the proper drill bit. I’ve used 7/32” and ¼” bits for a Polaris 500, but those sizes could be different on your machine.
Take the small drill bit and slide it into the throat of the slide. If the bit doesn’t fit, you need to back off the throttle cable until it does. If the cover doesn’t touch the bit, you need to tighten it up until it does. Either way, you want just a little bit of drag when you pull out the bit.
At this point, tighten the throttle cable by running the jam screw back down. Then tighten up the throttle cable, so it stays in place.
Next, take the slightly larger screw and slide it down the throat until it hits the valve cover. Back off the idle adjustment screw slowly until the bit slides through. This step helps you have enough room to make minor idle adjustments without syncing the entire carb in the future.
5. Repeat the process for the remaining carbs
Repeat step 4 for all of the remaining carbs. As long as you use the same drill bits, they will be in sync. Once you have done this, you can press the throttle and watch them react at the same time. All carbs should lift simultaneously when you open the throttle.
6. Reinstall carbs and test engine
Once you have synced all of the carbs, you can reinstall them back into the engine block if they were removed. You can also put any side panels back on if those were removed as well.
Fire up your engine and test the throttle to see if the adjustments worked. If you noticed a bouncy engine or poor performance, you should hear the difference almost immediately after making these adjustments.
Stay In Sync
Once you sync your snowmobile carbs, you’ll notice increased performance and be able to adjust them in the future. Take your time if it’s your first attempt, and make sure you install everything back together correctly.
This is an easy DIY maintenance task that doesn’t require specialized tools. I always recommend learning new skills that can help you enjoy your time in the snow. Give it a shot and let me know how it goes!
Have you ever adjusted the carbs on your sled? Do you have any tips that I didn’t mention? Let us know in the comments below!About Chaz Wyland