Carb Sync worked great!

[Metallicat]

My sled picked up 300 rpm on the top end after syncing the carbs and it runs much smoother now. Last year I was down in rpm's and didn't know why.

 

[mbw919]

There's nothing like a well tuned machine.
I did mine last year and gained a smoother idle, and maybe the mid range too. I never checked top end RPMs before or after though. Usually CV carb sync effects lower RPMs the most. Did you do it yourself? I've had a set of mercury manometers since the early 80s when I owned a Yamaha XJ750, and they still come in handy from time to time.

 

[hossZ28]

Can vacuum guages do the same job with the same accuracy?

 

[mbw919]

Can vacuum guages do the same job with the same accuracy?

Probably, but the tube manometer will most likely never get out of calibration. A vacuum gauge might contain springs, gears, and bourdon tubes that could change with age and end up inaccurate. It would require periodic calibration to ensure a set of gauges agree with one another. As long as the diameter of a manometer's tubes don't change (mine are made of glass), the accuracy should never change. Simple is good in this case. Motion Pro makes a decent looking one for $100 link. It would probably cost that much to have it done once at a dealer.

 

[Metallicat]

I used the Morgan carbtune tool.

 

[Metallicat]

I did the sync myself. My dealer wanted over $100 so I decided to just purchase the sync tool. I noticed a drop in rpm's last year and also a bit of an engine stumble at full throttle. It just wasn't as smooth or as powerful as the year before. Last year my sled could hardly break 100mph on the speedo on the best groomed trail whereas the year before it ran 108 mph on the speedo in similar conditions pulling higher rpm's. Yesterday I saw 105 on a trail with loose snow conditions so I'm sure it is running better this year. But now I'm turning nearly 8900rpm so I need to add a bit of weight to my clutch arms.

There's nothing like a well tuned machine.
I did mine last year and gained a smoother idle, and maybe the mid range too. I never checked top end RPMs before or after though. Usually CV carb sync effects lower RPMs the most. Did you do it yourself? I've had a set of mercury manometers since the early 80s when I owned a Yamaha XJ750, and they still come in handy from time to time.

 

[jlparker77]

I actually found a very accurate way to sync them is to use about 10 or 12 feet of clear vinyl tubing running down and back up between two carbs with about 2 feet of oil in it. Then you are actually measuring the true vacuum from one cylinder against the other instead of tube against tube like a manometer. And it is way cheap. I spent about 3 dollars building one.

 

[rancidjo]

I actually found a very accurate way to sync them is to use about 10 or 12 feet of clear vinyl tubing running down and back up between two carbs with about 2 feet of oil in it. Then you are actually measuring the true vacuum from one cylinder against the other instead of tube against tube like a manometer. And it is way cheap. I spent about 3 dollars building one.

do you have pics or specs on your guage setup?

 

[swmichvector]

if it doesn't snow soon i am going to do mine just for something to do. personally i like the mercury ones . the digital ones change to fast and the vacuum ones are less accurate.

 

[jlparker77]

The advantage to using this style (besides cost) is it compares directly between two cylinders. If they aren't exactly the same the difference shows up drastically in the level differences. Just don't ever unhook one while the engine is running or it will suck oil into the intake of the other.

 

[rancidjo]

The advantage to using this style (besides cost) is it compares directly between two cylinders. If they aren't exactly the same the difference shows up drastically in the level differences. Just don't ever unhook one while the engine is running or it will suck oil into the intake of the other.

THANKS - I'm going to build one of these over the holidays and sync my carbs.

 

[copo427ss]

The advantage to using this style (besides cost) is it compares directly between two cylinders. If they aren't exactly the same the difference shows up drastically in the level differences. Just don't ever unhook one while the engine is running or it will suck oil into the intake of the other.

are the top ends plugged? im a little confused on how your system works. could you take some more pics and give a little tuteral?

 

[rancidjo]

are the top ends plugged? im a little confused on how your system works. could you take some more pics and give a little tuteral?

I am going to model mine after this one:


http://www.obairlann.net/reaper/motorcy ... meter.html

Google homemade manometer, or DIY manometer and there is lots of info.

 

[jlparker77]

rancidjo, that one is basically the same design as mine. Just a little bit different pieces. One thing though, I would suggest oil instead of water. The water is too thin and it will bounce and aerate too easily. the oil will be easier to see and not seem as sporadic.

 

[rancidjo]

rancidjo, that one is basically the same design as mine. Just a little bit different pieces. One thing though, I would suggest oil instead of water. The water is too thin and it will bounce and aerate too easily. the oil will be easier to see and not seem as sporadic.

I thought that would be a problem with water. What wieght of oil do you use? I was thinking maybe even ATF or a lighter oil.