Manometer not moving at idle

[jkocr2]

So I built the homemade manometer but it doesn't appear to be working at idle, I used power steering fluid but it doesn't really move. If I give it gas it will move so I set the sync in the cables so it moves equally but I'm not sure if my idle sync is close. Should I try an even lighter fluid? Water maybe?

I used the dead cylinder to set the initial sync and adjust my mix screws but wanted to try and dial the sync in more with the manometer. The fluid moves just fine when I give it more gas. Idle is currently set to about 1250 according to the stock jumpy tach needle

I have a set of 74 carbs so I did this to install some barbs http://www.650central.com/barb install.htm

Any ideas? I'm pretty positive there are no leaks in the lines going to the carbs from the manometer

 

[retiredgentleman]

So I built the homemade manometer but it doesn't appear to be working at idle, I used power steering fluid but it doesn't really move. If I give it gas it will move so I set the sync in the cables so it moves equally but I'm not sure if my idle sync is close. Should I try an even lighter fluid? Water maybe?

I used the dead cylinder to set the initial sync and adjust my mix screws but wanted to try and dial the sync in more with the manometer. The fluid moves just fine when I give it more gas. Idle is currently set to about 1250 according to the stock jumpy tach needle

I have a set of 74 carbs so I did this to install some barbs http://www.650central.com/barb install.htm

Any ideas? I'm pretty positive there are no leaks in the lines going to the carbs from the manometer

There's no problem with using power steering fluid. Oil is actually lighter (lower specific gravity) than water; that's why oil floats on top of water.

The manometer is very sensitive. If you unbalance the carbs even a small amount, you should see the levels change by 6 to 12 inches. If you see that then the manometer is working. If you have the levels matched at idle, and rev the engine, the levels may go uneven by an inch or two, but that is normal. Sounds to me like the sync is OK.

 

[jkocr2]

The fluid doesn't dance around like I see in all the videos I watch. It's almost as if I'm not pulling enough vacuum at idle.

 

[retiredgentleman]

Well, my manometer doesn't move at idle either.

 

[jkocr2]

I guess I'll call it good then cause when I rev it up they both move equally up the tubes

 

[I am Carbon]

I prefer my carbs to in sync at 2500 to 3000 RPMs,
so I set them at that speed.
so they can be off at idle.
I think it makes for a smoother ride.

 

[jd750ace]

I prefer my carbs to in sync at 2500 to 3000 RPMs,
so set them at that speed.
so they can be off at idle.
I think it makes for a smoother ride.

I agree with Carbon. Although idle is the easiest set point, it's not the best for what you are trying to achieve. I use my idle stop to dial the motor up to about 2500 RPM for sync. You need the butterfly plates open some for the proper adjustment, as this is what you are actually moving, and it's a better set point, as you do not ride with the throttle closed. The highest vacuum value is at idle, but you also get pulses in the air box pressure if you have one, and you get a reversion effect at idle that is specific to the volume on the inside of your filters, and the distance to the back plate with pods. This makes the idle setting somewhat subjective, but things tend to average out pretty good with the plates open. If you use power steering fluid or ATF and install an inline restrictor to dampen some of the pulses and get them within 2-3 CM of each other you are doing well. Heavy oscillation at 2000-3000 rpm is indicative of air leaks, and the smallest leak can make a pretty good difference. I always use ATF. If a hose happens to get yanked off one carb, and you are not quick, the one still connected can ingest the fluid you are using. ATF or steering fluid will not damage the engine. It will die before it can hydro lock, and it just makes smoke and maybe lubes up the top end real good!

 

[jkocr2]

Thanks alot guys, i'll give it another shot tonight just to double check it. i dont think i revved it up to 2500-3k, i was probably closer to 2 grand but the levels would move evenly up the tubes.

 

[jd750ace]

If they were even at 2k you are probably fine, but it never hurts to go to a higher opening and make sure.