home made sync gauge

[DGXSER]

Ivan, I completely agree that my Banshee engine needs help. The hope is that with 500 miles or so on it, the compression will come back since the thing sat in a barn untouched for two or more years before I got it.

If the mfg used other means to compensate like single point fuel injection or a single carb, well you can only tune as close as the equipment allows you to. Kind of like you can't tune the single carb to give the best mixture to each individual cylinder, you just tune it so the engine revs the best and idles the smoothest (old school method anyway, never had an A/F meter). Yet, it seems everyone sees tuning each carbs mixture for that cylinder as an important step on these bikes. Hmmm...wonder why?

All I was explaining is the intention of the design to perform a "dynamic" synch is completely different than the effect of a bench synch. It was intentionally designed in with a given purpose. And yes, I will say that even on Thunderstruck I noticed a difference in the idle and how well it ran after I performed the running synch. On Banshee, it was incredible, the bikes idle jumped from 1200 up to 4-5k as I synched the carbs up, simply turning the idle screw backdown to 1200 and it stays there before and after revving it up to 6k right back to 1200. It also smoothed out the idle greatly and eliminating some backfiring I was having.

Your bike is yours. If it runs well for you and your happy with the performance ride safe and enjoy. I do not care who does or does not synch there carbs bench or otherwise. I do not care who does or does not tune the mixtures. If it runs well as is, ride it.

I just do not like misinformation being given out where someone who is trying to learn about these machines might read it. So I made an attempt to provide the technically correct information.

[Ivan]

So, by that line of thinking, all multi cylinder engines should have one carb per cylinder and should be synched, especially when operated in a crosswind or when ever the pressure differential on any one cylinder changes for any reason at all.

Dynamic sync is just icing on the cake. If your compression is all over the map, something other than syncing the carb sync needs attended to.

[DGXSER]

As to bench synching versus on bike in actual engine running, "dynamic" synching, the difference is actually in the engine itself.

If you have good equal length exhaust and all four cylinders have very close to the same compression, then the bench synch will be VERY close to the running or "dynamic" synch.

A bench synch very simply sets all four butterfly valves to be open the exact same amount. You then put the carbs on the bike with all the butterfly valves still equally open and start the engine then you adjust how far all four are open the same by adjusting your idle setting with the screw for that purpose on the carb set. (note, this is not the synch screws or the idle mixture screws.) Now all four are equally open an amount that lets your engine run at the RPM you like best for idle.

Now, you hook up the synch gages and find that all four are dang close, which I did find on Thunderstruck, or you realize they are way off like they were on Banshee since that engine's compression is all over the map.

The on bike, "dynamic" synch, is simply setting all four butterfly valves so that all four cylinders, at idle, create the same amount of vacuum. This basically means that all four cylinders are running the same. Again, depending on engine condition, this could be very similar to the bench synch settings, or way off from it. So a bench synch is NOT the same as a running or "dynamic" synch necessarily.

To say they are the same and there is no need for the "dynamic" synch is the same as saying to just set your idle mixture screws to the 2 turns out from seated, or whatever starting setting you like to use, and leave them there. There is no need to adjust them ever again. They will all be close enough, there is no need for doing any more adjustments. IMO, that is the same mentality and thought process. And equally wrong.

[cywelchjr]

After a little hunting this is the best deal I've found...
http://www.amazon.com/EMGO-VACCM-SYN...0819970&sr=8-2

I think I might just go this way, a time comes when its worth the extra $20 so save the head ache... And this way SWMBO wont look at me like a mad scientist when i'm in the garage with a huge length of tube and a bottle of trans oil...

Here is a better set for close to the same price in a 4 carb type. Very much like the set I got only with more adapters, which I slightly wish I had, but they work pretty good anyways.

[cywelchjr]

Try these ones, they are $70. Not sure the difference between the ones you posted and these but they are $10 cheaper....
http://www.amazon.com/EMGO-VACCM-SYN...0856908&sr=1-1

I got the same set in a 4 gauge set off ebay for like $50 or so. The 2 gauge set was like $35, so check, I think the one shown on ebay was for 4 cylinders.

[WMarshy]

Be aware that despite the picture that is a 2 carb set, as in you will get 2 vacuum gages and the rest of the stuff for 2 gages only.

Here is the link to the 4 gage/4 carb setup.

Try these ones, they are $70. Not sure the difference between the ones you posted and these but they are $10 cheaper....
http://www.amazon.com/EMGO-VACCM-SYN...0856908&sr=1-1

[cywelchjr]

Mine are like that more than not. I only have two speeds.

1) Catch me if you can
2) OH ****!

You can ask psycoreefer, I'm not that fast a rider. I will however blow past cages in my way if given the opportunity though.

[Ivan]

Mine are like that more than not. I only have two speeds.

1) Catch me if you can
2) OH ****!

[cywelchjr]

Yeah, what could be worse than all he butterflies closing at the exact same time?

All of them opening ALL THE WAY at the same time?

Especially if they did that without your consent.

[Ivan]

Yeah, what could be worse than all he butterflies closing at the exact same time?

[cywelchjr]

I completely agree. It seems to me the bench sync is under emphasized and the dynamic over emphasized. After I do a bench sync on a set of carbs, they idle smooth down to 600 RPM or less.

My figuring is that the sync on the bike is to account for any movement caused by installing. Otherwise why would we ever need to resync them? I agree that the bench sync is probably about 99% correct as long as the rack doesn't have any give to it when installing, but the dynamic sync will account for that, and I'm guessing that things shift a little over time as well, so syncing every so often is a good idea anyways.

[81xsproject]

I didn't use those phrases because they weren't necessary. I have no clue how someone could hydraulically lock a 1 liter engine on two tablespoons of liquid. There's no way that much would kill the engine, but it would smoke for a bit. It doesn't shoot up the tube nearly as fast as some make it out to be, and if it does, no big deal. Normally you can get an idea of what needs adjusted before the engine even starts.

Or, you could just use a small drill bit or piece of straight wire to ste them statically and leave well enough alone. I ran mine that way for several months before I built my sync gauge. Then I had to turn the sync screws all of 1/16 of a turn. Like I said, almost too sensitive.

I completely agree. It seems to me the bench sync is under emphasized and the dynamic over emphasized. After I do a bench sync on a set of carbs, they idle smooth down to 600 RPM or less.

[cywelchjr]

After a little hunting this is the best deal I've found...
http://www.amazon.com/EMGO-VACCM-SYN...0819970&sr=8-2

I think I might just go this way, a time comes when its worth the extra $20 so save the head ache... And this way SWMBO wont look at me like a mad scientist when i'm in the garage with a huge length of tube and a bottle of trans oil...

That's the set I have, and they work pretty well. Gave me a good sync and things run pretty smooth. I'd like someday to get something a little better, but those tend to be pretty spendy, especially considering that these do a good job.

[DGXSER]

After a little hunting this is the best deal I've found...
http://www.amazon.com/EMGO-VACCM-SYN...0819970&sr=8-2

I think I might just go this way, a time comes when its worth the extra $20 so save the head ache... And this way SWMBO wont look at me like a mad scientist when i'm in the garage with a huge length of tube and a bottle of trans oil...

Be aware that despite the picture that is a 2 carb set, as in you will get 2 vacuum gages and the rest of the stuff for 2 gages only.

Here is the link to the 4 gage/4 carb setup.

[Ivan]

Come on now Ivan, you can't just take what I said and boil it down to something so simple. It takes all the mystery and wonder out of the whole sync experience. I mean it's just not scary when you don't use words like "hydro-lock" and "IMPORTANT", or phrases like "KILL THE MOTOR" and "shooting up the tube."

I didn't use those phrases because they weren't necessary. I have no clue how someone could hydraulically lock a 1 liter engine on two tablespoons of liquid. There's no way that much would kill the engine, but it would smoke for a bit. It doesn't shoot up the tube nearly as fast as some make it out to be, and if it does, no big deal. Normally you can get an idea of what needs adjusted before the engine even starts.

Or, you could just use a small drill bit or piece of straight wire to ste them statically and leave well enough alone. I ran mine that way for several months before I built my sync gauge. Then I had to turn the sync screws all of 1/16 of a turn. Like I said, almost too sensitive.