Vacuum Take Off Adaptor For Carb Balancing

[MisterCinders]

I picked up a couple ft of vacuum hose at the local auto parts store. Its held up fine. Also, I put the hose on after the engine had cooled off. I wasn't in that big of a hurry.
Willie

You need the engine warm to do the vacuum synch.

I install the adapters with rubber caps while the engine is cold, then I warm it up.

Once its warmed up, I shut it down and connect the hoses to the adapters. Then I can check the synch, adjust etc.

Once synched, I can let it cool down a bit, but can change out the adapters and plugs while the engine is still a little warm.

With those permanent adapters, you would have to either (1) warm up the engine with the synch tool hooked up -- which might be ok, I guess; or (2) reach behind a warm engine to swap the caps and hoses, In both cases, you have to reach back into that heat to change the hoses back to caps, so you are waiting for the block to cool or threading the needle.

With the allen head plugs, you can work near the warm block using a driver.

[OldVet66]

MisterCinders, confusion reigns, willie and I were talking about connecting the permanent sync ports to crossover vacuum from cylinders 1/4 and 2/3. In addition to having convenient sync ports it is also a mod that increases low end power and smoothness.

[stucknarut]

The adapters are a lot less at Z1. Connecting the vacuum ports of 1/4 and 2/3 makes the bike run better. You will notice more low end power. You are connecting the carbs on the pistons that travel up and down together. One of the technical minded people could explain the dynamics. It's nothing new, I believe it was built in on some of the older 2 cylinder British bikes by the manufacturers. http://www.z1enterprises.com/Vacuum-...-5mm-4368.aspx

I believe you, just would love to hear the explanation from one of the technical minded people. I'm not one of them. Just thinking about it, downstream of the carbs you'd be moving fuel as well as air, seems like that would affect fuel mix and make one richer and the other leaner. Is that a good thing? Do you see any difference in the plugs?

[OldVet66]

I would like to hear that too, but willie and I both have done it and it works. I am assuming that not a lot have done it and that is why they are not chiming in. There were some threads a while back on the subject but I never heard a conclusion. I went ahead and did the mod, and got great results. I met "willie" at a rally. His bike had been modded, but whoever did it crossed all cylinders. We talked about it and later he changed it to cross only the cylinders that rise and fall together. He reported back later that the change did the trick and was very pleased with the results. In the mean time, I have added a Hayden Krank Vent Plus to my crank case vent and having vacuum on the crank case has added to low range power. My mileage has gone up to 41.5 mpg with pipes pods and a stage 3 jet kit. That is commuting in 70mph + traffic.

[MisterCinders]

So what kind of line do you use between the carb ports? It seems like regular line wears out and silicon line has problems (if I understand the posts here correctly).

[OldVet66]

Silicon is the best I have found yet, but it is not designed for fuel so replacing it every year or so seems prudent. It stands up to the heat right behind the cylinders nicely where the standard line gets soft and swells with gas and heat. I have the vacuum caps and spare lines in my "Airbox/toolbox". https://picasaweb.google.com/lh/phot...eat=directlink

[stucknarut]

Thinking about this more, maybe it helps keep the vacuum pulses in sync as the intake valves on those cylinders open?

Here's my thinking: syncing the carbs ensures they all pull the same vacuum, but you still might have a slight difference in the timing of the vacuum pulse based on valve wear and valve clearance. Linking the shared cylinders would "even out" the pulse and get air/fuel into the cylinders at the same time. Based on the power band, the GS valve lift/valve timing is engineered for best performance at high RPM, so it might make sense that the most impact is seen at lower RPM.

Actual experts, please correct me if wrong.

[Spyder]

Sometimes you really don't have to have the technical reasoning to know it just works. I plan on giving this method a shot. it's a very cheap mod, and ANYthing to get the mpgs' up is golden in my book.

Thanks for the tip, I'll chime in and give my results...

[Crazy_Russian]

back when i did stuff with the old Dneprs/Urals and K650's its the same trick we used, running an adapter plate with a nipple for 8-10mm vacuum line between the two cylinders, it gave more bottom end torque and power, which is quite nice when you are running 900+lbs bikes with a taller rear diff gears. Also, some with dual carburetor air cooled VW's, same principal. But with VW's it all depended on which carb you ran, as some of them ran like (__!__) with a sinc tube in between.

[Spyder]

When you've finished synching them, I suggest you use them to connect manifolds 1 with 4 and 2 with 3. I bet you'll be glad you did.
Willie

WOW ! ! ! Day and night difference. I just did this to my 750 and SO smooth in the bottom end of exceleration... Can't believe they didn't come this way stock...

Thank you very much for this tip Willie.

[OldVet66]

Now if you were to add a Hayden Krank Vent Plus to the Crankcase vent, You would gain twice the benefit to what you have just done. I am also seeing a significant mileage increase even running at high speed flowing with commuter traffic. At the price of gas today the valve will pay for itself in a relatively short time since I ride almost every day.

[Spyder]

How much is this valve setup and where can I find it?

[OldVet66]

Google Hayden Krank Vent Plus. There are vendors where you can get it for less than directly from Hayden. I got mine for $105.00 including shipping. One word of warning. Split the valve opened and look at the rubber umbrella valve. If it has JAMES in raised letters, it is a defective valve. James makes the valves, but the ones Hayden uses are not marked and work very well. Replacements are about 75 cents. We got two over here in Virginia that Hayden replaced immediately. It's most likely better to order it directly from Hayden, and save any possible angst (125.00). Here is a link to my setup. Directly off of the vent (and you would want too if you have a stock air box) the valve accumulates a bit of white jell in the return ports that would require periodic maintenance. The further away the better, mine is next to the clutch housing. https://picasaweb.google.com/lh/phot...eat=directlink

[Spyder]

Thanks, I'll look into it...

[OldVet66]

Here is Hayden's link. Disregard the horse power claims, they are after all designed for first generation Harley Evolution motors. It works best on the low end on inline fours. I noticed as much difference adding the valve as I did after crossing 1-4 and 2-3 with vacuum lines. Since you have seen the same you could appreciate the difference. The up to 6 mpg increase in my daily commute gas mileage was a real bonus. http://www.haydensm6.com/kvp.htm