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Vacuum Take Off Adaptor For Carb Balancing

  • Thread starter Thread starter EvilEnfield
  • Start date Start date
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EvilEnfield

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Hi, does anyone know where to get, or what to use as an adaptor to go in the vacuum take offs to balance the carbs? I've been going mental trying to come up with something all day. I'm in the UK. Thanks.
 
What vacuum gauge are you using?

Z1 Enterprises out of the USA sells some nice brass adaptors. Morgan sells some to go with their Carbtune. They are out of Belfast, so you'd probably get them in a couple of days.

http://www.carbtune.com/

Does the '81 have the same threaded synch ports as the later models?
 
Hi, I made the vacuum gauge, it has threaded synch ports, I think 5mm, at the moment I'm thinking of getting some bleed nipples, sawing the ends off and just winding them in, but 5mm nipples are hard to come by round here, this is a car town, there is only one motorbike shop and they are charging ?3 ($5) each.
 
I had the same question, good to know. So the sync ports on a Mikuni BS32 are 5mm?
 
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
 
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-Carb-Sync-Adapter-5mm-4368.aspx
 
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Thanks for the replies, in the end I used my mums 5mm aluminium knitting needle, threaded it, drilled a hole down it, chopped into inch long sections and screwed those in with the vacuum pipe over the end. cost = ?0.05p for electric. at some point I'll get some sort of 5mm screw cap to screw over and leave them on there permanently.
 
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adam said:
I actually just ordered these. I got really tired of not having a quick way of syncing without taking off the tank and removing my vacuum plugs and all that jazz. You could see if there is anything available near you. Here in the US they are available in 5mm and 6mm

http://www.amazon.com/Motion-Pro-Permanent-Brass-Adapter/dp/B0012TTA5E
Click to expand...

I've looked at those, but didn't like the idea of attaching hoses to such short ports when the engine is hot.

The vacuum port adapters that I use (also from Z1) have two long ones and two short ones. The long adapters go in the ports for 2 and 3, and keep my hands away from the head.

Replacing the screws after synching is not so bad, as I can use a hex driver, keeping my dainty hands out of harm's way.
 
I don't know how heat would affect the rubber vacuum caps. I use 4mm silicon vacuum hose to connect 1/4 and 2/3 without any heat problems.
 
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
 
Okay, it's the first time I've heard of connecting the vacuum lines to the carbs. So it really helps on the low end?
 
If it's standard vacuum line willie, it will soften up after a while. I don't know how much you ride that bike, I'm on mine just about every day, and had to replace the standard line in several months. I have had the silicon line on for just about a year with no problems, but there is gas in those lines so I will change mine soon, just in case. Yes it does help, mrbill5491, not a huge change but enough to make it well worth while.
 
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willie said:
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
Click to expand...

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.
 
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.
 
OldVet66 said:
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-Carb-Sync-Adapter-5mm-4368.aspx
Click to expand...

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?
 
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.
 
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).
 
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