my first quick question

[Zampano]

Is anyone near san diego who has a carbtune throttle body synch meter contraption and may want to exchange a synch for a six of the beer of your chosing?  I had my fuel injectors reconditioned and refuse to pay the dealer $96 to synch  :yow  What a racket.

thanks

[wmax351]

For that much, cheaper to get a set of carb gauges. The mercury ones used to be cheaper, I think I got mine for 35 dollars when I had a honda CB550 four. The gauges are ~70 for a set.

[F14CRAZY]

You don't trust clear tubes with oil?

[Motorhobo]

http://www.amazon.com/Vacuum-Carburetor-Synchronizer-Carb-Gauge/dp/B004MSJ7E6

http://www.ebay.com/bhp/carburetor-synchronizer

I called but he boobs don't come the motion pro.

F14crazy -- I need a sync too but don't relish the thought of spending that much money on something I'll use one every 20k miles. If you buy it I'd rent it from you -- I know that's slippery slope territory...

[F14CRAZY]

Are you talking about my oil filled tubes? I think I spent like $8 in Home Depot material putting it together (probably could have done it cheaper)

[Motorhobo]

Are you talking about my oil filled tubes? I think I spent like $8 in Home Depot material putting it together (probably could have done it cheaper)

So you got your throttle bodies synced with that contraption? How does that work? I can afford $8.

[F14CRAZY]

The measured amount of vacuum doesn't really matter, you just want them even. You hook up the clear tubing and adjust the throttle bodies so the oil levels in your tubes are equal, or close to being equal. The oil will kind of "pulse" at idle but just get the bouncing to be equal.

That's how I read to do it, and how I've done it at least

[Zampano]

I've used my own device a few times and maybe it's close to exact; but I'm still curious what the official meter would say. Almost just to compare. See how close I got it.

[Motorhobo]

If you get a minute maybe you could post something in the Lieberry -- it looks cool and cheap but I wouldn't have a clue what to do with it.

So you were able to use this to make adjustments, that is, it provided information that was useful?

[racinrich]

I just set all 4 air screws the same amount of turns out , 1 3/4 got a smooth idle and rpm was at 950 rpm . zampano's rig is easy enough to build and all you really are looking for is equal vacuum

[Zampano]

..what racinrich said.

I never tried just backing the screws out evenly but that might work just as well. My bike refuses to idle like it should, even when the dealer set the throttle bodies. But it's close enough for a neglected 22 year old machine.

The process is simple.
- Warm the bike up until the fan is kicking on/off. Adjust idle if need be (900 - 1000).
- Hook up contraption to the 3 ports. (n.b., I have an extra elbow on the 3rd port so that i could hook up the vacuum hose that runs around to the fuel pressure regulator. I'm pretty sure you can just leave that vacuum line hanging, however.)
- Back off first screw (most forward) 1 1/2 turns (1 3/4 is fine too. The object is simply to get them all sucking the same [insert joke here]
- Start the bike back up and slowly adjust the other two screws until all is even. You may want to blip the throttle between adjustments. They sort of need to settle a bit. You think you have them all even and then one will creep up or down.

I'm not sure if this is correct but I remember reading somewhere that you shouldn't adjust while the fan is running. So wait until it shuts itself off.

achtung!! -> make sure you know which screws you are adjusting. Don't touch the threaded screws with bits of blue paint on them. The ones you turn are flush and you only see the top/head of the screw. I don't have a pic, sorry.

This is what it looked like when it was idling.



I tried to attach a better picture but for some reason it failing to pass the NSA security team.

It's just a cheap brass T with nipples screwed into to attach the hoses. Also, that's car transmission fluid in there.

[Motorhobo]

Cool -- I will try this but I don't know when...lots of to-dos on the pre-winter checklist.

[Zampano]

no problem. If you happen to have access to an official carbtune type meter, definitely use that because they are more accurate and this adjustment really needs to be fine. The levels don't bounce around (they use mercury I believe.) Youtube search throttle body sync and you can see a lot of variations.

There are also these little in-line connectors which supposedly reduce or eliminate the bouncing of the levels. I didn't buy them b/c I was being uber-cheap and they would have added a whopping $6 or so. I can't think of what they're called but they are just straight plastic with small diameter inside (i think a small metal piece is in there). You put them in-line near where you will be connecting to the ports.

or, if it starts up and runs, just do nothing and ride the thing. Odds are touching one thing will expose another two items to fix. ha.

[wmax351]

I would think in terms of accuracy/variation between the 3 or 4 cylinders, this would be better than the mercury types. It's measuring the difference, rather than the actual vacuum.


The in-line connectors are just restrictors. One can make adjustable ones with the air valves from fish tank aerators. The other option is to add a small plenum inline with each of the lines. A small fuel filter perhaps (if you have carbureted bikes, the clear plastic ones would be good, and can be used later). All of these will stabilize the vacuum at the meter.