re-synching carbs

[Chester Gunn]

I decided that after riding the bike that the carbs were still not quite right. I got it all hooked up to the synch tool and got the bike started. For what ever reason I am not getting a reading on the 2 cylinder? When I turn the adjustment screw for the #2 carb, it effects the running of the motor, but it will not budge the meter. Does this mean that carb is not pulling a vacuum?

What should I do?

[81gs1100]

First off, I would start by inspecting the fitting running into the head, or where ever you are hooking up the sync gauges if you are not getting a reading that fitting could be plugged. Also inspect the hose you are using, is it split, pinched? Did you try one of the other hoses that are working?

You should be getting a reading even with a bad carb, you mention that the engine responds to adjustments made on that carb so it has to be functional.

You could alway do an RPM drop. Just slowly turn in the screw till the engine falls 50rpm and back it out 1/2 turn and center carbs 1/4

[Baatfam]

Swap the hose between #1 and #2 and make sure your gauge is just not stuck or leaking vacuum...

[81gs1100]

calibrate the gauge?

Have you calibrated the sync gauge?

Hook up the #1 hose to #1 cyl, then adjust the gauge to the middle, make a mark, or what I do is put a rubberband around the gauge so I can make sure all the readings are the same.

Then leaving the hose on the #1 cyl, hook it up to the #2 fitting on the gauge and adjust the gauge so that the ball moves to the same level in the middle as the #1 was set and go to fitting 3 & 4.

Once the gauge is set then hook up the gauge as needed to preform the sync.

[Nessism]

Make sure the vacuum line for the petcock is pluged or you will loose a lot of vacuum that way.

[mike_of_bbg]

On my friend's Yamaha we were getting no vacuum reading on #3 because his carbs were so far out of sync it was doing all of the work! Are the pipes equally hot? Not sure which one is the master carb on the 2-cyls (the one the throttle cable connects to). If that's the case you'll have to keep bumping the idle speed up because the closure of the other throttle plate might be holding the master open.

Is yours a vacuum petcock? Are you plugging that hose?

[Killer2600]

Make sure the vacuum line for the petcock is pluged or you will loose a lot of vacuum that way.

Yea you have to plug that hole otherwise you won't get a good reading and you'll be running wicked lean on #2 the entire time your attempting to sync.

[Chester Gunn]

WEll..

I use a carbtune II and they say that it doesn't have to be adjusted. In fact, I couldn't find an adjustment on the instrument. But, that's the good news. The bad news is that I ended up screwing up the slot on the number 2 adapter and tried to pull it out and ended up breaking it off in the hole. Soooo, I ended up pulling the carbs in order to get the adapter out, so I tried to finish up the sync by ear and I actually got it pretty close.

I only have one question, why didn't they put the holes on the top side of the manifolds instead of the bottom. That would have made it so much easier. If this was a bike I was going to keep long term, I might even consider putting sync bolts in the top...Probably wouldn't work, but it was just a thought..

Thanks for everyone's input..

[Chester Gunn]

But,

I really don't understand why I wasn't getting a reading on the #2 carb. The same thing happened last week when we tried to sync the carbs the first time. I know that it's not the manometer because I used it to sync the carbs on my 1200 Goldwing yesterday and everything was working fine. I tried swapping hoses and the hole nine yards, but never got a reading on the #2 carb. If someone could clear this mystery up for me, I would be in their debt..

[Killer2600]

I use a carbtune II and they say that it doesn't have to be adjusted. In fact, I couldn't find an adjustment on the instrument. But, that's the good news. The bad news is that I ended up screwing up the slot on the number 2 adapter and tried to pull it out and ended up breaking it off in the hole. Soooo, I ended up pulling the carbs in order to get the adapter out, so I tried to finish up the sync by ear and I actually got it pretty close.

I only have one question, why didn't they put the holes on the top side of the manifolds instead of the bottom. That would have made it so much easier. If this was a bike I was going to keep long term, I might even consider putting sync bolts in the top...Probably wouldn't work, but it was just a thought..

Thanks for everyone's input..

What bike is this, mine are easy access once the tank is off.

I really don't understand why I wasn't getting a reading on the #2 carb. The same thing happened last week when we tried to sync the carbs the first time. I know that it's not the manometer because I used it to sync the carbs on my 1200 Goldwing yesterday and everything was working fine. I tried swapping hoses and the hole nine yards, but never got a reading on the #2 carb. If someone could clear this mystery up for me, I would be in their debt..

Simple, the gauge isn't seeing any vacuum where you have it connected...either your connected to the wrong place, the hose or passage is clogged, you have a huge vacuum/air leak, or you created a huge vacuum leak (unplugging the petcock vacuum hose and not plugging the hole/hose)