Weird carb sync results

[klutch14u]

Bought a sync tool to check/sync my carbs on my newly purchased 2004. Finally got it hooked up today, results were a bit weird. The #2 (main/master) carb barely moves the needle, even while opening the valve on the line, it never goes all jumpy the way I've seen in numerous videos. But even syncing to it, adjusting the screw for carb #1 will eventually result in popping. I got them to match fairly well but when revving the bike, the needles don't seem to move together (like I've seen in numerous video's once sync'ed)

Took a video of it. I sometimes also have the odd noise when I set the ignition to 'RUN', I happened to catch it in the video. For clarity, the order of the gauges are 2,1,3,4 left to right.

 

[Jack Hammer]

One thing I noticed is that Vboost is not cycling. Is this a 100hp model? Also, the second gauge from the the left was more responsive. They are supposed to be fairly even.

 

[klutch14u]

One thing I noticed is that Vboost is not cycling. Is this a 100hp model? Also, the second gauge from the the left was more responsive. They are supposed to be fairly even.

I think that's the vboost cycling at :05 isn't it? It's drowned out by the weird grinding noise (which doesn't happen all the time). Agreed on the second gauge (#1 carb), part of the reason I'm posting this. In other videos I've seen, once sync'ed the gauges move together for the most part. These, not at all.

 

[Jack Hammer]

No, I don't hear Vboost cycling at all.

 

[Jack Hammer]

Turn ign on and look inside between left carbs. Do you see movement? It is very audible and visible. Vboost cycle starts the second you turn ign on. It goes full tilt then back to zero within about 4 seconds.

 

[klutch14u]

I don't want to get too off track here. Looking at this video, my bike definitely cycles like this when you turn the ignition on.

I'd love to figure out what that weird groan is and the sync issue which is really why I posted.

 

[Jack Hammer]

Ok, that is clear. I didn't hear it in your previous video at all, only the fuel pump.

 

[klutch14u]

Ok, that is clear. I didn't hear it in your previous video at all, only the fuel pump.

That second video isn't mine, just for reference. If you watch/listen to my original video, at :05 you can hear the very end of the vboost cycle, it's tough to catch with the radio and the weird groaning sound.

 

[Stephan]

Maybe check the vacuum hose connector stub #2 for foreign material? If there is any kind of restriction it may cause this lack of response.

 

[brian hicks]

These meters are sometimes total crap. Swap the connectors around and compare meter readings then you can identify if the meters are consistent or not. If the meter is twitching then it hasn't been dampened.

 

[klutch14u]

These meters are sometimes total crap. Swap the connectors around and compare meter readings then you can identify if the meters are consistent or not. If the meter is twitching then it hasn't been dampened.

Thanks. Yeah, I tried that and it was consistent for carb #2. Now I'm a little more worried about that weird groan when I turn the ignition to 'RUN'

 

[F 18 Driver]

Hello,

On the less expensive vacuum syncing tools. The gauges don't read accurately to one another…

Your first step is to zero out the gauges by remove the plastic lenses and adjust with screwdriver

Next, get yourself an old-school tach dwel meter…

Your idol seems to be very low. Be aware that the factory tach on board your machine are usually not very accurate at low RPMs… That's why you need to use old school meter for accuracy… Check manual for required RPMs. usually between 950 to 1000, but check the manual.

After all the above have been accomplished then start adjusting

Also, the little white air inlet valves can affect performance… Of the vacuum meter… Easily replaced at fish aquarium store.

As a side note, be aware that carburetor syncing only affects performance from idle to about 3000 to 3500 RPMs…

It is been my experience that the best tool for carburetor synchronization is the Morgan CARBTUNE PRO … This tool is very accurate .

Hope this helps.

F-18 driver

 

[Jack Hammer]

I bought my carb gauges long time ago for fifty bucks with adjustable dampers. Never failed, lot's of happy motorcycle owners. An expensive tool is not the thing, but a person using the tools. I never buy SnapOn because the prices are ridiculous, Pittsburgh does the same thing for a fraction of the price.

 

[F 18 Driver]

Hello, jackhammer

Very insightful comments and logic

However, by your own admission, you have no way of determining how imprecise the less expensive gauges are…

It's the science and methodology the old-school Mercury gauges use a different methodology than the round dial diaphragm type. Which results in a more precise vacuum reading for carburetor synchronization

Please pardon me for contradicting you but I think you deserve a little spanking

The person purchasing the tool has to understand its standards and deviations as to other tools available in the market and then decide if they're willing to sacrifice precision for price.

As you have stated supra price is your determining factor in tool purchase rather than precision.

Further, for your own edification.

My response to klutch14u was an attempt to help him understand the fluctuation within the tool he was using and possible solutions and alternatives.

 

[Jack Hammer]

Fair enough. Two different opinions. I'm cool with that, not the spanking part