Carb sync procedure for Carbtune

[Jstets]

Hi I'm new to syncing carbs on a vmax, I have a carbtune pro and I have the carbs synced when idling but they rise at different rates when applying throttle. Is this normal and if not how do I adjust. I know that on my intruder there is an idle adjustment and a throttle sync adjustment.

 

[PATMAX]

You need a manual but there are a few “how to videos” available. Do a search under carbs.

 

[Jstets]

You need a manual but there are a few “how to videos” available. Do a search under carbs.

I'm ordering one, I have read numerous threads on here which lay out the process for syncing and none mention syncing using anything other than the 3 sync screws. Like I said I followed the procedure for syncing them per the threads I've read, was just hoping a more knowledgeable member could answer if there is a throttle sync adjustment.

 

[one2dmax]

I'm ordering one, I have read numerous threads on here which lay out the process for syncing and none mention syncing using anything other than the 3 sync screws. Like I said I followed the procedure for syncing them per the threads I've read, was just hoping a more knowledgeable member could answer if there is a throttle sync adjustment.

What else are you looking for? Sync screw on the left sets the left pair, one screw on the right sets the right pair while the other screw sets pairs to pairs. Pretty much all there is to it.

 

[Jstets]

What else are you looking for? Sync screw on the left sets the left pair, one screw on the right sets the right pair while the other screw sets pairs to pairs. Pretty much all there is to it.

At this point I guess I'm really just trying to find out what I need to adjust so that the vacuum pulls equal when I twist the throttle, they aren't super far off but don't all rise equal and don't all peak equally. All I have experience wise to go off is syncing my 94 intruder and I had to adjust the throttle sync so the carbs pulled evenly as well as idle sync adjustment. Or is it alright that they don't pull all the same?

 

[Radioguylogs]

I have noticed the same phenomenon on some of my bikes. (They pull vacuum differently as you rev up from idle.)

I just shrugged my shoulders- don't know why, but they all seem to perform normally.

 

[one2dmax]

At this point I guess I'm really just trying to find out what I need to adjust so that the vacuum pulls equal when I twist the throttle, they aren't super far off but don't all rise equal and don't all peak equally. All I have experience wise to go off is syncing my 94 intruder and I had to adjust the throttle sync so the carbs pulled evenly as well as idle sync adjustment. Or is it alright that they don't pull all the same?

Unless you have exactly the same wear, casting, valve shimming, and other flow characteristics you will never get each cylinder to raise/lower a sync meter at exactly the same rate. You are shooting for a sync at idle or whatever target RPM you are looking for. Some like to sync theirs are 3 or even 4k so that it's as close as possible during a cruise scenario.

 

[Jstets]

Unless you have exactly the same wear, casting, valve shimming, and other flow characteristics you will never get each cylinder to raise/lower a sync meter at exactly the same rate. You are shooting for a sync at idle or whatever target RPM you are looking for. Some like to sync theirs are 3 or even 4k so that it's as close as possible during a cruise scenario.

Thank you for explaing, that clears everything up for me

 

[Parminio]

For what it's worth, I do not like the Carb Tune Pro at all. I've seen several people get some really wild readings off that thing.

I'm old school. I use old, simple, dial vacuum gauges.

You do need to set your idle up at around 1,000 - 1,100 regardless of the gauge you're using.

Not long ago, another fellow @Eric Cunningham on this forum had the same problem with the same exact tool: bouncing all over the place. I rode over to his house with my gauges and they were smooth as silk and perfectly level up and down the RPM range.

I think whoever used to make that Carb Tune Pro doesn't make it anymore and farmed it out to some half-assed third party. I wouldn't use one of those to tune my carbs if you paid me.

Edit to add:

Here is the thread on that: Carbtune results | Yamaha Star V-Max VMAX Motorcycle Discussion Forum (vmaxforum.net)

Watch that video and see if you're getting something similar. That's what his Carb Tune Pro was doing and it was just awful. I've seen several of them be that bad or worse.