Carb Sync

[JasonJ]

Hello, Im trying to Sync my V4 cyl VFR 750 dirt bike (its dirty :laugh: ).
I got the carbs synced ok and then put the intake and airbox back on with the filter and checked again. I had to fine tune the carbs agan but Cyl 3 was WAY high. I adjusted the linkage all the way out and got it better but its still high. Cant think of what would cause it to do that, I changed the cyl over to anoter tube on the vac guage to check it and same reading. I did not touch the PAJ but thats the only thing I can think could be causing it. When the vacume is high, dose that mean that cyl is getting more fuel than the base cyl or less?
The bike runs Way better now that I synced it but Im just worried about that one cyl. I still feel a bit of lug when diriving at constant speed and giving just a bit more throttle, but anything more than a slight crack and it feels great.

 

[Jaybird]

I am venturing past whay I remember about 4 cylinders, but I think some carbs have carb #3 as a standard and you must set your balls to it.
This may be what you are experiencing.

 

[mylesc]

...and you must set your balls to it.

Sorry, I couldn't pass that up :laugh:

 

[JasonJ]

LOL, my base carb is what Im calling #1. It may be called cyl 3 but I belive it is actually called cyl 1. Its the front left cyl that the throttle cable actuates directly, what Im calling #3 is the front right cyl. Stewing over it the only other thing I can think of is that the choke valve is not closing all the way and staying open a bit, Im going to hook the tubes back up to cyl 1 and 3 and run the throttel up a bit and see if they even out once they come off the pilot jet. I just dont want to suck any Mercury into the motor :yikes: .

 

[Jaybird]

I don't think you can suck the mercury into the tubes, but maybe so.
You could look at this nifty little tool...JCWhitney, $50

 

[JasonJ]

Grrrrrrrrrrrrrrrrr! now you did it.
Funny story about the tool
I have one I got from JCW like 5 years ago, used it once, it had 4 hydrolic dampended guages and could measure up to like 50 PSI fuel preasure as well as vacume. So I look in the box where it was and its not there, I turned my appartment inside out looking for it, call everyone I think may have barrowed it, and cant find it. My brohter says he has one he never used and dropes it off.
I open it up and cant belive it, its basicly 4 clear plastic capilary tubes with a resivior at the bottom, about 10 feet of clear tubing, brass fittings, and 1.5 OZ of Mercury in a bottle!!!! I had to dump the Mercury in the resivior, put the fittings in the intake, and connect the fittings to the top of the capilary tubes with the line. Crude, but it works. The tops of the tubes are open and if I rev the bike to high it looks like it would just suck the Mercury over the top of the tube and then gravity would allow it right down into the head :yikes: .

Kinda wigs me out using someting that has more warning stickers, lables and emergency info than a carton of cigeretts sitting on a gas pump next to an arch welder :eek: . I still have no idea how Im supposed to get the mercury back INTO the little bottle :bang: . Hey wat are these yummy looking little shiney balls all over the place?????? :rotfl:

 

[Jaybird]

OMG, that stuff is completely hazardous to your health. I would be very careful around exposed mercury. If you have kids around, throw that damn thing away. Actually, it needs to be disposed of at a HazMat facility.

 

[JasonJ]

I here ya man, I even waited to use it to keep looking for my gauges, but no luck, I cant belive they would just give you enough of that junk to basicly pollute a small towns water supply. I still have it sitting in the gauge, I have to get that stuff back in the bottle, thinking about sucking it up with my fuel saringe and getting it back in the bottle that way. As far as disposing of it, well I have to give it back to my brother since its his guage set.
Good news is I hooked the guages back up to cyl 1 and 3 and adjusted it a 3K RPM and now the bike runs like its supposed to, it was way off once I cracked the throttle off the idel, some reason that cyl is rich at idel, but hey, I dont ride it @ 1200 RPM right? Even with that one cyl out, the bike got almost 2X fuel milage as it did before I adjusted it. @ $2 a gallon I want it running right :laugh: .

 

[The Digi Sync]

I know this is an ancient post, but I thought other readers would like to note that there are newer Digital Carb/Throttle-Body Sync Tools on the market now that are so dead-on accurate that you can, as Jaybird mentioned, "set your balls to it".

These digital options are self-calibrating which make the job so easy that the Synchronization can be done in under 15 minutes on many motorcycles.