Had my F4i since mile 1 and I'm just over 82,000 miles now, in that time I've never adjusted the throttle bodies. Well, its not really happy idling all the time now [mostly when its cold and sometimes after a long cruise] and I'm thinking perhaps its a throttle body sync problem as otherwise its run excellent as always. I see motion pro all over, is it an ok tool or overpriced garbage? If I'm paying $100 for a tool I want to make sure its gonna last me a few decades.
CarbStix, bought in '86, still have/use 'em...currently unavailable (used mercury). I have no idea what liquid they use in the "new" ones but, it seems to me, it would be easy enough to make one for way less than $100. It's basically four thin clear plastic tubes about 18" long, sitting in a common sealed reservoir, held against a graduated background with four hoses comin' off the tops of the tubes. The hoses each get a restrictor (plug with a pinhole) and you have various available adapters for the hose to carb/throttle body connection. The graduations are numbered and at about 3/4" intervals but the numbers have never meant anything to me...I just look for the fluid in the tubes to line up across the board. Seriously, you can make your own, and they're simple stupid to use. Just don't do any big throttle chops. And why would I be giving it throttle if I'm adjusting sync? Because A) I want to see that the adjustments seat themselves and B) I don't set the sync for idle rpms.
I have the motion pro throttle body sync tool and it has worked great for me on three different bikes in the last 5 years. About a year ago I had to take out the adjustment screws clean the unit and put in new fluid (about 5 dollars). Can't complain
As simple as that DIY made it look, I can't see any reason not to do it. Make it as clean and fancy or down and dirty as you like. The important things are the sealed common reservoir and the restrictors. If I read it correctly (I just skimmed it), that guy bothered to compromise for a smoother idle after he set the sync at 4K. As I mentioned before, I don't sync for idle. If it stays runnin' at a reasonable idle rpm (it will) after the elevated rpm is synced, I call it done. Think about it, who cares how smooth it sounds at idle while you're poppin' on your helmet and gloves? What matters is when the cams start makin' the engine breath freely. That's where your "air pump" starts to smooth out, that's where you want it to start being balanced. Could be 2350, 2800, 3500...whatever. Sync 'em at your particular engine's initial smooth breathing rpm, then raise the rpm to see if there's any change in the sync. It's at these rpms that you want to let off the throttle gradually. If you chop the throttle, you'll suck fluid out of your tool. You'll only be able to take the rpms so high before the fluid just starts "boiling" and you won't get an accurate read. And pscook? Nice find!
I was looking at building my own, but I have a set of older mercury gauges (that need a bit of mercury, short story is that I had a Yamaha Venture that drank the mercury through one particular carb), and I picked up a set of dial sync gauges last spring. I'm just too lazy to use them. My only question regarding the DIY link I posted, shouldn't the contraption vent to atmosphere? I would think that would allow the fluid levels to drop more easily, thereby reducing the chance to suck fluid into the carbs. But I dunno, I would have to look at the motion pro sync that I have. I wonder if I could use oil instead of mercury, or if there is a direct replacement for mercury?
The DIY guy chose 2-stroke oil over ATF. I think I woulda gone with ATF if for no other reason than it looking cleaner. As a side, I'm sure the tube diameter/restrictor flow combination will have something to do with the chosen viscosity of the fluid. I don't get the feeling the DIY guy took too much of that into account, but his results are showing all that you need the tool to do. If you vent the reservoir, the fluid will get sucked straight into the engine. Technically, it will get pushed in, but that's bordering on another topic. Gauges require calibration every time you use 'em...an additional multi-step operation. While providing an actual vacuum reading (some manuals will specify a reading), gauges can also be used for troubleshooting a leak, bad valves, etc., but I forget what symptoms of those issues look like on gauges. The only reason I can think of to use a vacuum gauge, other than troubleshooting or getting a specified reading, is to check the vacuum at a steady WOT where you actually want like +1 psi (ram air not withstanding or in effect), but that's a flow issue, not a sync issue. Speaking of symptoms, check for air leaks and that your valve lash is in spec before doing a sync.
Im using it as an excuse to really tear into the bike. Resealing the front forks, new pads, coolant flush, valve clearance, check waxing unit is set correctly, replace cooling hoses etc. I'll do the sync last.
If you're going that far, might I suggest sending your injectors off to Melka for a proper cleaning and, maybe, install block-off plates to rid yourself of the excess plumbing under the hood?
Good idea! I almost forgot about melka and it was something I've been wanting to do. I'll leave the air, its worked fine and I don't have any mods besides a slip on.
It took me a minute, but I get it now. Dial gauges check the vacuum of each independent cylinder against the atmosphere, the fluid gauges compare the cylinders to each other from a common reservoir. So yeah, venting the reservoir to atmosphere would simply allow the strongest signal to draw the most fluid in the shortest amount of time. Not a great way to sync a TB or carb... I ended up with this contraption from a community garage sale. This is where it pays to be the "item reception focal." First dibs on the cool stuff. I'm going to give it a shot either next weekend or after my first race of the season, if I feel that ambitious. Otherwise I'll just race the F3 on the settings it came with from the last tuneup in, oh, 2005 or so. Maybe 2006? Whatever, it's a Honda, it ain't supposed to be fast, just reliable.
https://www.amazon.com/ABN-Carburet...13456&sr=1-3&keywords=carburetor+synchronizer I've been using this one for just over a year. I have a customers 00 gsxr 600 on the lift right now being sync'd and tuned. No complaints.
rough idle is a classic symptom of valves being out of adjustment too.. with 82,000 miles, may wanna check that too.
The British ones with the metal rods are the shit. Forget the name. The Motion pro unit is total garbage in comparison, but is better than nothing.
Yeah, that's the one. I thought I remember them being like 3 times that price. I only used one that I borrowed once, but I was amazed. For that money I wouldn't consider anything else.
