why, Why, WHY??!! ... won't it stay running...??!!

For Carb Sync = Morgan carb tune. Worth every penny.

 

8mm is correct. Once you have one set of bowls off the bottom screw is easy to get to with a phillips screwdriver. Make darn sure to return each item to the carb it came from. Slides, bowls and float needles are very important to get back where they belong.

 

Cleaned out all jets, pilot holes, bowls etc. Good tip regarding the guitar string too. Carbs went back on like a dream. Much thanks to all who posted positive input, suggestions and comments, bike is running now. I'm guessing it's in need of a carb sync. Why though, would the sync of the carbs be different, or thrown off from the way they were before taking them off? Sorry for the ignorant question, but remember,

""""since you seem to have no clue about how carburetors actually function or operate.""""

...but this clueless guy got it running again

 

There is always an exception to the rule, and you are obviously exceptional--most folks screw themselves up doing this job.

If you didn't adjust or fiddle with the screws that adjust the butterfly valve positions, then you haven't changed the "synch" from whatever it was. Unless someone messed with them, then they are still at the factory setting--no need to fix it if it isn't broke...

 

The flipside is that whatever sync was done to the carbs before is more than likely way off by now. Carbs need to be synced on a regular basis, just like valves need to be adjusted. Except carbs need to be synced more often. I used to do mine every spring, and they were almost always out.

Also, just because it runs doesn't mean your carbs are clean. My GS750 ran just fine on 3 cylinders until I rebuilt the carbs and cleaned out the clogged idle jet on the first carb, among other things.

 

Would solid mid-range throttle, yet low and high range throttle being a little rough, be indicative of a poor sync?

 

Could be, sure. Could also mean some jets or passages have fuel varnish in them still. Or some o-rings have gone hard and brittle. Or any number of other problems. Carburetors are very complicated precision devices and need all factors in good alignment to deliver smooth power and fuel mileage.

You might get lucky and find that a sync clears up your problems, maybe not. Try it and see, if you still have problems you should either have your carbs looked at by a pro, or look into doing a PROPER rebuild yourself with all parts disassembled, inspected, and replaced as necessary. All rubber parts on a 15 year old carb should probably be replaced during a rebuild regardless. You'll also need to set the float heights and tune the idle mixture.

 

Carb synch only affects the off-idle characteristics of the bike. Just a crack-low speed riding (five miles an hour in a school zone)...once your into mid range your on your needle, top end your off the main jets...

 

Not sure how VFR carbs are set up, tbo, but the round-slide Mikunis on my Suzuki you synced by adjusting the base position of the slide and needle so that they all pulled the same vacuum at idle. Then you increased and held the RMP at various points to make sure the sync held at 1/4, 1/2, and WOT. I'm pretty sure if one of the carbs is pulling more vacuum than the others at idle, it will be pulling more vacuum with the throttle open too.