carb sync question

Hello All, new to the forum. I purchased a 86 vfr500f interceptor 2 weeks ago. $400.00 couldn't pass it up. The guy told me he rebuilt the carbs, but had not taken the bike to the shop to get them sync'd. I have fairing, fairing/headlight stay, and nice guages on the way from ebay. After a new battery, I have been able to start the bike, but only after a squirt of starting fluid, and with the choke on. It runs rough, but when warms up a bit at least idles (still with choke on) . I figured at this point i should see how far out of sync the carb were, so I built a set of vac guages. while it was idling the reading were aprox #1 (10hg) #2 (40hg) #3 (17hg) #4 (21hg) fairly consistant at those readings. Are the carbs out of sync enough that it will almost but not quite start on gas? And after I sync them, should it then start on gas alone ok? One last question, where are the adjustment screw located?


Thanks for your help in advance,


Will R. Seattle,WA.

 

I don't know those carbs in particular, but the choke cable that either opens the enrichening circuit or closes the choke butterflies should be checked to make sure that it is doing what it is supposed to do.

And for what it is worth, it might be worth checking the valve clearances before you sync the carbs. If you were to sync the carbs and then have to adjust a valve, it will affect the vacuum readings.

Sorry I can't give you any specific help.

 

you should be within 2hg between any two carbs. I'd say your a tad off. your vac gauges should be should be sensitive but not bounce the needles. I'd sync the carbs first. Not knowing the guys knowledge with carbs you may have to take them off to manually align the throttle plate to by pass hole on each carb. They are visible from the manifold side of the carb. This is the initial setting before using gauges. The #4 carb is only adjustable with the throttle stop screw and is the base carb for all other adjustments. There is also a pilot screw adjustment procedure for idle. Which should also be done before using gauges. Hope the guy didn't mix any parts up between carbs. The 1&3 carbs use thinner needles and shorter slide compression springs. This is the way 750 carbs are set up and I'm assuming the 500 is the same. Do you have a factory manual? If not it might be wise to try and locate one. I don't trust Clymer or Hayes manuals for accuracy. Seems they always leave out something or give inaccurate info when you need it the most. When doing carb sync make sure your up to operating temps before any final adjustments. If you need more help let me know. I can fax you the procedures for the 750 motor. Oh yea put new plugs in it too. Yours are most likely questionable because of having to run that much choke.

 

In my experience the carbs being out of sync are not going to be causeing your problem. More likely the guy didn't get the carbs actually clean. He probably didn't get the slo jets/pilot jets clean. I may be misquoting the part but I don't think a sync will solve the issues, it will need to be done and it will help but not solve. Somewhere in my gagrage I have a Honda manual on the VF500 I'll see if I can find it.

 

Guys, I appreciate all teh help! I have now pulled the carbs off the bike. from previous inspection, the guys story that sole me the bike of completely rebuilding the carbs dosn't seem acurate. Aside from the fact that they are very dirty on the outside, the plugs for the pilot jet are intact on all carbs. So with the avice I am getting on here, Going to give the carbs a thorough going thru. Also, the little spring between cylinders 2 & 4 is missing. Do the still sell these?



Will R.

 

still at it

ok, so I have had a chance to examine the carbs, seems the PO tried to drill out the plugs for the pilot jets....but he drilled the wrong plugs on 2 carbs and stopped there... the pluggs he drilled into cover the hole for the shaft that goes through the butterfly valves on carbs 3 & 4. Is it a problen to have holse in thes plugs? While working on the carbs, have been busy on ebay. Now have the fairing stay, and a nice set of guages....and the fairing should be here any day now. I can't wait for the first ride !



Will R.