82 vs 83 carbs

[Lucky]

there has talk recently on 82 parts vs 83, petcocks & carbs particuarly. ?there was one consideration that hadn't been mentioned, & I thought it might be a good idea to bring it up...

Concerning carbs, there is one good reason to stick with the 82's on an 82 bike: Simplicity

With Yamaha's quest to improve performance by redesigning the carbs for 83 they did a good thing & a bad thing. ?they improved pilot screw location, although i'm not convinced the 83 is any more refined, but they also overly complicated the accelerator pumps (A/P).

If you don't have an 83 carb than you may not have seen the A/P controll valve on the 83's that's supposed to keep them from firing when the bike is off (to prevent flooding) ?There is a diaphram inside with a brass/rubber seal that is set at the factory & not supposed to be adjusted, it has locktite on the screw threads. ?the problem is that when this diaphram gets old & stiff, it doesn't leak fuel, but doesn't react properly to the vacuum forces on it either. Adjustment is the cure, & if it's not adjusted properly, it can cause a huge vacuum leak.

this adjustment is so sensitive that it can cause al manner of problems, but thankfully it's not something I have seen a lot of. ?

Those of you with 83 carbs, count your blessings if your not experiencing problems, & if the ratio of 82's to 83's that i rebuild is any indication, hopefully this will continue to be an occasional problem & not a common one. ?I'm not sure if it comes in those Ebay kits or not...

--Lucky

[Dave T.]

I was curious about the vacuum flapper update for a '82 model. I have the update, but it doesn't get rid of my stumble completely. I notice it vibrates a little more at 4500 rpm's and has the stumble.

Is the vacuum flapper specifically made for the 1983 model carbs? I know they are different and are 36mm instead of 34mm. I guess I could go back to stock jetting and see what happens. But I don't think it will help.

[Lucky]

An 82 carb, with the complete & proper update, clean, & properly adjusted should not stumble.  This is assuming the rest of the bike is in proper working order: Valves properly adjusted, exhaust in good shape, no charging system problems, electricals in good shape (i.e. coil connectors clean & tight, etc)

the only jetting changes I'd reccomend is that BOTH pilot air jets be changed to 135.

As far as I know, the tops of the airbox are identical (updated & 83) I know 83 airbox bottoms are slightly different to fit the 83 carbs.
--Lucky

[Dave T.]

I have also noticed that my stumble increases after 500 miles or so. I can get rid of it by spraying GUNK carb cleaner down the pilot air jets. Then after 500 miles, repeat. I wonder what plugs them? Dirty fuel or air? Both?

I know the V runs best with exceptionally clean carb jets and passages. But they tend to get dirtly quickly.

Anyone figure out a great fuel filter setup? This seems to be a big help. 8)

[Lucky]

it goes without saying that you should check your air filter if you havent in a while (year or more) also, look for excessive amounts of oil which is blow-by from the valve seals.  if it's really a lot your filter may be saturated & getting into the carbs, but I think this is really rare, for this bike.

The filters I favor are the plastic cone shaped ones with the sintered bronze element.  I've used so many of them on rebuilds the hardware store where I buy them is allways out of them... but I have to pick up more, so if you can't find one, let me know, i'll send you one.

on 82 carbs I mount them between the carbs in the line between the pump & choke bracket.  the small end of the cone sticks thru the hole for the fuel line.
On the 83's I mount it in the same position except that the line is lower, so it sits under the ft carb just above the intake.

--Lucky

[Dave T.]

I recently had oil leaking from my front carb boot (velocity stack to airbox bottom). I figured that I had lots of oil blowing out the crank vent. So I lengthend the rear hose to go up farther to the front cylinder vent/drain. No more leaky. The vapors from the blow by may be the culprit. I may try to vent the crank to the atmosphere again this winter.

I did put new valve seals in when I did the top end a year or so ago. Damn, they are expensive. $8 each! :o I may have to go through the valves again this winter & do a leakdown test. :-/

[Rick G]

A certain amount of  oil vapor  will build up in the bottom of the air box , especially if you ride it hard like I do.  I pull the tank and fairing lowers off when I wash it, to get all the "drool" off  I think I'll also  look into venting it to the atmosphere .