83 fuel tank boilover & hard hot start culpret

[Lucky]

I don't think many of us here have the chance to do side by side comparisons of 82 vs 83 fuel systems, but I have, & have a theory to put forth.

83's are prone to fuel tank boil-over & hard hot starting.

My thoughts on why:
--83 tanks are black. right there they will tend to absorb & store more heat.  if you have a chance to look, you'll see that all 83 tanks have a thick tar heat shield underneath.

--83 airboxes (which are different than 82 airboxes because they have to clear the redesigned carbs.) have A LOT more foam on the top cover, that seals up against the underside of the tank.  probably to direct more or cooler air into the flapper.

i've never heard this mentioned before, probably because 82 owners don't realise there is more foam on the 83 airbox & vice-versa.  plus i'm sure many of the airboxes. after 20 plus years have lost their foam.

So, it makes sense that all that foam is blocking cooler airflow from the bottom of the tank...and maybe from getting back to the R/R too?

What think yee?

--Lucky

[h2olawyer]

Lucky -

Your theory sounds good to me.  The only thing I'd alter is that many '82 tanks were black too.  And they didn'h have the "cool" gold striping to shave that .00001 degree either!

The engine heat seems to have a greater impact on fuel tank boil over than tank color.  My silver tank will boil over if I over fill it.  It can even happen when parked in the garage.  I have checked my vent & it is not plugged.  I haven't added a heat reflector to the underside of my tank yet but will probably do that sometime soon.  It only happened to me when I got it good & full, then rode right home - about 2 blocks - and parked it.  Barely got it on the centerstand and fuel was already cascading down the side of the tank.  Removed cap, burped air and let engine cool down.  Reattached cap & no more Mt. Vesuvius.

For now, I just fuel while on the center stand & stop filling just before the fuel reaches the bottom of the inner fill neck.  Haven't had any boil over problems following that formula.  I may get fewer miles per tank but I don't like riding more than 125 ~ 150 miles between rest stops anyway.  Need to get off on occasion to let my back & hands recover.  Makes for a good reason to stop for fuel every 100 miles or so when I'm on a longer ride.  Similar fueling procedure might work on 83s.

Just my $.02.

H2O

[GA_Wolf]

Like H2O, I just fuel on the centerstand and only to the lower tip of the filler neck.  It stopped my boil-over issues too.

[Kenny]

   I gave up fueling on the center stand as I can not get as much fuel in the tank. I have mentioned this before, I have insulated the bottoms of my tanks with a reflective foam stickon type insulation -even the 83's the sheilding on them is not the best, if you look at were the cap on the tank is you will see my reasoning as to fueling on the side stand,when on the sidestand the tank cap is at the highest position. I just give the side of the tank/bike a wobble while fueling and it lets the trapped air out. Another 82 vers 83 item to remember is that most 82's had  no fairing and had better airflow over and around the tanks surface. We only had black V's in 82 while all our 83's are red n white.
        Something else to think about.
              Cheers Ken S.  

[h2olawyer]

Kenny -

The reason you fill on the side stand is precisely why I fill on the center stand.  I don't want to get that much fuel in my tank.  It would leak out every time - even in cool weather.  I can still get more miles at one time than I want to ride out of my tank so putting a couple gallons + in every 100 miles or so works just fine.

I've only had to switch to reserve once in 20 years of ownership.  That was last summer when I spent many hours getting the carbs set just right & taking lots of short runs for testing.  With all the idling & heavy throttle use, I only got about 120 miles before I got to the reserve point.  Sure surprised me when it began to stumble really bad!  The extra 20 miles I'd get out of trying to fill the tank entirely just isn't important.

H2O

[Kenny]

  H2o,
      Try the reflective liner on your tank tunnel - it will make a difference.
  Sounds like you could get away with a cruiser style outfit ;)
                        Cheers
                                    Ken S

[h2olawyer]

Kenny -

No cruiser style for me.  Didn't say I ride slow, just that longer distances really get to hurting my hip joints.  Even hanging off the bike in corners doesn't keep it from happening.  Even if I put the reflective liner on, I'll probably continue to fill the same way.  There is not much difference in fuel volume anyway.  Just don't see that it's a big issue.  ;D

H2O

[ofstone]

hello guys,

I do not think the problem is the color of the tank or insulation issues. Mine 82 vision stil has foam on top of the airbox. The tank overflow i think is caused by the tank itself. The neck of the hole where you add the fuel is very long. (i never have seen this on any other bike) This causes some air to get trapped above the fuel level in the tank when tank is filled to maximum. When you fuel the bike, most of the times the fuel is cool because it comes from tanks out of the ground. That also causes the air above the fuel to cool down.
When the bike is running, or even is not running, the fuel and air will heat up. The fuel and air expands, but because the long filling neck the air cant get out and will push the fuel out of the bikes fuel cap.

It even happened to me when the bike was cold, and I refueled the bike from an barrel fuel that i had standing in the garage. When ik came back after 30 min the tank was completely soaked because the bike came out of a cool garage and now was standing in the sun. And that was even without running engine.

The reason a 83 bike does more overboiling than an 82 bike, must have something to do with the design of the tank(is it different than an 82 tank?) or the position of the fuel tank.
Maybee due to the better rear shock adsorber and air assisted front forks, the position of the fuel tank is more in a position were the fuel level closes off the fuel neck, and fuel will come out soner and/or more than an 82 bike.

I dont now this all for sure, but i just think it is a logical explanation. I also never have seen an 82 vision next to an 83 vision to compare the position of the fuel tank. Maybee one of you guys know this.

[Lucky]

The tanks are identical except the 83 has a different petcock and a fuel level sender.

The black tank is a contributing factor, but my main point is that the 83 airbox has a ton more foam on it compaired to the 82 airbox.  the 82 airbox has 2 small pieces, the 83 airbox has foam nearly all the way accross. this is blocking any possable airflow under the tank.  next time I have my tank off i'll take side by side pics & you'll see the big differance.

I don't think all that foam is needed, manufacturers rarely use anything extra, so my point is that IF your experiencing chronic boilover in the hot weather, try removing some of the foam.

--Lucky

[ofstone]

I think maybe my 82 vision has an airbox of a 83 vision, or at least  the cover because mine has foam al over the cover. I thing it maybee was used to hold the airbox in more firmly and to prevent the cover to begin vibrating maybee.
By the way i still have a normal flapper, not an vacuum operated flapper. I am trying to find a vacume operated one to eliminate the vision stumble.
I also found out that if i drive over an bump in the road the flapper fals down for a small moment and than the engine loses a bit power for a moment. It is not a big problem only a bit irritating when riding a long time at a constant speed.

Is it a major thing to change to vacuum operated flapper? do i have to change a lot like air/fuel nozzles?

[jasonm.]

some of you may be grabbing at straws. Both my '82 and '83 are black. Neither have a hot start problem. As far as boil over...I drilled 1/16" holes at 3 and 9 o'clock inside the filler neck. This allows for heat expansion without forcing the fuel up the filler neck.

[Lucky]

To clarify, i've never had a boil over problem either. it's just the massive abount of foam on the airbox seems an obvious block of airflow.  now that it's really hot out we'll see what happens....

[Extent]

Well I just experienced this for the first time this weekend, but the situation was probably a little more extreme.  I had been out riding in ~100* weather for an hour or so when we stopped for gas (this is much hotter than the weather around where I live) and I noticed after filling up that it was bubling over before I could even get the cap back on it.  As soon as it was done doing it's thing the level immediatly dropped back down into the tank and below the neck, so I defenatly think that making your vent holes in the top of the neck like Jasonm said will aleviate the problem.  In my case there's not guessing where the heat camefrom tho, so I've no idea how much the foam and heatsheald contributes (and I've got an 82 anyway)  IMO I think it would be better to not worry about the heat and cut the vents and that should prevent any possible boilover unless you way over fill it.

[Sable]

 ? ? I would like to see pix of the drilled vent holes if at all possible... I am one of those people who has to see something to be able to do it ;D
 ? ? I had an interesting thought.... did Yamaha have an update for '83 model air box? I thought that the reason for the two pieces of foam on the '82's was to make room for the air box band (item #26 on the on-line parts catalogue)... Even on the Yamaha on line parts catalogue, it shows the '83 air filter with two larger pieces of foam on either side of the air box band (item #41 on the on-line parts catalogue)?

 ? ?~Sable

PS - Does anyone out there still have the band on their air box?

[Blake]

Now i dont know about you guys, but right before i painted my 82 tank.. you could easily see the marks that the two foam pieces from the airbox made on the underside of the gas tank.  now that foams MAYBE 3/4" at most..   so its obviously a tight fit.  are the airboxes the same size on 82 and 83? or is the tunnel on the 83 higher?  

because (just going on my 82 and what i saw when measuring for k&n's), its a nice tight fit for the airbox under the 82 tank...to me it looked like the foam was there just to compensate for some vibration and to make sure it doesnt have plastic smacking right into the gas tank if there ever was movement..

just my observations

Blake

[gbranche]

PS - Does anyone out there still have the band on their air box?

Yup. When I refurbished the bike last year, and got everything all back together, I had no idea where that long bungee cord was supposed to go. A couple of months later I saw a post here that allowed the light bulb to come on. I re-installed the hold-down band the following weekend.

:)

Greg

[h2olawyer]

My airbox bungee strap is still in place and functioning great.  I forgot it once and had a major rattle under the tank.  Now when I take the airbox off, I put the strap right on top of it so I don't forget to put it back on.

How many of you have the clamps that attach the air horns to the tops of the carbs?  Mine were missing when I bought it.  The dealer's mechanic must have been in a hurry.  Didn't notice until I began going through everything a few years ago.  By then, it was too late to go back to the dealer & complain.  The dealership closed at least 15 years ago anyway.  Might see if they're still available, just to see if they make any difference in the carb / airbox seal.

H2O

[gbranche]

How many of you have the clamps that attach the air horns to the tops of the carbs?

Yup, I still have those too...

Greg

[jasonm.]

to drill the vents. Look down the filler neck. Using a 12" x 1/16" bit(this allows you some flex and easier to hold the bit). Drill 1/16" holes at 3 and 9 o'clock about 1/2" or so from the top. I believe there is a little groove around the filler neck at about 1/2" down. Can't say it any simpler. No digicam here.

[Lou]

How many of you have the clamps that attach the air horns to the tops of the carbs?

I replaced mine with similar-sized hose clamps