Airbox flapper

[George Milligan]

What would happen if you were rig the airbox flapper to stay open all the time? If the flapper stays closed until you hit 5,000 rpm's, and these carbs are very sensitive to vacuum aren?t you choking the carbs at low rpm's? I have a flooding problem once I get up to temp, and I'm thinking if I increase the air flow at low speeds, via rigging the flapper open it could help. Anyone ever try this before?

[Blake]

I was actually thinking of this same thing yesterday when i took the factory filter out of my 2001 suzuki intruder 1500 and simple pipeclamped a couple sheets of heating duct filter (goes underneath the grate cover)  when we did this..this bike has noticable kick now..and no stumble about mid way like it used to... only problem is at full throttle is seems to struggle slightly....(lack of rich enough mixture)   but i was thinking if this helped the intruder, why not the vision?  but then i thought that somebody tried to rig open the airbox already and got less than satisfactory results.  man... when i get some time this summer i REALLY want to put on seperate k&N's to the carbs. but the problem with that will be the jetting (ARGH!)   but then im thinking with seperate filters, you should be able to have the same jetting for both cylinders..  oh well...theres a big project ahead...



Blake

[jasonm.]

You have a problem. But the flapper won't fix it. Flooding is caused by a bad float or needle. If it is just rich then adjust the low speed screws between 3 and 4.5 turn CCW. This adjustment depends on altitude. I am at sea level and mine are about 4.5 out. My flapper is adjusted part way open via sliding the diaphragm actuator back as far as it will go. WHY? you ask. Because I don't want to wait for the thing to open. There is a notocable flat spot at 4000-4500rpm when it's set normally. But when open as it is now...it just goes. The only hesitation on my '82 is when it's cold(running less than 5 minutes) between 3000 and 4000rpm and I gas it hard. Once warm it's not there.

[Lucky]

keep in mind before you wire the door open or install K&N's that it's not just a case of open or shut, as the relationship between open and close changes, air VELOCITY changes (and hence negitive pressure on the jets)

just my .02
--Lucky

[Stormdancer]

My '83 had the air flap actually removed, rather than simply wired open.  Fortunately I have an '82 (I think) parts bike, and I just swapped out the air boxes.

The stumble I had always experienced around 4k-5k RPM vanished instantly.

Now, of course, I've got some other irritating problem, which I think is the rear carb gummed up AGAIN.  Grrr.

[Lucky]

have you installed an inline filter? if not you should, the "filter" in the petcock is virtually worthless...it's more of a strainer.

[Stormdancer]

Yeah, so I've noticed!  I had an inline, but removed it, thinking possibly it was causing the problem.  The tank was very recently cleaned & Kreemed, though, so hopefully there's nothing small and annoying in the gas.

But there probably WAS some rust and flakes that made it into the float bowls before this.  Better go get a fresh clean inline!

Can you believe the Yamaha dealer I took it to once said they couldn't fit a filter there?  Geez.  Kids today... no idea how to improvise!

[admin]

probably not a good idea.
of course the right way to get rid of the stumble problem
would be to install some nice 6 inch velocity stacks... What!? you say
there is a gas tank in the way?  oh yeah. :)

if you get the carbs super clean and adjusted right and you won't
have to worry about wiring up the airbox flapper.

just my .02


-Ron