airbox/snorkle removal?

[mjpxs11sh]

hey all! anyone have any tips on how to remove 81 Special Air Box? ive had the carbs off twice 4 cleaning, now thinking of installing 4 air filter pods to see how it runs. i had difficulty just moving it enough to remove carbs. i feel its lacking power and probably needs a jet kit. now has a Kirker 4/1, stock 110mains across all 4 carbs and 42.5 pilots. sock jet needles. they r too small, its too slow, i guess because Yamaha was trying to pass emission requirements. ive got thee carbs really runnin great and now want to tweak. do u have to change the pilot sizes when increasing main, jet needles etc? i heard that after market kits dont come with any :confused : thanx everybody

[DGXSER]

There is a common modification of drilling holes in the bottom of the airbox, in the center so the air remains filtered, to increase air flow to the carbs. You can also cut the snorkle off really short, and trim off the top mounting bracket of the air box so the top part will drop down after you pull it back off the carbs.

As to jetting, no, you do nto NEED to change pilot jets because you change main jets, and I am not familiar with there being any upgrade or change to the needle jets.

[BA80]

The Dynojet kits come with adjustable needles that is what you'll need if your going to switch to pods. Increasing airflow will lean out the fuel/air mixture.

I suggest you be CERTAIN that the carbs are the problem before you start changing things there. Lots of others use the stock setup with out any problems. Many other things can make it seem like a carb problem such as valve clearances,vacuum and centrifugal advance, coils or wires to name a few. Are you sure it's hitting on all cylinders when you throttle it, sometimes if the pickup coil wires are going bad it will idle fine even rev fine but under a load you'll lose 2 cylinders.

JAT

[mjpxs11sh]

The Beast

theres nothing wrong with the driveability. i just put this bike back together after 15 yrs of storage, cleaned carbs etc. but having an 85mph speedo and 110 mains in all carbs proves to me this engine has more to give. the previous versions had 137.5 mains, adjustable needle jets, etc. 1981 they covered the idle mixture screws and say " set at factory, do not adjust". to me the carb parts on the MKIII are in there to slow it down/emission related. the throttle position response is smooth thru all carb circuts. i feel it needs to breathe more and with that more fuel. i already have the filter pods from my 78 and figured i may as well use them with carb jet updates. my 78 was much faster than my 81. as far as the air box, is the only way to remove it is to cut the snorkel? i know its in there tight, but seems rediculous to have to ruin it. someones had to get it out and put it back in i would hope. Thanx Guys. all info is appreciated!

[BA80]

That's exactly why I have the earier carbs on my SG. Much more adjustable.

The earlier engines WILL run better because they have higher compression and bigger cams. They turn on a little later because of the longer cam duration but kick ass after about 3K.

I have a 2H7 engine in my SG now and it is a LOT quicker than the original 3J6 was.

Yamaha tried to make up the difference for the lower compression and shorter duration cams in the later engines with larger valves with some success but the older engines are still quicker.

[crazy steve]

....110 mains in all carbs proves to me this engine has more to give. the previous versions had 137.5 mains, adjustable needle jets, etc. 1981 they covered the idle mixture screws and say " set at factory, do not adjust". to me the carb parts on the MKIII are in there to slow it down/emission related....... as far as the air box, is the only way to remove it is to cut the snorkel? i know its in there tight, but seems rediculous to have to ruin it. someones had to get it out and put it back in i would hope. Thanx Guys. all info is appreciated!

While some of the changes to the carbs was emissions-related, that's not why the later bikes were slower. The '78-79 bikes had different cams, higher compression, and on the '78s, a different ignition curve. All of them had 'tamper-proof' idle screws, it's just that on the early bikes those plastic caps were much easier removed. The reason for the smaller jetting is the '80-81 carbs are considerably different internally; if you try to use the early jets sizes in the late carbs, the bike won't run at all.

As to getting the airbox in/out, yeah, it's not super easy. With the carbs already out, you have to drop the bottom half of the airbox off/out, then 'bend' the rubber snorkel around a bit to remove/install the main box. But use the right procedure, it's not that bad...

[mjpxs11sh]

air box removal

thanx Crazy! im never short on effort and will dedicate some time to remove it now that i know its possible!

[BA80]

'bend' the rubber snorkel around a bit

The snorkle will come right out of the airbox also.....

It's just a rubber piece with a groove for the edges of the hole in the airbox. But I'm still not sure it can be done with the carbs installed.

It's MUCH easier if you take the carbs off. No big deal.

[crazy steve]

You ain't getting that airbox out if the carbs are on; at least not in one piece! And don't pull that snorkel off the box, as it's a PITA to get it back in... BTDT...

[BA80]

You ain't getting that airbox out if the carbs are on; at least not in one piece! And don't pull that snorkel off the box, as it's a PITA to get it back in... BTDT...

That's been my experience with removing the airbox too Steve. And you are absolutely right about re installing the snorkle being a PITA.