80 gs850 intake exhaust question

[mvalenti]

I would like to loose the airbox and go with pods but keep the original exhaust. I have heard talk about possible needing to rejet. Where do I start and which direction am I most likely going to have to go in? Also, costs, on a tight budget here...

-Mark

[doctorgonzo]

I would like to loose the airbox and go with pods but keep the original exhaust. I have heard talk about possible needing to rejet. Where do I start and which direction am I most likely going to have to go in? Also, costs, on a tight budget here...

-Mark

I THINK they make a dyno jet kit for that bike. You need the Stage 3. Or, you can get washers and shim the needles, and buy new jets from Z1 or somewhere like that. Second option is cheaper (some), first is easier.

[Steve]

If budget is that tight, why not stick with the stock airbox?

What do you hope to gain by going with the pods?

At the very least, you will have to go up three or four sizes on the main jet and shim the needles about the equivalent of a full notch.
But, unless you uncork the other side of the engine with a header, you won't see a whole lot in the way of a power increase.
And, I have heard it said on the board that, for some reason, the 850s are the worst to try to re-jet. No idea why, it's just what I have read.

Costs? Most of it will be in the pods that you get. If you get K&N pods, figure on about $150. If you go with EMGO pods, figure on about $35 this time. The EMGO pods are not designed to be cleaned and re-used, so it will be about $35 every time you need to change your filter. The filter will also determine which jets you need, but jets are about $1.60 each, you will need four of whatever size you feel is necessary.
Staying with the stock airbox and jetting is FREE.

.

[mvalenti]

Thanks Steve & Dr,
Why? I like the look of the pods over the airbox... Unless I can trick it out somewhat... Not going for performance increase. Not yet anyway. Hmmm... got me thinking now... custom airbox....


-Mark

[mvalenti]

Custom airbox plenum

Got me thinking, I would like to keep performance the same and have a cool look... I came up with this quick model... what do you think? Of course to mimic the stock setup I would have to be as close to the original volume I would think. Its a custome plenum, with (2) hotrod 4.5 inch dia air filters at either end. I think I would prefer the louver kind tho....Comments?




-Mark

[doctorgonzo]

My concern would be not getting enough air to carbs 2 and 3, or rather "unequal" amounts of air. That looks like you'd have to jet 2 and 3 differently, and adjust the carb sync to not have 1 and 4 pull harder. Performancewise, probably not effective, BUT as the saying goes, it's YOUR bike, and so if aesthetics are more important than performance..

[Larry D]

You would like to do this because you like the look of pods instead of the airbox.......uhmmm....okay.......

How do like the look of jacking around with the jetting of your carbs ? To get the bike running properly you're going to have alot of trial and error....and money, to get it right. I've also read that 850's are particuliarly sensitive to pods, I have no idea why.


IMHO, the airbox was designed to work so you can spend your time riding, not pulling your hair out trying to get it run right.......but, it's your time and money.

[mcloud]

That would be way cool, not if but when you manage to pull it off.
The hard part will be to keep the air velocity even in the box.
Making it too small will cause high pressure drop, and like mentionned above, 1 and 4 will get all the air, starving 2 and 3.
Remember the GS's are sensitive on the air side.

Just a thought, how about starting from the airbox's original dimensions. Cut the dirty section (bottom half) and place your filters and covers on each end, like your model shows. This way you get to keep original boots.

[mcloud]

And subscribed, I'm curious on how your mod will turn out.
And I agree with you, the airbox arrangement is kinda ugly on the '79-'80

[mvalenti]

That would be way cool, not if but when you manage to pull it off.
The hard part will be to keep the air velocity even in the box.
Making it too small will cause high pressure drop, and like mentionned above, 1 and 4 will get all the air, starving 2 and 3.
Remember the GS's are sensitive on the air side.

Just a thought, how about starting from the airbox's original dimensions. Cut the dirty section (bottom half) and place your filters and covers on each end, like your model shows. This way you get to keep original boots.

I agree about "original dimensions" as stated in my post on keeping the volume as close as possible to the original. As for carbs 1 and 4 getting the majority of the air I thought the use of a plenum/airbox reduces that. The original airbox sucks from the sides also I believe. So, in theory, if the volume is kept the same or close, and the area of the openings in the inlet are the same or close performance should be close. In theory only of course. Everyone brings up great points and I appreciate them all! Thankyou.

-Mark

[rideOn]

Its a custome plenum, with (2) hotrod 4.5 inch dia air filters at either end. I think I would prefer the louver kind tho....Comments?
-Mark

this looks cool and i would love anything over having to screw with removing and re-installing the original aribox. but...if it ain't broke, why fix it?

i thought it would be cool (if possible) to fab a manifold to accommodate one big carb.

[mvalenti]

this looks cool and i would love anything over having to screw with removing and re-installing the original aribox. but...if it ain't broke, why fix it?

i thought it would be cool (if possible) to fab a manifold to accommodate one big carb.

The idea came to me from posts on another board, for a 4 into 1 manifold. When will the insanity stop? I hope not in the distant future..


Based on an oval style air cleaner... But you get the idea....

[Steve]

OK nice ideas, different from most that I have seen.

I don't think it's the volume of the box that you need to be concerned with, it's the restriction imposed by the size of the openings and the air filter. There needs to be some restriction, that's what will lift the slides on the CV carbs. If you open up the airbox and lower the restriction, there is less vacuum available to lift the slides, so you will have to do modifications along the lines of what the DynoJet kits do: drill a larger hole in the bottom of the slide.

Concerning the idea of a manifold and one carb, that type of manifold is already available. Look for a turbo kit manifold. Not sure how well it would work in a naturally-aspirated situation, as turbos con't care a whole lot about inequalities in a manifold, they just push the air through.

Getting back to the original question, though, it seems that you are willing to put in a LOT of time and effort and an unknown amount of money for custom-made parts, but you say you are "on a tight budget". I also find it interesting that you are willing to spend that much time and effort to change one small appearance area to your taste. Do you have plans for the rest of the bike, too, or is it staying somewhat stock? If this is merely a preview of what you have planned for the rest of the bike, please be sure to keep us informed, with LOTS of pictures.

.