jetting on 81 gs850g

[jaybo1]

Can you use pod filters on constant velocity carbs thats on my 81 GS850G. and if so what should i do with the breather hose that hooked into the factory airbox? And also what changes do i need to make as far as jetting goes?

[koolaid_kid]

You can use pods on CV carbs. I put a small filter on my breather hose on my GPz when I went to pods. Not sure on the jetting on an GS850.
Please note, pods and a header normally go together. It doesn't do that much good to allow more air to enter if you don't also allow more air to leave.
And may I ask what your goal is? Rejetting CV carbs for intake/exhaust mods is a tricky, time-consuming task. And the benefits, if you are looking for added horsepower, might not be that much.

[bwringer]

I'll add that removing the airbox on an 850 is ridiculously easy, so that's not a reason to switch to pods. Unless you're also installing an aftermarket header and pipe, there is NO reason to switch to pods and MANY reasons to stick with the stock airbox.

If you're not happy with the bike's power or the way it runs, get it running right before making changes -- seal the airbox, check the valves, and do all the other stuff on the big 850 list Basscliff has stashed somewhere. Don't skip anything.

A stock 850 that's running right is surprisingly fast and, with a few suspension upgrades, is an absolute pleasure to ride quickly. Many 850s are not running right, although I think we've made a little progress in the last few years.

[jaybo1]

its already got a header and aftermarket pipe, my main reason for wanting to go with pods is because i don't have an air box to put on it at all and i can get all 4 pods for 30 bucks. plus jets aren't that much either. so instead of buyin a new box and filter with new boots from the dealer or buying a used one off of ebay that may not be any good i'd rather go with the pods and re jet. i hope i don't sound rude just think its better to go with the pods in my case. i'm not trying to get more power at all. I just got this bike and trying to get it on the road.

[blowerbike]

hack hack cough hack is what you will have unless you install a st.3 jet kit and decent filters.
the emgo's are crap at best and cause tuning problems.
do it right or find a stock air box.

[mvalenti]

Stock Airbox

Just curious, what is it about the stock airbox that makes it work so good? Does anyone here actually know? I'm not being sarcastic, is it plenum volume, flow restriction, shape, or all of the above? Upon first inspection of my stock 850 airbox, it appears to be a large plenuum with restricted openings of a particular size on either end. Of course, most of this plenum is taken up by a rectangular air filtration system. I agree with the other poster with air in should equal air out in most cases (except blowers and turbos), and jetting accordingly. I'm probably missing something but I just dont see anything magical about the shape.

When I am at the point in my gs build I plan on running some experiments with regard to intake configurations. I'll post anything I can. Good luck and let me know what ends up working for you.


-Mark

[koolaid_kid]

OP, if you had given us all the info in the first post, you would have received more helpful information. We're not trying to be difficult, but we had insufficient information to answer the question accurately.
The real question should have been stated thus:
I have pods and a header/pipe on my 850. What jetting should I start with to get it in the ballpark? (Each bike will be different, so it will be up to you to fine tune it.)
Also, IMHO the Emgo pods you are looking at are junk. If you want pods, the only way to go are K&Ns. They are a lot more expensive, and there is a reason.

mvalenti, that is a valid question. The air intake and exhaust, coupled with the jetting and cams, are a tuned system. Suzuki spent a lot of engineering time and $$ to get it to play well together. When you change something, you upset the balance that Zuk so dilligently put together. After that, you are on your own.

[mvalenti]

suck suck suck.

[QUOTE=Suzuki spent a lot of engineering time and $$ to get it to play well together. When you change something, you upset the balance that Zuk so dilligently put together. After that, you are on your own.[/QUOTE]

Yes I get that.. I'm thinking it has to do with restriction, again I could be all wrong and probably are.

As for the K&N's better filters usually tout less restriction (better flow) and larger filter area and tighter filter mesh. They also probably have a more consistant product off the assembly line, less variance from filter to filter.

Does anyone know what the cfm is of the gs 850's? Would it be split equally to all 4 carbs?

Sorry to hijack the thread, but I think its a good one, especially for new owners of these older bikes.

-Mark

[koolaid_kid]

Stock air box - specially designed to allow the proper air flow, especially when cold. For example, on my GS1100E, the PO had removed the lid (to let in more air? IDK). It was difficult to start when cold, and took a long time to warm up. Even when warm, starting was questionable, requiring various amounts of choke. I covered the top with duct tape to emulate the lid being present and VOILA it started easier and warmed up a lot quicker. I built my own lid out of a sheet of ABS plastic, btw, so it looks quite nice now.
If you let too much air in, the jetting in the carbs are no longer correct (too lean) so it will not run correctly unless you rejet (a PITA on these carbs, but it can be done).
AFA the K&Ns, they use a surgical gauze for the filter material ($$) and they are oiled, which catches more particles. And you can wash them and re-oil them (carefully) and they are good as new. The EMGOs have none of these features.
AFA cfm, do you mean of the engine itself? That can be calculated, since you know the displacement and the RPM.

[mvalenti]

My question is towards the carbs, not the engine. I'm not sure I follow your reply "especially when cold". Can you elaborate? I'm guessing it warmed up quicker due to the fact it idled better with the duct tape, where would we be without this..

[koolaid_kid]

When it is cold, the choke circuit is in play, further complicating the AFR (Air Fuel Ratio).
By warm up, I meant until I was able to turn the choke off. Poor wording, but I'm time-slicing with trying to finish up the build of my GPz engine today since I am off work.
AFA the cfm of the Mikuni 34 carbs, they are identical so all you would need to know is one, then multiply it by 4 to get the total carburetor CFM. And I have never seen any specs on it myself.

[jaybo1]

koolaid kid,

just curious what about the Emgo pods makes them junk? do they not serve the purpose or to restrictive? I havn't bought into the K&N filters yet and probably never will. yes they are supposed to be a lifetime filter but i just can't see spending the 100 and something bucks for them sorry. i'm sure they are the best, but for me, i can't spend that much. these bikes have ran for years with ordinary filters. just wondering whats wrong with the Emgos?

[tkent02]

koolaid kid,

just curious what about the Emgo pods makes them junk? do they not serve the purpose or to restrictive? I havn't bought into the K&N filters yet and probably never will. yes they are supposed to be a lifetime filter but i just can't see spending the 100 and something bucks for them sorry. i'm sure they are the best, but for me, i can't spend that much. these bikes have ran for years with ordinary filters. just wondering whats wrong with the Emgos?

Emgos flow less, and and very inconsistent, making them hard to tune. They don't filter much either, it's just a folded screen which looks like a filter. And the intake sounds like crap. I have a set I will use for a quick test ride, or to loan out for a while, but it is obvious they don't work as well so I wouldn't use them permanently.
The K&Ns have a velocity stack shape inside, it seems to make them flow more consistently, and it is a true filter, not just a screen.
APE has some as good as K&N, well under $100, something like $40 - $60 for the set, can't remember for sure.

[jaybo1]

ok, thanks i will check into the APE ones

[mvalenti]

Any feedback on the replacable foam ones that jc whitney sells? about 50 bones for all four.