Pod filters question...Carb Jetting...etc

[havoK]

First bike project and trying to do it justice... I have a Gs 750e which was installed with emgo pods (not a fan...idling weird)...i would like to replace them for k&n's... i am pretty sure it is jetting issues... It has a definate issue with opening the throttle and bogging... Is there a settings to start with as far as jetting? Not sure if it has original jets currently...it does however have a 4-1 exhaust...not sure of manufaturer...so i am sure it was likely changed/altered...
Also, bike has a definate stutter in the throttle on the top end...jetting also, i'm guessing...
I read through the other posts etc, did not see a lot of this info related to the 750... Any help is welcome, and would be appreciated...
I have a few tools, but if i need something special, i would have to find that as well...
thanks...
havoK
ps...love this forum...looking forward to learning more from it...

 

[tom203]

Your mission is to determine what jets are in now, and go from there- don't assume anything and now would be a good time to clean carbs.

 

[Bustedknuckles]

chances are since you have emgo pods and there is popping and bogging, you are getting too much air, (needs jetted) ive been through this with 2 bikes and have used a stage one and a stage 3 and they fixed the problems, if you have a 4-1 factory exhaust (baffle intact) with Emgo pods you will need at least a stage 1 dyna-jet kit.

i know the emgo's dont filter as well as the k&n's so they let more air in. i believe many people here have gone with only K&N pod performance upgrades and the only thing that was needed was a stage 1 dynajet. if you go pods and an open exhaust you will need a stage 3

since you will need to take the carbs off to re-jet them, MAKE SURE you buy new intake boots and 0-rings, it is cheap and easy maintenance that will eliminate possible problems in the near future, and will ensure good operation. this can actually be another factor in you bogging and popping, if the boots are leaking air you will have even worse performance.

and of course, completely disassemble the carbs and clean them thourougly, and use compressed air! <very important for clearing any blockages or debris...

 

[havoK]

i really like the k&n brand, but do they hold up in the weather, they look like they are the paper/cotton filters?

 

[7981GS]

i really like the k&n brand, but do they hold up in the weather, they look like they are the paper/cotton filters?

I had a set of K & N filters on a bike for almost 30 years.
The bike has been through 3 hurricanes and plenty of snow storms.
They eventually shrink at the mounting and start to want to slide off.
I replaced them with Emgo's about 2 years ago. Works just fine.

(Note the frost on the engine and fuel tank)

I use K & N filter oil on them.

Daniel

 

[Billy Ricks]

i really like the k&n brand, but do they hold up in the weather, they look like they are the paper/cotton filters?

My set is about 23 years old and holding up fine. It's gauze between the mesh layers.

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. havoK,

Intake and exhaust combine to determine what jetting to use. Do you have a performance exhaust or stock? A Dynojet kit can take a lot of the guesswork out of the equation. Plus you'll get the slotted jet needles that make tuning the mid-range a lot easier. The Stage 3 kit is designed for modified intake and exhaust. As a general rule, you'll go up 4-6 sizes on the main jets, maybe 1-2 sizes up on pilot jet, raise the needles a slot or two. Then fine tune using plug chops and reading the color of your plugs at various throttle openings (idle, 1/4, 1/2, 3/4, wide open). Adjust jet sizes and needle position as necessary.

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Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...

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Thanks for joining us. Keep us informed. I will put you on my prayer list.

Thank you for your indulgence,

BassCliff

 

[Roybean]

A good rule of thumb is two jet sizes for each mod. Two sizes up for the pods and two sizes for the header if it is non restrictive.

You can buy the jets from Z1enterprises for a little over $2.00 each.

I go for the lowest price instead of jet kits. Jet kits are a lot better than they were when they started putting them out but if I can get the same results with 20 dollars worth of jets I am far ahead.

I would raise the needle up to the third slot.

There has been many a headache for riders trying to jet pod filters but once dialed in there is no more air box removal and install headaches.

Sometimes on bikes I work on,I may pull the carbs five times in a few hours. Roy

 

[Billy Ricks]

What year is your bike? It would help so we know what type of carbs you have. If you have CVs and a kit has never been installed you won't have adjustable needles. That's the one part in the kits that make them worth the money.

 

[havoK]

sorry, its a 1978 gs 750e...not sure if they (carbs) are stock, but are definately mikuni...can get a part # and will post soon...
Do I have to re-sync carbs if I change the needles out?

 

[Billy Ricks]

You have VMs which will have adjustable needles. Changing the needles won't mean re-syncing but they probably need syncing anyway.

 

[havoK]

was synched when i got it in the spring...ran it this summer to work and back, but its always been a little boggy on the low end and stuttery on the top...
i really like that everyone here is very helpfull...helps to keep the frustration away...thanks again!!

 

[verde]

I had a bit of a learning experience jetting the same model engine/carbs. You can read a fair amount of the details here, but that's probably a waste of time. The gist of my learning comes down to some key points, many touched on already:

-Valves(I had just redone mine so I knew they were good. I'd recommend doing a compression test at the very least. Mileage? Service records for last time the valve clearances were checked?)

-Sync(if you trust the sync from last spring that's on you, definitely check if you have to make valve adjustments)

-Clean carbs

-"Stage whatever" kits are a waste of money on these carbs if they even make 'em. Just jets and adjustments are all that's needed for riders like you or me. Maybe a rebuild kit if things are really bad though. Pull a float bowl off and pull the pilot and main jet out. You should be able to find the size engraved on them, and then you can figure out what other jets to order.

Once all that's good to go, my recommendations for a starting point:

fuel screws: 1 turn out from lightly seated
air screws: 1.5 turns out from lightly seated
Pilots: 17.5's
Mains: 125's
Needles: 4th notch down.

That's about where they were on my '78 with just foam filter element on the carb mouths and stock headers only. Just about spot on with same filter set up on my '79 and looooooooong weird straight pipes built off the factory 4-2(it definitely had better bottom end performance than the '78). You would most likely be slightly rich which is safer on the valves than slightly lean, and you can adjust from there as you develop a feel for it.

 

[MisterCinders]

You have VMs which will have adjustable needles. Changing the needles won't mean re-syncing but they probably need syncing anyway.

You have to pull the slides to remove the needles. Once you do that, you have to re-synch.

 

[TheCafeKid]

You have VMs which will have adjustable needles. Changing the needles won't mean re-syncing but they probably need syncing anyway.

Yes, they will.
To get to the needles on VM carbs, you have to pull the slide assembly out, which requires removal of the throttle control shaft they are all linked to. So every time you pull the slides your sync will be messed with to some degree.

Havok, not to sound like I jerk, but I myself have answered two or three other posts regarding jetting for pods and or a pipe for this bike to other members in the last couple days, so you didn't search very hard

But, to hash it all again, without knowing what you have in the carbs for jets, you're gonna have to break them down and find out. It would also be a good time to go ahead and strip, soak, clean and replace the internal Orings to assure that you have a good clean set to begin the "fun"of jetting your carbs for your pipe/pods set up. Take inventory of what's in them for main jets, pilot jets and needle clip position. You will want to know all of that

For your current set up, youre going to likely need mains in the 117.5-122.5 range. They're not horribly expensive, so I'd suggest buying sets of all three sizes so you don't have to wait around should one size be incorrect.
Your stock pilot jet (#15) SHOULD be fine, but sometimes people decide to use
A 17 in it instead. Your needle clip position should be moved probably down one notch (toward the point) but you may find two notches is necessary, or you may find using an extra washer to shim it between notches works best.
It's going to require some small amount of experimentation and alot of patience on your part. We can give you a ballpark setting but without seeing,hearing and riding it we really can't tell you exactly where you need to be.
The fuel screws (the ones on the bottom of the carb) should be about 1 turn out from lightly seated, the air screws (on the side) should be about 1.5 turns out. Be careful when tightening them to seated that you don't over tighten and break the small brittle tips of the screws off in the carb bodies or you'll have more problems.

Hope this helps...

 

[verde]

Keep the same orientation of the throttle shaft (as in do not let it spin 180 degrees) and it should hold the sync ok or at least be so close you'll still be withing the margin of error on a manometer. Wiggle each slide linkage as you tighten the bolts back in in ever so slightly to make sure they seat flat. Mine held the sync just fine this way(once I finally did it). I loosen the throttle shaft and only slide it out half way to do two carbs, then slide it half way out the other way and do the other two. That way there's no chance of me mixing up parts between carbs or spinning things around. And TheCafeKid's suggestion of getting sets from 1117.5-122.5 sounds much better for your set-up than my "start at 125's and figure it out from there" mentality.

 

[havoK]

thanks everyone, i think i have the info needed, the current needles do not have any engravings on them, but i can get 117s and start there...

 

[MisterCinders]

thanks everyone, i think i have the info needed, the current needles do not have any engravings on them, but i can get 117s and start there...

Not sure I understand this.

117s for mains are likely too small, so pick up some 120s and 122.5s at least to keep options open.

Your needles should have 5 notches in them with a clip/washer that can be moved to adjust their height. You want to move the clip down (richer) at least one step, probably 2, depending on where it is set now. I have the same bike, and set my needle at the 4th slot (one from the bottom).

You can fine-tune the needle setting by adding a washer on top of (or below) the clip ring to raise/lower the needle to a point between slots.

If your needle is currently at slot 2, go to 4. If 3, you might need to go to five, or 4 with a washer.

For pods and 4-1 pipe (same set up as I have), you need to check the numbers on two parts.

1. Main jet. Stock for our bikes is 100 or 102 IIRC. The number will be stamped on the top of the jet. If you cannot read it, just get new main jets. They are not expensive, and it's better to know what your dealing with.

2. Pilot jet. This is the small screw with holes along the side that goes next to you needle/main jet assembly. It has no o-ring. The stock pilot for our bike is 15. The number is stamped on the side near the top. It can be very hard to read. You should pick up a set of 17.5 pilots. Again, these are cheap. Some people need to increase the pilot for pods/pipes. I did this, but the idle circuit ended up being too rich, so I went back to 15s.

There will be more trial and error to get the jetting right for pods/pipes. I still haven't worked out all the kinks myself. Still, I hate the stock air box, and don't regret changing to pods. The bike came with a 4-1, but I like the sound of my pipe too.

Good luck.

 

[MisterCinders]

My bad, I thought you had pod filters and a 4-1. If you only have the pipe, you probably don't need to up the pilot jet, and 117.5 mains might be enough. Also, you might only need one slot down on the needle jet for pipes but no pods.

 

[havoK]

i have 4-1 pipe, and pods...so i can get 120s & 122.5s for the mains, also will get the 17 pilots...not sure what a good starting turn-out on both is...(i know to turn in soft, and bring back, but how far?)
i have the air screws (outside screws) set to 1 1/4 turns out
the needles are currently on 2, will set to 4...
the blueing on my pipe was there when i got the bike...not sure if its changed...
i still need to get the plugs out, and see what they look like as well...



On a side note...not sure if this is a bad thing...I noticed while cleaning the carbs, three of the intakes look like this...

One looks like this...is that bad? Is it missing a guide/needle slide.?..(will this affect and is it severe?)

sorry the pics are not great, but i think one of the carbs is missing a needle guide, brass ring on the bottom of the carb intake...the needle just goes down into the main jet without a guide... new to this, thought maybe the other three were repaired/fixed...not sure where to find this, if i need it...?