Thinking of changing to individual pod filters

[TheCafeKid]

I'm not trying to discourage you from doing it but I'm curious as to what is so big and unsightly about the airbox when it's covered up by the side covers?

He removed his side covers and is planning on relocating the batt and electronics to under the tail cowl.

 

[cowboyup3371]

He removed his side covers and is planning on relocating the batt and electronics to under the tail cowl.

Ahh, sorry, missed that part. Thanks.

 

[GS750]

I'm with you Ajay, mine is bone stock. I think a perfectly running GS looks really cool, but I'm all about function stock or otherwise. when they run like they are supposed to they look allot cooler to me.

As I believe that I said earlier, hope you never have to ride in the rain

I just acquired an airbox for my 77 -GS750 so I will have a set of K&N's here to get rid of in about a week or 2

 

[kb_air]

As I believe that I said earlier, hope you never have to ride in the rain

I just acquired an airbox for my 77 -GS750 so I will have a set of K&N's here to get rid of in about a week or 2

what you want for them?

 

[Guest]

I have pods on mine and have ridden in rains that have filled up my boots without any complaint from the bike. I don't think that is an issue at all.

 

[kb_air]

I have pods on mine and have ridden in rains that have filled up my boots without any complaint from the bike. I don't think that is an issue at all.

what kind of pods do you have? why would these cheap pods be any different than nothing at all? k&n's are near 200 bucks for a set of four, and there are 100 different others (that look better imo) for like.. 40 bucks for the set.

 

[Guest]

K&N's. https://picasaweb.google.com/lh/photo/JuQYiaX-xt7wpPYo6_5QzkSZDkUcVTs9uJaEULWC518?feat=directlink

 

[AJ]

what kind of pods do you have? why would these cheap pods be any different than nothing at all? k&n's are near 200 bucks for a set of four, and there are 100 different others (that look better imo) for like.. 40 bucks for the set.

Try $108 on Amazon for K&N RC-2454.

 

[TheCafeKid]

And the clock has started.....

 

[kb_air]

anyone know what stock size pilot jets are in a 1978 gs750?

 

[kb_air]

i found some for 75 bucks on ebay, right size etc. k&n's. now when haynes says engine number, are they referring to the last digits of the vin?

 

[GS750]

what you want for them?

probably wouldnt be worth the cost of postage. To post em from here (Australia) to USA would probably be more expensive than you could buy em for new over there, especially since the Au$ is stronger than the US$ at the moment.

 

[TheCafeKid]

i found some for 75 bucks on ebay, right size etc. k&n's. now when haynes says engine number, are they referring to the last digits of the vin?

They're referring to the engine number. It's stamped into the top of the cases on the flat spot to the right of your oil fill cap. The VIN (frame) and engine numbers never matched. The frames and engine will built seperately and usually one or the other sat on a shelf until it was needed and then mated to the other.
The frame number (stamped into the steering mast on the right side, behind and in between the top and bottom triple clamp) is the VIN. It is also located on a foil sticker on the front of the steering mast as well as the DOM (date of manufacture) Many times this sticker has been partially removed, torn or damaged or even painted over. Technically it is illegal in most states to remove it, however I've never had anyone from the law or BMV say anything because the VIN is stamped into the frame as well.

Your pilot jets, assuming its a bike destined originally for the US market and no one has fiddled around with them prior, will have #15 pilot jets. Your mains, assuming the above as well, will likely be 102.5. The pilot jet, as I said in your other thread, should be adequate for running pods and pipe, as there is usually enough adjustment in the fuel screw (the one on the bottom of the carb at the front of the float bowl) and air screw (the one on the side of the carb body) to get the pilot mix correct. Keep in mind the pilot circuit only is in use from idle to roughly 1/4 throttle. From there to about 3/4 or slightly more the needle jet and jet needle are the circuit in use. Above that and you're on the main jet solely. However the needle circuit is fed by the main jet, so if the main is too small, the needle circuit will not receive enough fuel.

For your set up, and assuming you've adjusted your valve clearances recently (and if you haven't, I strongly urge you to do so, and they need to be checked every 3k miles...failure to maintain the clearances will result in many issues, including hard cold starting, loss of compression, and ultimately burnt valves and serious damage to the combustion chamber, PLUS the valve clearances being in spec will have fairly dramatic bearing on the jetting needs and changes you're going to need to make...I'm not trying to be a hard ass, but these things are must do items or you're goin to find yourself very frustrated when trying to get the bike running well..)
This is what I recommend:

Main jet: 120 or 122.5. I'd suggest ordering both so you have them on hand.
Pilot jet: stock #15
Needle clip position: moved down one slot toward the point (this richens the needle circuit, you may find you have to move it down one more, or even shim it to an in between the two slots)
Fuel mix screw 1 turn (full 360 degree=1 turn) from lightly seated
Air mix screw 1.75 turn from lightly seated

Give that a try, report back and let me know what's going on.
Also, this will be very helpful for both you and anyone helping you dial it in;
Many mistakenly will come on here and say things like "it runs fine until 3500-4000 rpm and then bogs out and then takes off again," or " it won't rev over 6K" or something like that when referring to carburetion changes. RPMs in reality have little to nothing to do with what's going on. What they need to say is something like "it craps out at about half throttle" or "above 1/4 throttle it falls on its face.." as this is really more descriptive of what's actually happening.
Engine speed doesn't determine, especially on mechanical carbs like yours, what circuits in the carb are in operation. Throttle position does.
So what you should do to really help yourself understand what circuit(s) are at fault is mark your throttle with tape in 1/8 turn or 1/4 turn increments. Closed throttle being the starting point and WOT being the ending point.
If you then go for a test ride and the bike starts to stumble, buck or bog out, you can look at the position(s) in the throttle range and say, "ok she's struggling at 1/2 throttle...that means the needle circuit is what i need to look at.." and so on. That way you're not only coming back to us and are able to describe which circuit is having issues, but also you're not messing with a circuit that, at least right now, isn't the problem and in turn causing more problems than fixing anything.
Lastly, when making changes, concentrate on the following:
These carbs need to be tuned from the pilot circuit up (vs the main down like the CV type carbs on later models). Meaning, start with making sure you have a relative smooth idle, and that the bike will run on its own without trying to apply throttle to keep it running. If you use the starting points for jetting I gave you above, that should be the case.
The bike also needs to be WARM when doing your testing. When the bike isn't at operating temps, fuel condenses on the cylinder walls, and the bike will run a little lean at first. As it warms up, it will richen up. This will also clue you in on which direction you may need to make changes once you start testing and tuning the needle and main circuits. If the bike seems to respond better when it's cold than it does when it's warmed up, you're likely a little too rich somewhere on the needle or main, and if it responds better once it's HOT you're probably a little lean. Ambient temps will also play a little havoc on podded bikes. Cold air is denser, and hot air isn't. If it runs better when it cool out, you're also likely a little rich. If it seems to run sloggy and wet when it's hot out, same thing....
Finally, when making a change in your jetting, ONLY DO ONE THING AT A TIME. This way you'll know if it helped or not. If you do a couple things, and something helped or made it worse, you'll have no idea which of the things you did that it was, and you'll spend a lot of time chasing your tail.

Hope this helps....

Man I should write this up and see if frank will make it a sticky.

TCK

 

[kb_air]

They're referring to the engine number. It's stamped into the top of the cases on the flat spot to the right of your oil fill cap. The VIN (frame) and engine numbers never matched. The frames and engine will built seperately and usually one or the other sat on a shelf until it was needed and then mated to the other.
The frame number (stamped into the steering mast on the right side, behind and in between the top and bottom triple clamp) is the VIN. It is also located on a foil sticker on the front of the steering mast as well as the DOM (date of manufacture) Many times this sticker has been partially removed, torn or damaged or even painted over. Technically it is illegal in most states to remove it, however I've never had anyone from the law or BMV say anything because the VIN is stamped into the frame as well.

Your pilot jets, assuming its a bike destined originally for the US market and no one has fiddled around with them prior, will have #15 pilot jets. Your mains, assuming the above as well, will likely be 102.5. The pilot jet, as I said in your other thread, should be adequate for running pods and pipe, as there is usually enough adjustment in the fuel screw (the one on the bottom of the carb at the front of the float bowl) and air screw (the one on the side of the carb body) to get the pilot mix correct. Keep in mind the pilot circuit only is in use from idle to roughly 1/4 throttle. From there to about 3/4 or slightly more the needle jet and jet needle are the circuit in use. Above that and you're on the main jet solely. However the needle circuit is fed by the main jet, so if the main is too small, the needle circuit will not receive enough fuel.

For your set up, and assuming you've adjusted your valve clearances recently (and if you haven't, I strongly urge you to do so, and they need to be checked every 3k miles...failure to maintain the clearances will result in many issues, including hard cold starting, loss of compression, and ultimately burnt valves and serious damage to the combustion chamber, PLUS the valve clearances being in spec will have fairly dramatic bearing on the jetting needs and changes you're going to need to make...I'm not trying to be a hard ass, but these things are must do items or you're goin to find yourself very frustrated when trying to get the bike running well..)
This is what I recommend:

Main jet: 120 or 122.5. I'd suggest ordering both so you have them on hand.
Pilot jet: stock #15
Needle clip position: moved down one slot toward the point (this richens the needle circuit, you may find you have to move it down one more, or even shim it to an in between the two slots)
Fuel mix screw 1 turn (full 360 degree=1 turn) from lightly seated
Air mix screw 1.75 turn from lightly seated

Give that a try, report back and let me know what's going on.
Also, this will be very helpful for both you and anyone helping you dial it in;
Many mistakenly will come on here and say things like "it runs fine until 3500-4000 rpm and then bogs out and then takes off again," or " it won't rev over 6K" or something like that when referring to carburetion changes. RPMs in reality have little to nothing to do with what's going on. What they need to say is something like "it craps out at about half throttle" or "above 1/4 throttle it falls on its face.." as this is really more descriptive of what's actually happening.
Engine speed doesn't determine, especially on mechanical carbs like yours, what circuits in the carb are in operation. Throttle position does.
So what you should do to really help yourself understand what circuit(s) are at fault is mark your throttle with tape in 1/8 turn or 1/4 turn increments. Closed throttle being the starting point and WOT being the ending point.
If you then go for a test ride and the bike starts to stumble, buck or bog out, you can look at the position(s) in the throttle range and say, "ok she's struggling at 1/2 throttle...that means the needle circuit is what i need to look at.." and so on. That way you're not only coming back to us and are able to describe which circuit is having issues, but also you're not messing with a circuit that, at least right now, isn't the problem and in turn causing more problems than fixing anything.
Lastly, when making changes, concentrate on the following:
These carbs need to be tuned from the pilot circuit up (vs the main down like the CV type carbs on later models). Meaning, start with making sure you have a relative smooth idle, and that the bike will run on its own without trying to apply throttle to keep it running. If you use the starting points for jetting I gave you above, that should be the case.
The bike also needs to be WARM when doing your testing. When the bike isn't at operating temps, fuel condenses on the cylinder walls, and the bike will run a little lean at first. As it warms up, it will richen up. This will also clue you in on which direction you may need to make changes once you start testing and tuning the needle and main circuits. If the bike seems to respond better when it's cold than it does when it's warmed up, you're likely a little too rich somewhere on the needle or main, and if it responds better once it's HOT you're probably a little lean. Ambient temps will also play a little havoc on podded bikes. Cold air is denser, and hot air isn't. If it runs better when it cool out, you're also likely a little rich. If it seems to run sloggy and wet when it's hot out, same thing....
Finally, when making a change in your jetting, ONLY DO ONE THING AT A TIME. This way you'll know if it helped or not. If you do a couple things, and something helped or made it worse, you'll have no idea which of the things you did that it was, and you'll spend a lot of time chasing your tail.

Hope this helps....

Man I should write this up and see if frank will make it a sticky.

TCK

wow, a lot of good information here. thanks.