Another pods/jets/exhaust question

[Guest]

I'm building my own 2 into 1 exhaust for my GS 450 S twin. I've got a single canister muffler from a later GSX 600. I want to change the airbox out to pods on the carbs. However, I am worried about posts I've read about jet problems when changing intake and exhaust setups. Any advice, general info or warning? Leave well enough alone? It runs fine as it is.

[posplayr]

I'm building my own 2 into 1 exhaust for my GS 450 S twin. I've got a single canister muffler from a later GSX 600. I want to change the airbox out to pods on the carbs. However, I am worried about posts I've read about jet problems when changing intake and exhaust setups. Any advice, general info or warning? Leave well enough alone? It runs fine as it is.

you will need to rejet

[GregT]

You MAY need to rejet...a young guy local to me is running a 450 with 500 pistons as a racebike. Standard 450 carbs not rejetted running open - no pods or aircleaners at all. The 450 carbs seem to be strangely insenstive.

Use 1 1/2in OD headers around 27in to the junction. Tailpipe 1 3/4in OD for a street pipe 1 7/8OD for a race pipe. tailpipe as long as possible - 24in at least.

[Krunk_Kracker]

You MAY need to rejet...a young guy local to me is running a 450 with 500 pistons as a racebike. Standard 450 carbs not rejetted running open - no pods or aircleaners at all. The 450 carbs seem to be strangely insenstive.

Use 1 1/2in OD headers around 27in to the junction. Tailpipe 1 3/4in OD for a street pipe 1 7/8OD for a race pipe. tailpipe as long as possible - 24in at least.

Racing is totally different. He's staying up in the RPM's all the time.


OP, rejet. It's always better.

[pete]

How much later is the GSX? Emissions laws may mean it's as restrictive or more restrictive than the stock GS pipes is my guess.

The advice I've had from Tranzac for the 2 to 1 they'll be making me soon along (to go with my K&N's) is probably 1 clip down (richer) on the needles and 2 sizes up on the mains, and the pilot will probably be ok. This was just best guess baseline stuff from them based on me wanting a freer flowing muffler.

I'm not sure what dimensions they'll be making the pipe to yet, I'll see when I get the bike down there, but Greg I still have those ones you gave me a while ago handy.

At the end of the day you'll need to do plug chops to see how it's going, and I expect to be doing the same myself.

One compulsory item though... you must post pic's

[GregT]

[QUOTE=Krunk_Kracker;1430940]Racing is totally different. He's staying up in the RPM's all the time.

much to my surprise it starts, idles and can be ridden round the pits quietly with no apparent flat spots or hesitation.
BTW the tracks here are quite tight and technical - so midrange is at a premium.

[thevillaindylan]

I ditched the airbox. I went up to a 127.5 on the main and 20 on the pilot on my 450T. I also used two washers to step up the needle. I'm running K&N pods and a Mac 2 into 1. I used a Gunson Colortune and a Morgan Carbtune to smooth it out. I'm pretty happy with the way it runs right now, this is the best combo i've found so far.

[TheCafeKid]

Racing is totally different. He's staying up in the RPM's all the time.


OP, rejet. It's always better.

Excellent post!
This is completely true. For good street-ability you will need to rejet. This also why heavy polish and port jobs aren't a good idea because you need some of that turbulence the "dirty" ports create to help atomize the fuel mixture. Race bikes spend the majority of their time in the upper circuits ( top of the needle, needle to main jet transition stage and main jet) thus you only need be close with the mains. They also tend to use mechanical carbs which not only come with adjustable needles but don't rely as much on a specific air flow design to actuate any slides. Mechanical carbs are also easier to tune IMO because you have more control not only over each circuit but control over air and fuel introduction within those circuits separately.

Most CV carbied bikes for the stree when fitted with pods and a pipe suffer in the mid circuits (pilot needle transition stage and needle stage) more than anywhere else. This is in large part due to the design of the stock needles. The taper is much too slow for the amount of air being introduced with free flowing filters such as pods. They are also not a tunable needle which is necessary even with a jet kit to get the transition stages smooth and to eliminate the lean staggers as the bike moves through the circuits and when it is running just off idle.

I'm not sure if a jet kit is available for your bike. Most companies didn't devote a whole lot of research into developing them for smaller cc bikes that weren't used for racers. However, given that your bike is more or less half of a GS850, or GS1000 maybe using half of one of those kits with the smaller of the optional jets that come with them will get you where need to be if no other options are available. The mains will be easy to figure out really. What you're after with these kits are the needles. Theyre designed to feed the necessary fuel to the motor in the middle stages where this set up often suffers the most.
And please, do yourself a favor and don't use those crap EMGO pods. They're worthless, and filter nothing and don't flow well. They actually make tuning the bike near impossible. APE makes some K&N knockoff filters that do the job well, and can be had for half or less of the real deal if money is tight.

[pete]

I ditched the airbox. I went up to a 127.5 on the main and 20 on the pilot on my 450T. I also used two washers to step up the needle. I'm running K&N pods and a Mac 2 into 1. I used a Gunson Colortune and a Morgan Carbtune to smooth it out. I'm pretty happy with the way it runs right now, this is the best combo i've found so far.

Good info! Thanks for sharing

Excellent post!
This is completely true. For good street-ability you will need to rejet. This also why heavy polish and port jobs aren't a good idea because you need some of that turbulence the "dirty" ports create to help atomize the fuel mixture. Race bikes spend the majority of their time in the upper circuits ( top of the needle, needle to main jet transition stage and main jet) thus you only need be close with the mains. They also tend to use mechanical carbs which not only come with adjustable needles but don't rely as much on a specific air flow design to actuate any slides. Mechanical carbs are also easier to tune IMO because you have more control not only over each circuit but control over air and fuel introduction within those circuits separately.

Most CV carbied bikes for the stree when fitted with pods and a pipe suffer in the mid circuits (pilot needle transition stage and needle stage) more than anywhere else. This is in large part due to the design of the stock needles. The taper is much too slow for the amount of air being introduced with free flowing filters such as pods. They are also not a tunable needle which is necessary even with a jet kit to get the transition stages smooth and to eliminate the lean staggers as the bike moves through the circuits and when it is running just off idle.

I'm not sure if a jet kit is available for your bike. Most companies didn't devote a whole lot of research into developing them for smaller cc bikes that weren't used for racers. However, given that your bike is more or less half of a GS850, or GS1000 maybe using half of one of those kits with the smaller of the optional jets that come with them will get you where need to be if no other options are available. The mains will be easy to figure out really. What you're after with these kits are the needles. Theyre designed to feed the necessary fuel to the motor in the middle stages where this set up often suffers the most.
And please, do yourself a favor and don't use those crap EMGO pods. They're worthless, and filter nothing and don't flow well. They actually make tuning the bike near impossible. APE makes some K&N knockoff filters that do the job well, and can be had for half or less of the real deal if money is tight.

As far as I'm aware, the 80 - 82 450's only have a stage 1 kit available from Dynojet, but not sure if this will be enough.

Rapidray thinks his adjustable needles that he sells will work for these, but he only sells a kit of four, so you'll have two spare.

I did however discover that I have adjustable needles in my 82 450E...

My plan at the moment with K&N's and the Tranzac exhaust will be to go down one notch on the needle and up two mains and see how that goes.

I can't see me getting a colour tune or anything fancy like that, so I'll be relying on plug chops to tell me how it is.