TOPIC:

Irish-Kawi wrote: Seems to be easy to just agree to disagree and let it be

Brett

Sounds like a plan.

I cut the cap.



Before/after



I took it for a 25 mi. spin and it worked great. I got the snappiness it had before I put the 4-1 on and seems to want to just get there! I think I need to make some pilot screw adjustments but i think we're golden otherwise. I'm definitely not doing anything else until I get my big old Muzzy mounted.

I found the first spot for the UNI vent when the time comes. it just needs to be opened slightly to fit.

Nice glad to hear it is working for you, definitely curious to hear what if any changes when you put in the extra UNI's

Brett

I hope we didn't chase you away tri650.

tri650 wrote: I have a 82 Gpz 750 with stock set-up for jetting and stock airbox. It has an aftermarket 4-1 header that flows into a Supertrapp exhaust. I know I can get more out of this motor with some jetting tweeks but don't want to go the pod route. I love the looks of the pods but worried about getting the jetting right. Wondering if drilling into the airbox will provide the needed extra air if I go bigger on jets and possibly raise the needle. Anyone done this?

Going back to the original post from tri650, I did want to offer one thought.....

Now before I get bashed over the head or start a flame war or something I know that our bikes are two totally different animals. End of the day though the engines are similar and the same principles are still valid. Much like you tri650, I love the look of pods as well but will not put them on my bike for a number of reasons and I use the stock airbox too. As others have said in this post before Ma' Kawi tunes these bikes very lean right from the factory and the same is true with my GPz750, would reasonably assume the same is true for you 650. On my bike I have been dealing with air and fuel challenges lately too, I swapped in a stock replacement K&N filter inside of the airbox and just doing that leaned out my pilot circuit enough that it stumbles and hesitates under 3800rpms. Nothing else was changed just the filter and nothing more. That means that I am getting significantly more (much more IMHO) air into the engine which is causing the lean out condition. What this tells me and the point I am trying to make is that I seriously doubt and would be hard pressed to be convinced that in this situation especially with your smaller displacement 650 that the stock airbox will be a limiting factor in flow or performance for you. No harm in richening the jetting if you need it, but I just can't imagine in any way that the airbox needs modifying to accommodate the extra fuel. As I said in my case with a larger engine and much higher lift and duration cams etc for the GPz the airbox is not limiting me in any way and I in fact need to add more fuel to my AFR and not more air...

Can certainly modify the airbox if you wish but I don't see it as a necessity but rather a want based on all the available data and facts.

Hope this helps but you and anyone else are certainly welcome to disagree with me.

Thanks,
Brett

GPzMOD750 wrote:

Irish-Kawi wrote: Seems to be easy to just agree to disagree and let it be

Brett

Sounds like a plan.

I cut the cap.

Before/after

I took it for a 25 mi. spin and it worked great. I got the snappiness it had before I put the 4-1 on and seems to want to just get there! I think I need to make some pilot screw adjustments but i think we're golden otherwise. I'm definitely not doing anything else until I get my big old Muzzy mounted.

I found the first spot for the UNI vent when the time comes. it just needs to be opened slightly to fit.

Btw in case you hadn't considered it there are a few more things to consider when you're cutting up the test airbox and making changes to it

Most of us gear heads look at getting more... More air, more fuel, more power etc. What is often times forgotten is that more is not always better. In the case of the airbox the goal is more power via more air by "de-restricting" the factory airbox. What isn't considered here are the characteristics the that "more air", meaning that the quantity of air going in is not necessarily the most important thing about it. We haven't considered or talked about the turbulence of the air, density, temperature, laminar or non-laminar flow patterns as well as velocity of the air as well. In the case of cutting off the tube from the cap. It may or may not flow more volume of air but at what cost. If the airflow is no longer laminar (smooth, think lazy river vs rapids where Rapids are equivalent to non-laminar fluid flow) then that creates additional turbulence which affects atomization of the fuel as it passes through the carbs as well as the efficiency of filling the cylinders and therefor burn rate and power. We also don't know if it affected th velocity i.e. Speed of the air as its delivered to the carbs and intake. The effect is similar to the turbulence affects above. Honestly in our cases this likely has little bearing or impact since we aren't dyno testing or looking at the flow rates or thermodynamic efficiency of the engine, but that doesn't mean it should be ignored or dismissed either

Happy motoring

Brett

Hmmm....Not saying impossible but I wouldn't believe too much of any of these until I saw A and B testing at various RPMs, with and without partial throttle settings and all tested on a real Dyno.
Seat of the pants is mostly BS and so easy to be fooled.
These original engineers were pretty damn hard core about max power with what they had... although I do concede, noise is part of the performance package and sometimes compromises are made.

missionkz wrote: Hmmm....Not saying impossible but I wouldn't believe too much of any of these until I saw A and B testing at various RPMs, with and without partial throttle settings and all tested on a real Dyno.
Seat of the pants is mostly BS and so easy to be fooled.
These original engineers were pretty damn hard core about max power with what they had... although I do concede, noise is part of the performance package and sometimes compromises are made.

You hit the nail completely on the head here, we are really just taking stabs at this and guessing trying to make changes and interpret how you and I "feel" they respond. No two bikes are the same and something that works on one brilliantly may be a terrible change on another. Ma' Kawi as you said spent a lot of time and a lot of money to get the final package that we see here in stock trim, I struggle to believe that I am going to outwit that level of thought and money and time. Yes noise management is part of the equation but I would argue that it is No.2 priority behind performance. Ma' Kawi engineers certainly took those variables I spoke to in prior posts into consideration when designing these things, just struggle to see how I will improve on it dramatically in any way.

Brett

+1 The airboxes were not just slapped together without considering performance and noise. Here's some info that some may not have seen; a link to a Cycle World comprehensive pod test back in the day and an article quoting a Mikuni engineer who helped design airboxes. Both are related to stock street engines and airboxes vs. pods. Ed

kzrider.com/forum/3-carburetor/585949-po...-a-free-lunch#585949

650ed wrote: +1 The airboxes were not just slapped together without considering performance and noise. Here's some info that some may not have seen; a link to a Cycle World comprehensive pod test back in the day and an article quoting a Mikuni engineer who helped design airboxes. Both are related to stock street engines and airboxes vs. pods. Ed

kzrider.com/forum/3-carburetor/585949-po...-a-free-lunch#585949

Attachment poddoc-2-3-4.jpg not found

Yeah! That's a killer article...
Spoken from one who does have headers and pods on his KZ1000.... LOL.
But it took lots of $$, many many MANY hours of messing with ignition, pilot jet, needle, mains and idle mixture settings to get it dialed in pretty good.... But even so.. the best Qtr mile time I ever got with this thing at about 700ft MSL, (years ago) was only an 11.67 ET.
But it felt ass pouching fast and loud as hell with the baffle opened up...

650ed wrote: +1 The airboxes were not just slapped together without considering performance and noise. Here's some info that some may not have seen; a link to a Cycle World comprehensive pod test back in the day and an article quoting a Mikuni engineer who helped design airboxes. Both are related to stock street engines and airboxes vs. pods. Ed

kzrider.com/forum/3-carburetor/585949-po...-a-free-lunch#585949

Brilliant read and article Ed, and exactly what I was stumbling and bubbling through while trying to get across haha. Air is not looked at or seen as a gas in terms of engineering these bikes and how to tune and get performance out of them, it is treated as a liquid because in these conditions it behaves as a liquid. That means that there are man many many variables to consider as was touched on in that article. Unless someone has a fluid dynamics degree and engineering experience we just aren't going to outsmart these guys

Brett

You're not taking into account the trade offs. EPA Regs, noise Regs, and such. Once those things are changed, the intake has to be modified as well. What works well on a lean bone stock bike, won't work on one that has HP mods. I ordered those filters and I'm sure they will help.
Steve

GPzMOD750 wrote:

Irish-Kawi wrote: Seems to be easy to just agree to disagree and let it be

Brett

Sounds like a plan.

I cut the cap.

Before/after

I took it for a 25 mi. spin and it worked great. I got the snappiness it had before I put the 4-1 on and seems to want to just get there! I think I need to make some pilot screw adjustments but i think we're golden otherwise. I'm definitely not doing anything else until I get my big old Muzzy mounted.

I found the first spot for the UNI vent when the time comes. it just needs to be opened slightly to fit.

And another one could replace the bottom vent tube.


.