KZ750N2 Spectre - Reinstall factory airbox

Hi all,

This question is one I have seen sort of addressed in other posts but I haven’t quite gotten my head all around it, yet. I have never messed with carburetors, emissions, or airflow components before and I am certain I have no clue what I don’t know but I’m determined to try and get this right.

When I bought this bike last year and it had already been modified with pods and the PO mentioned that he had the carbs rejetted. He gave me most of the original parts, including the airbox. It has a broken screw top and I’m guessing that’s likely why he opted to go to pods. What isn’t in the box of parts is the emissions system that connects to the right and left top side of the valve cover. In its place on the bike he just connected the two ports together with a single hose. 

So here’s my quandary. I’m definitely interested in restoring the airbox. I like the idea of the engine running as designed; better airflow, cleaner air mixture, theoretically optimum performance, etc… but I really don’t know exactly what I need to replace. I do know I have to pull the carbs and install stock jets and I obviously need to find a solution for the broken airbox top, but do I also need to replace the emissions components? Are there any performance issues or trade offs either way? And were I not to reinstall it, what would I need to look out for? Would I simply block off the unused ports? Are there trade offs I’m not thinking of?

Or maybe, at this point, I should uncomplicated the situation and just give the carbs a tidy clean up and stick with the pods? 

Any advice on this would be greatly appreciated and if I missed a thread that already covers this, my apologies and please just point my ignorant butt in the right direction.

Many thanks - B

As far as I've read, it doesn't really affect performance; most people take it off. I ran a hose between the ports on the valve cover and made a small plate to cover the hole in the upper part of the airbox; I think I do still have the old valve from my bike, so if you do want it for some reason it's yours. 

the Kawasaki clean air system is passive & helps to reduce smog emissions.  a valve cover without the smog provisions could be installed. you'd need one from an 80s model w the blanking flanges. KZ650CSR KZ700/750 ZX750 ZN700/750.  try to find one that uses the same gasket as the Spectre for a cleaner fit. also, the airbox orifice will need to be plugged.

eb #275150277367

www.partzilla.com/catalog/kawasaki/motor.../cylinder-head-cover

McThing post=862391 but I really don’t know exactly what I need to replace. I do know I have to pull the carbs and install stock jets and I obviously need to find a solution for the broken airbox top, but do I also need to replace the emissions components?

If you reinstall the stock airbox you would need to return the carburetors to use all of the stock jets and settings.  I recommend this change.  I did this recently (pods to airbox) on my Z1R and it runs much better than it ever did with pods.

The clean air system should have no impact at all on the jetting or carburetion.  If you don't have the air solenoid valve that feeds the ports on the head, you would need to plug the extra hole in the center front of the airbox.  But otherwise you can take or leave the clean air system.  It shouldn't change how the bike runs.

The screw top for the air box looks similar to the 650 version. Also my 750 e1 has a similar screw top, might expand your search results. I haven’t looked for interchangeability. Might be an option. 

Thank you all for your input.

I think I will forgo the air solenoid/emissions unit if it’s of no consequence.  

Just one more question to get this all straight. In the fiche, I see that there are also two smaller hoses coming off of the air solenoid unit, which I am guessing are supposed to connect to overflow ports on the carbs.

As it sits now, there are two clear open hoses connected to those carb ports that run down and back, resting over the crankcase and ending just past the breather cover. 

I can leave those “as is”, correct?
 

Also, Ghostdive, thanks for the kind offer and I love that pink Spectre! Looks like you’ve already walked down this road I’m on and I will review your threads for info.

And H1Vindicator and Mikaw, I was able to source a nasty looking airbox off of EB late last night for $11 (don’t ask about the shipping, grrr) It ain’t pretty but I only need the one part and that looked to be intact.

wrote:

Thank you all for your input.

I think I will forgo the air solenoid/emissions unit if it’s of no consequence.  

Just one more question to get this all straight. In the fiche, I see that there are also two smaller hoses coming off of the air solenoid unit, which I am guessing are supposed to connect to overflow ports on the carbs.

As it sits now, there are two clear open hoses connected to those carb ports that run down and back, resting over the crankcase and ending just past the breather cover. 

I can leave those “as is”, correct?

 

The hoses from the clean air valve connect to two carburetor vacuum ports. Those ports must be capped if the clean air system is removed. The bowl vents do vent to atmosphere.

the clear tubing could be the vents between the 1-2 & 3-4 carburetors. and unrelated to the clean air system. with pods the po should have capped a couple of vac ports on 2 of the carburetors, usually #1 & #4.  one of the other 2 vac ports would have been capped at the factory. the remaining vac port is for the petcock; capped when using a manual fuel valve. the vac ports are high up on the engine side of the carburetors.