1982 750 Spectre

Will running this bike without the airbox cause it to die at high rpms (5400rpm)? This bike was just gone thru and everything checks out good. The carbs have been rebuilt. It idles great and cranks easy. When you rev it up it dies at around 5400rpms. The air box has not been installed yet. This is a bike that I am considering buying from a friend.

It could be as simple as a partially plugged fuel filter, if one is installed. If one isn't installed the carbs probably need a thorough cleaning and install that fuel filter. Also, if there is no filter, I have seen the tubes that run between the carbs get FULL of so much crap that I could barely get a round toothpick through them!!!!!

mitch.dail wrote:

Will running this bike without the airbox cause it to die at high rpms (5400rpm)?

I think it might. It could be running so lean at wide throttle that it stops getting enough fuel to pull hard.

Bounty has a point. Its lean plus you are sucking in all kinds of bugs into the engine. And it would be wise to get a new fuel filter and if the bike doesn't have one, get one. It decreases the amount of times you will need a carb cleanout. No offence Wg!

If it is set up for an air box and filter (meaning jetted right and adjusted) then she will certainly not run correctly without them. Thats why you do that. But how did it get adjusted without the airbox and filter? I can see the jets since you would most likely use stock jets if you intend to use the orig setup. You might have to do a little adjusting when you get the box on. But I think what you are describing has to do with the missing airbox and filter.

Thanks to everyone for all the help. Reassembled the air box and now this 1982 kz750-n runs like new.