Hey, new guy here with an 86 4-Zinger. Some questions.

[screamingdemon]

I'm new to this site but have been a member on eveything2stroke.com for quite some time. My wife and I bought our son a Yamaha 4-Zinger and are planning on fixing it up for him. I figured since before the 4-Zinger came about there was the 3 wheel version. Which I'm sure many of y'all are well versed in. I have a few questions regarding it and the limited amount of info I've found pertaining to my questions.

Ok so, I was looking to put a clamp on K&N air filter on the back side of the carb to delete the airbox. As of right now the oil injection system is still on it. I have a large supply of Klotz premix I bought for my TRX250R and after having bad lucky with oil injection on my Blaster I'm planning on removing it from the 4-Zinger. Now I've read some people saying that with just an airbox delete I wouldn't need to rejet it. Anyone done this and can hold this to be true?

[350for350]

I'm not at all familiar with your machine, but usually you do have to rejet when you delete the airbox. The factory setup is fairly restrictive (just follow the path the air has to take to get to the carb). You get a lot more air flow when it's straight to the filter so it will run lean without rejetting.

[Racer-X]

Why delete the air box? You're not gonna free up very much power on it versus what happens when it gets wet. If your boy has another machine to ride that's one thing but if not then that little zinger will only be a fair weather machine.. I have an open air filter with a pre filter bag on my 250r and water is kryptonite to it. Even going through a small puddle will suck in enough water to stall it out and or make it run like crap for a few minutes. A few times it was a major problem out in the woods. So I only bring it out on nice dry days and i have to stay away from water and if I do have to get near water, I go very slow and try not to hit the throttle and suck up any water. My advise is remove the restrictor plates on the header, the screw on the throttle if its still there, and maybe remove the baffle from the muffler and call it a day. Going open air filter is only for racing where you're not going to encounter water.