I have recently purchased a 92 LT250r, fresh motor,new pipe/silencer,clutch,tires/rims,
plastic,etc. The frame has been gusseted and painted as well. My question is about the airbox. The previous owner was running a uni foam filter.
The problem is the filter doesn't appear to be sealing 100%. I have tried many times to fit the filter correctly thinking the last guy installed it wrong,but it still seems unfiltered air can make its way into the motor.
Would a K&N filter solve this, or is the airbox a poor design from suzuki?
I am really happy with this machine and would not trade it for anything. Any comments,
tips, or problem areas to look for are greatly appricated. ZOOKMAN.

 

zookman, personally i think the airbox design on them is bad. the problems i have seen with them are a lot of them have holes burned into them by the exhaust, but the biggest pain in my opinion is that it's very difficult to get the filter in and out of. I'm work at a fab shop and can weld pretty good, so i built a custom aluminum. For two reasons, one to be easily to get the filter in/out,two give my bike that trick look, and three i made it so i could take it out while the motor was in the bike si=o that i could clean it. To answer your other question a K&N filter comes with a foam seal that you sticks inside your airbox to seal it off good. A prefilter would also help block the bad stuff going through the filter.

 

I don't think that there is a problem with the design of the airbox, but it is a little hard to get the air filter in. I use K&N on both of mine and the foal seal does a good job of sealing. I can't say anything about the uni because I have never used one, but maybe it is the design of the uni filter that is the problem. Get a K&N with the prefilter and keep it clean.

 

the problem encountered in the 91-92 LTR's when putting a K&N directly on the carb is the fact that the rear shock is so close to the carb. for those that aren't familiar with this year, the carb boot routes around the shock due to different suspension design and airbox relocation done in '91.
i have kept the stock airbox on mine partly because of this fact, my opinion of the 91-92 is that the stock airbox is the best configuration.

i have wondered if another RAD valve from a different year RM would allow the use of a slip-on K&N more easily, some of them turn to one side or the other tou route around the shock... but i haven't gone in dept to find out which ones will do what is needed to clear everything in the area so that a hole isn't rubbed into the filter or pushed off of the carb to allow unfiltered air in.

 

I use an UNI on my 89' but I put a liberal amount of grease, (preferably wheel bearing grease as it doesn't liquefy in high heat as easily during the summer) around the flat part of the prefilter lip where it contacts the airbox. Screw it tight and if you want to take the time, remove the boot once and inspect the filter seal from the other side to look for obvious leaks. It probably wouldn't hurt to put a bead of silicone caulk between the airbox and the boot too, I did. I also use Torco foam filter oil on my foam air filters. Its incredibly sticky. Every time I clean my filters the outside is dirty but the inside is immaculate.