I spoke with a local service technician at a dealership in my area regarding used quads. I'm in the market for a couple of sport quads and wanted to ask someone who works on them, what typical repairs I can expect on the year/models I am interested in and what he recommends when considering a used quad. One thing he said is sticking with me and I need more than one opinion.

He told me to avoid any quad with a K and N air filter, because they kill top ends. He said they do not do a good job of trapping tiny dirt and dust particles. I live in Phoenix Arizona and there is a lot of dust around here and I, as do many others, go to the dunes from here. He must see a lot of them to say that.

I am a trail rider and have absolutely no interest in racing, but I absolutely know that many people want to make their trail rider, or dune quad into a racer and have to wonder if all the modifications people are doing is really best for the bike for what they are doing? Obviously, with proper maintenance, this may not be an issue at all, but then again, I see a lot of people take a generally low maintenance sport quad designed for trail riding, and try to add racing modifications to it and may not do any more maintenance than before.

Racers rebuild their top end frequently, so they may not care if the air filter lets a little more dust through because they want the performance. I know K and N claims their filters are 99% effective compared to stock with increased flow, but I can't imagine the technician would throw K and N under the bus for nor reason. He must see a lot of that sort of thing come into the shop.

What are your thoughts on buying a used sport quad in the dusty Arizona desert using a K and N filter?

 

I have heard the same thing in the past and I was given a bit different approach. I will share with you the way it was explained to me.

-Have you ever seen a rainbow vacuum cleaner?
-Yes?
-Have you ever used one?
-No, but I saw one in use one day. I noticed when my buddy took the lid off all the dirt seemed to be sitting on top of the water reservoir designed to catch the water.
-Exactly, a rainbow vacuum works perfect until the water is covered with a small layer of dirt, then dirt is reflected off the water and allowed to pass back out of the system.

If you take that and relate to the K&N filter the same principal applies. The oil in the filter is designed to trap the debris in the air before it passes into the engine. This works great until the entire filter is covered with a small layer of debris (dust). Once this happens, debris is allowed to pass through the intake, top end and expelled out the exhaust. I would imagine that with "proper" maintenance a K&N filter would be fine however, as you mentioned in your post, most people do not perform proper maintenance. If you have the extra money to clean your filter evertime you ride then it will probably be fine, if you ride often, this will get old fast.

Just my $0.02

 

I wonder why the service guy said top end rebuild? Wouldn't that be the valves? Wouldn't the rings score the cylinder if dirt got past the air filter? Why would you only need a top end rebuild if this was the case? Even if you had a K and N filter that wasn't cleaned after each ride, wouldn't oil changes help protect the cylinder?

 

The service tech probably got a few engines like I got a hold of that had K&N filters that weren't maintained well.I rebuilt two 500 four stroke engines(usually bullet proof) and several two strokes that just allowed too much dirt in and galled the pistons and cylinder walls up. If you ask around you'll probably find most techs don't like K&N filters on machines that are subject to a lot of dirt! Street use is where they do shine! A lot of people love em,but they usually use a prefilter sock and service the filters on a reasonable basis. Just my old on this is that the factory equipped filters or a foam filter such as UNI traps more dirt without the worry of dirt damaging the engine as much.But any filter needs to be checked regularly if operated in dirty,sandy areas. OPT

 

I think I am going to look for stock bikes with really good tires and maybe a set of paddles thrown in. Its tempting to get one thats already been modified with some cool extras', but you just dont know what they were doing to it, or if they maintained it the way they should have after putting all that performance stuff on it.

 

K&N does not do as good of a job filtering fine silt/dust particles as foam, period. However, they are actually much better in sand than foam as they can filter the larger sand grains fine while foam tends to clog up very easily. If the machine you are buying is 100% duner, K&N would be preferred. If it EVER sees dusty conditions then foam is better. Foam also performs better in mud with a decent filter oil choice.

I also think foam is a little more forgiving in regards to poor maintenance. I have seen several top ends ruined from a poorly maintained K&N. While valves can get damaged, it is usually the cylinder walls that get scored/rings destroyed first.

 

I run a K&N w/Outwear on my YFZ 450 and have had no problems with top ends to this point. My motor was built 3 years ago and I just did a compression the other day and its damn near as tight as it was the day it was built. The key to a K&N is to wash it and re-oil after every ride nothing less. I ride in the Las Vegas desert during the winter months and it gets dusty here...in the summer months I ride in Utah and it can get a little dusty there also.. but really all I can say is MAINTENANCE when you use a K&N...Otherwise buy a Unifilter if your lazy.... :0)

 

what does a K and N air filter do? filters the air but allows more air to pass. The only way more air can pass it is to have less restriction (air filter) so if air is getting by quicker and easier then the filter is not stopping it allowing the dirt to flow by as well. Wrapping it with a pre filter over the k&n defeats the purpose. You may as well keep the stock air filter. using the pre filter just added more air restriction which reduces the air flow and stops more dirt. All you do here is spend $50 on a filter that does the exact same thing as your stock filter. Also, its not worth having an aftermarket air filter if your not going to change the whole intake and exhaust systems. People swear by them,but then they rebuild there stuff a few years later. wonder why?!!

 

I have ridden nearly 9000 miles in the last 3 years and when I still have great compression in my motor can't be all that bad. ;-)

 

ill admit, i have not heard that very often. im glad you have gotten great results. I see in your post above mine that Maintenance is kept on your atv. you are a prime example if you take care of it,it will last. Most people will check the air filter once every 2 years if they ever look at all.