Remove the airbox lid and snorkel?

[Jaguar]

This is for those of you wanting to get more horsepower out of your ride, what to do and what NOT to do.
First, what to do:
1) measure your engines squish clearance and lathe down the head to bring the squish velocity within the 10-15 m/s range. Register at the Torqsoft site to use their squish velocity calculator. (http://www.torqsoft.net/register.php)
2) Install an iridium spark plug (NGK BR8EIX) and gap it to .032" (.8mm)
3) remove the sound dampening layer inside the stock pipe or replace it with an aftermarket pipe.
4) make sure you have good compression (and replace the rings if you don't) and then jet your carb to perfection.
5) replace your low performance stock CDI with an adjustable performance CDI.
6) clean out the stock silencer

Remove the airbox lid and snorkel?
I hate it when people advise others to totally disregard a well thought out design that does a good job of preventing muddy water from entering into the engine and wearing everything down. Also muddy water can cause the throttle slide to stick. Before I learned this lesson my throttle stuck wide open while racing motocross after the engine inhaled muddy water because I had listened to rookies advice to take off the air box snorkel. (Worse advice is removing the airbox lid)
Only if you live where there are no streams, no puddles, and it never rains should you ever consider listening to this advice. (Sahara desert?)
Granted, the snorkel does limit the air intake a little bit but unless you are prepared to fabricate something that is as equally protective should you take it off.
Oh, and did I mention how much fun it is to have to split the cases and press apart the flywheel to replace a worn out rod bearing?

[G22inSC]

I thought the general consensus was not to gap Iridium plugs?

[Jaguar]

normal plug gap is around .7mm and I gapped my iridium at .9mm because it helped so much that way at low-mid range. Denso recommends to gap their iridium plug at .8mm. Iridium sparks at a lower voltage with a standard gap, so to make it spark at the same voltage as before (with a standard plug) it has to be gapped wider. Doing so exposes more fuel/air to the spark because it's longer. This has beneficial effects on power due to less misfires and a quicker start of flame propagation.

[adam728]

I rode plenty of mud and water with no airbox lid and never had an issue. MX bikes don't even have lids, and I spent years trail riding and racing enduros on all sorts of them. KDX, KX, YZ's. Surprised you were able to get mud in there.

[jjavaman]

I took the snorkel out and Swiss chess'd the top. Loud honk now when I gas it as well as roost!!!!

[panici33]

So lid or no lid?

I was wondering this the other day. I plan on getting some go-fast parts this summer and I would need to relocate a few things if I removed the lid.

[jjavaman]

I'm to lazy to relocate anything, that's why I drilled holes in it.

[Jaguar]

Adam, I notice your bike is the newer design (´95-up) which may allow less splashed water up to the top of the airbox than the older design (which mine was). So maybe the snorkel is not as necessary on the newer ones. But I like to be scientific about everything and so I´d like to find out from owners of the newer model is whether or not there is ever any dried muddy spots on top of the airbox when you take the seat off. If there is then you do need the lid and snorkel. And for those of you who think an oiled air filter will keep the muddy water from entering, then think again. The oil catches dry particles, whereas the water which doesn´t stick to the oil carries the dirt right on past the filter.

[bufftester]

First I will agree that there are a few things you should do for horsepower gain....aftermarket pipe and silencer, head/carb work (RB is the best IMO). For best performance the bike needs to breathe, and that means altering the lid/snorkel. I have run both E and H model bikes without the lid with no issues whatsoever (and i live and ride in the Pacific NW, home to a temperate rainforest and the wettest place in the continental US). Unless you are making a habit of crossing seat deep creeks at regular intervals you will gain performance with out sacrificing reliability removing the snorkel and/or lid. Under the most ideal conditions, an Iridium plug is going to gain you anywhere from 1-3%. I consider the cost/gain ratio to be low. And as far as rod bearing wear it is generally a result of poor lubrication. Ingestion of a small amount of water in a 2T motor will cause the bike to run like crap for a bit, but it isn't going to contribute to bearing failure unless you're riding around in submarine mode all the time and never changing oil and running the bike jetted lean.

[Jaguar]

I´ll admit that the mx track was very muddy that day
so it may just depend on what conditions you ride in and whether or not you race.
If you ever find dried muddy water spots on top of your airbox then your bike needs protection.

My preference now is to remove the snorkel, enlarge the intake hole, and then put my own design of "snorkel" in place (read the details on my site).

What really sucked about when the mud sucking happened is that I was in 1st place in the 2nd moto and I had placed 2nd in the 1st moto which means I would of placed 1st for the day. That was the only race that I got that close. I didn´t realize that I was so much better than the others at racing in the mud. It´s kinda like driving on the ice in that all your movements and acceleration and braking needs to be smooth.

[TheRadBaron]

This post has really got me thinking. My '89 Came without the airbox lid when I bought it and at first I didn't even realize that there was supposed to be one there. I haven't put many miles on the bike in wet/muddy conditions but I did go crashing into a creek one time and had the bike run like a dog for a while afterwards. I figured that the air filter got saturated so I looked into the air box lid and discovered than mine had been removed and that many people remove them to help breathing. At the time I looked around for one but there weren't any on eBay and no one here had one for sale. It sort of went into the back of my mind until I read this thread.

I agree with both sides of the debate, really. Protecting your intake from water and mud is important and something that I intend to do to my bike. However, I hate the thought of reducing the performance of the bike. I've spent a lot of time and money improving the performance of the engine and I don't want to undo any of that. The thought of clean water getting onto the filter and hurting performance for a bit is one thing, but I can't stand the thought of water-borne grit getting through the filter and grinding up my engine. I'd like to be able to blast through mud and water without worrying if I'm doing some serious damage. I read through Jaguar's airbox lid mods on his website and decided that I'd go a similar route to try to find a compromise between protection and performance. I found a used lid and snorkel so I have something to work with now.

I ran some numbers. The stock rubber snorkel has an inside diameter of roughly 20mm x 80mm for an area of 1600 sq.mm. The area of bore of the 35mm carb comes out to about 960 sq.mm, so the airbox lid intake is about 66% larger than the area of the carb. I don't know enough about the dynamics of airflow to say why this presents a restriction but it must since it's accepted that removing the lid increases airflow. I'm planning to remove the snorkel and cut the hole a lot larger. I mocked it up and the hole will be about 77mm x 90mm for an area of 6930 sq.mm. This is more than 4 times the area of the original snorkel. I'm going to build a raised lip around the hole and add a deflector inside the airbox that will deflect any water or mud away from the filter and towards the bottom of the airbox. The red lines in the picture below represents the rough dimensions that the new hole will be.

Hopefully this will give adequate protection without compromising engine performance. I'll post more pictures as I make progress.
Hey Jaguar, would you be able to post any pictures of your lid? I'm curious as to how it looks. Your description on your page is good but a picture would help a lot. Thanks.

[Jaguar]

66% larger is enough. But any inlet presents some restriction. I propose that the performance boost people are feeling is because removing the snorkel causes the mixture of fuel/air to then be a bit leaner which is what the bike needs in most cases since the jetting comes too rich from the factory. I say keep the snorkel and jet the carb to perfection.

[Bitteeinit]

I also wanted to remove my snorkel, but here's an example of fairly typical riding conditions here:
[youtube]HQ6dA_7eOKY[/youtube]
[EDIT] No clue why embedding isn't working... Here's the link:


I don't often to actual river fords/crossings, but big puddles aren't exactly rare, and it's tricky to know how deep they'll be unless I've ridden the trail before (and I tend to ride trails only once or twice, so I don't get to know them ever that well). So anyways, I've decided to keep my cover. It's unlikely water will go in, but I prefer to play it safe.

[Julien D]

I have had my 89 through some of the muddiest junk you can imagine in the mountains of Northwestern NC. Never a problem without an airbox lid. You pretty much have to submerge the entire bike for it to be a problem, at which point even the snorkel would not help. The performance increase is due to more airflow, which will indeed help if you are jetted overly rich. It will also just help in general, as unrestricted airflow is key to performance in all combustion engines.

[Jaguar]

better safe than sorry. Man, I hate having to tear down the engine. I´d rather spend that time riding.
With the stock setup, if it runs better and better by dropping the needle and you can´t get it to go lean enough then you need to get a leaner needle. (R1173N)

[Julien D]

It's not about adding more air just to lean out the mixture. It's about having the highest volume of proper air/fuel mix that the engine is capable of breathing in. Certainly a helluva lot more performance gain there than swapping in an iridium plug.

[Jaguar]

using the flow pressure calculator at http://www.gates.com/catalogs-and-resou ... calculator

35mm carburetor:
1.38" (35mm) hose diameter, flow rate 235 gallons/minute, 4" length, .00118 specific gravity of air, 1cp viscosity of air;
pressure loss .01 psi

20 x 80mm snorkel:
1.77" hose diameter, flow rate 235 gallons/minute, 4" length, .00118 specific gravity, 1cp viscosity;
pressure loss .00 psi

I had to increase the distance to 1 foot to get .01 psi across the snorkel and .02 psi across the carb. Thats shows a 1:2 ratio which means the pressure drop across the snorkel is around .005 psi.

The crankcase vacuum is a maximum of -7 psi.
So .005 is .07% that of 7.

.07% !!!

[offshoretitan]

That's impressive that you were able to calculate that - kudos to you and to gates.com. I tend to agree with you: leave the lid and snorkel in place; jet the carburetor to perfection; clean the air filter after every ride. I happen to also have the vforce 3 reed cage installed and think that helps as well. I'm more interested in woods riding than a lot of WOT, maybe I would feel differently if looking to maximize top end speed, but I think my bike runs great with the lid in place...

Lastly, it's not just the water encountered during the ride but also washing the bike afterwards. It's not hard to get water (and dirt) flying up under the seat when the bike is being washed.

[Julien D]

Interesting indeed. I know what both my bikes felt like before and after, so I'll leave the lid in the waste bin. Have never had a problem running without it. Not sure if using the right cp would matter. Try .00018 cp and 1 sg.

[Jaguar]

those figures for specific gravity and viscosity is for normal air at sea level.
Put the snorkel back on and use the leaner needle that Freddette recommends and try 1 step leaner main jet.