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Losing Your Lid

This is an all or nothing mod, you either do the full mod, cut the air box lid down like I describe below, use a K&N filter, and rejet the carb, or you don't do anything else to the airbox.

If you take the snorkel off the airbox you will create a lot of turbulence in the air box, so DON'T DO IT!!

Roger at
Revolution Racing has been a real stand up guy in helping me with the various mods to this bike. I imagine that he has forgotten more about VTRs than I can ever hope to learn. I have been told that if I remove the top of the air box, to make the retaining ring (what is left of the air box lid) as short as possible. I found that cutting it at about 6 mm is as thin as you can go while keeping rigidity in the retaining ring.


If you were to use the stock paper filter it would not last, as it is now exposed to the elements, and if it gets wet it would disintegrate.

With this mod you will hear an increased intake noise, I personally like this, 
when you open the gas, you get a huge intake HOWL!! 
Sounds cool to me, but if you don't like that kind of sound, don't do the mod.

Roger informs me that is mod is usually done in conjunction with his "Stage One" engine modification, which includes Moriwaki Stage one cam shafts, Moriwaki intake funnels, ported and gas flowed cylinder heads, Dynojet kit, a K&N filter and Moriwaki Stage one race exhaust.. 

I'm doing this mod with a stock engine, K&N filter, Dynojet Stage one kit, the full titanium Moriwaki "Zero" street exhaust and that is about it. I will rejet the carbs, and I have been told that a 188/185 main jet combo (larger jet on the front carb which runs cooler) and with the clip on the 4th notch from the top of the Dynojet needles. I may have to use the washer "Shims" if I find a bit of a flat spot in the mid-range. 

If you want to set you bike up the best, you really need to spend the cash on some Dyno time.


Air Box with the snorkel and inside wing removed

Everything above that ridge near my thumb
 has got to go

The piece of wood should be flat and be just larger
 than the air box itself

you can see the wood is just a bit bigger
 than the air box lid.

Here it is screwed to the wooden base.

Getting set-up to run it through the saw. The blade guard has to be removed to do this, so be very careful.

A view from the back of the table saw looking at the back of the blade

OK now it is cut on three sides

I left this last bit, as I did not want to have the cut off piece falling into the blade

I cut the last bit by hand, and then ran it through the saw to clean it up.

OK there it is, it was an air box lid, now it becomes an air cleaner retaining ring.

Here it is after I sanded and carved the edges, a smooth edge is better than a sharp one.

6 mm thick, just like Roger said it should be!!


I installed the different jetting and had a go, it is VERY LOUD with the intake sucking howl, I like it!!
I need to get some more time to jet it further, it needs more gas, I think.... It was running a bit lean with the stock air box, and the stock air cleaner, with two #180  main jets. going the full lid slice and the K&N filter has to move a lot more air, so, I may have to got up above the 188/185 set-up I have now. Maybe 190/188, plus I need the shims under the needle clips, or even one notch richer on the clips.

Yes Dyno Time....

Some looks at what the retainer ring looks like installed on the airbox holding
 the K&N filter in place.

I was so used to putting the little clips on the screws that hold the thin rubber sheet beside the air box that I installed them when I took this picture. I removed them after, as I think they would only produce turbulence in the air flow going over the edge of the retaining ring.

I found the 188/185 main set-up maybe a bit too lean, and the needles were too lean as well.
 I will try some shims under the needle clips, or to the 5th notch
 I may also go one size bigger on the jets. 190/188.

I need some dyno time to sort this, but I want to get as close as possible
with the seat of the pants Dyno!

Update #2

March 21st 2003

I changed to the 190/188 main jets with the shims under the needle clips (clips in the 4th notch from the top). The bike ran better, but it still is kind of rough. Next to try is oiling the K&N filter, lightly. If that still does not work then I will go to the 192/190 main set-up, and if need be the 5th clip position. I'm using the stock intake funnels on the carbs, this is most likely the biggest problem I'm having. I would love to put the Moriwaki intake funnels on there, this could cure some of the problems I'm having, but at 22,000 yen a set, I will wait until I see a set on auction. I may have to up the size of the slow jets as well to get a bit smoother off idle transition.


I have some more fiddling to do, and I really need to get down to a Dyno and do some runs.


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