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Spark arrestor....yes or no?

11890 Views 23 Replies 8 Participants Last post by  CFM
When I went to the races sunday, I met a guy that had just bought a z-400 the day before...he wasn't racing it...not broken in yet. But he also has the DRZ-400S. The same engine that's in a Z. He said that he took the end-cap of the DRZ and removed the spark arrestor. He told me that it opened it up a bit and makes it sound like a Yz426. He put the end-cap from the DRZ on his Z-400 and it really does make a difference in the sound. He let me use it in one of the races, but I didn't notice any difference in power. I was wondering if any of you have thoughts or ideas on this.
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at most tracks i go to its illegal at the counter not to have a spark arrester. if you want just get a sheet of screen door screen stuff. make sure it is plastic and hose clame it over the hole. after 15 minutes it should melt through and you wont have any. if you want to stay legal, get the metal crap, and that should do it.

I appreciate the advice...but what I want to know is should it make a difference in the performance. He was telling me that the more airflow you get the better. but I would have to modify the airbox to accomadate taking the spark arrestor out wouldn't I? Otherwise I don't really see it doing any good.
read my reply in the other topic. I didnt modify the airbox at all yet, not until i get a full pipe on. It runs fine, sounds better! and i didnt have to rejet. I didnt feel any bog in it yet, and as i said in my other post, it felt a little better in the throttle response on the low, but it could just be my imagination. :?: :?: :?: Nonetheless, it does sound better than the wimpy sound from the stocker unmodded
: and only about an hour of your time. The 1 3/8 holesaw fits perfectly tho....then u can just cut the end of the arrestor off if u wanna save a little time, but i think it looks better if u go the whole 9 yards!
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If you're fully stock and you only open up your exhaust, you'll take a hit at the top end (as I experienced @ the dunes).

The throttle seemed to respond a bit better and engine stalled at a lower RPM.

If you take the noise baffle off of your snorkel, you'll definitely need to re-jet.

----- copied from ------
Here's a list of what I've done (besides adding armor) all prices don't include tax or shipping & handling and are in US funds

(Free) cut out pea-shooter from stock exhaust pipe
(Free) remove snorkle cap and cut holes in top of airbox
($5) 140 Main Jet (has not been trail tested, may need 145 or 150)
($0.20) two No.4 washers to raise needle height (has not been trail test, may need to use only 1 washer or 3, it definitely needs a washer)
($5.00) speaker fabric to act like an "outwear"
($22) Uni filter
($208) 22Hx12Wx10wheel Realtors on Douglas Red Labels 0.190
($14) 13 tooth front sprocket
($0.78) 7/8 inch clip to hold on new sprocket
Total ~$255

The re-jet, exhaust hack, Uni filter and air-box hack (Total:~$32) have definitely helped the Z's low end. It seems to stall at a much much lower RPM. It hits the rev limiter a bit faster now (according to my butt-dyno)

You can spend $70 for the alba K&N and outwears + $60 for a dyno jet kit or you can do what I did for 1/4 of the price.

If you have any specific questions, feel free to PM me or reply here. I always check threads I've posted in.
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Guys, I am new to this so what in the world is "rejetting"? I did take of the baffle which makes my Z sound meaner. Do I need to rejet? And if so, how in the heck do I go about doing that? :? Please Help..
I know how you feel. Back when I had my first quad, I had no idea what people were talking about when they said "rejet" Basically, when you do something to make the engine "breathe" better, like opening up the airbox or putting on a less restrictive pipe, you have to change the amount of gasoline entering the carb in order to maintain the proper air-fuel ratio. You do this by changing to a "bigger jet" with a larger opening in it. The bigger jet allows more fuel into the carb. Here's a link that someone else had posted (I think it was Resq) that may help you...

Still clueless, do not understand. I am totally "out in the blue" to these kind of engines. ????????? :? Everytime I am on my Z, it revs out on every gear when drag racing. Is it suppose to do that? Maybe it is just me. :oops: What can I do. Help!Help!
If it revs out in every gear, then you're not shifting soon enough. The best thing to do if you took the baffles out is find someone who knows how to rejet so they can show you. It's hard to learn it on your own or even through a forum, although it can be done. It takes a bit of research and understanding how the carburator works before you can rejet.
Re: Clueless?

Everytime I am on my Z, it revs out on every gear when drag racing[/b]
what do you mean "revs out" ?
as in hit the rev limiter?
Revs out?

Well, I don't know if you call it reving out but it kind of sputters at the top of each gear. Maybe I am not changing gears soon enough. I felt more power before I took out the baffle than now. What can I do to give it a more power? A slip-on maybe? :? :? :?
i learned all about quad from exriders, and now this. did everything by myself. get a service manuel. they will get you out of trouble when all hell happens. just listen carefully.

If you're fully stock and you only open up your exhaust, you'll take a hit at the top end (as I experienced @ the dunes).

The throttle seemed to respond a bit better and engine stalled at a lower RPM.

If you take the noise baffle off of your snorkel, you'll definitely need to re-jet.

Corpsie: Where exactly is the "Noise Baffle" on your "snorkel"?
I know where the snorkel is (located at the front of the airbox), but I didn't know it had a noise baffle.
Let me know.

Well, you are either hitting the rev limiter or you are running lean at the high end. If you took off the noise baffel, you'll need to rejet.

If you want to be a 400EX slayer and do a better job keeping up with Raptor's, you can do what I did

- cut out pea shooter on stock exhaust
- removed noise baffle from snorkle
- cut open top of air-box lid
- use speaker grill cloth as imitation "outwears" over air-box lid
- unifilter

Main Jet: 140 (may need to be changed to a 145)
Needle: adjusted by using two No.4 washers to raise it.


From the airbox, you have the rubbery tube (the snorkel) and at the end of the snorkel there is a hard plastic piece. That hard plastic piece is the noise baffle.
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Thanks Corpsie. Would you have any pics of your Z from the exhaust? If you do, please post some. Also, where can I get the jets?
thx corpsie
picture of exhaust cut out

Look carefully and you'll see (or can imagine) how I drilled out the area around the pea shooter until I could pull it out.

For jets, go to any ATV/Dirt bike store, tell them you have a Mikuni 36mm carburetor. You need jets with round heads. The stock jet is a small round head. I accidently bought one with a big head and it still fit (hooray!)

dynojet site: go down the screen and click "Q312". It's the instructions for rejetting our ATV's. You basically won't need the instructions, just use the picture to get familar with what you are looking for.
Thanks Corpsie, I will give it a try. I will keep you posted.
corpsie: why didn't you cut off the spark arrestor with the screen on it. Wouldn't that help out power wise as well?

The screen isn't that big of a restriction, plus I need it to be legal in certain parks, plus it's the "right thing" to do by leaving it in.

If you're skilled with a soldering iron, you can probably cut a hole in the solid back plate of the spark arrestor and put some screen in there too.
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