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Discussion Starter #1
I posted this on the kodiak forum but thought I would add it here as this would work on the grizzly’s ..........
So I am going to do some experimenting with the factory exhaust tip on my 17 kodiak . I will be using a butt dyno and listening for exhaust popping to see if I get better response and flow. I have a EHS fuel controller with the canned kodiak tune, so if I do get some exhaust popping I can adjust which tells me I’ve increased my flow.
Ok so my first experiment is cutting apart the factory tip and removing the tail pipe intrusion into the spark arrestor. The spark arrestor has 2 welded spots to grind off so you can remove it.( first photo you can see I had to grind a lot of the weld off to remove the screen, apparently they didn’t want it to come off ) and then I cut the 4 inch pipe that went into the arrestor. I tack welded the arrestor back on and reinstalled into the muffler. I didn’t get a chance to ride the kodiak last night as it was getting late but i did start it and it did seem to iimprove the sound a bit. I’ll get a chance tonight to give it a few test hits around the house to see what the butt dyno tells me. 3rd photo is my reinstall tack weld for the spark arrestor. I also snapped a photo of the inside of my muffler. You can see the factory holes in the baffle.
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Discussion Starter #2 (Edited)
Ok guys I made some test runs on my first mod ( removing the tail pipe intrusion into the arrestor ) it sounded deeper but I did not notice any significant gains . I did my second mod to the factory spark arrestor, I ground off the welds on the end cap and pulled it off. I then installed my redneck spark arrestor screen (stainless window screen ) over the end with some mechanic’s wire twisted up to hold it on. I wanted to put something on it for a bit of restriction.

Threw it back together and immediately noticed the even deeper exhaust note.Now with my other mods I’ve already done I could nail the throttle and the front end would rise but not pull the wheels of the ground unless I gave it some help. I’m not going to lie the first hit of the throttle surprised me and it pulled a small wheelie, I hit it a few more times and pulled a couple more and noticed some popping from the exhaust . So I definitely made some gains. Got it in the garage and in park I would hit the throttle and had quite a bit of popping off mid throttle. So I raised my fuel programmer by a 1/2 point then a full point and that eliminated the mid throttle popping on decel. Full throttle hits I did the same ended up 1 point higher to eliminate the decel popping. So as of now with zero money, just some time I’ve picked up some power .
 

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Discussion Starter #3 (Edited)
Heres the photos to go with the above post . I couldn’t get the photos to copy/ paste so I had to screen shoot em
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Discussion Starter #4
I ordered this spark arrestor to replace the factory one for $12. It should be here Saturday so I’ll do some more testing
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There is a few post of guys doing exhaust tip mods on the 16-18's. I linked mine below. I got to the 1-1/4" from reading other guys thoughts on sound VS 2R tip which is 2". I might make a 1-3/8" or 1-1/2" ID in the future?? Right now just cruising with the 1-1/4" ID tip you can't tell it has a tip on except when you nail the throttle and at idle it has more rumble for sure but just cruising down the trail I can't tell any difference over the stock tip noise wise.

FYI, USFS sparkarrstor screen size is maximum .023". I believe I added links in my post.

 

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Discussion Starter #6
There is a few post of guys doing exhaust tip mods on the 16-18's. I linked mine below. I got to the 1-1/4" from reading other guys thoughts on sound VS 2R tip which is 2". I might make a 1-3/8" or 1-1/2" ID in the future?? Right now just cruising with the 1-1/4" ID tip you can't tell it has a tip on except when you nail the throttle and at idle it has more rumble for sure but just cruising down the trail I can't tell any difference over the stock tip nose wise.

FYI, USFS sparkarrstor screen size is maximum .023". I believe I added links in my post.

I’m keeping my stock tip as for now I like the sound with out it being loud. Did you install a spark arrestor on yours ?
 

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I’m keeping my stock tip as for now I like the sound without it being loud. Did you install a spark arrestor on yours ?
Yes, I just bought some .022" opening Stainless steel screen mesh that would pass USFS spark arrestor test. I cut it out about 4" in diameter and fastened it through the bolt holes. My tip is not loud at all. Look at my thread.
 

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Discussion Starter #8
Yes, I just bought some .022" opening Stainless steel screen mesh that would pass USFS spark arrestor test. I cut it out about 4" in diameter and fastened it through the bolt holes. My tip is not loud at all. Look at my thread.
My end goal with this, is seeing what improvement I can get while still using the factory tip. Nice job on the tip you made, I’m also swapping the tip bolts out for stainless.
 
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Here is a picture from 2R of a 700 tip, with screen shown to the side.
For older bikes like the 660's we cut the spot welds on the factory tip securing the spark arrestor and used the factory spark arrestor with the 2R tip.
As for the screws, stainless is a good replacement, and to prevent carbon build up to seize the screws, when I think of it I give mine a 1/4 turn out then re-tighten to break the bond.
 

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Discussion Starter #10 (Edited)
Here is a picture from 2R of a 700 tip, with screen shown to the side.
For older bikes like the 660's we cut the spot welds on the factory tip securing the spark arrestor and used the factory spark arrestor with the 2R tip.
As for the screws, stainless is a good replacement, and to prevent carbon build up to seize the screws, when I think of it I give mine a 1/4 turn out then re-tighten to break the bond.
From my testing the factory spark arrestor is very restrictive on my 700. I want to keep the stock tip as we want to ride maine some day and no exhaust mods are allowed . So a factory tip with my aftermarket spark arrestor shouldn’t get a second look. Plus $12 for a arrestor vs $60 for a 2R is easier to handle. I’m not looking for all out max performance, I’m experimenting to gain the best flow from the stock tip while not making it significantly louder .
 

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:)
I guessed from your #6 post a picture of the screen would help you, and others, in the future before they remove the tip.
 
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I have been doing something similar , I started a thread enquiring whether anyone had managed any beneficial gains from messing with the factory set up.

Similar route to you by the looks of things👍
 
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I doubt if there is much benefit to exhaust mods unless you increase the intake flow substantially, and I'm not sure different filter cause enough air flow increase to be felt. Different filter can filter better, but for increased air flow to a significant degree, I'm not sold on this yet.
I 'increased' the intake opening area @200% over the stock opening, so maybe the 2" tip is doing something. I know the fire from the backfire is longer and the sound is a deeper growl which I like, but I'm not sure there is more forward bite from the tip.
 

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I was hoping that my various attempts and also the ehs unit / 2r tip combo , would if nothing else keep her cooler.
The cat must be a huge heat soak and generally the warmest place in the mudguard is the slope section of the left rear area, up towards the rack. That is the cat location , but I guess also the point where the exhaust has a degree of bend as it goes up to the can.
when I ran mine with the cat gutted out and the modded Spark arrester basket in to try and tone down the hideous noise , I noted that the whole steel basket assembly was glowing bright cheery red , just as the cat core was, so still tremendous heat even as far as the exhaust exit.
obviously the flow at higher rpm moves the hot air further faster , then hits a wall before exiting the tip , but I would have thought at idle and slow running speeds the heat would be able to easape much easier and create less peripheral heat soak into the machine and plastics etc🤷🏼‍♂️
 

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Discussion Starter #15
:)
I guessed from your #6 post a picture of the screen would help you, and others, in the future before they remove the tip.
Got ya;). Only problem a flat screen would not work. notice in my second photo in my first post the dimple that the factory spark arrestor Slid over/ was welded to.
 

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I doubt if there is much benefit to exhaust mods unless you increase the intake flow substantially, and I'm not sure different filter cause enough air flow increase to be felt. Different filter can filter better, but for increased air flow to a significant degree, I'm not sold on this yet.
I 'increased' the intake opening area @200% over the stock opening, so maybe the 2" tip is doing something. I know the fire from the backfire is longer and the sound is a deeper growl which I like, but I'm not sure there is more forward bite from the tip.
When you say you increased the intake opening how/ what did you do ?
 

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The only way I know to get the temp down at the cat is to increase the air flow through the exhaust without adding gas to to the intake, as in going downhill for the power which increases the airflow without more gas than at idle.
I learned this with a truck pulling trailers going downhill loaded in the winter. After a mile of this coasting in gear, the engine temp dropped so the cat cooled too much and the cat clogged up needing replacement.
It was on a new truck under warranty, so I learned a good lesson without extra expense.
 

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Got ya;). Only problem a flat screen would not work. notice in my second photo in my first post the dimple that the factory spark arrestor Slid over/ was welded to.
Grinder maybe needed :)
 

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Discussion Starter #19

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When you say you increased the intake opening how/ what did you do ?
I drilled a bunch of big holes in the air box lid.
I don't remember the actual numbers, but the stock snorkel was about 7"s of opening, so with that much ( probably was cancelled out but still available) I added these holes;
https://flic.kr/p/fKjh1X each small hole is 1/2", the 2 big holes are 3/4".
 
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