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A question concerning carb and exhaust mod.

5K views 14 replies 6 participants last post by  Scrapper 
#1 ·
I want to mod the exhaust and do the .22 cent mod as well as ditch the snorkel.
1. I plan on using the hole saw mod to remove the chamber and open up the exhaust a bit. Along with this I have ordered the down pipe to bolt onto the end.
2. Second is the washer under the needle mod and turn out the idle mixture screw.
3. Third is ditching the snorkel.

My question is will I need to re-jet due to this? I dont have access to a residual oxygen sensor yet and I dont want to run lean and I dont feel I have enough experience yet to read the spark plug accurately.
 
#3 ·
I haven't changed my jetting either from stock. What hole saw are you using size wise? If you make a cut that is outside that indented section at the back of the can you will remove a lot of baffles and it will be LOUD! If you stay inside the indented section it removes just the tweety tube and still increases flow and isn't that loud.....just saying....you can always go larger but you can't easily fix the larhe hole....again just saying...beware!!!:13:
 
#5 ·
I'll go and measure the indentation on a stock 08...be right back......OK...back...if you make a hole bigger that 1 3/8" you will remove the entire tweety baffle and it's outer case. You want to leave that outer case in the muffler to keep the noise levels down to acceptable levels imho. You can always make it larger IF you want more noise and more flow. I never saw the need to it personally. I di however drill out my spark arrester to increase flow. I never go into an area that requires the use of a spark arrester so that is a non issue for me. I started out with a 1/8" hole and worked my way up to 1/2" all the time seeing what each gole size sounded like before moving up to the next level. Like I said once you have drilled it, it is near impossible to undrill it!! BEWARE!!!
The spark arrester in the stock can is a inverted cone shaped piece of steel about a foot inside the can. If you shine a flashight down the hole you can see it. It requires a drillextention to get deep enough to be able to drill it out. The 1/2" hole I did I used a drywall drill used to make holes for wiring etc. It's just a mild steel drill bit but is 20" long...plenty of oil and slow drilling and it went through no problem.

The result was it flowed very well and didn't have anywhere near the loud obnoxious bark the large hole mod has.

Yes you are correct about how to drill the first hole. Jam a piece of wood into the original hole and centre the drill bit that way.
Truthfully..it is much easier to use a good 1/8" drill bit and drill all the way around the indented area next to the outlet pipe and just clean it up aterwards....seriously. That way you also can make 100% sure you aren't hitting the outer case or shell of the baffle you want to leave in. IF you make a mistake with a hole saw you won't know until it finally breaks through to see where it has cut through ......plus the end of the can is hard and will eat a hole saw fast if spun too quickly and not constantly fed oil to keep the temps down on the teeth.

Your can and your choice....in the end so to speak...so choose wisely.

Good luck.....:13:
 
#6 ·
If you take the outside edge out of the tweety tube, you may as well cut the last 3" straight off the can...it will be an empty box at that point....that is why it is so loud!....just saying....

I disected a can once just to see.......there really isn't much in there if you go that far. It's almost a straight through exhaust that is forced to go through two 3/4" sized tubes before getting out of the can.:13:
 
#9 · (Edited)
:13:

OK, here you can see that if you take just the perforated tweety tube out the hot gasses are still forced to travel past the spark arrester cone and through the outer case of the tweety tube. IF you take the outer case of the tweety tube the hot gasses are able to pass through those 5/8" holes and then find their way straight out the end of the exhaust without being redirected past the spark arrester. Also I have never seen a can with any fibreglass left in it yet.
 
#10 ·
Alright now that is just awesome and completely changes how I am thinking about this mod. I cannot in good conscience bypass that spark arrestor considering all of the forest roads I ride on. Guess I will have to think on this a bit more before doing any work. Thank you.
 
#13 ·
I have been running the CV carb all summer on the bike and just reinstalled the flatslide onto the stock 08 engine to see what it will feel like. So far I have only started it and saw that it ran fine. Haven't had the chance to ride it yet, hopefully tomorrow, if all goes as planned, it will stay on untill I tear the bike down for a complete overhaul over the winter months.
So I understand your concerns.....I had only run the flatslide carb for a few days or a week can't remember before I had issues not related to the carb but took the carb off to take it out of the equation to solve the issue I was having. If that makes any sense....lol.

I do not want to stain this site with the past BS from the other site so I will not get into it here....sorry.:13:
 
#15 ·
here we are 2 yrs later and i just came across this mod. originally it was to take the tweet out of gen 1's however on gen 2's i havent heard a tweet yet. not sure why possibly larger holes in the chamber? anyway on gen 1's and 2's would this help in HP? help it breathe more?
 
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