Exhaust Is this pipe I made hindering performance?

The-DMV

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Feb 5, 2017
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So, I have a Skyhawk 66cc engine, and I'm still messing around with the jetting and I'm having issues with the CNS carb, but I want to make sure that the exhaust isn't part of the problem? Does this look like a decent design? I had to weld it to fit the bike. That extension after the expansion chamber concerns me a little.

I'm not getting a lot of power from the engine, and with my 36 tooth sprocket on the back, the engine doesn't want to rev very high. I'm not sure how many rpm's I'm getting, but it's probably 60% of what the engine can rev to, I'd guess.



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Street Ryderz

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Oct 14, 2016
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3,560
So, I have a Skyhawk 66cc engine, and I'm still messing around with the jetting and I'm having issues with the CNS carb, but I want to make sure that the exhaust isn't part of the problem? Does this look like a decent design? I had to weld it to fit the bike. That extension after the expansion chamber concerns me a little.

I'm not getting a lot of power from the engine, and with my 36 tooth sprocket on the back, the engine doesn't want to rev very high. I'm not sure how many rpm's I'm getting, but it's probably 60% of what the engine can rev to, I'd guess.



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Thats really nicely done!The chamber design is not the best out there by any means but it looks like the engine can breath well thru it as long as like mentioned above the baffle isn't over packed!Did you play with different header lengths be for it was all welded up? The difference of even an inch can have a huge effect on the timming of the return wave and if your not seeing any real gain that is most likely the culpret!What issuses are you having with the carb?
 

The-DMV

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Feb 5, 2017
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I didn't play around with different lengths, this is just what ended up fitting the best. I'm not very knowledgeable on how the exhaust resonance is supposed to work, so I'd appreciate any guides.

I ran the engine as a straight pipe for a while, and it revved higher and ran faster than when I had this exhaust hooked up. It ran a #70 main jet then, but now it needs more than a #72. I don't have a bigger jet right now, so I have to use the fuel enrichment circuit to add more fuel at full throttle to get it to run right. What would cause the bike to need so much more fuel? Also, I somehow snapped the top plate on the carb in half taking the thing apart like I always do, so I JB welded it back together and got it running again. I'm considering getting a different carb with a better design, because I'd rather have something that just works, or is easier to work with.
 

Street Ryderz

Well-Known Member
Joined
Oct 14, 2016
Messages
3,560
I didn't play around with different lengths, this is just what ended up fitting the best. I'm not very knowledgeable on how the exhaust resonance is supposed to work, so I'd appreciate any guides.

I ran the engine as a straight pipe for a while, and it revved higher and ran faster than when I had this exhaust hooked up. It ran a #70 main jet then, but now it needs more than a #72. I don't have a bigger jet right now, so I have to use the fuel enrichment circuit to add more fuel at full throttle to get it to run right. What would cause the bike to need so much more fuel? Also, I somehow snapped the top plate on the carb in half taking the thing apart like I always do, so I JB welded it back together and got it running again. I'm considering getting a different carb with a better design, because I'd rather have something that just works, or is easier to work with.
Oic what you mean,I run the cns v3 carb also and it can be deciving if you dont set it up right!Those carbs firstly have a very restricted air filter so much so that if you take it off you can go up a half dozen or so jet sizes to dail it in properly for the top end and thats in part because the size is 2mm larger than the stock nt!When you add fuel with the enrichment circuit does it pull again?I found that the pilot jet was rich and needed the air screw adjusted 2 and 1/4 turns out from closed when used with the stock filter and the needle had to be lowered or the clip raised to the top and that yes a #72 jet worked best again with the stock filter!With the pipe you could try to reduce the stinger dia and lengths to help get it right without having to change the header length it should help to do that because the current section is huge and probably makes the chamber act as if it were longer!
 
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