Exhaust pipe (with photos)

BMPoland1993

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Just mounted a new exhaust on my gokart. 40mm pipe in a L bent shape. Will post photos tomorrow. Not only is it extremely loud, the kart seems to be a bit slower...

I was hoping for some increase in power, yet the opposite happened.

Anyone know why?
 

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Hellion

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The straighter the pipe, the better.

The only reason it should be 40mm is if that's the size of your exhaust port.
And since there's no pics, I will assume it's not only L bent, but has a 90 degree right angle instead of more of a gentle J shape.

Never write first, then add pics. It infuriates people for some reason.
In fact, a photo in the post with no text whatsoever is 10x better, lol
:roflol:
 

BMPoland1993

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Ok chaps, I've just got out of my buggy. Been riding it for 20 minutes or so. I might have solved the issue, here's the deal:

At lower rpms, with the pedal depressed all the way, the kart does seem to be slower than with the stock muffler. Acceleration is less, and the top speed seems to be lower too.

However, I tried depressing the gas pedal gradually, 1/4 throttle at the beginning, as it gains some speed I go on to 3/4. I leave it there for a few seconds and then I go full throttle. The kart goes to accelerate some more, and top sped is significantly greater than with the stock muffler.

In my opinion the new exhaust changed the characteristics of the engine entirely. Lower acceleration but overall higher top speed.

Might adjust that by adding a bigger rear sprocket, so I get that little bit more off the line.
 

madprofessor

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By my reckoning that 40mm is about 1.6" diameter pipe. Since that appears to be something similar to a Predator non-hemi 212cc engine with a CVT, looks like you've got too much pipe diameter. A single inch ID of pipe would be plenty, and helps create a slight draft exhausting the head. Others will argue the merits of that, but I don't want to start another ruckus.
Hard to tell how many teeth on that rear sprocket, but it looks like it might be a 60, that should be okay. Your strange acceleration power band(s) sounds to me like your CVT belt behind that shroud is slipping. Kudos by the way, putting the shroud on for safety (and rain-proofing).
 

BMPoland1993

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By my reckoning that 40mm is about 1.6" diameter pipe. Since that appears to be something similar to a Predator non-hemi 212cc engine with a CVT, looks like you've got too much pipe diameter. A single inch ID of pipe would be plenty, and helps create a slight draft exhausting the head. Others will argue the merits of that, but I don't want to start another ruckus.
Hard to tell how many teeth on that rear sprocket, but it looks like it might be a 60, that should be okay. Your strange acceleration power band(s) sounds to me like your CVT belt behind that shroud is slipping. Kudos by the way, putting the shroud on for safety (and rain-proofing).
Its a 420. The sprocket is a 54 tooth. I'm pretty sure the belt isn't slipping :)
 

Hellion

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...Others will argue the merits of that, but I don't want to start another ruckus.

Start another ruckus, start another ruckus! I didn't know you were so troublesome...


What some may call a ruckus, others may call just a discussion.


Sounds like his issue may still persist. With a centrifugal clutch start-offs may be slow but with a TAV it should be pretty gutsy and neck-snappy.
I think some carb tuning on the low and high end may be in order. It sounds like it's "falling on its face" {bogging} just a bit.
 

madprofessor

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Okay, your 420 with the 1.6" I.D. pipe now has 2 sq. in. of exhaust I.D., and to my surprise my 1" I.D. exhaust on my hotrodded 212 is only 0.8 sq. in. I.D., your new exhaust should only help it. Wondering if Hellion's right about it bogging down, too much air and not enough fuel.
You've got the basic first stage upgrades with the hi-flow intake and the free exhaust. If you've still got the OEM jets in the carb it's all a waste, and would explain the bogging. First stage should include larger both main and low jets. What have you got in there?
 

Denny

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If you have a 30 series cvt you may indeed be overpowering it. If you have a 40 series make sure you are using a Genuine Comet or Manco belt. Cheap aftermarket belts tend to have a greasy feel, slip badly and don’t last long. Over powering your cvt tends to bury the belt in the shieves making the engine feel boggy and restrict rpm. In my experience.
 

madprofessor

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If you have a 30 series cvt you may indeed be overpowering it. If you have a 40 series make sure you are using a Genuine Comet or Manco belt. Cheap aftermarket belts tend to have a greasy feel, slip badly and don’t last long. Over powering your cvt tends to bury the belt in the shieves making the engine feel boggy and restrict rpm. In my experience.
Ditto on everything he said, right down to burying the belt in the sheaves. Bought a snap ring pliers set just to work the snap ring on my driven pulley, so I could tighten the spring to #3 spot. Cheap Chinese CVT belt was burying into the sheave and locking it up.
I still think you're belt's slipping, convinced of it even. Pop that shroud off and prop the rear end up off the ground. Use the rear brakes for resistance, and see what happens when you floor it.
 
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