Ok back to my yz400d shifter kart build the next thing on my check list is exhaust an since I am already sinking way more money into breathing new life into this old trick kart than I ever expected to I really cant see spending 500$ on expansion chamber alone since it won't work on the cart anyways in 77 the yz 2 stoke bikes all had left side exhaust an i need right side exhaust an i am kind new to the 2 stroke world can anybody point me to a cheeper option were i can maybe find a used right side pipe from something else newer that will alow my old beast to run the way it should
Shifter Exhaust help
- Thread starter josh89
- Start date
Or maybe even a 2 stroke race quad exhaust something I'm lost
Rat
Well-known member
Just go with a newer style exhaust. It's on a Kart not a dirtbike so clearance shouldn't be a major problem.
The only 2 significantly important things is that the flange matches the port (or you are able to make your own that does) and the pipe being used is for the same displacement machine, or reasonably smaller like a 250, 300, or 350 (you get a little more out of the powerband that way).
As long as you don't significantly change the functional header length from port to the diffuser, you can cut, twist, and reweld as needed; same said for the chamber itself TBH if you have a decent enough welded and the skills with it.
I'm not a fan of 2 strokes, but I can make them wind them up fit to blow, the pipe is 90% of the tuning so dead to rights it's the single most important part of the engine build to spend on and get right.
Sure you can straight pipe them but they are painfully loud that way. The bigger reason not to do that would be your powerband only exists at the precise length and diameter of the given pipe that the refractory wave reaches the exhaust port at the right point of its open duration to get the scavenging boost off it; it's a metric monolith of math and trouble to only maybe get right.
The only 2 significantly important things is that the flange matches the port (or you are able to make your own that does) and the pipe being used is for the same displacement machine, or reasonably smaller like a 250, 300, or 350 (you get a little more out of the powerband that way).
As long as you don't significantly change the functional header length from port to the diffuser, you can cut, twist, and reweld as needed; same said for the chamber itself TBH if you have a decent enough welded and the skills with it.
I'm not a fan of 2 strokes, but I can make them wind them up fit to blow, the pipe is 90% of the tuning so dead to rights it's the single most important part of the engine build to spend on and get right.
Sure you can straight pipe them but they are painfully loud that way. The bigger reason not to do that would be your powerband only exists at the precise length and diameter of the given pipe that the refractory wave reaches the exhaust port at the right point of its open duration to get the scavenging boost off it; it's a metric monolith of math and trouble to only maybe get right.
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anderkart
Moderator
Lots of guys that built shifter karts on a limited budget cut their dirtbike's stock chamber into sections, then reassemble/weld it all back together in a shape better fits their kart. You might loose a few horse power, but your kart will still be scarry fast.
The only problem with cutting an making factory work is the fact that all I had from the original dirt bike was the engine an harness I bought 7 years ago an I finally decided what I was gonna do with it so I have nothing to go off of except the flange on the motor an the only stock pipes I can find 500$ ton1200$ bucks an im probly gonna habe to cut an reshape it anyways
Denny
Canned Monster
Sometimes you got to pay if you want to play. You could look for the formula to make the expansion chamber and make your own. Got to be on the web somewhere?
So do u think it would run proper on a yz250 pipe I have found an older fatty pipe for one of those I can get for around 100$ I'm just afraid to make the plunge with out advice as to weather the thing will cutting an changing directions or flange sizes is no problem for me just want to make sure my machine is gonna run with it
Rat
Well-known member
Absolutely.
It definitely is.
Without all the brain melting maths...
Header length determines the rpm that the powerband hits (for a 2stroke a straight pipe is all header)
The defuser and forward chamber angle determines how much of a kick in the seat there will be, or lack of in favor of gradual gains.
The mid chamber determines how long the rpm range is for the peak scavenging boost.
The rear section determines how much fall of there is in the over rev after the powerband has been exceeded. Shorter flatter angle can be like hitting an rpm wall
Rat
Well-known member
You should show some pics so we know what toy this is for and what type of clearance you have where.
Looking at the 77 YZ400 D/E pipes both stock and aftermarket... I can safely say they had a timid powerband based on the geometry.
Definitely designed with road use in mind as were most 70's bikes not marketed specifically as a Trail bike. Enduro bikes were exactly what are now called Dualsport, geared low in the final for mud and muck making 1st essentially useless under most conditions, but geared well enough internally to compensate and do 55-60 without screaming the top end off; of course the old Honda Parallel OHC twins were really good at reving high and hard considering it took 10k to be at red line with and engine that would rev 12.5k stock without fault.
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Ok guys here it is the first pic is how I got it I did some trading an got a ttr90 with a bent valve I'm a mechanic for a living so naturally since i got for a old junk pulon pro chain saw i spent a couple bucks new valves i laped in new rings an gaskets an traded it for this cart with a old clone engin that was two weeks ago so its still not much to look at but here it is i plan to do a full restoration
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BaconBitRacing
Well-known member
Kart only a mother could love. I'm sure once you're done with it it'll be fast, reliable, and pretty. Every resto starts somewhere. Just remember to take before and afters so you can see how far it's come.
I'll be tuned in for any updates!
I'll be tuned in for any updates!
Rat
Well-known member
Now it's clear why a left bound exhaust is problematic. Looks like gobs of room for a fat pipe on the right without doing much more than adding support brackets for it.
anderkart
Moderator
Looks like you have that motor mount welded to the frame, Is that just temporarily tacked? If your gonna build your own motor mount you should clamp it around the 2 frame rails so you can simply loosen the bolts to slide the mount to adjust the chain, like this Yamaha shifter kart mount: 