KX 65 Expansion Chamber Fab Continued

rek4385 · Nov 14, 2010

Ok the kids went to bed early so I thought I would start a new thread reporting back to you with my progress. I have taken more away from these forums then I have given to it. So I hope this helps someone that is in a similar situation of minimum tools, time and money!

So my original question , Found here: http://motorbicycling.com/f13/exhaust-fabrication-expansion-chamber-25186.html . Basically my question was how in the world am I going to take a dirt bike expansion chamber and connect it to my exhaust port of my 49cc 2 stroke? After a number of responses I realized 3 things A:Realized that this forum consists of a lot of experienced fabbers B: I came to my senses to stop looking online for a flange and just buy a piece of steel and fab it myself.

So this is what I did.

I received my expansion chamber on Saturday ,Ebay sale, from a guy in Texas and could not be anymore pumped. I call it a piece of art , a beauty ,a finely crafted sound chamber designed to harness a sound wave and its pressure<---(Definitely not a wiki definition) Here is the pipe.

Like I said I am so pleased with it because it really fits well with my frame and pedals. The bend is pretty much perfect for the application and will require minimum fabbin to make it clear everything and has plenty clearance.

Ok so you all know what the exhaust port off of your chinese girl looks like but here is what I am working with for the inlet of the chamber.

I really am open to suggestion at this point in time because I have an idea at this point and time and I hope it is the best and works. I fabricated a flange and I am pretty embarrassed guys by it aesthetics. I did all of this with only an angle grinder, a hand drill, files, sand paper and other basics. So bare with me, it sits flush on the jug and I am hopeing and praying I can get a 45 degree copper elbow welded or brazed to it. Which opens another question...do you think I will run into any problems joining these two different metals? Can I expect to have this brazed or welded?

(Continued on next post)

rek4385 · Nov 14, 2010

This is what It will look like after it is welded. The 45 degree angle works perfect for the fit. I am now left wonder the best way to connect the chamber to the bend. It has a 1 inch female end in which obviously accept another 1 inch copper pipe. The 1 inch copper pipe barely slides into the chamber inlet so I figure I can fab and seal that up or some how take advantage of the gasket found on the inlet of the pipe by working a pipe over top of it.

I will try to post some updates. I realize that this chamber was designed to be put on a 65cc dirtbike. I am not stressed on gaining ultimate preformance from it. I am just looking forward to get everything working. I am also looking forward in how this bad boy will sound. I am a low end torque lover so the short pipe to the chamber does not help my case so well see how it does just like that.

So If you guys had any insight to pass on. Pass on to me what I am up against with joining copper to a 1/8 steel flange or ideas to connect the flange to the chamber if it be via building additional flanges, or slip over with exhaust springs (not knowing what there full purpose is) I imagine they would come in handy.

bairdco · Nov 14, 2010

i suggest getting a small grinding bit for your drill and match your flange with the exhaust port. if it's matched, it'll flow better, and optimize the performance of the pipe.

i would also forget about the copper pipe. if you don't have a buddy to weld it for you, i'd take it to a good independent muffler shop and see if they can fab it up for you. offer them a twelve pack and they'll probably give you a good deal.

i just figure that if you're taking all the trouble to do it, you should get it done right so you don't have any problems or regrets down the line...

FileStyle · Nov 15, 2010

I would start by fabbing up a exhaust flange and then cut a 2" piece of handlebar or of the like and weld that to the new flange. mount it to the motor temporary. then mount your pipe where you want it. then by using different parts of a handle bar (ram horns) or tubing you connect point A to point B and tack weld into place then remove for final weld. Do not use the copper fitting! it's easier than it sounds really. When you weld or fab a intake or exhaust make sure you weld, what would be the inside (motor side) of flange. after your weld ,grind clean, file surfaces. if you weld on the outside of flange you wont have room for your bolt heads!

rek4385 · Nov 15, 2010

Appreciate the reply fella's.Just want to say this ultimately sucks not have a welder to mess around with.I also quickly learned that propane torch will not Quickly getting back to you....

bairdco said:
i suggest getting a small grinding bit for your drill and match your flange with the exhaust port. if it's matched, it'll flow better, and optimize the performance of the pipe.
i would also forget about the copper pipe. if you don't have a buddy to weld it for you, i'd take it to a good independent muffler shop and see if they can fab it up for you. offer them a twelve pack and they'll probably give you a good deal.
i just figure that if you're taking all the trouble to do it, you should get it done right so you don't have any problems or regrets down the line...

Two people now have said to forget about using copper pipe! Down below I will ask why? I think you guys are trying to tell me something! Ill have to source another pipe. I know there are a lot of options out there and options that I could get out of the trash but I cannot source anything else yet.

I agree with you about doing this right maybe even spending a couple extra bucks and giving it to somebody that actually has the right tools . There is actually a blacksmith in town (never knew they still existed) I am trying to track him down and run some stuff past him.

FileStyle said:
I would start by fabbing up a exhaust flange and then cut a 2" piece of handlebar or of the like and weld that to the new flange. mount it to the motor temporary. then mount your pipe where you want it. then by using different parts of a handle bar (ram horns) or tubing you connect point A to point B and tack weld into place then remove for final weld. Do not use the copper fitting! it's easier than it sounds really. When you weld or fab a intake or exhaust make sure you weld, what would be the inside (motor side) of flange. after your weld ,grind clean, file surfaces. if you weld on the outside of flange you wont have room for your bolt heads!

Thats what is driving me nuts, when you have the right tools this is easy I know! Ughhh
Ok so painstakingly with the angle grinder I can fab up a flange. I did bend the copper pipe in a way that it allows clearance for the bolts (oval shape), you do have a point that once welds are in place i may run into trouble. So thinking in the direction of fitting the tube into the flange so to weld it from the inside this obviously is the best way. Because my lack of tools its difficult to drill an accurate hole to fit the 45 degree tube into it...again i may have to bite the bullet and have somebody do this.

I must ask what is going on with the copper fitting...in other words why not? Is it going to flex on me when it heats or does it not make a good weld to steel. Your the second guy to say that. You were going in the direction of setting a temp set up with tacks to make sure everything fits. Maybe at this point in time this copper fitting will be temp while I fab a flange the right way.

hurricane · Nov 15, 2010

rek4385 said:
I must ask what is going on with the copper fitting...in other words why not? Is it going to flex on me when it heats or does it not make a good weld to steel. Your the second guy to say that. You were going in the direction of setting a temp set up with tacks to make sure everything fits. Maybe at this point in time this copper fitting will be temp while I fab a flange the right way.

Here is the short version, brass/copper to steel cant be joined properly and will break in a very short amount of time.

culvercityclassic · Nov 15, 2010

This is a picture of the flange that I use and how it is welded to the pipe. Just so you get an idea.

You should have a welding company help you with this project, it will be worth it in the end.

Also follow the advice that has been given to you on this subject.

I have also sent you a PM. I will help you the best I can since distance is an issue.

BTW thats a nice chamber you purchased.

CCC

timboellner · Nov 15, 2010

I know how building with limited tools and resources can be.
I don't have a welder but have successfully joined steel to copper many times.
The pipe I built several hundred miles ago was brazed together with an acetylene Tubo torch that I use everyday in the air conditioning trade.
I made my own flange from flat steel I bought at home depot.
Traced the outside of my copper fitting onto the steel.
Used drill bits and a file to get the hole just big enough to slide the fitting into the hole
so it sits flush on the backside of the flange.
You can get Berzomatic WB-5 bronze brazing rods on Amazon or a local hardware store.
(Suburban Hardware in my area.) They are about $5 if I remember.
I know copper isn't the ideal choice but it's what I had,so it's what I used.
I used 1- 1/8" OD ACR tubing.
I haven't gotten any leaks nor is the pipe at all bendable.
Here's a picture of my pipe I fabbed up this past summer.
It takes a decent amount of heat to get the rods to flow. I don't think a propane torch would get nearly hot enough to melt this stuff. Mapp gas I'm not too sure about either.
Good luck with your pipe and don't give up , that thing looks gnarly.
TIM

timboellner · Nov 15, 2010

Here's a pic of another pipe I joined steel to copper.
This one is holding up well also.
I do suggest making some type of sturdy bracket to help support the weight of your pipe though..
TIM

hurricane · Nov 15, 2010

Ok I stand corrected, dont weld it just braze it .. LOL

thanks for the pictures gentlemen, I guess even old welders can learn a new trick or two

culvercityclassic · Nov 15, 2010

Ya know us tradesman can be very creative.

rek4385 · Nov 16, 2010

I have to write this post in 10 minutes! I had the copper and steel brazed as a temporary setup before I get a proper flange and steel tubing.I wish I had a picture to make it interesting for any of you that are following.This thing sounds amazing. Will post a couple pictures soon of the progress....

culvercityclassic said:
This is a picture of the flange that I use and how it is welded to the pipe. Just so you get an idea.

You should have a welding company help you with this project, it will be worth it in the end.

Also follow the advice that has been given to you on this subject.
I have also sent you a PM. I will help you the best I can since distance is an issue.
BTW thats a nice chamber you purchased.

CCC

In following some of the advice said here. I sent the flange it to a blacksmith who did good work and at a cheap price. . I am glad that I did this because I see what I will need to do to make this all work and tweak everything ...and do it right. I sent you a PM back buddy.I also checked your website ....your builds are at a totally different level then what I am working with here. I am going to turn on cable TV one day and see you on a TV show called CCC "Cali Creative Customs or culvercitycustomcreations"

Rreally nice builds.....

timboellner said:
I know how building with limited tools and resources can be.
I don't have a welder but have successfully joined steel to copper many times.
The pipe I built several hundred miles ago was brazed together with an acetylene Tubo torch that I use everyday in the air conditioning trade.
I made my own flange from flat steel I bought at home depot.
Traced the outside of my copper fitting onto the steel.
Used drill bits and a file to get the hole just big enough to slide the fitting into the hole
so it sits flush on the backside of the flange.
You can get Berzomatic WB-5 bronze brazing rods on Amazon or a local hardware store.
(Suburban Hardware in my area.) They are about $5 if I remember.
I know copper isn't the ideal choice but it's what I had,so it's what I used.
I used 1- 1/8" OD ACR tubing.
I haven't gotten any leaks nor is the pipe at all bendable.
Here's a picture of my pipe I fabbed up this past summer.
It takes a decent amount of heat to get the rods to flow. I don't think a propane torch would get nearly hot enough to melt this stuff. Mapp gas I'm not too sure about either.
Good luck with your pipe and don't give up , that thing looks gnarly.
TIM

Thanks for the good words. The blacksmith was able to braze the sucker on as a temp set up to see what needs to be trimmed and tweaked. gentlemen...this thing sounds gnaryly. Its like a completely new bike when it comes to looks and sounds. I will need to fab a muffler. My standards of loud is a little left wing. "The louder the better" but in this case , after 5 minutes of riding. I walked away with mild tinnitus (ringing of the ears)

This is just too much fun guys....

hurricane said:
Ok I stand corrected, dont weld it just braze it .. LOL

thanks for the pictures gentlemen, I guess even old welders can learn a new trick or two

I wont run this copper on steel flange for very long but it appears it has integrity and will get my feet wet....

culvercityclassic said:
Ya know us tradesman can be very creative.

They are a dieing breed of the american culture of "just take it to someone to fix it and not have to put thought into it. "

rek4385 · Nov 17, 2010

While waiting for a proper flange and preparing to perfect this setup I installed the chamber. This is what it looks like.

Has awesome sound. Improved low end torque and a noticeable power-band at high RPM's ....getting up hills is no problem. It seems the pipe is tuned for the top of my RPM range. For some reason it is four stroking alot and will have to reasearch in how to improve low end power. I know the distance from the chamber to the exhaust port will solve this but because of clearance issue I have no extra room to play with. May have to play around with the tubing size of the mufflers exit or length of piping before the muffler? None the less and I am very happy everything came together like it did thanks to you guys!

timboellner · Nov 17, 2010

Nice pipe man.
I saw one on E bay last night for $25
It wasn't in as good of condition as yours though.
Glad it's gonna work out for you.
Raise the clip on your carbs needle jet, maybe it'll get rid of that 4 stroking.
You might want to invest in some kind of shrouding for your pipe to keep the heat away from your right leg.
Burns suck.
Tim

rek4385 · Nov 17, 2010

timboellner said:
Nice pipe man.
I saw one on E bay last night for $25
It wasn't in as good of condition as yours though.
Glad it's gonna work out for you.
Raise the clip on your carbs needle jet, maybe it'll get rid of that 4 stroking.
You might want to invest in some kind of shrouding for your pipe to keep the heat away from your right leg.
Burns suck.
Tim

appreciate that man. I got mine for $15 ...$25 shipped. Mine has a couple dings but yeah its in good condition. I thought that the extra flow would lean the thing out but it proved the contrary. It was slightly humid today and warm so well see what it does in the cold. Yeah I still have alot of work to do and a shroud will be in the works.......Burns suck and they hurt worst the following day lol.

Take care....

The Mechtician · Dec 8, 2010

Dude, nice work! I subscribed to this thread with great interest since I had the same idea myself, nice to see that I can ride someone else's coattails and not have to do too much thinkin! Lol

JK. When I first saw your pic of the copper 45 and your homemade adapter plate I was skeptical, but seeing it installed it looks pretty decent. Quick (possibly stupid) question though: did you build up & shape the transition inside your adapter from the rectangular exhaust port shape to the round pipe shape? Reason I ask is that port matching and creating smooth flow transitions will take the "lightswitch" out of the power delivery and make it more linear. You could also try extending the adapter/header pipe to make it longer, which will bring the power down lower in the rpm range. I doubt you'll be wringing the thing at 11,000+ rpm all the time, which is where it's tuned for in its original application

Just a suggestion, once again my compliments, nice build!

camlifter · Dec 8, 2010

the so called 4 stroking ( don't know why people call it that since it's impossible) is from the engine running too rich now, with the better pipe all the unburnt fuel you used to be wasting out the exhaust is now being sonic waved back into the chamber giving a rich mixture, you'll need to use a smaller jet or solder and redrill the stock one. once you get the jetting right it wiil run even better.

max350 · Dec 9, 2010

rek4385 said:
Ok the kids went to bed early so I thought I would start a new thread reporting back to you with my progress. I have taken more away from these forums then I have given to it. So I hope this helps someone that is in a similar situation of minimum tools, time and money!

So my original question , Found here: http://motorbicycling.com/f13/exhaust-fabrication-expansion-chamber-25186.html . Basically my question was how in the world am I going to take a dirt bike expansion chamber and connect it to my exhaust port of my 49cc 2 stroke? After a number of responses I realized 3 things A:Realized that this forum consists of a lot of experienced fabbers B: I came to my senses to stop looking online for a flange and just buy a piece of steel and fab it myself.

So this is what I did.

I received my expansion chamber on Saturday ,Ebay sale, from a guy in Texas and could not be anymore pumped. I call it a piece of art , a beauty ,a finely crafted sound chamber designed to harness a sound wave and its pressure<---(Definitely not a wiki definition) Here is the pipe.

View attachment 30940 View attachment 30941 View attachment 30942

Like I said I am so pleased with it because it really fits well with my frame and pedals. The bend is pretty much perfect for the application and will require minimum fabbin to make it clear everything and has plenty clearance.

Ok so you all know what the exhaust port off of your chinese girl looks like but here is what I am working with for the inlet of the chamber.
View attachment 30943
I really am open to suggestion at this point in time because I have an idea at this point and time and I hope it is the best and works. I fabricated a flange and I am pretty embarrassed guys by it aesthetics. I did all of this with only an angle grinder, a hand drill, files, sand paper and other basics. So bare with me, it sits flush on the jug and I am hopeing and praying I can get a 45 degree copper elbow welded or brazed to it. Which opens another question...do you think I will run into any problems joining these two different metals? Can I expect to have this brazed or welded?
View attachment 30944

(Continued on next post)

If you can weld, make a new header that I made for my Yamaha DT 50
expansion Chamber

The Mechtician · Jan 21, 2011

camlifter said:
the so called 4 stroking ( don't know why people call it that since it's impossible)

I've noticed others using this term as well and wondered what it meant, it didn't make any sense to me. Good to know I'm not the only one! lol!

What would be the correct terminology? When I hear a 2 stroke make that honking farting noise I say that it's missing or misfiring (that's exactly what it's doing because it's too rich, as you mentioned). Am I on meth?

Sorry for the thread jack, carry on

Incidentally, nice header you've got there max350!

corgi1 · Jan 22, 2011

Ok my 2 cents,dremal out the flange to fit the exhaust port properly ,,useing two short tubes and longer round headed allen bolts ,attatch the flange to the motor and tac the tubes to the flange,remove the flange and add a exhaust port size tube to the flange and braze in place,,,now make a conector tube for between the flange and thenice exhaust pipe(about 2 inches is all)with a stop washer or a couple pins to keep it from going all the way into the exhaust ,,,re-bolt the flange to the motor,slip the conector in the end of the new muffler and over the exhaust port tube extention and secure with springs

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