Doks Cafe Racer Build

[Chainlube]

Picked up a second hand exhaust for 30$. Way too late and way to loud to give it a proper test, but just from the quick pull I did down the street, seemed to get a bit more bottom and mid response. Tomorrow I rejet and hopefully start looking at a cheap slip on muffler.
View attachment 211667

They make the stingers too big on those things, 22mm OD. Probably 19mm is as big as you want to go, or 16mm ID. You can change the torque curve by slipping the stringer inside the convergent cone to the half way point.

This is one I remanufactured to be useful.

 

[MadDokKustoms]

They make the stingers too big on those things, 22mm OD. Probably 19mm is as big as you want to go, or 16mm ID. You can change the torque curve by slipping the stringer inside the convergent cone to the half way point.

This is one I remanufactured to be useful.

View attachment 211671

I'm putting a silencer on the end. Very new to tuned exhausts. Why is the bigger stinger a issue? And how would I put the stinger into the cone? Does it just slide?

 

[Chainlube]

I'm putting a silencer on the end. Very new to tuned exhausts. Why is the bigger stinger a issue? And how would I put the stinger into the cone? Does it just slide?

I made that one from 3/4" seamless. I had to reduce the size of the outlet on the convergent cone to get it to close around the new pipe.
A smaller pipe returns the pulse wave at a different rate and not so much goes out the tail. Too big of stinger reduces the size of the return pulse and too small of a stinger starts to back fill the cylinder reducing the volume for the new charge.

Those little pipes aren't made right anyway, but are an improvement over stock. You might get a bit of improvement if you welded a smaller muffler on the end of it. It would definitely quiet it down.

When I made the one for that bike, I incorporated the muffler into the stinger. I used a stock muffler chopped down. I drilled a million holes into the pipe and the muffler slipped over it. Stuffed it full of pink insolation (really packed it in there too) and then capped it off.

 

[MadDokKustoms]

So I found out why the pipe was so cheap... the mounting arm was holding on by hopes and dreams. Snapped right off at the first bump. Looks like im riding to work with the stock exhaust on monday and carrying the tuned exhaust in my bag. before it blew the gasket from no weight support, it sounded mean and pulled amazing!

@Chainlube , would welding a washer with a 19mm opening at the end of the pipe be better? or should the smaller opening be after the silencer?

 

[Chainlube]

So I found out why the pipe was so cheap... the mounting arm was holding on by hopes and dreams. Snapped right off at the first bump. Looks like im riding to work with the stock exhaust on monday and carrying the tuned exhaust in my bag. before it blew the gasket from no weight support, it sounded mean and pulled amazing!

@Chainlube , would welding a washer with a 19mm opening at the end of the pipe be better? or should the smaller opening be after the silencer?

I've never tried it that way, I buy 3/4" seamless for that purpose, you can always chop it off and try something else if it doesn't work. I think the ideal stinger ID is 15mm, so maybe drill out a fender washer to 5/8" will work. 5/8" is almost 16mm, which isn't too bad.

 

[MadDokKustoms]

I've never tried it that way, I buy 3/4" seamless for that purpose, you can always chop it off and try something else if it doesn't work. I think the ideal stinger ID is 15mm, so maybe drill out a fender washer to 5/8" will work. 5/8" is almost 16mm, which isn't too bad.

awesome! ill see if i have a 15mm drill bit at the shop when i go to work on monday.

 

[robe]

I have one of those pipes and I put the Amazon glass pack on it with a 3/4 copper street elbow in the end. I had to take the temper off and crimp the narrow end so it would fit. Seems to be about right for this mainly stock motor. Not a tuned pipe but a big improvement in torque over the stock exhaust.

 

[MadDokKustoms]

Bracket welded up and installed. Ripped it around the underground parking garage. Wow! What a difference! The silencer also keeps it to a nice throaty growl instead of a chainsaw bwaaahhhh pop pop pop. Out of all days for rain... noticed it was a bit hard to start with the velocity stack (had to remove choke) would a hotter plug (I'm running a ngk 6) help this out? Or failing that, I'm thinking of 3d printing a cap with a hole for the velocity stack just for cold starting that can be popped off when the bike is started.

 

[GW's Motorized]

I dig that frame, what brand and make is it?

 

[MadDokKustoms]

I dig that frame, what brand and make is it?

Glad you like it! Its a Super Cycle San Pedro. just a fair warning though, it is aluminum. but it seems beefy. cant wait for the summer so i can start fiberglass work. Next week I start beefing up and reinstalling the fenders.