HuaSheng 142F vs Honda GXH50 vs Dax XC50s

[GreenMantis]

I have a good question: The exhaust pipe. I read that the recomended size should be 7/8", is that ID or OD? The pipe I have on there now is only 3/4" ID, which seems to work well enough. To go with a larger pipe, with the orientation that I have, I'll have to either fabricate one from scratch, or seriously bend one that is available, as my exhaust port faces rearwards. Needless to say, I really would rather avoid that, if I can. And the pipe and muffler that I have on it now is perfect, otherwise, and it was only $20, too.
Funny, my options on a larger pipe, if I fabricate, I can run it straight, but if I use an existing header, I have to bend it, the latter would force me to invest $80-$100 on a pipe bender, so it's not as easy of a decision as it seems like. Go figure.

 

[IbedaYank]

Greenmantis

First of all a pipe bender is made for pipe a tubing bender is made for tubing.
these work good for bending small tubing and are less then $50

get one at lowes homedepot menards or other building supply

 

[Quenton Guenther]

We tested a lot of exhaust designs and found the 7/8" ID to produce the most power on a dyno. The smaller pipe resticted the flow and also caused the motor to run about 40 degrees hotter.

Have fun,

 

[breaksalltherules]

Hey Quenton,

On the exhaust manifold you use, is it 7/8" as well as the pipe?

 

[Quenton Guenther]

We normally cut the chrome pipe off about 2" from the motor and slide the 7/8" I.D. pipe over the manifold. The stock pipe is almost 7/8" I.D. and a simple clamp affixes the pipe to the manifold. We had a few manifolds made, but was too expensive [cost more than the chrome pipe].

Just for the record............
A stock HS motor with the new Q-Matic Pacesetter drive installed managed to turn the DYNO [Roller Road] to 41.5 MPH. The motor was stock except for the flex pipe kit, and only had about 40 Miles on it prior to the test. Several recent road tests has also logged 41.5 MPH on the electronic speeedometer, indicating the Roller Road tests in Dawson Springs, KY were very accurate.

My Twin powered Whizzer only managed to hit 75 MPH, as the front motor was having issues [running very lean and popping & cracking]. Had to hold my hand over the inlet of the front carburetor to keep the front motor firing. Oh well! back to the "drawing board".


Have fun,

 

[breaksalltherules]

Ok thanks for the info Quenton.

Does the manifold being a slightly smaller ID than the 7/8" restrict the air flow?

 

[Quenton Guenther]

The manifold [cut-off pipe] has the same I.D. as the exhaust port, and works well in making the change to a slightly larger pipe, however the pipe must have a slight restriction at the exit. The slight restriction is needed to create a small amount of "back pressure", and can make as much as 3 MPH on the top end.
The motor we just tested on the "Roller Road" dropped 3 MPH using a un-restricted pipe, and 2 MPH when the air filter was removed. as the motor was running slightly lean.

In other words it doesn't take much to lose 5 MPH on the top end.

 

[breaksalltherules]

Good to know, thanks. Right now, I am running a 3/4" ID high temp silicone line off the exit port on the stock muffler on my Super Titan. It keeps the exhaust so quiet that the intake is actually louder than the exhaust!

But I see I should switch to a 7/8" line for better flow. Because I can't weld the silicone to the header like a metal pipe, the only way I see connecting it to an exhaust manifold is if the manifold is just a slightly smaller OD than the 7/8" line or maybe a little bigger so I can slide the silicone line in (?)

I'm trying to ditch that stock muffler and probably going to use a Briggs and Stratton cigar muffler at the end.

Though right now, it is nice to be able to disconnect the silicone line when I'm in a metro area and want to be heard for safety reasons. Maybe I could just do Tarzan calls the whole time I'm ridding. Might get people attention!

 

[breaksalltherules]

Hey Quenton,

The site said your private messages are full so I just posted the reply here.

"Sounds great, thanks. Just let me know if you find another manifold or the damaged chrome pipe.

I have a 15mm walbro carb on it, high and low speed adjust with a high flow air filter and torquer v stack. That pipe will compliment it very nicely."

The manifold [cut-off pipe] has the same I.D. as the exhaust port, and works well in making the change to a slightly larger pipe, however the pipe must have a slight restriction at the exit. The slight restriction is needed to create a small amount of "back pressure", and can make as much as 3 MPH on the top end.
The motor we just tested on the "Roller Road" dropped 3 MPH using a un-restricted pipe, and 2 MPH when the air filter was removed. as the motor was running slightly lean.

In other words it doesn't take much to lose 5 MPH on the top end.

 

[Quenton Guenther]

Hi,

Sorry, but I get so many messages it is difficult to keep the section below the maximum allowed. I just deleted several hundred messages so it should be good for a month or two.

I checked the stock room and we don't have any of the aluminum exhaust manifolds left, however I still have one defective pipe and we can cut it to make the necessary manifold.

Let me know what is best for you.

Have fun,