Jemco Exhaust for 1978 XS 650

[Superdriver]

Hello. I am considering getting a set of Black Jemco high Exhaust for my 1978 XS 650 I would appreciate any feed back on their quality and fit issues and if anyone has pictures of the system that would be wonderful. I talked to Greg at Jemco by email and he said they need about 8 weeks lead time to produce the system once the order was in. Thanks. Bill

 

[Charles13]

They seem very well built but they use a pretty wide radius on the head pipes.

 

[Superdriver]

They seem very well built but they use a pretty wide radius on the head pipes.

Thank you. Is that a good thing or a bad thing LOL

 

[halfmile]

Jemco pipes are well made but the left cyl pipe bend is just pathetic. I suppose they do that for equal length head pipes but still ugly. Gunn Design has a great looking set of high pipes that are left side exit. Classic Bike Shop has the best price on high pipes but you will have to add your own mufflers. I hate to say it but Omar`s was on top of the game for tracker exhaust and Gary Hoos offered great flat track pipes, both of which are long gone.

 

[Superdriver]

Jemco pipes are well made but the left cyl pipe bend is just pathetic. I suppose they do that for equal length head pipes but still ugly. Gunn Design has a great looking set of high pipes that are left side exit. Classic Bike Shop has the best price on high pipes but you will have to add your own mufflers. I hate to say it but Omar`s was on top of the game for tracker exhaust and Gary Hoos offered great flat track pipes, both of which are long gone.
View attachment 247766View attachment 247767View attachment 247768View attachment 247769

Thank you very much. That is very helpful. Greg from Jemco Quoted $1,195.00 plus tax for the high pipes. I will look at the Gun Design unit also. Yeah ,its weird what happened to Omars. Their offering was excellent and then it just stopped without explanation. Take care. Bill

 

[arcticXS]

I guess having the mufflers on the LH side is more "flat track authentic", but IMHO, the mufflers on the RH side looks better when parked on the side stand Another thing is that both Jemco and Omars use 1 3/4" head pipes, which everyone say is too large for anything but a full race application. I would really love to have a set of Jemco, but with 1 1/2" headers and tighter bends on the headers. If length is an issue, then the mufflers could be moved back 4-6"....

 

[Superdriver]

Thank you very much. I’m not sure I understand the issue with the 1 and 3/4 inch header pipes. I would have guessed that lather is better for more freedom of exhaust flow. I wish I understood the issue better. It does make sense that the bigger the pipe the more awkward it is to bend smoothly. Take care. Bill

 

[Superdriver]

Thank you very much. That is very helpful. Greg from Jemco Quoted $1,195.00 plus tax for the high pipes. I will look at the Gun Design unit also. Yeah ,its weird what happened to Omars. Their offering was excellent and then it just stopped without explanation. Take care. Bill

I meant to say that bigger would be better for more exhaust flow not Lather LOL

 

[arcticXS]

Thank you very much. I’m not sure I understand the issue with the 1 and 3/4 inch header pipes. I would have guessed that lather is better for more freedom of exhaust flow. I wish I understood the issue better. It does make sense that the bigger the pipe the more awkward it is to bend smoothly. Take care. Bill

The general consensus is that a smaller diameter pipe gives a higher gas velocity and stronger pressure waves in the exhaust system, which in turn improves the scavenging of exhaust and even helps pulling in the fresh charge. This will result in more mid range power.
Thinking about the exhaust as a pure outlet pipe for exhaust gas, where larger equals better is not correct. Look at the pipes on a newer Yamaha XSR/ MT 700, and you will notice they are quite small, maybe 35 mm OD. And that is a 70+ hp engine....

 

[Superdriver]

Thank you for the clarification.being more restrictive now makes sense. It’s like water flow out of a large pipe to the pressure flow when it is squeezed through a smaller hole. Take care. Bill

 

[jetmechmarty]

Thank you for the clarification.being more restrictive now makes sense. It’s like water flow out of a large pipe to the pressure flow when it is squeezed through a smaller hole. Take care. Bill

If the fat pipe is what you want, the exhaust flow can be corrected. See MMM at 650 Central.

 

[5twins]

Yes, with those inserts, you get the best of both worlds. They fool the motor into thinking it has smaller diameter pipes, which it likes up close to the head, but you get the better flow of a larger pipe farther away from the head.

 

[Vincenthdfan]

If the fat pipe is what you want, the exhaust flow can be corrected. See MMM at 650 Central.

View attachment 247846

Yep, got a set to go with my Omar's Mile pipes when I bought them.

 

[arcticXS]

I still wonder what is best, a pipe diameter that is "ideal" for the engine displacement and state of tune, or an oversized header with these inserts. Or maybe even stepped or tapered headpipes. I know that inserts are also popular in Harley circles, but I have never seen any oem or even aftermarket headers with similar setup.

 

[jetmechmarty]

I still wonder what is best, a pipe diameter that is "ideal" for the engine displacement and state of tune, or an oversized header with these inserts. Or maybe even stepped or tapered headpipes. I know that inserts are also popular in Harley circles, but I have never seen any oem or even aftermarket headers with similar setup.

650 Central also has Torque Peak Optimzers that go into the end of the header. Choose diameter based upon RPM requirements.

 

[Superdriver]

If the fat pipe is what you want, the exhaust flow can be corrected. See MMM at 650 Central.

View attachment 247846

thank you very much .I will check them out. I think Omars used to sell something like That. Take care. Bill

 

[Superdriver]

Yes, with those inserts, you get the best of both worlds. They fool the motor into thinking it has smaller diameter pipes, which it likes up close to the head, but you get the better flow of a larger pipe farther away from the head.View attachment 247865

Excellent picture. thank you.

 

[Superdriver]

I still wonder what is best, a pipe diameter that is "ideal" for the engine displacement and state of tune, or an oversized header with these inserts. Or maybe even stepped or tapered headpipes. I know that inserts are also popular in Harley circles, but I have never seen any oem or even aftermarket headers with similar setup.

Thank you. take care. Bill

 

[Superdriver]

650 Central also has Torque Peak Optimzers that go into the end of the header. Choose diameter based upon RPM requirements.

Thank you.

 

[Charles13]

650 Central also has Torque Peak Optimzers that go into the end of the header. Choose diameter based upon RPM requirements.

These really complete the effect that the torque inserts start effectively increasing the overall velocity, not just out of the head. But then again why not just go with a smaller pipe? Unless the look of a bigger pipe is important to you.