Thread: New exhaust - loss in power

Hi
I received my new Lifan exhaust for my 91 CT70 and installed it. Right off you can tell it has a lot less power. The exhaust that was on the bike was Honda OEM, but perhaps baffles had been removed. The old exhaust has a sheet metal patch welded on the muffler end. I thought maybe it was repaired due to damage - but it may have been done to remove baffles? The engine does not seem excessively loud, but I am used to bigger bikes.
Anyway I thought the lack of power might be my imagination - since the new ehaust did not have the "cracK' of the old one.
But it isnt.

With the new exhaust I can hold the bike back from moving - while applying the fron brake and holding fast with my feet and under the strain seems that the engine does not respond as well.
With the old exhaust I am not able to hold it back.
My questions"
Should there be that much difference?
Do I need to compensate for the increased back pressure?
Can a change in the carb settings or timing compensate for this?
Thank you.
Rata222

I doubt that it's your imagination unless mind power alone has suddenly made you stronger All of the Chinese repops I've seen have a tiny outlet, much smaller than OEM CT70...even with the removable baffle in place. That's just a sign of the times; the pipes were designed for 49cc motors and tighter noise standards. You might be able to get some power back by rejetting the carb, but not much. Fact is, if the engine isn't misfiring at low speed, the richer mixture resulting from the restricted exhaust should actually make the engine pull harder at this rpm. Top speed is where I'd expect to see the biggest difference. Rich air/fuel ratios (below the misfire threshold) are good for acceleration, but dampen peak power.

Replace the original pipe for a direct A/B comparison. If performance returns to normal, then you'll have to address the restriction of the new pipe.

Thanks Racerx.
I swapped out the pipes several times this weekend to make sure. It seems to have less power at all speeds.
I rebuilt the carb this weekend (using same jets). I adjusted the carb according to the book, with each exhaust - same results.
I may go ahead and buy an oem exhaust.
I have had the bike 3 weeks and am enjoying the heck out of it. I really appreciate all the people on this site, like yourself, that pass along thier knowledge.