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Old 06-13-2013, 02:29 AM
Russ McClay's Avatar
Russ McClay Russ McClay is offline
Motorized Bicycle Senior Member
Join Date: Jan 2013
Location: Taipei
Posts: 85
Default Re: She Just Ain't Climbing Like She Used To - Standard China Girl 66cc

Hey Map --

Originally Posted by mapbike View Post
Russ, I think you have already answered you own question here, you removed the end cap of the exhaust and you got your low end torque back for pulling those hills, seem the obvious problem is that over time you have developed some flow restriction in the exhaust, I would take a long steel rod and by hitting it with a hammer I would punch several larger paths through the honey comb looking stuff you will see up inside your exhaust muffler and then put the end cap back on and give it a try.
Thank you for the reply!

Today I got to really test my theory at lunch. I rode up to Yang Ming Shan National Park on the steep back road without the cap. The little bike had more power than when it was first broken in. It screams! All the places where I had to pedal (when the speed dropped to about 15 mph) I cruised at 18 to 19 mph. This is a huge difference! It's loud, but in the mountains it doesn't matter. Actually it sounds awesome. Also. The top end is still there.

I bought my kit directly from a factory in China which shipped it here to Taiwan. The muffler doesn't have any of the EPA honeycombs. Here's the end cap:

Inside I see a larger diameter tube (1/2 inch maybe), that's capped. That is inserted through a very thin metal disk which is the size diameter as the inside of the muffler. There is a gap all around it between it and the muffler inside. There is also a hole in it for the cap tube to fit into.

The large tube and disk and screw rod are all welded into the muffler.

My thinking now is just to unscrew the fastener nut and pull the cap when I need to climb and throw the cap in my tool bag. Then when I'm on the flats and in the city, I'll just let the muffler cool off a few minutes and put it back in. All this until I get a real expansion chamber.

I've also thought about cutting off the pipe that is connected to the cap and bending that disk. But am reluctant to do that, or drill holes...

As for the oil, I've already backed off a bit. Going with about 36:1 for starters.

I would like to say that all motors are different, so I don't suggest any running without the cap.

Motor safe!
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