I thought I would post a note about my Keihan Systems stainless steel mufflers that I have put on my 1998 EV. Their construction is top notch. They were easy to install; I had installed a Keihan Systems crossover on my EV several months ago. I applied a bit of Permatex Ultra Copper to each slip joint as I installed each component. I clamped each joint with stainless clamps I ordered from Keihan Systems. Here's a photo of the right side muffler. Hard to tell from stock.
Keihan Systems advertises these mufflers as OEM replacements (or something like that). That's what I wanted. But they are "boomier" than stock. They fit in the middle between stock mufflers and Bubs. That was a pleasing surprise.
Now for some important details. I have been doing a lot of work on this scooter attempting to get it to run well. I bought a pair of used EV mufflers from Fotoguzzi and was able to get things working pretty good, not perfect, but pretty good (see my other thread on Attention To Throttle Bodies Seals And Fuel Injectors). For the stock mufflers I tuned the fuel injection pulse width (CO level) on the ECU using an exhaust gas sniffer. I chose to use my Innovate Systems AFR datalogger (using an AFR of 13.2 +1/-0 as my reference). The "sniffer" I built reached into the stock mufflers to near the end baffle (a distance of 10 or so inches IIRC).
After I installed the Keihan Systems mufflers I tried to use the same "sniffer" to set the CO level. What a shock! It wanted to read an AFR of >25. "That can't be!" I thought. I turned off the engine and went into the house.
As I was lying in bed last night it occurred to me that the end baffle in the Keihan Systems muffler must be deeper in the muffler body. That would explain why so much "O2-rich air" was getting to the end of the sniffer. When I got up this morning I measured the distance from the outlet of the muffler to the "end" baffle. It measured 22 inches! Holy Cow! No wonder these sound like a cross between Bubs and stock mufflers.
Here's a photo that shows the approximate locations of the end baffle on an OEM muffler (yellow line) and the end baffle on the Keihan Systems muffler (red line). Just a tad different.
So, I soldered another 12 inches on my sniffer and set to adjusting the CO level. I set it to an AFR of 13.3 at idle. Then Judy and I went for a long ride on Farm-to-Market and paved County Roads - lots of twists and turns, uphills and downhills, and other road conditions that would require downshifting at speed. I wanted to see if I had managed to "kill the backfiring and popping" with the many things I have been doing to this old scooter.
The ride was great! I had absolutely no backfiring and popping when shutting off the throttle at RPMs above 5000, and when downshifting at speed when going into sharp corners. The bike pulled very well on uphills with both of us and some gear onboard. After we got home and the engine cooled a bit I pulled the right spark plug. It "read" just a touch rich. I think I can fix that now. I will fill up with gas and calculate my mileage tomorrow.
And the sound of the Keihan System mufflers? Judy said it was "Very, very nice!" I'll take her word for it.
Cheers!
Bill
